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

ben ben at veritechmeasurements.com.au
Tue Sep 2 10:17:23 EDT 2014



----------------------------------------
From: "ben" <ben at veritechmeasurements.com.au>
Sent: Tuesday, September 02, 2014 11:25 PM
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 

Hello all,  

I agree that the M version was made for military customers only, being a US 
Navy contract in about 1990. Aside from the thermal converter Wideband V 
input, key differences I am aware of between 4920 and 4920M are that the M 
version does not have mV ranges below 0.3V, and the M version has Filter 
options of only 100Hz and 10Hz (not additional 40Hz). Programming of Filter 
uses different syntax too. 

After a question from another member I have scanned my paper copy of the D 
4920M Users manual, but its a bit of a mess. I will take it to work 
tomorrow and re-do it again properly, then upload it to KO4BB and BAMA.  
Hopefully the Calibration and Service manual will follow in short order. 

I can confirm that calibration of values 0.3V to 1000V use a thermal 
converter. As well, calibration of 100mV (0.3V range) will require a 
micropot and DC voltmeter.

--- I have an alternative version of this email sitting in the Moderators 
in-tray which has attached a PDF of a paper presented at MSC 1990 
conference (202kB file size). If returned to me I will find another site to 
post the paper - it makes good reading.  If interested please email me and 
I can send it out individually. Otherwise, the whole MSC 1990 conference 
proceedings, including the Datron 4920M paper, can be found here -> 
msc-conf.com/wp-content/uploads/proceedings/MSC1990.pdf

More to follow,
regards,
ben



----------------------------------------
From: "Stephen Grady" <grady.steve at gmail.com>
Sent: Tuesday, September 02, 2014 7:54 PM
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 

The Datron 4920M was a special version of the 4920 made for the military, 
the major difference is the M version has a 50 Ohm (N-female) wideband 
input and only the N-female input for the low frequency input. Whereas the 
4920 has a Binding Post Input as well as the N-female input. I am not aware 
of the specs for the wideband input but the low frequency input will be the 
same for both models.

I intend to reply in some detail soon on the calibration of these 
instruments (and this will also apply to the Fluke 5790) and the principals 
of AC calibration below 100mV as Charles has raised the issue of using 
attenuators to do lower voltage measurements.

Kind Regards,

Stephen Grady
Sydney, Australia

-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces at febo.com] On Behalf Of 
acbern at gmx.de
Sent: Tuesday, 2 September 2014 5:54 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 
day left

folks,

does anybody know the difference in specs between a 4920M and the standard 
4920. No data on the web.

thanks



> Gesendet: Sonntag, 31. August 2014 um 23:41 Uhr
> Von: "Charles Black" 
> An: "Discussion of precise voltage measurement" 
> 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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> >>
> >>
> >
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