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Bypassing error 120 for Keithley 2200-20-5

2200-20-5, 2200-30-5, 2200-32-3, 2200-60-2, 2200-72-1, 2220-30-1, 2230-30-1
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jrstein92
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Joined: October 3rd, 2013, 9:11 am
Country: United States

Bypassing error 120 for Keithley 2200-20-5

Post by jrstein92 » October 3rd, 2013, 9:22 am

I hope this is the right place to ask this. Currently I am working on using the Keithley 2200-20-5 to power a thermoelectric cooler, and am using a LabView code to adjust the voltage in a PID controller manner. The code so far seems to work as intended, but after some time in running it, the program stops because of an error 120, "Parameter Overflow," introduced in the instrument. The only text I can find describing this error is in one of the user manuals, which states, "Parameter of type Numeric Value overflowed its storage" for the error.

I'm not exactly an expert when it comes to interfacing instruments with LabView. I have the instrument adjusting its voltage every 250ms, and I figure this error is the result of the instrument trying to store too many different voltage changes, changing the voltage too drastically, or it can't keep pace with the demands to change voltage that fast. I figured this forum would be the best place to ask what is the nature of this error and how I can go about preventing the error or circumventing it from stopping my program.

I've attached my code in case it helps. Currently the voltage can't be set higher than 3 within the code, so I don't think the instrument is being fed impossible voltages to generate.
Attachments
PID controller 2.vi
(158.82 KiB) Downloaded 1665 times

Qing S
Keithley Applications
Keithley Applications
Posts: 17
Joined: January 31st, 2011, 10:04 am
Country: United States
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Re: Bypassing error 120 for Keithley 2200-20-5

Post by Qing S » October 7th, 2013, 6:56 am

Hello.
I tried your Labview code by stripping out the DAQ related actions and keeping the power supply ones. To make things simple, I fed a constant voltage in the while loop.

I ran the program for more than 1/2hr and did not see an errors. So, I need more description on the fail symptoms in order to duplicate the problem. Did you write it to a file? Can I see the file that showed an interruption due the described fail? Any other information related to the cause of the fail would be helpful.

Thanks,
Qing

jrstein92
Posts: 2
Joined: October 3rd, 2013, 9:11 am
Country: United States

Re: Bypassing error 120 for Keithley 2200-20-5

Post by jrstein92 » October 7th, 2013, 10:46 am

Qing,

I actually was able to begin bypassing the error by running an error in/out signal through the drivers. Doing so let me see the error occur without the program interrupting, and it seems the error was caused by brief instances of negative voltage being sent to the power supply, which the power supply isn't capable of generating. I thought I had prevented this by telling the program to set the voltage to 0 in cases of positive error (which would send out a negative voltage), but perhaps the sequencing of my wires still let negative signals through. Once finding this out, all I had to do was make sure the voltage could never be set negative by using an absolute value operator, and I haven't seen the error since.

Qing S
Keithley Applications
Keithley Applications
Posts: 17
Joined: January 31st, 2011, 10:04 am
Country: United States
Contact:

Re: Bypassing error 120 for Keithley 2200-20-5

Post by Qing S » October 7th, 2013, 11:35 am

Alright. I'm glad you figured out the cause and a solution.
Let me know if you have any other issues. I'll be happy to help.

Qing

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