Re: [volt-nuts] New HP3458A
Randy, Congratulations on your 'new' 3458A. The 'CALRAM' back-up was just recently covered. There are two options: 1. Remove the NVRAM, read its contents with a programmer, program a new NVRAM and install the new NVRAM. I chose that option, installing sockets for the 'CALRAM' and the two other NVRAM's that are used for other, non-calibration, purposes. Be sure to let the NVRAM cool all the way down before trying to read it. Learned by experience with that one. 2. Read the 'CALRAM' via HPIB and the MREAD command (many steps involved but can be done as a program with your laptop/desktop), use that data to program a new NVRAM (I suspect there is a way to 'program' the NVRAM by HPIB as well but I don't recall ever reading anything about it on the list), remove the old NVRAM and install the new NVRAM. When I read the contents of the 'CALRAM' with a programmer and with the MREAD command, they matched exactly. However, when you do an ACAL, the CALRAM contents change. Does your unit have the single EPROM or the 6 EPROM version of the firmware? Also what version of firmware do you have? The latest is REV 9. REV 8 is 'out there' on the net. If you purchase an exchange display, and you have the single EPROM version of the A5 Outguard Controller Assembly, the REV 9 EPROM is $24.10 per the Keysight website. Might be worth adding to the order. The 6 EPROM version is $220. Also, what is the serial number? You can get a good idea of age by the serial number. Also, the various covers inside often will have dates of manufacture on them and the chips, etc., will have date codes, including the NVRAM's. Also, you can add option 001 by plugging some memory chips, specific details I don't recall right now. As far as the reading when shorted, I recall the Calibration Manual calls for a piece of copper wire to short the input terminals. It looks like a flying 'U' when properly fashioned. The Calibration Manual gives the details, IIRC. Good luck. Joe -Original Message- From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On Behalf Of Randy Evans Sent: Friday, August 15, 2014 8:40 PM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] New HP3458A I would like to thank everyone that replied to my query on what to look for in my new HP-3458. I did find that the AUTO ZERO button does work fine, thanks to Bill's comments. I had looked in the manual, just not far enough. The display is still perfectly readable but i would like it to be perfect. I am particularly interested in the exchange display for $272 (better than $700 for a new one, as Todd suggested). Does someone have a contact number at Keysight that I could call (my experience is that one can spend a lot of time calling around until the right person is finally found). I certainly need to figure out how to copy and replace the NVRAM - I lost the calibration on my Datron 1082 by not realizing the memory backup battery died and now I need to calibrate it myself (the HP3458A should make that doable, I hope). Any suggestions would be greatly appreciated. I believe it has been covered before on Volt-Nuts and I need to go through the past discussions to find it. One question I have for the group is what should the display typically show with the input shorted? I see a reading of about -.0025 mV. That seems rather high. I tried several different banana cables (gold plated, tin plated) used to short the input terminals to see if thermocouple effects might be responsible but there was no change in the reading. Still learning. Thanks, Randy On Fri, Aug 15, 2014 at 8:06 AM, Jason Watson watson.ja...@gmail.com wrote: I've also seen excessive Guard to Low leakage when varistor RV501 has gone bad (it's located on the front/rear switch pcb and it's possible to replace it while leaving the circuit board in place if you are careful). HP/Agilent/Keysight Part number is 0837-0196, cross referenced to a Harris Corp. V430MA3A. On Fri, Aug 15, 2014 at 10:46 AM, Stephen Grady grady.st...@gmail.com wrote: Randy, I have come across a few 3458A's that had leakage between Guard and Low when te guard is in external guard position. This was due to a leaky external guard switch and/or leaky front rear switch. This can be quickly determined by measuring resistance between guard and low with guard external. This normally in not an issue except when you are using 3458A to measure voltage with low above earth potential say in a bridge the guard low leakage will be loading other arm of the bridge. Kind Regards, Steve Grady Sydney, Australia -Original Message- From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On Behalf Of Randy Evans Sent: Friday, 15 August 2014 1:22 PM To: volt-nuts@febo.com Subject: [volt-nuts] New HP3458A I picked up a used HP3458A today, which I needed for some precision DC measurements i need
Re: [volt-nuts] New HP3458A
-0.0025mV does seem a little excessive, I think that may be out of mfr. specifications if I'm remembering right. Charles is right you don't want to use banana plugs, at least for low dc volts stuff. The service manual has a good picture of how you should use a section of clean copper wire to short the terminals. Also make sure you've done an ACAL recently and that the ambient temperature hasn't changed by more than 1 deg. C since doing it. The air filter is also a good call, I've seen the internal temperatures change by 2-3 degrees just by having the air filter dirty. Use the TEMP? command to get the internal temperature. Use the CAL? 58, CAL? 59 and CAL? 60 commands to get the internal temperatures when the last calibration was performed. There shouldn't be more than a 5 deg. C difference or else there are adders you have to start throwing on the accuracy spec's. Finally after all of that the input offset voltage is still high, running a CAL 0 command in both the front terminal and rear terminal positions with the input properly shorted will re-'zero' the instrument. Make sure the cal security is turned off to be able to run the CAL 0 command. All that is well detailed in the service manual too. On Sat, Aug 16, 2014 at 8:48 AM, J. L. Trantham jlt...@att.net wrote: Randy, Congratulations on your 'new' 3458A. The 'CALRAM' back-up was just recently covered. There are two options: 1. Remove the NVRAM, read its contents with a programmer, program a new NVRAM and install the new NVRAM. I chose that option, installing sockets for the 'CALRAM' and the two other NVRAM's that are used for other, non-calibration, purposes. Be sure to let the NVRAM cool all the way down before trying to read it. Learned by experience with that one. 2. Read the 'CALRAM' via HPIB and the MREAD command (many steps involved but can be done as a program with your laptop/desktop), use that data to program a new NVRAM (I suspect there is a way to 'program' the NVRAM by HPIB as well but I don't recall ever reading anything about it on the list), remove the old NVRAM and install the new NVRAM. When I read the contents of the 'CALRAM' with a programmer and with the MREAD command, they matched exactly. However, when you do an ACAL, the CALRAM contents change. Does your unit have the single EPROM or the 6 EPROM version of the firmware? Also what version of firmware do you have? The latest is REV 9. REV 8 is 'out there' on the net. If you purchase an exchange display, and you have the single EPROM version of the A5 Outguard Controller Assembly, the REV 9 EPROM is $24.10 per the Keysight website. Might be worth adding to the order. The 6 EPROM version is $220. Also, what is the serial number? You can get a good idea of age by the serial number. Also, the various covers inside often will have dates of manufacture on them and the chips, etc., will have date codes, including the NVRAM's. Also, you can add option 001 by plugging some memory chips, specific details I don't recall right now. As far as the reading when shorted, I recall the Calibration Manual calls for a piece of copper wire to short the input terminals. It looks like a flying 'U' when properly fashioned. The Calibration Manual gives the details, IIRC. Good luck. Joe -Original Message- From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On Behalf Of Randy Evans Sent: Friday, August 15, 2014 8:40 PM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] New HP3458A I would like to thank everyone that replied to my query on what to look for in my new HP-3458. I did find that the AUTO ZERO button does work fine, thanks to Bill's comments. I had looked in the manual, just not far enough. The display is still perfectly readable but i would like it to be perfect. I am particularly interested in the exchange display for $272 (better than $700 for a new one, as Todd suggested). Does someone have a contact number at Keysight that I could call (my experience is that one can spend a lot of time calling around until the right person is finally found). I certainly need to figure out how to copy and replace the NVRAM - I lost the calibration on my Datron 1082 by not realizing the memory backup battery died and now I need to calibrate it myself (the HP3458A should make that doable, I hope). Any suggestions would be greatly appreciated. I believe it has been covered before on Volt-Nuts and I need to go through the past discussions to find it. One question I have for the group is what should the display typically show with the input shorted? I see a reading of about -.0025 mV. That seems rather high. I tried several different banana cables (gold plated, tin plated) used to short the input terminals to see if thermocouple effects might be responsible but there was no change in the reading. Still learning. Thanks, Randy On Fri, Aug 15
Re: [volt-nuts] New HP3458A
Randy, I have had two 3458a that had bad front / rear switches. It was easy to determine during the calibration of the Cal 0 that failed. A copper short across both of the inputs, as per the calibration procedure, showed more than .5 ohm in 2-wire mode on the lowest range. The resistance was not stable and seemed to settle slowly. The switches were available and not hard to replace but probably not something I would attempt with a ROR unit. The pixels can have some burn-in, but I don't know if Agilent/Keysight would fail a cal for dead pixels. There was no indication that they looked at this during the calibration. They use the GPIB port and probably would fail it if the display was not readable during self-test. A call to Keysight would probably help. I think the displays are in the $700+ range. That reminds me, you should check the GPIB port. Mine was not functioning when Agilent received the meter, but then it started working when they bench tested it. It almost cost me $2700 . The ACAL ALL passing all tests would be a good sign, but I am not sure if it indicates that the SCAL calibrations will pass. Someone else can probably help with that potential issue. The age of the NVRAM is important. Can you determine when they were replaced ? Todd Sent from my iPad On Aug 14, 2014, at 23:22, Randy Evans randyevans2...@gmail.com wrote: I picked up a used HP3458A today, which I needed for some precision DC measurements i need to make. It passes all the self tests and the Auto Cal but is there any thing else I can check ( I have a 14 day RR). It reads a 10V standard I made within a few tens of ppm, but it's not a 732A but that is at least comforting. It also reads an ESI 10Kohm standard resistor dead on. The only problem is that the display has some faint pixels in some locations, with three in the second row for every digit location dead. Likely a pixel driver I would think. I am not too familiar with it yet but I noticed when I push the auto zero button, the display has a blinking square until I hit a measurement mode button; e.g., DCV, ACV, OHM, etc. Is this normal? Regards, Randy Evans ___ 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] New HP3458A
Randy, I have come across a few 3458A's that had leakage between Guard and Low when te guard is in external guard position. This was due to a leaky external guard switch and/or leaky front rear switch. This can be quickly determined by measuring resistance between guard and low with guard external. This normally in not an issue except when you are using 3458A to measure voltage with low above earth potential say in a bridge the guard low leakage will be loading other arm of the bridge. Kind Regards, Steve Grady Sydney, Australia -Original Message- From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On Behalf Of Randy Evans Sent: Friday, 15 August 2014 1:22 PM To: volt-nuts@febo.com Subject: [volt-nuts] New HP3458A I picked up a used HP3458A today, which I needed for some precision DC measurements i need to make. It passes all the self tests and the Auto Cal but is there any thing else I can check ( I have a 14 day RR). It reads a 10V standard I made within a few tens of ppm, but it's not a 732A but that is at least comforting. It also reads an ESI 10Kohm standard resistor dead on. The only problem is that the display has some faint pixels in some locations, with three in the second row for every digit location dead. Likely a pixel driver I would think. I am not too familiar with it yet but I noticed when I push the auto zero button, the display has a blinking square until I hit a measurement mode button; e.g., DCV, ACV, OHM, etc. Is this normal? Regards, Randy Evans ___ 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. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ 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] New HP3458A
Randy, I have not been able to do accurate work with banana plugs. Too much thermal mass. For best results use copper wires into the cross holes of the banana jacks or small gold plated copper spade lugs crimped on the ends of the test leads. Cheap at Radio Shack. Both work fine. Remember to do an ACAL every time you want accuracy. I think my 3458A is about +5 PPM/C for four wire resistance (10K ohm) on differences of Temp?. Also clean your air filter and record the Temp? after so you know when to clean it again. If you try to use high impedance resistance standards (LN Cheap ones) they will not measure correctly unless DELAY = 10 seconds on my system. Charlie On 8/15/2014 6:39 PM, Randy Evans wrote: I would like to thank everyone that replied to my query on what to look for in my new HP-3458. I did find that the AUTO ZERO button does work fine, thanks to Bill's comments. I had looked in the manual, just not far enough. The display is still perfectly readable but i would like it to be perfect. I am particularly interested in the exchange display for $272 (better than $700 for a new one, as Todd suggested). Does someone have a contact number at Keysight that I could call (my experience is that one can spend a lot of time calling around until the right person is finally found). I certainly need to figure out how to copy and replace the NVRAM - I lost the calibration on my Datron 1082 by not realizing the memory backup battery died and now I need to calibrate it myself (the HP3458A should make that doable, I hope). Any suggestions would be greatly appreciated. I believe it has been covered before on Volt-Nuts and I need to go through the past discussions to find it. One question I have for the group is what should the display typically show with the input shorted? I see a reading of about -.0025 mV. That seems rather high. I tried several different banana cables (gold plated, tin plated) used to short the input terminals to see if thermocouple effects might be responsible but there was no change in the reading. Still learning. Thanks, Randy On Fri, Aug 15, 2014 at 8:06 AM, Jason Watson watson.ja...@gmail.com wrote: I've also seen excessive Guard to Low leakage when varistor RV501 has gone bad (it's located on the front/rear switch pcb and it's possible to replace it while leaving the circuit board in place if you are careful). HP/Agilent/Keysight Part number is 0837-0196, cross referenced to a Harris Corp. V430MA3A. On Fri, Aug 15, 2014 at 10:46 AM, Stephen Grady grady.st...@gmail.com wrote: Randy, I have come across a few 3458A's that had leakage between Guard and Low when te guard is in external guard position. This was due to a leaky external guard switch and/or leaky front rear switch. This can be quickly determined by measuring resistance between guard and low with guard external. This normally in not an issue except when you are using 3458A to measure voltage with low above earth potential say in a bridge the guard low leakage will be loading other arm of the bridge. Kind Regards, Steve Grady Sydney, Australia -Original Message- From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On Behalf Of Randy Evans Sent: Friday, 15 August 2014 1:22 PM To: volt-nuts@febo.com Subject: [volt-nuts] New HP3458A I picked up a used HP3458A today, which I needed for some precision DC measurements i need to make. It passes all the self tests and the Auto Cal but is there any thing else I can check ( I have a 14 day RR). It reads a 10V standard I made within a few tens of ppm, but it's not a 732A but that is at least comforting. It also reads an ESI 10Kohm standard resistor dead on. The only problem is that the display has some faint pixels in some locations, with three in the second row for every digit location dead. Likely a pixel driver I would think. I am not too familiar with it yet but I noticed when I push the auto zero button, the display has a blinking square until I hit a measurement mode button; e.g., DCV, ACV, OHM, etc. Is this normal? Regards, Randy Evans ___ 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. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ 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
[volt-nuts] New HP3458A
I picked up a used HP3458A today, which I needed for some precision DC measurements i need to make. It passes all the self tests and the Auto Cal but is there any thing else I can check ( I have a 14 day RR). It reads a 10V standard I made within a few tens of ppm, but it's not a 732A but that is at least comforting. It also reads an ESI 10Kohm standard resistor dead on. The only problem is that the display has some faint pixels in some locations, with three in the second row for every digit location dead. Likely a pixel driver I would think. I am not too familiar with it yet but I noticed when I push the auto zero button, the display has a blinking square until I hit a measurement mode button; e.g., DCV, ACV, OHM, etc. Is this normal? Regards, Randy Evans ___ 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.
