Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left
Hello Stephen, I agree that the 4920's will often drift more than their spec after 1 year. I find it more convenient to derate them slightly - and use them wisely. Note the manual states their absolute specs are valid for 6 months, but I still maintain them on a 1 year cycle. Even when de-rated they still have very good short term stability over 10 minutes and for weeks after. On the discussion of inputs at low points in ranges, I find this is where the 4920M's will most often cause calibration failures against their specs. Perhaps optimistically, Datron has specified their absolute reading spec at, say, 3V range, to be +-30ppm of reading (40 to 20kHz) for any input from 30% to 100% of range. No floor or percentage of range limiting spec is stated. When the sad day finally arrives and I need to repair units I would resort to cannibilising parts from these 4920M's just to keep my more capable 4920 going. regards, ben. From: Stephen Grady grady.st...@gmail.com Sent: Monday, September 01, 2014 5:37 AM To: Discussion of precise voltage measurement volt-nuts@febo.com Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left Charlie, The Error Ur is an under-range error; you have to apply an input above 10% of the range before it will display a reading. The 4920's are a very nice instrument. Their only problem is that they are all so old that they are reaching the stage where some components are drifting excessively or failing. I have come across 4920's that are drifting a little (more than there spec) between cals (and yes they need to be cal'd annually), another 4920 I came across had an intermittent failure in one of its power supplies. Kind Regards, Stephen Grady Sydney Australia -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Charles Black Sent: Monday, 1 September 2014 3:19 AM To: b...@veritechmeasurements.com.au; Discussion of precise voltage measurement Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left Hi Ben, I am going to check this out today to find if it might be helpfull around here for my AC calibration. It has an error message: Error Ur so some fixing is going to be needed. On the back it says it's got Option 80, whatever that is. Charlie On 8/31/2014 5:37 AM, ben wrote: Hello all, Just a heads up. I noted there is a lonely Datron / Wavetek 4920M AC voltmeter for sale on ebay, starting at US$650 (ending in 1 day !). I have little idea of its true working state or not (picture shows it powered on). If fully working it would be a good buy for an AC voltmeter that is, I reckon, better than an HP 3458A. Only drawback with these models is the voltage input shell is always earthed, not floating. I have two of these 4920M's already, not really tempted by a third. I have a paper copies of operator, calibration, and service manual if anyone interested. regards, ben. ___ 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. --- 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.
Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left
charlie, you can expand these tvcs by range resistors to work as higher voltage tvcs. if you do it right (rf-type setup) you can work up to a couple hundred khz with just minor additional error beyond its error in its orgininal voltage range. need to calibrate them however. using an attenuator is not a good idea, too unprecise. still tvcs are the most precise way to measure, if done right. pretty tme consuming though. but you need them e.g. to calibrate a 4920. adrian Gesendet: Sonntag, 31. August 2014 um 21:41 Uhr Von: Charles Black cbl...@centurytel.net An: Discussion of precise voltage measurement volt-nuts@febo.com Betreff: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left Hi Stephen, Thanks for the info on the 4920M. It might be that I should pass on this but it is nice to know that it is probably working. If I don't have the necessary items needed for calibration it might still be a good source uncalibrated. I was hoping that the 4920 had better minimum voltage out steps than my present Rigol 4062 for 3458a AC calibration. I have two EL 1400 0.25V voltage thermal converters that I was trying to use in a test setup but they had such a low voltage range that I was forced to use my ATV-60 attenuator. It all kind of worked but a 0.1 db minimum step is a little course for easy use. The Rigol also suffers from this malady. Charlie On 8/31/2014 1:06 PM, Stephen Grady wrote: Charlie, The Error Ur is an under-range error; you have to apply an input above 10% of the range before it will display a reading. The 4920's are a very nice instrument. Their only problem is that they are all so old that they are reaching the stage where some components are drifting excessively or failing. I have come across 4920's that are drifting a little (more than there spec) between cals (and yes they need to be cal'd annually), another 4920 I came across had an intermittent failure in one of its power supplies. Kind Regards, Stephen Grady Sydney Australia -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Charles Black Sent: Monday, 1 September 2014 3:19 AM To: b...@veritechmeasurements.com.au; Discussion of precise voltage measurement Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left Hi Ben, I am going to check this out today to find if it might be helpfull around here for my AC calibration. It has an error message: Error Ur so some fixing is going to be needed. On the back it says it's got Option 80, whatever that is. Charlie On 8/31/2014 5:37 AM, ben wrote: Hello all, Just a heads up. I noted there is a lonely Datron / Wavetek 4920M AC voltmeter for sale on ebay, starting at US$650 (ending in 1 day !). I have little idea of its true working state or not (picture shows it powered on). If fully working it would be a good buy for an AC voltmeter that is, I reckon, better than an HP 3458A. Only drawback with these models is the voltage input shell is always earthed, not floating. I have two of these 4920M's already, not really tempted by a third. I have a paper copies of operator, calibration, and service manual if anyone interested. regards, ben. ___ 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. --- 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://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left
Hi Adrian, I had some trouble testing my EL 1400's with my precsion attenuator (1.2Ghz B/W) not having a small enough minimum step for easy setting. It was fairly stable though. I checked everything with my scope and it was fairly flat to 20mhz with a gentle falloff to 30mhz if I remember correctly. The EL 1400's are useable to 300mhz with corrections that I don't have. I will keep an eye out for a low priced 4920. It will have to be broken bad enough to be low priced though. Charlie On 9/1/2014 3:29 PM, acb...@gmx.de wrote: charlie, you can expand these tvcs by range resistors to work as higher voltage tvcs. if you do it right (rf-type setup) you can work up to a couple hundred khz with just minor additional error beyond its error in its orgininal voltage range. need to calibrate them however. using an attenuator is not a good idea, too unprecise. still tvcs are the most precise way to measure, if done right. pretty tme consuming though. but you need them e.g. to calibrate a 4920. adrian Gesendet: Sonntag, 31. August 2014 um 21:41 Uhr Von: Charles Black cbl...@centurytel.net An: Discussion of precise voltage measurement volt-nuts@febo.com Betreff: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left Hi Stephen, Thanks for the info on the 4920M. It might be that I should pass on this but it is nice to know that it is probably working. If I don't have the necessary items needed for calibration it might still be a good source uncalibrated. I was hoping that the 4920 had better minimum voltage out steps than my present Rigol 4062 for 3458a AC calibration. I have two EL 1400 0.25V voltage thermal converters that I was trying to use in a test setup but they had such a low voltage range that I was forced to use my ATV-60 attenuator. It all kind of worked but a 0.1 db minimum step is a little course for easy use. The Rigol also suffers from this malady. Charlie On 8/31/2014 1:06 PM, Stephen Grady wrote: Charlie, The Error Ur is an under-range error; you have to apply an input above 10% of the range before it will display a reading. The 4920's are a very nice instrument. Their only problem is that they are all so old that they are reaching the stage where some components are drifting excessively or failing. I have come across 4920's that are drifting a little (more than there spec) between cals (and yes they need to be cal'd annually), another 4920 I came across had an intermittent failure in one of its power supplies. Kind Regards, Stephen Grady Sydney Australia -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Charles Black Sent: Monday, 1 September 2014 3:19 AM To: b...@veritechmeasurements.com.au; Discussion of precise voltage measurement Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left Hi Ben, I am going to check this out today to find if it might be helpfull around here for my AC calibration. It has an error message: Error Ur so some fixing is going to be needed. On the back it says it's got Option 80, whatever that is. Charlie On 8/31/2014 5:37 AM, ben wrote: Hello all, Just a heads up. I noted there is a lonely Datron / Wavetek 4920M AC voltmeter for sale on ebay, starting at US$650 (ending in 1 day !). I have little idea of its true working state or not (picture shows it powered on). If fully working it would be a good buy for an AC voltmeter that is, I reckon, better than an HP 3458A. Only drawback with these models is the voltage input shell is always earthed, not floating. I have two of these 4920M's already, not really tempted by a third. I have a paper copies of operator, calibration, and service manual if anyone interested. regards, ben. ___ 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. --- 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://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing
