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

Charles Black cblack at centurytel.net
Mon Sep 1 13:20:41 EDT 2014


Hi,

The auction winning bid was $1432. I was outbid by two people and never 
had an effect on the auction at all!

Charlie


On 9/1/2014 1:51 AM, ben wrote:
> 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.steve at gmail.com>
> Sent: Monday, September 01, 2014 5:37 AM
> To: "Discussion of precise voltage measurement" <volt-nuts at 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-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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>>
>
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