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Products => Test Equipment => Topic started by: chrisr on August 16, 2020, 06:42:51 pm

Title: Keithley DMM6500 SCPI - Run mode and release instrument
Post by: chrisr on August 16, 2020, 06:42:51 pm
Hi there,

first off: please excuse any stupidity from my side - as you may see, this is my very first post on this forum.

Due to corona lockdown I got myself a treat for my homelab - a Keithley DMM6500.

Being lazy, one of the application would be a "Measuretyper". In short this uses a USB connected foot switch and a small application that, when the button is pressed, grabs the current reading of the multimeter and types it into any open application (such as Excel, notepad, etc.).
To keep the instrument happily running and user operatable, I used the Control REN to deassert the instrument after reading and therefore put it in local mode again. This worked perfectly fine for Hewlentsight's 34465A and 34401A (both via GPIB and USB) I got at work but for the DMM6500: no love.

So the problem comes in two pieces:

One is that, once I sent a "READ?"-Query the instrument goes to Remote mode and stops continuous measurements. For each read, another value is sampled but I'd love to have the sampling like "ok, that's the right value, send it over!".
I know that the DMM has a extensive triggering system but could not find how to return to this mode (at least in the reference manual).

The other thing is that I can't put it back to local mode. In fact I tried all Control REN messages but the DMM seems to ignore it.

I'd be delighted if someone could give me a pointer! :)

Setup: DMM6500 connected via USB, VISA is R&S (because NI's is too bulky IMO)

Thank you very much in advance!

Chris
Title: Re: Keithley DMM6500 SCPI - Run mode and release instrument
Post by: sequoia on August 17, 2020, 01:46:33 am
SYST:LOC should work? 
Title: Re: Keithley DMM6500 SCPI - Run mode and release instrument
Post by: chrisr on August 17, 2020, 02:32:37 pm
Quote from: sequoia on August 17, 2020, 01:46:33 am
SYST:LOC should work? 

Unfortunately it doesn't.  (I also couldn't find this command in the reference manual)
Title: Re: Keithley DMM6500 SCPI - Run mode and release instrument
Post by: voltsandjolts on August 17, 2020, 03:18:50 pm
Search the user manual for 'logout' command
Title: Re: Keithley DMM6500 SCPI - Run mode and release instrument
Post by: chrisr on August 17, 2020, 04:11:15 pm
Quote from: voltsandjolts on August 17, 2020, 03:18:50 pm
Search the user manual for 'logout' command

that's it - thank you!

I now also found how to put the DMM back in continuous acquisition: TRIG:CONT REST does the job.

The following code does exactly what I want:
Code: [Select]
import pyvisa
import time

rm = pyvisa.ResourceManager()
dmm = rm.open_resource("USB0::0x05E6::0x6500::xxxxx::INSTR")

val = dmm.query("READ?")
dmm.write("TRIG:CONT REST")
time.sleep(0.001)
dmm.query("LOGOUT")

print(val)

The pause (YMMV) seems to be necessary to avoid a race condition.