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3706 with 3721 multiplexer

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sagifa
Posts: 6
Joined: December 8th, 2015, 11:23 pm
Country: Israel

3706 with 3721 multiplexer

Post by sagifa » December 8th, 2015, 11:44 pm

Hi
I build a testing Jig using 3706 DMM with 3721 switch card.
I have some questions:
1. In my Jig there are voltage measurement and current measurement. I want to use my 3721 card. for the volts measurement its fits great, but there is any way to measure current with it? (I have about 28 channels to switch for current measurement)
2. In some specific tests i need to test the every signal by a oscilloscope / spectrum analyzer. for that I want to use the 3721 to switch the signals to the oscilloscope. what is the best way to connect the MUX output to the oscilloscope? by which connector?
and if I do so, can I switch currents by all the card channel to the oscilloscope?

thanks,
Sagi

Norbert W
Keithley Applications
Keithley Applications
Posts: 227
Joined: October 21st, 2010, 7:18 am
Country: Germany

Re: 3706 with 3721 multiplexer

Post by Norbert W » December 9th, 2015, 12:56 am

Hello,

(please have a 3721 simplified schematic 'two pole mode' from the datasheet at hand when referring to the below comments)

the multiplexer card 3721 has two current channels (41, 42); you can expand that in multiple ways -
depending on your application needs:
1.) If the currents must not be interrupted while or between measurements then the use of a shunt
resistor per channel and measuring the voltage drop for each channel will work.
2.) If the currents can be interrupted while other channels are measured you can use the built in
current measurement capability by using one or both multiplexer banks just for switching and
connecting their output to one of the current input channels (e.g. 41).
If you want to use 28 current channels you have to share one bank for voltage and current measurements.
In this case you don't want to connect the output of this bank to a switching channel but you can use
an unused channel - which you close with the channel to be measured - to be connected to a current input
channel (e.g. 41).

sagifa
Posts: 6
Joined: December 8th, 2015, 11:23 pm
Country: Israel

Re: 3706 with 3721 multiplexer

Post by sagifa » December 9th, 2015, 1:26 am

thanks for the help! I understood.
my voltages measurement and currents are separate tests. so I dont have a shared bank for voltages and currents.

About my second question- in other test I want to connect the MUX output to a other test equip. (oscilloscope).
The way to make it is by connecting the output pins (8, 24 in the 50 pins connectors) to the oscilloscope or there is another way?

Thanks again!

Norbert W
Keithley Applications
Keithley Applications
Posts: 227
Joined: October 21st, 2010, 7:18 am
Country: Germany

Re: 3706 with 3721 multiplexer

Post by Norbert W » December 10th, 2015, 1:49 am

Hello,

yes you can use the output of the bank you use for current measurements - or equivalent the current channel input where you connect it to.
If you want to skip the relay contacts further you could consider contacting the D-sub analog input connector on the rear side of the
instrument (Amps and LO pins).

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