Re: [volt-nuts] GPIB Issue with 3458A
Todd, Since the KE5FX NVRAM download software works, that would seem to indicate the GPIB is working, wouldn't it (download completes and checksums OK)? Randy On Sat, Dec 30, 2017 at 9:52 PM, Randy Evans <randyevans2...@gmail.com> wrote: > Todd, > > The minimal quick test would be greatly appreciated if you have the time. > I know this is above and beyond what I would expect but it would be really > useful to see if there is any hope for the GPIB on this unit. I will do > the service note 13 procedure in the morning. > > Thanks again, > > Randy > > On Sat, Dec 30, 2017 at 8:58 PM, Todd Micallef <tmical...@gmail.com> > wrote: > >> Randy, >> >> Short of swapping out the A5 digital board I have no other ideas. If you >> don't have a NI or Agilent adapter, I am sure I can find a spare for you >> to >> test. >> >> There is a Service Note 3458A-13A that deals with GPIB communication >> failures. There is a test within the document to see if a shorting jumper >> needs to be installed. >> I can try reducing the code to something minimal for a quick test if you >> want. It will take some time in the morning. >> >> Todd >> >> On Sat, Dec 30, 2017 at 11:18 PM, Randy Evans <randyevans2...@gmail.com> >> wrote: >> >> > Todd, >> > >> > Same as before. Still not working. All it does is print out "HP3458A" >> on >> > the output console and then just sits there. >> > >> > Randy >> > >> > On Sat, Dec 30, 2017 at 7:43 PM, Todd Micallef <tmical...@gmail.com> >> > wrote: >> > >> > > Randy, >> > > >> > > I just remembered that I changed the duration from 30 minutes to 2 >> > minutes >> > > to speed up the test. I forgot to change it back. >> > > >> > > Todd >> > > >> > > On Sat, Dec 30, 2017 at 10:27 PM, Todd Micallef <tmical...@gmail.com> >> > > wrote: >> > > >> > > > Randy, >> > > > >> > > > I just sent it. I haven't modified Martin's code yet. That can be >> done >> > > > once you confirm it works for you. >> > > > >> > > > Todd >> > > > >> > > > On Sat, Dec 30, 2017 at 10:12 PM, randyevans2688 < >> > > randyevans2...@gmail.com >> > > > > wrote: >> > > > >> > > >> Todd, >> > > >> If you don't mind, just send the code directly to me. >> > > >> Randy >> > > >> >> > > >> Sent from my Verizon, Samsung Galaxy smartphone >> > > >> Original message From: Todd Micallef < >> > > >> tmical...@gmail.com> Date: 12/30/17 6:40 PM (GMT-08:00) To: >> > > Discussion >> > > >> of precise voltage measurement <volt-nuts@febo.com> Subject: Re: >> > > >> [volt-nuts] GPIB Issue with 3458A >> > > >> Randy, >> > > >> >> > > >> I have not written anything else for the 3458A using EzGPIB. If >> you >> > > have >> > > >> a >> > > >> National Instruments or Agilent adapters, I have a handful of >> Python >> > > code >> > > >> I >> > > >> use to measure some of my standards. >> > > >> >> > > >> If you are reading the temperature from the HP meter, I would think >> > that >> > > >> the problem lies in how the triggering is configured. The >> triggering >> > has >> > > >> been changed in this script so it may work for you. There was an >> > > >> additional >> > > >> command added for disabling the buffer. >> > > >> The code can be posted here, if possible or I can email it to you >> for >> > > >> testing. >> > > >> >> > > >> Todd >> > > >> >> > > >> On Sat, Dec 30, 2017 at 9:26 PM, randyevans2688 < >> > > randyevans2...@gmail.com >> > > >> > >> > > >> wrote: >> > > >> >> > > >> > Todd, thanks for the help. Where will you post the new code? >> > > >> > BTW, do you have any very simple code that is likely to work. I >> am >> > > >> > interested in seeing if anything other than KE5FX's memory dump >> > >
Re: [volt-nuts] GPIB Issue with 3458A
Todd, The minimal quick test would be greatly appreciated if you have the time. I know this is above and beyond what I would expect but it would be really useful to see if there is any hope for the GPIB on this unit. I will do the service note 13 procedure in the morning. Thanks again, Randy On Sat, Dec 30, 2017 at 8:58 PM, Todd Micallef <tmical...@gmail.com> wrote: > Randy, > > Short of swapping out the A5 digital board I have no other ideas. If you > don't have a NI or Agilent adapter, I am sure I can find a spare for you to > test. > > There is a Service Note 3458A-13A that deals with GPIB communication > failures. There is a test within the document to see if a shorting jumper > needs to be installed. > I can try reducing the code to something minimal for a quick test if you > want. It will take some time in the morning. > > Todd > > On Sat, Dec 30, 2017 at 11:18 PM, Randy Evans <randyevans2...@gmail.com> > wrote: > > > Todd, > > > > Same as before. Still not working. All it does is print out "HP3458A" > on > > the output console and then just sits there. > > > > Randy > > > > On Sat, Dec 30, 2017 at 7:43 PM, Todd Micallef <tmical...@gmail.com> > > wrote: > > > > > Randy, > > > > > > I just remembered that I changed the duration from 30 minutes to 2 > > minutes > > > to speed up the test. I forgot to change it back. > > > > > > Todd > > > > > > On Sat, Dec 30, 2017 at 10:27 PM, Todd Micallef <tmical...@gmail.com> > > > wrote: > > > > > > > Randy, > > > > > > > > I just sent it. I haven't modified Martin's code yet. That can be > done > > > > once you confirm it works for you. > > > > > > > > Todd > > > > > > > > On Sat, Dec 30, 2017 at 10:12 PM, randyevans2688 < > > > randyevans2...@gmail.com > > > > > wrote: > > > > > > > >> Todd, > > > >> If you don't mind, just send the code directly to me. > > > >> Randy > > > >> > > > >> Sent from my Verizon, Samsung Galaxy smartphone > > > >> Original message From: Todd Micallef < > > > >> tmical...@gmail.com> Date: 12/30/17 6:40 PM (GMT-08:00) To: > > > Discussion > > > >> of precise voltage measurement <volt-nuts@febo.com> Subject: Re: > > > >> [volt-nuts] GPIB Issue with 3458A > > > >> Randy, > > > >> > > > >> I have not written anything else for the 3458A using EzGPIB. If you > > > have > > > >> a > > > >> National Instruments or Agilent adapters, I have a handful of Python > > > code > > > >> I > > > >> use to measure some of my standards. > > > >> > > > >> If you are reading the temperature from the HP meter, I would think > > that > > > >> the problem lies in how the triggering is configured. The triggering > > has > > > >> been changed in this script so it may work for you. There was an > > > >> additional > > > >> command added for disabling the buffer. > > > >> The code can be posted here, if possible or I can email it to you > for > > > >> testing. > > > >> > > > >> Todd > > > >> > > > >> On Sat, Dec 30, 2017 at 9:26 PM, randyevans2688 < > > > randyevans2...@gmail.com > > > >> > > > > >> wrote: > > > >> > > > >> > Todd, thanks for the help. Where will you post the new code? > > > >> > BTW, do you have any very simple code that is likely to work. I > am > > > >> > interested in seeing if anything other than KE5FX's memory dump > > > program > > > >> > will work on my HP3458A. > > > >> > Thanks again, > > > >> > Randy > > > >> > > > > >> > Sent from my Verizon, Samsung Galaxy smartphone > > > >> > Original message From: Todd Micallef < > > > >> tmical...@gmail.com> > > > >> > Date: 12/30/17 6:13 PM (GMT-08:00) To: Discussion of precise > > voltage > > > >> > measurement <volt-nuts@febo.com> Subject: Re: [volt-nuts] GPIB > > Issue > > > >> with > > > >> > 3458A > > > >> > Randy, > > > >> &g
Re: [volt-nuts] GPIB Issue with 3458A
Todd, I tried adding the line but it made no difference. Randy On Sat, Dec 30, 2017 at 12:19 PM, Randy Evans <randyevans2...@gmail.com> wrote: > Todd, > > Does it matter where I put the line in the Init_Device procedure? > > > procedure Init_Device; > begin; >EZGPIB_BusWriteData(gpib_address,GET_ID);// Get ID of meter >if EZGPIB_BusWaitForData(gpib_address,meter_id,Timeout) then > EZGPIB_ScreenWriteLn(meter_id); > >EZGPIB_BusWriteData(gpib_address,TRIGGER_SOURCE);// Hold trigger > until meter can be setup >EZGPIB_BusWriteData(gpib_address,'INBUF ON'); >EZGPIB_BusWriteData(gpib_address,AUTO_ZERO); >EZGPIB_BusWriteData(gpib_address,OUTPUT_FORMAT); > end; > > > Randy > > On Sat, Dec 30, 2017 at 11:20 AM, Todd Micallef <tmical...@gmail.com> > wrote: > >> Randy, >> >> I am the person that wrote that EzGPIB script. It was my first before I >> moved on to Python and I have only written a couple for the different >> meters I have on hand. Version 1.01 is the most current version I have for >> the 3458A. >> I see that I should have added at least one more command to the meter >> initialization. The additional init command is used in the scripts on >> xDevs. >> >> Add the following line in the Init_Device procedure >>EZGPIB_BusWriteData(gpib_address,'END ALWAYS'); >> >> This tells the meter to send an EOI on every read. >> >> I am looking for one of my Prologix adapters or I would test this. When I >> find it, I will also test it. I want to make sure there are no further >> issues. >> Also, do both meters run the same firmware versions? I wonder if the HP >> meter is using a much older version. >> >> Todd >> >> On Sat, Dec 30, 2017 at 10:42 AM, Randy Evans <randyevans2...@gmail.com> >> wrote: >> >> > Todd, >> > >> > I have version 1.01. Yes, please e-mail me your modified version. >> Maybe it >> > will help. >> > >> > Thanks, >> > >> > Randy >> > >> > On Sat, Dec 30, 2017 at 4:24 AM, Todd Micallef <tmical...@gmail.com> >> > wrote: >> > >> > > Randy, >> > > >> > > Is there a version number at the top of the file? I had two versions >> > (1.00 >> > > and 1.01). I can't remember all that changed between the two since it >> has >> > > been a while but I did find an additional timeout code that limited >> the >> > > wait time for reading data to 1 minute. I am guessing I had a problem >> > with >> > > mine and added it. >> > > >> > > I can email it to you if you want to try it. If it works for you, I >> will >> > > have Illya update it on xDevs. >> > > >> > > Todd >> > > >> > > On Sat, Dec 30, 2017 at 12:39 AM, Randy Evans < >> randyevans2...@gmail.com> >> > > wrote: >> > > >> > > > I am still unable to get my HP-3458A to work with the xdevs program >> > > > "HP3458A_Measure_DMM_Noise.488" (https://xdevs.com/article/dmm >> _noise/ >> > ). >> > > > It >> > > > works fine with my Agilent 3458A and with a friend's HP-3458A and >> his >> > > > Agilent 3458A using the EZGPIB program. The SW versions are >> identical >> > > with >> > > > my friend's DMMs, the HP units are (8.2) and with the Agilent units >> are >> > > > (9.2). However, both of my units work fine with the KE5FX GPIB >> Toolkit >> > > > HP3458.EXE program to download the NVRAM CAL data. This would seem >> to >> > > > indicate that my HP-3458 GPIB works at least partially. >> > > > >> > > > Does anyone have a EZGPIB program that I could try to run (that is >> > > > different from the Xdev program)? It would be nice to see if I >> could >> > get >> > > > something to work other than the HP3458.EXE program. Or if any one >> has >> > > > some ideas on what to look for. >> > > > >> > > > Thanks, >> > > > >> > > > Randy Evans >> > > > >> > > > On Tue, Dec 26, 2017 at 7:24 PM, Randy Evans < >> randyevans2...@gmail.com >> > > >> > > > wrote: >> > > > >> > > > > I am hoping some of you experts might be able to assist with a >> > strange >> > >
Re: [volt-nuts] GPIB Issue with 3458A
Todd, I have swapped cables, moved the Prologix adapter to both meters (Agilent works, HP doesn't), tried Martins code as well as Xdevs's. I have not tried another PC yet, maybe the next step. Here is the code that Martin modified for two meters, as well as the modified Xdev's code per your directions (V1.02). Thanks, Randy On Sat, Dec 30, 2017 at 3:55 PM, Todd Micallef <tmical...@gmail.com> wrote: > Randy, > > I will continue to look for my adapter. I haven't used it for quite a > while. > > I have seen similar issues and swapped cables, moved the adapter to the > other meter, etc... One of my cables was bad from one side of the connector > to the other (on the same end of the cable) and caused me lots of wasted > time. Weird reading errors were happening. > > Would you email me Martin's code so I can test it here and I will see if > anything can be done to replicate your issue. > > Todd > > > On Sat, Dec 30, 2017 at 6:42 PM, Randy Evans <randyevans2...@gmail.com> > wrote: > > > Todd, > > > > I tried adding the line but it made no difference. > > > > Randy > > > > On Sat, Dec 30, 2017 at 12:19 PM, Randy Evans <randyevans2...@gmail.com> > > wrote: > > > > > Todd, > > > > > > Does it matter where I put the line in the Init_Device procedure? > > > > > > > > > procedure Init_Device; > > > begin; > > >EZGPIB_BusWriteData(gpib_address,GET_ID);// Get ID of > > meter > > >if EZGPIB_BusWaitForData(gpib_address,meter_id,Timeout) then > > > EZGPIB_ScreenWriteLn(meter_id); > > > > > >EZGPIB_BusWriteData(gpib_address,TRIGGER_SOURCE);// Hold > trigger > > > until meter can be setup > > >EZGPIB_BusWriteData(gpib_address,'INBUF ON'); > > >EZGPIB_BusWriteData(gpib_address,AUTO_ZERO); > > >EZGPIB_BusWriteData(gpib_address,OUTPUT_FORMAT); > > > end; > > > > > > > > > Randy > > > > > > On Sat, Dec 30, 2017 at 11:20 AM, Todd Micallef <tmical...@gmail.com> > > > wrote: > > > > > >> Randy, > > >> > > >> I am the person that wrote that EzGPIB script. It was my first before > I > > >> moved on to Python and I have only written a couple for the different > > >> meters I have on hand. Version 1.01 is the most current version I have > > for > > >> the 3458A. > > >> I see that I should have added at least one more command to the meter > > >> initialization. The additional init command is used in the scripts on > > >> xDevs. > > >> > > >> Add the following line in the Init_Device procedure > > >>EZGPIB_BusWriteData(gpib_address,'END ALWAYS'); > > >> > > >> This tells the meter to send an EOI on every read. > > >> > > >> I am looking for one of my Prologix adapters or I would test this. > When > > I > > >> find it, I will also test it. I want to make sure there are no further > > >> issues. > > >> Also, do both meters run the same firmware versions? I wonder if the > HP > > >> meter is using a much older version. > > >> > > >> Todd > > >> > > >> On Sat, Dec 30, 2017 at 10:42 AM, Randy Evans < > randyevans2...@gmail.com > > > > > >> wrote: > > >> > > >> > Todd, > > >> > > > >> > I have version 1.01. Yes, please e-mail me your modified version. > > >> Maybe it > > >> > will help. > > >> > > > >> > Thanks, > > >> > > > >> > Randy > > >> > > > >> > On Sat, Dec 30, 2017 at 4:24 AM, Todd Micallef <tmical...@gmail.com > > > > >> > wrote: > > >> > > > >> > > Randy, > > >> > > > > >> > > Is there a version number at the top of the file? I had two > versions > > >> > (1.00 > > >> > > and 1.01). I can't remember all that changed between the two since > > it > > >> has > > >> > > been a while but I did find an additional timeout code that > limited > > >> the > > >> > > wait time for reading data to 1 minute. I am guessing I had a > > problem > > >> > with > > >> > > mine and added it. > > >> > > > > >> > > I can email it to you if you want to try it. If it works for you,
Re: [volt-nuts] GPIB Issue with 3458A
Todd, The routine looks like this on the Output Console: HP3458A 24.4 0 1 The 0 pops up after several seconds and the 1 after even more seconds later. No other output after the 1. The temperature reading is OK but no voltage readings. Thanks for the assistance but I likely have a hardware issue. I did the service note 13A test and the unit passed it fine. I will have to do more troubleshooting on my own but I really appreciate the help. Randy Evans. On Sun, Dec 31, 2017 at 6:09 AM, Todd Micallef <tmical...@gmail.com> wrote: > Randy, > > I put together a quick script for testing your connection. I have emailed > it to you but attached it here for others if needed. It will be easier than > running the other program. > > Todd > > On Sun, Dec 31, 2017 at 9:00 AM, Dr. Frank <frank.stellm...@freenet.de> > wrote: > > > Randy, > > > > I doubt, that your hp unit is defective, as it might work under certain > > circumstances, and also the FW version 8.2 vs. 9.2 will not make any > > difference, as only a few pair of bytes are different. All versions of > the > > A5 board are designed to be completely interchangeable over all versions > of > > 3458A instruments. > > > > I have another theory, which deals with the hardware version difference > > between the agilent and the hp unit. > > > > Your agilent unit might already have the 66547, full SMD board for A5, > > whereas the hp will for sure have one of the old 66505/515, through- hole > > boards, Rev A, B, or C. Illya has all of them pictured in his first 3458A > > repair blog. > > > > All the old versions (A, B, C) have GPIB bus transceivers, TI 75ALS160 > > for the data bus, and NS 75161 for the handshake signals. > > The new SMD board has TI 75ALS160 / TI 75ALS161, instead. > > > > So, the handshake bus uses a different logic family for the new board, > and > > therefore, the logic levels / immunity might be slightly different. > > > > My hp3458A has got the REV C A5 board, and it's from 2000. > > Since 2009, I run a similar datalogging program for capturing LTZ1000 > > output versus time, each 4 seconds, on an old PC with WIN98, Turbo > Pascal, > > an XT bus GPIB card from CEC, with the NEC chip. > > > > This program and hardware ran properly for years, (decades), until more > > and more errors during the 24h acquisition runs occured, vaguely > reminding > > me of your trouble. > > The output values were always correct, but frequently, 10sec time-outs > > ocurred, giving zero readings in the datalog. This time-out is obviously > > related to the handshaking mechanism. > > Finally, I found out, that the old ATX PSU was failing, especially its > > input snubber network was gone defect, which probably created big EMC > > spikes. > > After replacing the PSU, all these errors vanished completely. > > > > My conclusion was, that the GPIB bus is susceptible to such EMC > > disturbances, although it's solid TTL logic. > > As obviously the handshake signals were affected only, their higher > > susceptibility to disturbances may be caused by the difference in the > logic > > family of the transceiver IC. The agilent 3458A might be more tolerant to > > that, having the ALS161 version, instead. > > > > So you might also look for EMC problems in your lab, like SMPS, LED > lamps, > > or a defective PC power supply. > > > > Maybe, these Prologix adaptors (clones?) have critical logic levels, > > especially on the handshake bus, or an improper ground. > > You might search for these signal problems directly on the GPIB cable. > > > > Frank > > > > ___ > > volt-nuts mailing list -- volt-nuts@febo.com > > To unsubscribe, go to https://www.febo.com/cgi-bin/m > > ailman/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.
Re: [volt-nuts] GPIB Issue with 3458A
I am still unable to get my HP-3458A to work with the xdevs program "HP3458A_Measure_DMM_Noise.488" (https://xdevs.com/article/dmm_noise/). It works fine with my Agilent 3458A and with a friend's HP-3458A and his Agilent 3458A using the EZGPIB program. The SW versions are identical with my friend's DMMs, the HP units are (8.2) and with the Agilent units are (9.2). However, both of my units work fine with the KE5FX GPIB Toolkit HP3458.EXE program to download the NVRAM CAL data. This would seem to indicate that my HP-3458 GPIB works at least partially. Does anyone have a EZGPIB program that I could try to run (that is different from the Xdev program)? It would be nice to see if I could get something to work other than the HP3458.EXE program. Or if any one has some ideas on what to look for. Thanks, Randy Evans On Tue, Dec 26, 2017 at 7:24 PM, Randy Evans <randyevans2...@gmail.com> wrote: > I am hoping some of you experts might be able to assist with a strange > problem i am having trying to make automated measurements using EZGPIB with > an Agilent and an HP 3458A. I have a program given to me by Martin > Reynolds, which is a variant on the Xdevs noise measurement program. > Martin's program continuously reads the voltage measurements sequentially > from the two meters and then stores then in a measurements file, along with > the temperature measurements from both meters. The program works fine on > his Agilent and HP 3458As. > > On my two 3458As, it takes the temperature measurements just fine but only > takes a voltage measurement from the Agilent unit. The HP unit will not > make any voltage measurements although I can see both the 3458As in talk > states and, of course, it does sent the temperature measurements. However, > if I turn the HP unit off and then on again, the HP will start to take > voltage and temperature measurements and send them to the PC. > > Any ideas on what might be causing the strange behavior? > > Thanks, > > 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.
Re: [volt-nuts] Neon bulbs for HP 3420B or 419A chopper
Is there a relaible source for the GT-NE6H1925T neons? Mouser has them for special order and I suspect they want a high minimum quantity. A source in China lists them but I'm not sure I trust a Chinese source. On Sat, Jan 6, 2018 at 8:19 AM, David C. Partridge < david.partri...@perdrix.co.uk> wrote: > An update the A2B neons didn't work, but: > > George Kerber sent me a few GT-NE6H1925T neons. I pulled two out the > packet and installed them in the chopper, and wonder of wonders the correct > waveform appeared at the test point. > > This is a great step forward. The earlier neons I tried had way too low > a firing voltage so both fired. These fired at about 95-100V with a > sustain at about 68V and do alternate. > > Dave > > -Original Message- > From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. > Partridge > Sent: 18 November 2017 14:08 > To: 'Discussion of precise voltage measurement' > Subject: Re: [volt-nuts] Neon bulbs for HP 3420B or 419A chopper > > I'm in the process of getting some A2B neons from Mouser. > > Dave > > ___ > 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] Low noise reference
I have a question for the group. I was looking at an article for building an ultra-low noise voltage reference by Walt Jung, published in Electronic Design June 24, 1993 and a URL to the article is below. I want to filter the output of an LTZ1000 based 10V reference I am building and this circuit has a very low freq corner of 1.6 Hz. I was concerned about the leakage through R1-C1. If C1 had as little as 1ua leakage, it would drop the voltage through R1 by 1 mV. The spec on 100 uF electrolytic and tantalum capacitors show a leakage of 20 ua at rated voltage so this could be of great concern. However, at the low few tenths of a volt that should be across C1, the capacitor should have a much lower leakage amount, which is the theme of the article. To get a better appreciation of the issue, I connected a precision 0 to 10 V source (100uV resolution steps) to a series combination of a 1 Kohm resistor and a 100 uF electrolytic and, later, another 47uF tantalum and a 47 uF electrolytic capacitor. In all cases the leakage, as measured with a Keithley 414 picoammmeter, showed a leakage or around 0.08 uA at 10V and varying 0.04 to 0.12 uA, around .1uA at 1V and varying , and around 1 pA at 0.1V, but with widely varying leakage current of 0.5 to 1.5 pA, with occasional peaks of -0.5 to 2 pA. This would equate to about +/- 2 uV voltage variation across R1, making a 10 V 0.1ppm stable voltage reference of questionable value. I also tried a 0.68 uF polystyrene capacitor and also saw leakage current variations, although much less than the electrolytic and tantalum capacitors, as one would expect. Thinking the problem might be the the picoammeter, I put a 100 megohm 0.1% precision resistor in place of the capacitor across the precision voltage source set for 0.1 V and measured the current through the resistor at a very stable 0.9 pA on the Keithley 414 (sb 1pA but accurate enough for my measurements - the resistor shielded box likely has some sub pA leakage also). Note that I used shielded cables for all measurements, and the resistor and capacitor were in a shielded box, as well as the 100 Mohm calibration resistor. Touching the cables or boxes did not change the picoammeter reading at all, indicating to me that the shielding was reasonable. I suppose the best approach is to build it and characterize it, but it's not fruitful if someone has already done this. So my question is: has anyone built this circuit and characterized it, particularly over temperature for stability at the sub ppm level? Thanks, Randall Evans http://waltjung.org/PDFs/Build_Ultra_Low_Noise_Voltage_Reference.pdf ___ 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] GPIB Issue with 3458A
I am hoping some of you experts might be able to assist with a strange problem i am having trying to make automated measurements using EZGPIB with an Agilent and an HP 3458A. I have a program given to me by Martin Reynolds, which is a variant on the Xdevs noise measurement program. Martin's program continuously reads the voltage measurements sequentially from the two meters and then stores then in a measurements file, along with the temperature measurements from both meters. The program works fine on his Agilent and HP 3458As. On my two 3458As, it takes the temperature measurements just fine but only takes a voltage measurement from the Agilent unit. The HP unit will not make any voltage measurements although I can see both the 3458As in talk states and, of course, it does sent the temperature measurements. However, if I turn the HP unit off and then on again, the HP will start to take voltage and temperature measurements and send them to the PC. Any ideas on what might be causing the strange behavior? Thanks, 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.
