Bill, I am trying to figure out the MATH function without much success. The 3458
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 > 732A. > > Sorry for the long dissertation. Friends get mad at me for being so > detailed sometimes. > > Bill > > ----- Original Message ----- > From: "Randy Evans" <randyevans2...@gmail.com> > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Sent: Sunday, August 24, 2014 7:22 AM > Subject: Re: [volt-nuts] 732A and Prologix received > > > > Bill, > > > > I have convinced myself that the problem I an seeing is due to thermals. > > If I move the cables (with gold-plated banana plugs) using a small towel > > rather than letting my hand touch the plugs, it is much more stable. If > I > > then hold the banana plug with my hand after the reading has stabilized, > > the reading drifts rapidly upward. I am trying to check the stability of > > the reading but I haven't figured out the MATH function yet. I assume > this > > is a programmed function using GPIB only? > > > > The stability I am seeing by manually recording readings (using NLPC of > 100 > > and 1000) is much greater than what you are measuring on your system. > Not > > sure how to ascertain if it's the 3458A or the 732. The value of the > > readings are very different between the two - the 3458 reads about 50 uV > > high on the 10 V output and about 12 uV low on the 1V output. Rather > large > > differences (this is after an ACAL). I need to find some better cables > to > > make sure the errors are not due to thermals again. > > > > Randy > > > > > > On Sat, Aug 23, 2014 at 10:21 AM, Bill Gold <wpgold3...@att.net> wrote: > > > > > Randy: > > > > > > I get 6 volt 4 amp/hr (or 4.5 amp/hr) batteries and they will fit > > > perfect. Power Sonic PS-640, Genesis NP4-6, Panasonic LC-R064R5C and > > > others > > > that are in this size and package. Order from one of the usual > electronics > > > distributors like Allied, Mouser, Digikey. This is a very common > battery > > > as > > > it is used in a lot of "EXIT" signs so they are lighted when the power > goes > > > out. I don't see how the 12V 7AH will fit as they are too large. I > guess > > > you could use a 12V 5AH (PS1250) as it is the same size as 2 x 6 volt 4 > AH > > > but the terminals are in the wrong place so you will have to "nibble" > out > > > the aluminum plate that holds them in the 732A battery pack. You have > to > > > be > > > careful if you use the 12v 5AH as you will have 4 extra battery > connection > > > leads to deal with and connect correctly. I would stick with the 6V > 4AH. > > > New batteries will last around 12 to 14 hours before the "CAL" light > goes > > > out when AC power is not applied. So shipping to Cal Lab can be a > problem > > > if it is a distance away, or you have to use a shipper like UPS or > FEDEX > > > and > > > you ship the night before and then use their "Morning delivery" and the > Cal > > > Lab is expecting your 732A. Same on the way back to you. Of course > you > > > could always strap another battery on the 732A and hook it up to the > "ext > > > power" plug to last longer. I have seen it done. The issue is to get > the > > > Cal Lab to charge the extra battery before they ship the 732A back to > you. > > > > > > When you remove and work on the battery pack always have the AC > power > > > plugged in. The "CAL" led will stay on because the 18.6 v regulated > supply > > > is working. > > > > > > The "CAL" light is to indicate that power has not been lost to the > > > Reference Amp or other associated circuits. When the raw supply > (battery) > > > voltage drops below about 21 volts the "CAL" light will go out. Below > that > > > voltage the heater circuits will not work correctly and the 18.6 volt > > > regulated supply will not regulate. The requirement is that the > Reference > > > Amp be kept "alive" at all times to maintain the output voltage that > was > > > measured at the time of the most recent Calibration or Certification. > When > > > the semiconductor junctions are unbiased and cool off when power is > lost, > > > and then power is restored the result will be a different 10 volts than > > > before the power failure. My experience is that after all of the years > > > that > > > these units have been powered up, this won't happen and when power is > lost > > > and then restored, even months later, the 732A will come back to almost > > > exactly the same 10 volts as when they lost power, usually with in 0.2 > PPM > > > after 24 hours of "warm up". > > > > > > What type of hookup leads are you using when measuring the 1 volt > > > output? What is the PLC set to? I always use 100 PLC to measure this. > If > > > you don't have "low thermal" connection leads you can experience uV > changes > > > for a minute or more after plugging in the leads due to the "thermals" > > > generated because of the difference in temperature between the banana > jacks > > > on the 732A and the banana plugs of the leads. I have found that even > just > > > plugging in the lead will generate a thermal difference because of > > > difference of temps and some heating due to the physical act of just > > > inserting the plug because of friction between the jack and plug (my > theory > > > at any rate). You have to allow at least a minute or more before being > > > able > > > to make a measurement after plugging in the leads. I just measured the > > > variation of the 1 volt output of my 732A and using my 3458A and I got > a > > > total difference of 0.159 uV over 40 measurements using 100 PLC on the > 1 > > > volt range of the 3458A. Using the MATH function and all of the data > you > > > can collect. That was after waiting for several minutes after plugging > in > > > the leads. > > > > > > I hope all of this helps. > > > > > > Bill > > > > > > > > > > > > ----- Original Message ----- > > > From: "Randy Evans" <randyevans2...@gmail.com> > > > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > > > Sent: Friday, August 22, 2014 9:03 PM > > > Subject: Re: [volt-nuts] 732A and Prologix received > > > > > > > > > > Todd, > > > > > > > > Thanks for the info. I have several Panasonic 12V 7 AH batteries > that > I > > > > keep topped off and they have very low current draw (~2 to 3 mA at > 13.5 > > > > VDC) when charged and at their float voltage, so I am pretty sure > they > > > are > > > > in good condition. I will look at getting those in the units after I > > > > ascertain the condition of the 732. > > > > > > > > So now I have a what appears to be a functioning 3458A and a 732A but > > > they > > > > slightly disagree. I am like the man with two watches that disagree > on > > > the > > > > time - which is correct? For the moment, i am only concerned with > > > > stability. The need for absolute accuracy will come later. > > > > > > > > Randy > > > > > > > > > > > > On Fri, Aug 22, 2014 at 8:06 PM, Todd Micallef <tmical...@gmail.com> > > > wrote: > > > > > > > > > Randy, > > > > > > > > > > You have two possible choices. It can be configured with 4 x 6v 4Ah > > > > > batteries or 2 x 12v 7Ah batteries. Hopefully the previous owner > has > > > > > modified the battery pack already. A couple of mine needed a > nibbler > > > tool > > > > > to remove enough of the aluminum cover that fits over the tops of > the > > > > > batteries. The original cover will short out to the battery tabs > > > regardless > > > > > of the battery configuration if this is not done. > > > > > > > > > > You can find larger capacity batteries that will give you slightly > more > > > > > battery life. I lost a couple sets of mail-order batteries after a > few > > > > > extended outages. I would recommend going with locally bought > batteries > > > > > instead of the cheaper mail order. My local Batteries Plus will > > > typically > > > > > have some warranty if I remember correctly. Moving forward I will > only > > > use > > > > > 2 12v batteries and pre-charge them on a battery charger to > equalize > > > them > > > > > before putting them in the 732A. I think the cheap batteries did > not > > > > > discharge equally, and would not recover when power was applied. > > > > > > > > > > Inspect the back plane for damaged traces and look at the > capacitors. I > > > had > > > > > a few that looked questionable. So far, I have replaced all the big > > > caps > > > on > > > > > the pre-regulator and regulator boards. My feeling is that once > these > > > go > > > > > online, they should run as long as possible between repairs. > > > > > > > > > > The battery charger circuit may need adjusting. I tweaked mine and > it > > > > > seemed to work fine. > > > > > > > > > > Todd > > > > > > > > > > > > > > > On Fri, Aug 22, 2014 at 10:42 PM, Randy Evans < > > > randyevans2...@gmail.com> > > > > > wrote: > > > > > > > > > > > I received my Fluke 732A today. Just powered it up but it needs > new > > > > > > batteries. Any suggestions for sources (I haven't opened up the > unit > > > > > yet - > > > > > > I want to make sure it works before doing that). Also received > the > > > > > > ProLogix USB-GPIB adapter. I plan on using Mark Sims' CAL ran > data > > > > > dumper > > > > > > program to get the CAL data from my 3458A. Should be a busy > weekend. > > > > > > > > > > > > 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. > > > > > > > > > _______________________________________________ > > > > 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 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 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.
