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Agilent 34970A /34902A Channel won't open

Jsommer

Jul 21, 2020
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Jul 21, 2020
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I am using an Agilent 34970A data acq unit and a 34902A multiplexer card with Agilent BenchLink Data Logger 3. I used this many years ago and it was placed in storage. I recently moved and wanted to resurrect the unit to measure mV readings vs. time. I have the thermocouple on channel 111. I turn the knob to 111 and push the "open" button since it says "OFF". The card says "CARD IN SCAN" briefly and but the channel doesn't open. I am an old chemist and rather a rookie at this. Did the Mux card brake during the move? the data acq unit? Anything I can check? Thanks!
 

shrtrnd

Jan 15, 2010
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Jan 15, 2010
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If you've previously configured any multiplexer channels for scanning, you can't independently close or open individual relays on that module. Turn the knob to 111, press the 'close' pushbutton first, then press the 'open' pushbutton to see if that clears it. (The 'card reset' pushbutton will sequentially open all channels on the module in the selected slot)
A wide variety of reasons for scanning problems.
You can set the scan interval from between 0 seconds to 100 hours. Once you initiate a scan, it'll continue until you stop it, or until the scan count is reached. Do you have a scan interval that is too short entered into memory?
To select interval scanning and set a scan interval time (hours, minutes, or seconds), push the 'Interval' pushbutton.
To initiate the scan press the 'scan' pushbutton (and you should see the count-down time on the front panel).
To stop the scan, press and hold the 'scan' push-button. (if you're using a remote, send the ABORT command).
I'm thinking you've got a very short scan interval time logged in memory from the last time you used the 34970A, and maybe it needs
to be cleared and reset(?)
Another possibility why the channel won't 'open', is a stuck relay. Maybe toggling the 'open' and 'close' pushbuttons a few times might unstick it(?).
I'd try looking at those obvious potential issues before getting deeper into the weeds on this.
 
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