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2110 DMM- Therocouple reading max speed

2000, 2001, 2002, 2010, 2100, 2110
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ejensen
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2110 DMM- Therocouple reading max speed

Post by ejensen » April 18th, 2013, 4:16 pm

I am connecting to my new 2110 DMM using LabVIEW VISA (via USB) VIs and am trying to get the max speed possible in reading a thermocouple temperature (Type K). I have set up the system (Immediate Source, moving average) and then have a basic VI to read out (READ?) the temperature values. I only seem to be able to get about 5.1 readings/second. In my data acquisition routine this is the bottleneck. I had expected to be able to get it to go faster than that. As far as I can see the DMM is running at 5.5 digits. Is it possible to get it to run thermocouple readings faster than this (I was hoping for 10/s or more)?

Jane S
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Re: 2110 DMM- Therocouple reading max speed

Post by Jane S » April 19th, 2013, 6:06 pm

Hello,
Here's the speed specification of 2110.

Speed
At 5½ digits, the Model 2110 delivers up to 200 readings/s via the USB remote interface. At the fast 4½-digit setting, it reads up to 50,000 readings/s and up to 30,000 readings/s into the buffer, making it ideal for production and monitoring applications in which speed is critical.

It occurs to me that it is a matter of setting up your specific test function.

See the link below on how you can achieve high reading rates on the 2110 DMM application notes and on how to use the instrument for temperature measurements.

http://www.keithley.com/support/keidoc_ ... ation+Note

Jane

ejensen
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Country: Canada

Re: 2110 DMM- Therocouple reading max speed

Post by ejensen » April 20th, 2013, 3:34 pm

I have read through the 2110 manual and cannot see any method to reduce the acquisition time for a thermocouple measurement. I ran a timing loop on several hundred :READ? loops (synchronous read via USB VISA routines) and plotted the times below. For the thermocouple, the times are roughly 170ms, but there are regular intervals of 225ms and up to 255ms read times.

To compare, with the DMM on DCV mode, I got 18-19ms loop times (middle plot) on a 1PLC integration time (makes sense as 1PLC is about 16.7ms). If I set the DMM on 0.001PLC, 1 get 1-2ms loop times (I used the millisecond timer in LabVIEW so this is limited by the timer resolution).

The thermocouple read loop speed corresponds to around 9 power line cycles, and I cannot see any method to make this go faster, based on the 2110 manuals. If I am mistaken here, I would really appreciate any suggestions.

I have not tried reading into the DMM buffer, as I need to be able to associate each temperature reading with near-simultaneous readings from other instruments.

Image

Andrea C
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Re: 2110 DMM- Therocouple reading max speed

Post by Andrea C » April 22nd, 2013, 3:47 am

Looks like the thermocouple measure function does not support the faster reading rate:
2110_integration_time.JPG
model 2110, integration time
2110_integration_time.JPG (40.97 KiB) Viewed 16171 times

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