[volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left

[acbern at gmx.de]

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" <cblack at centurytel.net>
> An: "Discussion of precise voltage measurement" <volt-nuts at 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-bounces at febo.com] On Behalf Of Charles Black
> > Sent: Monday, 1 September 2014 3:19 AM
> > To: ben at 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.
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