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3721 Switch Configuration

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jaime_g
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Joined: September 23rd, 2014, 6:14 am
Country: United States

3721 Switch Configuration

Post by jaime_g » September 28th, 2016, 10:39 am

The Keithley 3721 Dual 1 x 20 Multiplexer card specification states that it can be configured to have two independent banks for a 1 x 20 setup each or a single 1 x 40 setup. I am not clear on how to configure the 1 x 40 setup. For my application I need to configure a 3721 in the third slot of a 3706 system switch for a 1 x 40 multiplexed setup.

What backplane relays do I need to enable, 3913 only, or 3913 and 3923?

Also, is there any issues if the 3721 is configured for a 4 x 16 multiplexed set up. In this case, i use the first four relays on bank 1 to multiplex them to the other 16 relays. See enclose PDF diagram.

Best regards,

Jaime Arevalo
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3721_ 4x16 Multiplex Config.pdf
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jaime_g
Posts: 91
Joined: September 23rd, 2014, 6:14 am
Country: United States

Re: 3721 Switch Configuration

Post by jaime_g » September 28th, 2016, 6:19 pm

I read the user's manual and was able to understand what the back-plane switches do. They are used to connect external equipment to the 3721 via the DB15 analog back-plane connector at the rear of the 3706. Therefore, I was incorrect in trying to use the back-plane switches to configure the 3721 card as a 1 x 40 multiplexer.

The 3721 datasheet states that "Banks can be connected together via relay creating a 1 x 40 multiplexer." Does this statement means using an external relay? Or, is there a 3721 relay that can be closed to produce the 1 x 40 configuration?

Jaime Arevalo

Andrea C
Keithley Applications
Keithley Applications
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Re: 3721 Switch Configuration

Post by Andrea C » September 28th, 2016, 6:39 pm

Jamie,

The backplane relays allow some really flexible configurations.

You are correct that the backplane relays can be used to switch in different external equipment and those connections are available on the DB15 connector.

But for the purpose of creating a 1x40 MUX from the two 1x20 banks in the 3721, if you closed the same backplane relay in each of the two banks, then you have effectively connected the two banks together to create the 1x40.

For the 3721, the backplane relay numbers are defined as "slot + 9 + bank + two digit relay number". See page 2-79 in the 3706A Reference Guide.

Andrea

PS: do you have the 3706A with the internal DMM? And do you use the DMM to measure? The DMM connects on backplane relays #1 and #2.

jaime_g
Posts: 91
Joined: September 23rd, 2014, 6:14 am
Country: United States

Re: 3721 Switch Configuration

Post by jaime_g » September 29th, 2016, 8:23 am

Andrea,

Thank you for your prompt response.
We have three 3706 with the DMM option. For our current application the DMM it is not used. We actually utilize SMU 2612s to perform our voltage and current measurements. We need the accuracy and speed of the 2612 SMUs.

Last night, before I went home i realized that I could close the back-plane relays for the corresponding 3721 card to have a common point between Bank 1 and Bank 2. For example, if i would like to have a 3721 card on the third slot of the 3706 in a 1 x 40 multiplexed configuration I could close 3911 and 3921, or 3912 and 3922, or 3913 and 3923, or ... 3916 and 3926, or 3917 and 3927.

My question is, in order to obtain a 1 x 40 multiplexed setup in the 3721, what is better, to close all back-plane switches (X911-X917 and X921-X927) or will it be sufficient closing just one pair? If the latter is the preferable method, which pair should be closed?

Thanks,

Jaime Arevalo

jaime_g
Posts: 91
Joined: September 23rd, 2014, 6:14 am
Country: United States

Re: 3721 Switch Configuration

Post by jaime_g » September 29th, 2016, 8:41 am

Andrea,

One more thing, I used the 3706 web browser to design the test signal path, is a good tool to scan the relay chain to verify the routing between instruments and DUTs. However, I have not been able to get the back-plane switches (X911-X917, X921-X927) to close for any of the 3721 cards I have installed on the 3706.The back-plane relays are displayed as a two rows of 3 blue circles each without the armature ?? When I click on any of them there is no sound or evidence that they are closed.

Is this a 3706 web browser issue? Or am I missing something in using the application?

Thanks,

Jaime Arevalo

jaime_g
Posts: 91
Joined: September 23rd, 2014, 6:14 am
Country: United States

Re: 3721 Switch Configuration

Post by jaime_g » September 29th, 2016, 1:20 pm

Andrea,

I found the answer to my quandary on how to implement the 1 x 40 multiplexing on the 3721 card.

It turns out the interlock Hi and Lo pins for each bank need to be connect together via an external jumper. For Bank 1 the jumper is placed between pins 33 and 50. For Bank 2 the jumper needs to be placed between pins 1 and 34. To verify these connections are made I send the command

Code: Select all

print(slot[3].interlock.state
, if the 3706 response is 3 then both interlocks are engaged.

Then I send instruction

Code: Select all

slot[3].interlock.override = slot.ON
. Now, the DMM input backplane relays (3911 and 3921) can be closed to connect both banks.** Relays 3911 and 3921 are shown in the 3706 web browser as being closed.**

Using the first 4 relays on bank 1 and bank 2 of the 3721 card in slot 3 I am able to multiplex up to 8 x 16 test paths.

I hope this information is helpful.

Regards,

Jaime Arevalo

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