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2612B Synchronization Method

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jaime_g
Posts: 93
Joined: September 23rd, 2014, 6:14 am
Country: United States

2612B Synchronization Method

Post by jaime_g » December 1st, 2016, 4:42 pm

I am using LabVIEW 2016 to measure a diode breakdown voltage using both SMU2612A & SMU2612B, I have enclosed a PDF of the vi. The vi shows a hard-coded delay of 300 ms. This is not the best way to control the timing of the SMU operations.
What would be the preferred way to synchronize command completion of the SMU with the application program? Is it sufficient to use the function waitcomplete()? or will it be best to use service requests then poll the status event register for the OPC bit?

Regards,
Jame Arévalo
Attachments
SMU2612A Config Commands.pdf
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brian.d.smith
Keithley Applications
Keithley Applications
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Joined: June 10th, 2013, 6:00 am
Country: United States

Re: 2612B Synchronization Method

Post by brian.d.smith » December 2nd, 2016, 1:19 am

It is not clear to me what you are trying to synchronize and why. Are you performing parallel test of multiple devices on a wafer? Do you have a mix of 2600A and 2600B instruments?

Please explain your test setup and procedures in detail.

jaime_g
Posts: 93
Joined: September 23rd, 2014, 6:14 am
Country: United States

Re: 2612B Synchronization Method

Post by jaime_g » December 2nd, 2016, 7:34 am

Brian,

I have 3 automated test stations two of them have an SMU2612A and a TDS3052C oscilloscope the third ATS has an SMU2612B and a MDO3014 scope.
These automated test systems measure the electrical performance of solid state relays. The input of each relay is an opto-coupler diode which enables two output MOSFETs.

Among the parameters we measure are the input forward voltage and input reverse breakdown voltage. These measurements are performed using channel A of the SMUs.

Each ATS also measures the output leakage current at 95V, the output withstand voltage at 1µA and the output ON resistance with 0.8A applied to the MOSFET. These measurements are performed on each MOSFET and with the MOSFETs connected in series and in parallel. For the output tests we use both SMU channels. The devices are tested one a time in a sequential manner.

I am not trying to synchronize SMUs. What I am looking for is the preferred algorithm to ensure that the commands use to program the SMU to measure these parameters are processed by the instrument before I send additional commands. One way to do this is in LabVIEW is to place a delay between the VISA API WRITE and READ. However, this approach to find he appropriate time delay by trial and error is a time consuming exercise.

I need more control over the timing of the instrument operations to ensure the SMU response is ready to be read before retrieving the data from the instrument buffer or writing additional commands. For example, how long do I need to wait for the SMU to respond to the *RST command before I can send additional commands to set up the instrument for a particular measurement. After I send a series of commands to set up a measurement, how long do I need to wait for data from an averaged measurement to complete before reading the the data.

Looking forward to your response.

Jaime Arevalo

Vince W
Keithley Applications
Keithley Applications
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Joined: September 22nd, 2010, 12:27 pm
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Re: 2612B Synchronization Method

Post by Vince W » December 4th, 2016, 9:57 am

Hi Jaime,

Assuming you are NOT using overlapped measurement commands, you can simply turn on prompts to see when the last command is completed.
With prompts on, the instrument will prompt you with TSP> if there are no errors and TSP? if there are errors. The instrument can also send the >>>> prompt, but only when you are in the middle of downloading multi-line scripts.

To enable prompts, send the command localnode.prompts=1. To disable prompts, send localnode.prompts=0.

When prompts are enabled, every command that is sent (including the command to turn prompts on) will cause a prompt to be returned to the controller, so you may have to adjust your program.

If you don't like the prompts approach, then the more intricate method would be to configure and monitor the status and service request registers for when the specific type of operation of interest completes. Appendix E of the 2600B Series Reference Manual discusses this in detail. If you are using GPIB (only if), you can poll for the SRQ status byte.

Vince
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