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Synch'ing smua and smub buffers on 2602A

Models 2601, 2602, 2611, 2612, 2635, 2636
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andyTPE
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Joined: October 15th, 2010, 2:48 pm
Country: United States

Synch'ing smua and smub buffers on 2602A

Post by andyTPE » December 21st, 2011, 6:27 pm

Hello 2602A users,

I am looking for some advice on how to best configure a 2602A. My application requires configuring smua and smub on a 2602A and then making measurements at well-defined intervals. smua is set as a voltage source, smub is set as a current source. Routine would look something like:

1.set smua=0 V
2.set smub to I and meas V 5x
3.set smub=0A
4.set smua=V and meas I 5x
5.delay(5)
6.smua meas I 1x
7.set smua=0 V
8.set smub to I and meas V 5x
9.set smub=0A

Now, I have this implemented as a user script where the measurements from smua and smub are written to their respective nv buffers. However, I would like to improve on this code since the problem is that I believe the timestamps in the two buffers are independent i.e. the t=0 timestamp is created when the first result is written to the that particular buffer. The issue is that I do not know the time delay between making the measurement in 6 and that in 8. For the current meas in 6, it is only relative to the first current meas in 4 and similarly, the V meas in 8 is stamped relative to the first meas in 2.

Any ideas?

Thanks

andy

Nathan S
Keithley Applications
Keithley Applications
Posts: 254
Joined: February 28th, 2011, 6:17 am
Country: United States
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Re: Synch'ing smua and smub buffers on 2602A

Post by Nathan S » December 22nd, 2011, 7:12 am

Andy,

Probably the easiest way for your issue would be to use the smuX.nvbufferY.basetimestamp command for each SMU. You can print the value for both smuA and smuB and then have a time difference between when their respective measurement timestamps are. You can then use that to synchronize your data between those two. Otherwise, if you are using the trigger model, you can have the measurements taken off of the same timer or EVENT_ID. However, if your code is not using the trigger model of the 2600A family, it would be a substantial rewrite for you.

For reference, the basetimestamp command is on page 330-331 of 808 of the PDF version of the 2600A Reference Manual Rev. E available at http://www.keithley.com/support.

andyTPE
Posts: 10
Joined: October 15th, 2010, 2:48 pm
Country: United States

Re: Synch'ing smua and smub buffers on 2602A

Post by andyTPE » December 22nd, 2011, 8:23 am

Hi Nathan,

Thanks for the advice. I like the idea of using the basetimestamp, since as you note, there is little modification to my code. However, it looks like the precision on the basetimestamp return is limited to 1 sec. So according to the basetimestamp the readings for smua and smub were stored at the same time. However, I know that smub data started to be stored at least 50 ms later than smua.

Am I missing something or is this a limitation of the basetimestamp return?

Thanks

andy

Nathan S
Keithley Applications
Keithley Applications
Posts: 254
Joined: February 28th, 2011, 6:17 am
Country: United States
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Re: Synch'ing smua and smub buffers on 2602A

Post by Nathan S » December 22nd, 2011, 8:39 am

Unfortunately, basetimestamp only has 1 second resolution, so yes, this is a limitation of that command.

andyTPE
Posts: 10
Joined: October 15th, 2010, 2:48 pm
Country: United States

Re: Synch'ing smua and smub buffers on 2602A

Post by andyTPE » December 22nd, 2011, 12:50 pm

Hi Nathan,

Thanks for the confirmation. My ATE system is pretty flexible, so it is relatively straightforward to write another tsp function based around event triggering. I have not used triggering and the EVENT_ID before so could you provide me with some guidance e.g. do you know if there is an illustrative example script available. I briefly perused the manual, but the bulk of the triggering discussions seemed to be on accepting or transmitting a trigger to a hardware port. In this case, I would ideally want a software trigger that 1) kicks of the measurement/stimulus that has been configured but not executed and 2) a timestamp on that trigger. Any pointers would be very welcome.

Thank you for all your ideas so far,

Andy

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