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.
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