Re: [volt-nuts] 732A and Prologix received
I have used the pomona spades, mainly to interface the low emf pomona banana cables to binding posts. I have stopped this, reasons being, they are large and worse, that the pomona spring loaded insulation tube that covers the banana plug conductor uses such a strong spring that slowly the plug works its way out of the spade. this btw also happend to me when I used the pomona low emf binding posts together with the pomona low emf banana cables. overall I m not happy with these. so, due to lack of options, I changed to self-made twisted shielded pair of high grade teflon/kapton silver plated copper cable with gold plated copper spades (crimped). I use them not only with the 3458a but also with nanovolt meters. these have higher resolution and accuracy in low level measurements than the 3458a. emf voltages were never an issue with these cables if properly used. I have posted some results doing 34420a stabilty measurements on the pmel forum, and the results are convincing (purpose was actually not to test the cables but the stability of the 34420a, but the emf issue is a part of this of course. we use the 34420a to do low voltage precision measurements on thermal converters where the full scale signal sometimes is 1mV). that btw also relates to don's statements below, I do not concurr with his comments about copper telurium as cable and spade material and so on. this material, as stated here many times, is used because it is machinable, for copper spades one would not use it. the 34420a factory cable uses copper cable and copper spades, not telurium-copper. if there was a problem, it would be worse with the 34420a than with the 3458a because of its low level ranges. and again, I have not seen any problems in a chain of (output to input): 1.copper-tellurium post from e.g. 8 digit calibrator 2.crimped copper spade, gold plated 3.silver plated tsp copper cable 4a.crimped copper spade to copper-tellurium post or 4b.soldered copper connector(34420) my consistent results over more than a year using them. Gesendet: Montag, 25. August 2014 um 06:33 Uhr Von: Orin Eman orin.e...@gmail.com An: Discussion of precise voltage measurement volt-nuts@febo.com Betreff: Re: [volt-nuts] 732A and Prologix received On Sun, Aug 24, 2014 at 1:46 PM, Don@True-Cal truecalservi...@gmail.com wrote: Randy all, You have correctly concluded that some (maybe not all) of your measurement problem is thermal EMF being added or subtracted in series within your measurement interconnect. This thermal EMF is generated at the junction of dissimilar metals when accompanied with thermal gradients between the test lead and device terminals. You have to eliminate both the dissimilarity of the metal junctions as well as minimize the thermal differences. The terminals of the 3458A as well as the 732A are Beryllium Copper so you want to use the same test lead terminals. Forget the typical Tin plated lugs or even Gold plated as both are not Beryllium Copper and constitute dissimilar metals. The best solution (as usually the most expensive) is to use a set of Fluke 5440A-7005 (48) cables. I also have just as good results using the much more flexible Pomona 11174A (lugs end always stay connected to the 732A) or 11058A with more convenient shielded banana plugs. The Fluke cable has the added Guard built in but be sure to also use a Guard lead with the Pomona cabled. The Guard lead does not need to be low thermal EMF. DIY cables is usually not a good idea because the lead wire to terminal also constitutes just as critical of junction. The above cables use Tellurium Copper wire which is usually hard to find and hard to crimp properly and NEVER solder. 11058A and 11174A are discontinued at Keysight. However, Pomona 5295 spade to banana cables are available (5295-36 at Mouser et al) and claim that they are designed to minimize thermal EMFs. Datasheet is here: http://www.mouser.com/ds/2/159/d5295_1_01-51722.pdf Any comments on these as an alternative? Orin. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] 732A and Prologix received
Randy: Sorry my fault. You have to use the RMATH command to get the various values stored in the registers. See the RMATH command in the User's Guide for a list of what registers you can read. I sure haven't found any other guides other than the 4 manuals. User's Guide, Quick Reference Guide, Calibration Manual, and Assembly Level Repair. It is just a matter of reading the guides and trying to remember what commands are available. It took me a lot of time to figure out what commands I use now. I am sure I am missing other commands that might be useful. Bill - Original Message - From: Randy Evans randyevans2...@gmail.com To: Discussion of precise voltage measurement volt-nuts@febo.com Sent: Sunday, August 24, 2014 6:04 PM Subject: Re: [volt-nuts] 732A and Prologix received Bill, I am trying to figure out the MATH function without much success. I input the sequence you said (I looked up the instructions to understand what you did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and it shows up on the display when I input BLUE F1. I hit ENTER and it takes the 40 measurements and the MATH symbol shows on the display during the measurements. After the SMPL symbol no longer blinks I hit MATH 2 and I get a MATH ERR symbol on the display. I tried it a couple of times and the same result so I am doing something wrong. Is there a better source for explaining how to do front panel masurements than the User Guide, which seems oriented at programming automatic rather than manual measurements. Randy On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold wpgold3...@att.net wrote: Randy: The MATH function is accessible from the keypad. I don't have an IEEE interface right now that works. You can also program the numeric keypad keys to have preprogrammed functions. DEFKEY I have made my own low thermal measurement leads from Pomona #4892 banana plugs and Belden #9272 wire. Why 9272, because it was handy at the time. It is tin plated copper, shielded twisted pair 20 ga. I have plans to do custom cables with 16 ga. bare copper wire that I will twist and then put a braided shield over it. I simply cannot find what I want so I will build my own cable. I have done something like this before and it worked fine. When I get a round toit. I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have used in the past to verify my homemade low thermal leads as described above. Frankly I cannot see any difference between using the 1756 cables and my homemade cables once I give them a few minutes for the thermals to go away. As far as I can tell and measure the differences, if any, are below 0.1 ppm at 10 volts. Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all adjustable you may be seeing a misadjusted 1 volt from the 732A. As far as the instability of the readings it is hard to determine which is causing the problem. I have programed (DEFKEY) a numeric keypad key #1 with the following code. MATH 14;NRDGS 40;TRIG 4;TRIG ; So what this does is set the MATH to Statistics (store high reading/low reading/ and mean of the readings) in the registers, the number of readings to 40, the trigger to hold (which keeps the meter from triggering until I press ENTER and then trigger the sequence of 40 readings when I push the ENTER button. You can do all of this manually from the keypads but since I use this sequence a lot I have preprogrammed it. This is after I set digits to 8 and PLC to 100. Once those 40 readings are finished then you can access the various MATH statistic registers, using the menu, by entering MATH and then a 2 for low, a 4 for mean, and 13 for high. Of course you could do all of this through the IEEE also. The 3458A has a very rich set of measurement commands. I am still learning all of them. It depends upon what I am trying to accomplish. Since the 1.018 and 1.0 volt outputs are passive and derived from resistive dividers from the 10 volt, I don't see how they could contribute to the varying readings you are measuring. I think I would put a short on the input of the 3458A and manually set the range to 1 volt and then observe the variations that way without the 732A involved. When I do this I see a variation from low reading to high reading of 0.125 uVolts and then another 40 I get 0.155 uVolts. This is without the GUARD connected to the low side of the measurment terminals, GUARD connected doesn't seem to affect the readings. So that is the base noise of the 3458A without the 732A, somewhere below .2uVolts. When hooked up to the 732A 1.0 volt output I got a variation of 0.159 uVolts using the same 40 reading method above. I would use this to determine where your problem might exist. Just having the meter input shorted will point you in the right direction. Meter, cables or
[volt-nuts] Access to Volt-Nuts Web site
For some reason I can no longer access the Volt-Nuts web site. Has anything changed on the permissions list? Is anyone else having this problem? I get the following message: You don't have permission to access /pipermail/volt-nuts/ on this server. Thanks, Randy ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Access to Volt-Nuts Web site
Randy: It doesn't work for me either. Same error message. Must be down for some reason. Time-Nuts is down also. Bill - Original Message - From: Randy Evans randyevans2...@gmail.com To: volt-nuts@febo.com Sent: Monday, August 25, 2014 7:28 AM Subject: [volt-nuts] Access to Volt-Nuts Web site For some reason I can no longer access the Volt-Nuts web site. Has anything changed on the permissions list? Is anyone else having this problem? I get the following message: You don't have permission to access /pipermail/volt-nuts/ on this server. Thanks, Randy ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] 732A and Prologix received
Tellurium Copper is usually not used for a device's terminal posts but used as the lead wire due, as you say, for the malleability to crimp well and flexibility. The point I was making is to use the same interconnect test lead material throughout as the DUT terminal posts. The 3458A and the 732A both use Beryllium Copper alloy making that type interconnect lug or plug the best choice to minimize the dissimilar metal EMF or Seebeck voltage. The 34420A uses pure copper rather than an alloy terminal and for the same reason, minimal Seebeck voltage is realized with a pure copper interconnect. Any type of Silver or Gold plating on the terminal or wire will introduce the undesirable dissimilar metal properties, both at the plating junction and at the plating metal to DUT terminal. The NI website had this chart that quantifies the Seebeck voltage best: When two, dissimilar metals are joined a voltage is created. This voltage is known as the thermal electromotive force (EMF) or the Seebeck voltage. The Seebeck voltage is dependent on the temperature of the junction and the composition of the metals joined. The specific metal-to-metal junctions result in specific temperature coefficients (µV/°C), also known as Seebeck coefficients. The following table lists the most common metals and their respective Seebeck coefficients. JunctionµV/°C Copper-Copper 0.3 Copper-Gold 0.5 Copper-Silver 0.5 Copper-Brass3 Copper-Nickel 10 Copper-Lead-Tin Solder 1-3 Copper-Aluminum 5 Copper-Kovar40 Copper-Copper Oxide 500 Granted, Gold and Silver are the next best choice, and is certainly why they are satisfactory, but using either warrants a more critical temperature gradient issue. If your measurements were satisfactorily convincing, than you probably had no appreciable junction temperature differences. Don Johnson -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of acb...@gmx.de Sent: Monday, August 25, 2014 5:37 AM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] 732A and Prologix received I have used the pomona spades, mainly to interface the low emf pomona banana cables to binding posts. I have stopped this, reasons being, they are large and worse, that the pomona spring loaded insulation tube that covers the banana plug conductor uses such a strong spring that slowly the plug works its way out of the spade. this btw also happend to me when I used the pomona low emf binding posts together with the pomona low emf banana cables. overall I m not happy with these. so, due to lack of options, I changed to self-made twisted shielded pair of high grade teflon/kapton silver plated copper cable with gold plated copper spades (crimped). I use them not only with the 3458a but also with nanovolt meters. these have higher resolution and accuracy in low level measurements than the 3458a. emf voltages were never an issue with these cables if properly used. I have posted some results doing 34420a stabilty measurements on the pmel forum, and the results are convincing (purpose was actually not to test the cables but the stability of the 34420a, but the emf issue is a part of this of course. we use the 34420a to do low voltage precision measurements on thermal converters where the full scale signal sometimes is 1mV). that btw also relates to don's statements below, I do not concurr with his comments about copper telurium as cable and spade material and so on. this material, as stated here many times, is used because it is machinable, for copper spades one would not use it. the 34420a factory cable uses copper cable and copper spades, not telurium-copper. if there was a problem, it would be worse with the 34420a than with the 3458a because of its low level ranges. and again, I have not seen any problems in a chain of (output to input): 1.copper-tellurium post from e.g. 8 digit calibrator 2.crimped copper spade, gold plated 3.silver plated tsp copper cable 4a.crimped copper spade to copper-tellurium post or 4b.soldered copper connector(34420) my consistent results over more than a year using them. Gesendet: Montag, 25. August 2014 um 06:33 Uhr Von: Orin Eman orin.e...@gmail.com An: Discussion of precise voltage measurement volt-nuts@febo.com Betreff: Re: [volt-nuts] 732A and Prologix received On Sun, Aug 24, 2014 at 1:46 PM, Don@True-Cal truecalservi...@gmail.com wrote: Randy all, You have correctly concluded that some (maybe not all) of your measurement problem is thermal EMF being added or subtracted in series within your measurement interconnect. This thermal EMF is generated at the junction of dissimilar metals when accompanied with thermal gradients between the test lead and device terminals. You have to eliminate both the dissimilarity of the metal junctions as well as minimize the thermal differences. The terminals
Re: [volt-nuts] 732A and Prologix received
well, your last point is the issue, how can you have a temperature difference within a few microns of material in said connections. theory is one thing, but in reality it does not happen due to the givens of the setup. therefore in practice it is irrelevant if the wire is silver or gold plated or pure copper. otherwise the gold plated spades and tellurium copper posts from pomona and others would be nonsense. and other than the mysterious fluke wire I have never seen a tellurium-copper wire from any wire manufacturer. Gesendet: Montag, 25. August 2014 um 17:02 Uhr Von: Don@True-Cal truecalservi...@gmail.com An: 'Discussion of precise voltage measurement' volt-nuts@febo.com Betreff: Re: [volt-nuts] 732A and Prologix received Tellurium Copper is usually not used for a device's terminal posts but used as the lead wire due, as you say, for the malleability to crimp well and flexibility. The point I was making is to use the same interconnect test lead material throughout as the DUT terminal posts. The 3458A and the 732A both use Beryllium Copper alloy making that type interconnect lug or plug the best choice to minimize the dissimilar metal EMF or Seebeck voltage. The 34420A uses pure copper rather than an alloy terminal and for the same reason, minimal Seebeck voltage is realized with a pure copper interconnect. Any type of Silver or Gold plating on the terminal or wire will introduce the undesirable dissimilar metal properties, both at the plating junction and at the plating metal to DUT terminal. The NI website had this chart that quantifies the Seebeck voltage best: When two, dissimilar metals are joined a voltage is created. This voltage is known as the thermal electromotive force (EMF) or the Seebeck voltage. The Seebeck voltage is dependent on the temperature of the junction and the composition of the metals joined. The specific metal-to-metal junctions result in specific temperature coefficients (µV/°C), also known as Seebeck coefficients. The following table lists the most common metals and their respective Seebeck coefficients. Junction µV/°C Copper-Copper 0.3 Copper-Gold 0.5 Copper-Silver 0.5 Copper-Brass 3 Copper-Nickel 10 Copper-Lead-Tin Solder 1-3 Copper-Aluminum 5 Copper-Kovar 40 Copper-Copper Oxide 500 Granted, Gold and Silver are the next best choice, and is certainly why they are satisfactory, but using either warrants a more critical temperature gradient issue. If your measurements were satisfactorily convincing, than you probably had no appreciable junction temperature differences. Don Johnson -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of acb...@gmx.de Sent: Monday, August 25, 2014 5:37 AM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] 732A and Prologix received I have used the pomona spades, mainly to interface the low emf pomona banana cables to binding posts. I have stopped this, reasons being, they are large and worse, that the pomona spring loaded insulation tube that covers the banana plug conductor uses such a strong spring that slowly the plug works its way out of the spade. this btw also happend to me when I used the pomona low emf binding posts together with the pomona low emf banana cables. overall I m not happy with these. so, due to lack of options, I changed to self-made twisted shielded pair of high grade teflon/kapton silver plated copper cable with gold plated copper spades (crimped). I use them not only with the 3458a but also with nanovolt meters. these have higher resolution and accuracy in low level measurements than the 3458a. emf voltages were never an issue with these cables if properly used. I have posted some results doing 34420a stabilty measurements on the pmel forum, and the results are convincing (purpose was actually not to test the cables but the stability of the 34420a, but the emf issue is a part of this of course. we use the 34420a to do low voltage precision measurements on thermal converters where the full scale signal sometimes is 1mV). that btw also relates to don's statements below, I do not concurr with his comments about copper telurium as cable and spade material and so on. this material, as stated here many times, is used because it is machinable, for copper spades one would not use it. the 34420a factory cable uses copper cable and copper spades, not telurium-copper. if there was a problem, it would be worse with the 34420a than with the 3458a because of its low level ranges. and again, I have not seen any problems in a chain of (output to input): 1.copper-tellurium post from e.g. 8 digit calibrator 2.crimped copper spade, gold plated 3.silver plated tsp copper cable 4a.crimped copper spade to copper-tellurium post or 4b.soldered copper connector(34420) my consistent
Re: [volt-nuts] 732A and Prologix received
On 8/25/2014 11:02 AM, Don@True-Cal wrote: Silver or Gold plating on the terminal or wire will introduce the undesirable dissimilar metal properties, both at the plating junction and at the plating metal to DUT terminal. Why? Any Seebeck effect is immediately offset in the opposite direction, since both junctions are (under normal conditions) at essentially the same temperature (e.g. there's a copper-gold thermocouple, the minimal thermal resistance of a micron of gold on the contact(s), then a gold-copper thermocouple). It seems to me that the improved consistency of the contact outweighs any loss from the thermocouples. A more typical contact would be copper-nickel plate-gold plate, but the concept is the same. Unless there is heat flowing through the entire assembly so one thermocouple is warmer than the offsetting one (e.g. shortly after plugging in a banana plug warmed by body heat), they simply cancel. Even if connecting gold plated to nickel plated contacts, it works out the same - a copper-nickel-gold-nickel-copper connection is completely offset. It's when the offsetting thermocouples occur across a temperature gradient that you have problems. -- Mike ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] AC calibration
Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim Verzonden met Windows Mail Van: Bill Gold Verzonden: maandag 25 augustus 2014 15:40 Aan: volt-nuts Randy: Sorry my fault. You have to use the RMATH command to get the various values stored in the registers. See the RMATH command in the User's Guide for a list of what registers you can read. I sure haven't found any other guides other than the 4 manuals. User's Guide, Quick Reference Guide, Calibration Manual, and Assembly Level Repair. It is just a matter of reading the guides and trying to remember what commands are available. It took me a lot of time to figure out what commands I use now. I am sure I am missing other commands that might be useful. Bill - Original Message - From: Randy Evans randyevans2...@gmail.com To: Discussion of precise voltage measurement volt-nuts@febo.com Sent: Sunday, August 24, 2014 6:04 PM Subject: Re: [volt-nuts] 732A and Prologix received Bill, I am trying to figure out the MATH function without much success. I input the sequence you said (I looked up the instructions to understand what you did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and it shows up on the display when I input BLUE F1. I hit ENTER and it takes the 40 measurements and the MATH symbol shows on the display during the measurements. After the SMPL symbol no longer blinks I hit MATH 2 and I get a MATH ERR symbol on the display. I tried it a couple of times and the same result so I am doing something wrong. Is there a better source for explaining how to do front panel masurements than the User Guide, which seems oriented at programming automatic rather than manual measurements. Randy On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold wpgold3...@att.net wrote: Randy: The MATH function is accessible from the keypad. I don't have an IEEE interface right now that works. You can also program the numeric keypad keys to have preprogrammed functions. DEFKEY I have made my own low thermal measurement leads from Pomona #4892 banana plugs and Belden #9272 wire. Why 9272, because it was handy at the time. It is tin plated copper, shielded twisted pair 20 ga. I have plans to do custom cables with 16 ga. bare copper wire that I will twist and then put a braided shield over it. I simply cannot find what I want so I will build my own cable. I have done something like this before and it worked fine. When I get a round toit. I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have used in the past to verify my homemade low thermal leads as described above. Frankly I cannot see any difference between using the 1756 cables and my homemade cables once I give them a few minutes for the thermals to go away. As far as I can tell and measure the differences, if any, are below 0.1 ppm at 10 volts. Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all adjustable you may be seeing a misadjusted 1 volt from the 732A. As far as the instability of the readings it is hard to determine which is causing the problem. I have programed (DEFKEY) a numeric keypad key #1 with the following code. MATH 14;NRDGS 40;TRIG 4;TRIG ; So what this does is set the MATH to Statistics (store high reading/low reading/ and mean of the readings) in the registers, the number of readings to 40, the trigger to hold (which keeps the meter from triggering until I press ENTER and then trigger the sequence of 40 readings when I push the ENTER button. You can do all of this manually from the keypads but since I use this sequence a lot I have preprogrammed it. This is after I set digits to 8 and PLC to 100. Once those 40 readings are finished then you can access the various MATH statistic registers, using the menu, by entering MATH and then a 2 for low, a 4 for mean, and 13 for high. Of course you could do all of this through the IEEE also. The 3458A has a very rich set of measurement commands. I am
Re: [volt-nuts] AC calibration
fred, generally you raise a good point, I had the same issue of calibrating an ac voltage to a high level of accuracy. you need this e.g. to validate the self.cal of a 3458a or other precison stuff like the 8506a0. what i would recommend to do if you want to keep costs down is: in a nutshell, get a thermal converter in the lowest range you need and a second one on range above. build a set of resistor range extenders (rf type with appropriate connectors and housings) to expand the range to where you need to be max. get one of the thermal converter calibrated (the higher one usually, and you need to havr good cal lab, should be 10ppm accuracy) and use it to calibrate the rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for thermal converters! at higher frequencies, due to reflections and stray capacitance/inductance influences, the accuracy decreases. the resistor range extenders though, if build up correctly, only have a few ppm impact (there is a paper from nist on that, but this is only typical). you can calibrate all converters to the one you got externally calibrated. do some research in the web, when you do the calibration, you need to determine the so-called constant N. then do an ac, dc+, ac, dc-, ac measurement between the the two and establish the deviation, also establish the error propagation. the end result will be a set of highly precise (low inaccuracies9 thermal converters good enough to calibrate a 3458a an better devices. if you want to spend the money, you could also buy a set of converters/range resistors (with/without a 540), that typically is a few k altogether, while a single device sometimes is available for below 100 bucks. you need to have a stable 7.5 digit nanovoltmeter though for the measurements of the tvcs (34420a or 2182 typically ) and precision (stable) dc and ac sources. but in the end, all you need is a single calibrated thermal converter. adrian Gesendet: Montag, 25. August 2014 um 18:38 Uhr Von: Dave M dgmin...@mediacombb.net An: Discussion of precise voltage measurement volt-nuts@febo.com Betreff: Re: [volt-nuts] AC calibration Well, you sort of answered your own question. The equipment is called a Thermal Transfer Standard, but instead of thermistors, it uses a thermocouple. Look at the manual for the Fluke 540B (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how it's done. Basically, the AC source is input into the transfer standard, and the standard's internal reference voltage is adjusted for a null on the galvanometer. Leaving the reference voltage setting alone, a DC voltage is input into the unit, and the DC source is adjusted for a null on the galvanometer. At that point, the AC voltage source is equal to that of the DC voltage source. Ther are thermocouple-type thermal converters used for RF voltage measurements with the transfer standard. They aren't cheap, and you have to have a converter for each range of voltages that you need to measure. The thermal converters used with this type of transfer standard isn't great (50 MHz or so typical), but their accuracy far surpasses that of the thermistor type sensors. There are other brands and models of thermal transfer standards, but I have a Fluke model 540 and a few thermal converters. That's why I referred you to the manual for it. Cheers, Dave M pa4...@gmail.com wrote: Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] AC calibration
Adrian, Do you have a link or title for the NIST paper that you mentioned? Dave M acb...@gmx.de wrote: fred, generally you raise a good point, I had the same issue of calibrating an ac voltage to a high level of accuracy. you need this e.g. to validate the self.cal of a 3458a or other precison stuff like the 8506a0. what i would recommend to do if you want to keep costs down is: in a nutshell, get a thermal converter in the lowest range you need and a second one on range above. build a set of resistor range extenders (rf type with appropriate connectors and housings) to expand the range to where you need to be max. get one of the thermal converter calibrated (the higher one usually, and you need to havr good cal lab, should be 10ppm accuracy) and use it to calibrate the rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for thermal converters! at higher frequencies, due to reflections and stray capacitance/inductance influences, the accuracy decreases. the resistor range extenders though, if build up correctly, only have a few ppm impact (there is a paper from nist on that, but this is only typical). you can calibrate all converters to the one you got externally calibrated. do some research in the web, when you do the calibration, you need to determine the so-called constant N. then do an ac, dc+, ac, dc-, ac measurement between the the two and establish the deviation, also establish the error propagation. the end result will be a set of highly precise (low inaccuracies9 thermal converters good enough to calibrate a 3458a an better devices. if you want to spend the money, you could also buy a set of converters/range resistors (with/without a 540), that typically is a few k altogether, while a single device sometimes is available for below 100 bucks. you need to have a stable 7.5 digit nanovoltmeter though for the measurements of the tvcs (34420a or 2182 typically ) and precision (stable) dc and ac sources. but in the end, all you need is a single calibrated thermal converter. adrian Gesendet: Montag, 25. August 2014 um 18:38 Uhr Von: Dave M dgmin...@mediacombb.net An: Discussion of precise voltage measurement volt-nuts@febo.com Betreff: Re: [volt-nuts] AC calibration Well, you sort of answered your own question. The equipment is called a Thermal Transfer Standard, but instead of thermistors, it uses a thermocouple. Look at the manual for the Fluke 540B (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how it's done. Basically, the AC source is input into the transfer standard, and the standard's internal reference voltage is adjusted for a null on the galvanometer. Leaving the reference voltage setting alone, a DC voltage is input into the unit, and the DC source is adjusted for a null on the galvanometer. At that point, the AC voltage source is equal to that of the DC voltage source. Ther are thermocouple-type thermal converters used for RF voltage measurements with the transfer standard. They aren't cheap, and you have to have a converter for each range of voltages that you need to measure. The thermal converters used with this type of transfer standard isn't great (50 MHz or so typical), but their accuracy far surpasses that of the thermistor type sensors. There are other brands and models of thermal transfer standards, but I have a Fluke model 540 and a few thermal converters. That's why I referred you to the manual for it. Cheers, Dave M pa4...@gmail.com wrote: Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. When the people fear the government, there is tyranny. When the government fears the people, there is liberty -- Thomas Jefferson
Re: [volt-nuts] AC calibration
Look up the phrase AC thermal transfer standard. Using a heater/thermocouple element in a vacuum is the tried and true way of linking an AC voltage to a DC reference. -Chuck Harris OBTW, trimming your quoted posts is considered friendly. pa4...@gmail.com wrote: Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] AC calibration
There is one more thing that enters into this discussion and that is reversal errors on the DC. The complicates the transfer somewhat. AC is always going + and -. DC is in one direction so you have to then reverse the voltage to the Thermal Transfer Standard and then take the average of the two readings. That is why there is a Reversal switch on the 540B. When you are using a fixed voltage High Frequency Thermal Converter you need an external DC reversal switch in addition to other equipment. You also need an AC/DC transfer switch so that you don't have to disconnect the AC source and then hook up the DC source manually. See the 540B again. All Thermal Transfer Standards have some reversal error. This is controlled by the internal construction of the unit and exactly where the glass isolation bead is located on the heating element. The thermocouple converter used in the 540B is selected to have a very low reversal error, but always will have some error. The error is fixed so you can approximate a DC measurement once you have characterized the particular converter. I can't remember now but I think there can be up to around .05% reversal errors on some converters, while the ones selected for the 540B are under .01%. Read the FLUKE Calibration: Philosophy in Practice for further information. Bill - Original Message - From: Dave M dgmin...@mediacombb.net To: Discussion of precise voltage measurement volt-nuts@febo.com Sent: Monday, August 25, 2014 11:38 AM Subject: Re: [volt-nuts] AC calibration Well, you sort of answered your own question. The equipment is called a Thermal Transfer Standard, but instead of thermistors, it uses a thermocouple. Look at the manual for the Fluke 540B (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how it's done. Basically, the AC source is input into the transfer standard, and the standard's internal reference voltage is adjusted for a null on the galvanometer. Leaving the reference voltage setting alone, a DC voltage is input into the unit, and the DC source is adjusted for a null on the galvanometer. At that point, the AC voltage source is equal to that of the DC voltage source. Ther are thermocouple-type thermal converters used for RF voltage measurements with the transfer standard. They aren't cheap, and you have to have a converter for each range of voltages that you need to measure. The thermal converters used with this type of transfer standard isn't great (50 MHz or so typical), but their accuracy far surpasses that of the thermistor type sensors. There are other brands and models of thermal transfer standards, but I have a Fluke model 540 and a few thermal converters. That's why I referred you to the manual for it. Cheers, Dave M pa4...@gmail.com wrote: Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] Fluke 732A battery module (and possible circuit replacement)
I have a 732A that is missing its battery module. Does anybody have or know of a source for a replacement? Also, would there be any interest in a replacement circuit assembly for the battery module? It would probably consist of a small board that plugs into the 2x6 pin edge connector and another small board with the ballast lamp/diode/resistor/thermistors and connections for the battery/switch/external power jack. The two boards would be connected by a short ribbon cable and would allow one to add batteries to a 732A that is missing the battery module. It would not be a complete battery module with the metal frame and backplate... ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] 732A and Prologix received
Why? Let me count the ways. You can never count on any Seebeck voltage to be immediately offset, there are far too many variables. Best example I can think of...why is there an Ohms Offset Compensation feature on any good high resolution DMM. 1) Try measuring a 1 or 10 Ohm resistor with your 3458A in 4-wire mode using inexpensive nickel-plated leads and even allow plenty of time for everything to thermally stabilize. Using Ohms Offset Compensation, enable and disable it and observe the difference. If the Seebeck voltages were all immediately offset, as you say, there would be no difference. But there most certainly is. Or simply, why is there a need for ohms offset compensation feature if all Seebeck voltages cancel each other out. Sure, nickel-plated is a horrible choice but if it all canceled, what difference would it make how bad is. 2) The cal lab workhorse calibrator is the 5700A/5720A. In between trips back to Fluke for full calibration, there is an interim external calibration procedure using the 732B, 742A-1 742A-10k. If someone used a set of gold-plated interconnects for this procedure, they would be laughed out of the lab and the calibrator would be useless until recalibrated properly. A set of 5440A-7002 (banana plug) cables comes with this calibrator (5440A-7003 spade lugs for 5720A) and recommended for the calibration procedure but other Beryllium Copper or pure Copper cables are also acceptable. 3) Lab air drafts will never allow true thermal symmetry around the DMM or DUT terminals. To convince yourself, place an oscillating fan several feet back from the DMM and DUT terminals and using the 1 or 10 Ohm setup from above, again with the nickel-plated leads, watch the variations. Sure the fan and the nickel-plated exaggerates the issue but it quickly dispels the notion that all the Seebeck voltages are canceled out. BTW, the plating layer temperature on a plated terminal will be somewhere between the temperature of the base metal and mating terminal it's connected to. This is not just theory, my 40+ years in the cal lab is driving my arguments but it never hurts to have physical-science on your side. Don Johnson -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Mike S Sent: Monday, August 25, 2014 11:03 AM To: volt-nuts@febo.com Subject: Re: [volt-nuts] 732A and Prologix received On 8/25/2014 11:02 AM, Don@True-Cal wrote: Silver or Gold plating on the terminal or wire will introduce the undesirable dissimilar metal properties, both at the plating junction and at the plating metal to DUT terminal. Why? Any Seebeck effect is immediately offset in the opposite direction, since both junctions are (under normal conditions) at essentially the same temperature (e.g. there's a copper-gold thermocouple, the minimal thermal resistance of a micron of gold on the contact(s), then a gold-copper thermocouple). It seems to me that the improved consistency of the contact outweighs any loss from the thermocouples. A more typical contact would be copper-nickel plate-gold plate, but the concept is the same. Unless there is heat flowing through the entire assembly so one thermocouple is warmer than the offsetting one (e.g. shortly after plugging in a banana plug warmed by body heat), they simply cancel. Even if connecting gold plated to nickel plated contacts, it works out the same - a copper-nickel-gold-nickel-copper connection is completely offset. It's when the offsetting thermocouples occur across a temperature gradient that you have problems. -- Mike ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fluke 732A battery module (and possible circuit replacement)
Mark, If you need any scans or measurements, let me know. I have one that will be disassembled for the next 24hrs. I can get this for you tomorrow evening before I replace the batteries. Todd Sent from my iPad On Aug 25, 2014, at 21:10, Mark Sims hol...@hotmail.com wrote: I have a 732A that is missing its battery module. Does anybody have or know of a source for a replacement? Also, would there be any interest in a replacement circuit assembly for the battery module? It would probably consist of a small board that plugs into the 2x6 pin edge connector and another small board with the ballast lamp/diode/resistor/thermistors and connections for the battery/switch/external power jack. The two boards would be connected by a short ribbon cable and would allow one to add batteries to a 732A that is missing the battery module. It would not be a complete battery module with the metal frame and backplate... ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fluke 732A battery module (and possible circuitreplacement)
It might be nice to do a lithium pack including all the safety controls. The down side is you would not be able to ship it by air. Tom - Original Message - From: Mark Sims hol...@hotmail.com To: volt-nuts@febo.com Sent: Monday, August 25, 2014 9:10 PM Subject: [volt-nuts] Fluke 732A battery module (and possible circuitreplacement) I have a 732A that is missing its battery module. Does anybody have or know of a source for a replacement? Also, would there be any interest in a replacement circuit assembly for the battery module? It would probably consist of a small board that plugs into the 2x6 pin edge connector and another small board with the ballast lamp/diode/resistor/thermistors and connections for the battery/switch/external power jack. The two boards would be connected by a short ribbon cable and would allow one to add batteries to a 732A that is missing the battery module. It would not be a complete battery module with the metal frame and backplate... ___ ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] Fluke 732A battery module (and possible circuitreplacement)
I thought about a lithium pack, but that would probably require a new power supply board or extensive mods to the current one. The charging system for lead-acid batteries and lithium batteries is quite a bit different. Not sure what it would take to reliably/safely cobble a lithium compatible charger system onto the Fluke lead-acid circuit. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] 732A and Prologix received
Not that I know of. Just wait and when you don't see a SMPL on the display it is done. But then with 1000 PLC that is around 16.66 seconds per reading times 100 readings is somewhere around 28 minutes and there is probably some overhead time so around 30 minutes. Not from the front panel at any rate. Bill - Original Message - From: Randy Evans randyevans2...@gmail.com To: Discussion of precise voltage measurement volt-nuts@febo.com Sent: Monday, August 25, 2014 9:23 PM Subject: Re: [volt-nuts] 732A and Prologix received Is there any way to tell when the function key routine is complete? In the case of taking multiple readings using the DEFKEY and MATH function, I don't see any indication when the routine is complete. In one particular case, I am taking a 100 readings with NLPC set for 1000 so its a long while before it's complete, but i have to guess when it's done. Thanks, Randy On Sun, Aug 24, 2014 at 6:04 PM, Randy Evans randyevans2...@gmail.com wrote: Bill, I am trying to figure out the MATH function without much success. I input the sequence you said (I looked up the instructions to understand what you did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and it shows up on the display when I input BLUE F1. I hit ENTER and it takes the 40 measurements and the MATH symbol shows on the display during the measurements. After the SMPL symbol no longer blinks I hit MATH 2 and I get a MATH ERR symbol on the display. I tried it a couple of times and the same result so I am doing something wrong. Is there a better source for explaining how to do front panel masurements than the User Guide, which seems oriented at programming automatic rather than manual measurements. Randy On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold wpgold3...@att.net wrote: Randy: The MATH function is accessible from the keypad. I don't have an IEEE interface right now that works. You can also program the numeric keypad keys to have preprogrammed functions. DEFKEY I have made my own low thermal measurement leads from Pomona #4892 banana plugs and Belden #9272 wire. Why 9272, because it was handy at the time. It is tin plated copper, shielded twisted pair 20 ga. I have plans to do custom cables with 16 ga. bare copper wire that I will twist and then put a braided shield over it. I simply cannot find what I want so I will build my own cable. I have done something like this before and it worked fine. When I get a round toit. I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have used in the past to verify my homemade low thermal leads as described above. Frankly I cannot see any difference between using the 1756 cables and my homemade cables once I give them a few minutes for the thermals to go away. As far as I can tell and measure the differences, if any, are below 0.1 ppm at 10 volts. Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all adjustable you may be seeing a misadjusted 1 volt from the 732A. As far as the instability of the readings it is hard to determine which is causing the problem. I have programed (DEFKEY) a numeric keypad key #1 with the following code. MATH 14;NRDGS 40;TRIG 4;TRIG ; So what this does is set the MATH to Statistics (store high reading/low reading/ and mean of the readings) in the registers, the number of readings to 40, the trigger to hold (which keeps the meter from triggering until I press ENTER and then trigger the sequence of 40 readings when I push the ENTER button. You can do all of this manually from the keypads but since I use this sequence a lot I have preprogrammed it. This is after I set digits to 8 and PLC to 100. Once those 40 readings are finished then you can access the various MATH statistic registers, using the menu, by entering MATH and then a 2 for low, a 4 for mean, and 13 for high. Of course you could do all of this through the IEEE also. The 3458A has a very rich set of measurement commands. I am still learning all of them. It depends upon what I am trying to accomplish. Since the 1.018 and 1.0 volt outputs are passive and derived from resistive dividers from the 10 volt, I don't see how they could contribute to the varying readings you are measuring. I think I would put a short on the input of the 3458A and manually set the range to 1 volt and then observe the variations that way without the 732A involved. When I do this I see a variation from low reading to high reading of 0.125 uVolts and then another 40 I get 0.155 uVolts. This is without the GUARD connected to the low side of the measurment terminals, GUARD connected doesn't seem to affect the readings. So that is the base noise of the 3458A without the 732A, somewhere below .2uVolts. When hooked up to the 732A 1.0 volt output I got a
