[volt-nuts] 3458A Questions - The Sequel

Charles Black cblack at centurytel.net
Sat Oct 29 20:21:12 UTC 2011

Hi Joe,

The RS-232 bus is easy cheap and reliable but too slow for the 3458a.  
The 3458A can send a lot of data over the bus very quickly so at the 
time the IEEE bus  was an easy choice.

I bought the IEEE-488 PCI card on eeBay and also a long long cable. 
Later I decided to spring for a GPIB-ENET/100 for $200 to free up the 
single PCI slot in my PC and to be able to be further away with out the 
long IEEE-488 cable. Both were National products and worked well once 
the manual was thoroughly read.

I use National Instruments National Instruments Measurement and 
Instrumentation Explorer which is a free download from NI which is part 
of the NI VISA install. It can see your IEEE-488 devices and let you 
send text commands to them. It also has the Spy program that lets you 
monitor the actual text sent and received in real time. Just remember to 
alter the ID command test from the *IDN? to ID?. Also "BEEP" works. Case 
doesn't matter. You will get a communication error if you don't set 
"END" to ALWAYS in the 3458a menu.

On 10/29/2011 12:23 PM, J. L. Trantham wrote:
> Charlie,
> Thanks for the data.  Before I can make any intelligent comments about the
> stability of my 'system', I am going to have to solve the HPIB issue and
> find a way to communicate with the 3458A.  I solved RS232 with the 7081.
> Too bad the 3458A doesn't have RS232.
> Joe
> -----Original Message-----
> From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
> Behalf Of Charles Black
> Sent: Saturday, October 29, 2011 2:13 PM
> To: Discussion of precise voltage measurement
> Subject: Re: [volt-nuts] 3458A Questions - The Sequel
> Hi Joe,
> Your noise and drift on your 731B is more than I see on my Datron 4910.
> I have no experience with the 731B but my 4910 is very similar in
> specifications to a 732B. My major drift with my 3458a measuring a 4910
> cell is the room temperature. It is about 10 microvolt per degree C. My
> peak to peak noise is dependent on NPLC settings up to 200 where it
> becomes very usable with only a minor improvement at NPLC = 1000. NPLC
> 1000 is useful to get the ultimate accuracy on my system since it
> integrates out some of the lowest frequency noise in the 4910. I use
> shielded #24 cable with no connectors.  The wire is tin plated Tefzel
> STP but that seems to only cause 0 to 10 nv errors and reaches thermal
> stability much faster than my otherwise identical #22 STP. I have
> included two recent plots of one of my Datron 4910 Cells (it has four
> cells which perform similarly) to illustrate NPLC settings. Notice the
> downward drift in both plots that is caused by changes in room
> temperature and the peak ti peak noise which I assume is 4910 noise. The
> 4910 noise spec is 0.04 PPM RMS and my cells are well within that.
> I tried using connectors but only the gold plated spade lugs were af any
> use to me. Most of my issues had to to do with thermal mass. To use
> banana plugs I had to wait and wait. Dual gold plated banana plugs
> (about 1mv thermal offset at first) never stabilize on my 3458A. I have
> too many air currents I guess. Fortunately no connectors works perfectly
> here and is the cheapest too.
> Enjoy your new (to you) 3458A.
> Charlie
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