Measure current with Keithely 2110

[FK6789]

Hi,

I'm trying to measure current with a Keithley 2110 Multimeter (LabVIEW 8). The current in sleep mode is around 3uA and has a peak at 9mA and with 0.1ms width, I would like to capture the pulse and especially the peak.
I am sending SCPI command in my LabVIEW code, I have set the NPLC to 0.001, turn off the Auto range. I read from the datasheet that the device is capable of max 50000 readings/sec, I read also that the :SAMP:COUN 50000 is the number of sampling between tow trigger, but I can't figure out how to configure the trigger to achieve the maximum readings per second. Here is the part of SCPI command I am sending :

:FUNC 'CURR:DC'
:CURR:RANGE:AUTO OFF
:CURR:RANGE 0.01
:SENSE:CURR:NPLC 0.001
:TRIG:DEL:AUTO OFF
:TRIG:DELAY 0.0
:PER:APER 0.01

:TRIG:SOUR IMM
:SAMP:COUN 5000
:TRIG:COUN 1
:TRIG:DEL:AUTO OFF
:TRIG:DEL 0
:READ?

I appreciate any help.

Thanks.

[cstorey]

You want to use a DMM to capture a 100us pulse?   I'd go back and read the specs for the K2100 carefully, but I doubt this DMM is up to that task.  Glancing at the specs, I see a mention of 4.5 digit mode able to do 2000 S/s but nothing about 5000 S/s.  (Sorry that was for 2100, not 2110!) Usually DMM vendors quote the speed for DC voltage measurements, not DC current which tends to be much slower. 

Your SCPI commands look fine, there's probably a section in the manual about how to optimize for speed.  Have a look at this post - https://forum.tek.com/viewtopic.php?f=32&t=66#p164127

Basically turn off all auto ranging, auto-zero, turn off display updates, turn off filtering, set resolution to 4.5 digits, etc..  Even to get moderately fast reading speed you will need to further mine the manual for tips and the appropriate SCPI commands.  But you should contat Tektronix and Keithley to help you with this.  There's also a mention in how to calibrate reading rate as 21xx series has no internal timestamp.

You mention LabVIEW code, but post just SCPI.   Do you get an error and thus no measurement is triggered?  What errors do you get?    

My quick guess why the DMM isn't reading is this DMM only has 2000 internal reading memory, so it probably chokes on the ":SAMP:COUN 5000" command.  Try just 1000 readings until it works.

Craig

[Minions]

Have you tried to walk before running?  Start simple by requesting one piece of data first for your configuration.  Once that works, move to 5 samples to verify your settings against a DC or AC input.  Start with a large delay 100ms then tighten your delay parameters over time.  You might be able to uncover the real issues.  It makes sense why you get no response from looking at your post.  You have configured everything; however, where is your triggering function?  It typically requires either one or both of the commands below:

*TRG
INIT

for most of the SCPI commands in order to inform the equipment to begin capturing data for the READ? query to process a proper response. 

[FK6789]

Hi,

Thanks for your reply.

What I understand is there is no INIT command neither *TRG in Labview drivers for 2110, in the datasheet, it says that the READ? command has INIT inside, and when we use trigger in BUS mode then we should run *TRG command. (As I understand), but I havent found it in vi drivers.

Anyway, I solved my problem by increasing the trigger delay to 0.0001 sec, with lower delays the vi hangs while reading the measurements. 

Still, I cannot measure in BUS mode.