Hi: We've got 10 thermocouples on a MUX80 on a T-7 Pro running in DAQFactory in single ended mode. The have developed a mystery temperature offset, and would like to run them in differential mode, but can't figure out how to code it. Here is the working DAQFactory startup sequence code for the single ended:
How do I specify differential channels?............... Thanks!
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All I see in your screenshot is 10 calls to eWriteName to set some channels to the 0.1V range. Note that you could use AIN_ALL_RANGE if you want to set the same range for all analog inputs:
https://labjack.com/support/datasheets/t-series/ain
Further note that if you use the Thermocouple AIN-EF to do your thermocouple math it will set the range to 0.1V for you.
For differential, you just need to specify the proper negative channels. For AIN0 you would write:
AIN0_NEGATIVE_CH=1
... which says the negative channel for AIN0 is AIN1.
https://labjack.com/support/datasheets/t-series/ain
For the extended channels on the Mux80, you have to look at Table 2:
https://labjack.com/support/datasheets/accessories/mux80
For example, AIN55 is a valid positive channel, and AIN63 is the valid negative channel for AIN55, so you would write:
AIN55_NEGATIVE_CH=63
Thanks very much for that.
As a test, I am trying to do a differential input at channel 78 (AIN78). I have the positive on the MUX80 at X4 on the AIN6 terminal, and the negative at AIN86, or DAC0 on the X4. I have a 1M resistor from DAC0 to ground.
In DAQFactory, I added this line to the startup script:
LJM_eWriteName(identifier, "AIN(78:86)_NEGATIVE_CH", 10)
I get a reading, but it is non-plausible. What am I missing? ...........Thanks.
You want to set the negative channel for AIN78 to a value of 86, so I would think something like:
LJM_eWriteName(identifier, "AIN78_NEGATIVE_CH", 86)
... but, AIN78 is a negative channel per Table 2 so that won't work:
https://labjack.com/support/datasheets/accessories/mux80
You could do positive=86 and negative=94, so something like:
LJM_eWriteName(identifier, "AIN86_NEGATIVE_CH", 94)
To test connect VS and GND as follows to get expected readings:
AIN86 to VS, AIN94 to GND, AIN86=5V (or 0.1V if set to 0.1V range)
AIN86 to VS, AIN94 to VS, AIN86=0V
AIN86 to GND, AIN94 to VS, AIN86=-5V (or -0.1V if set to 0.1V range)
Appreciate the fast support. Thanks!