U6 showing high negative pressure without any operations

2 posts / 0 new

Tue, 05/24/2016 - 08:26

Raghu

I am using Labjack U6 to measure pressure (transmembrane pressure; TMP) of bioreactor using Cole-Parmer ±0.25%-Accuracy Compound Transmitter (specs: 0.5 to 5.5 V Output and -14.7 to 15.0 PSI). My bioreactors TMP was nearly 3 to 8 PSI. But without connections, the U6 showing -11.912 PSI in scaled column with 0.92 V in voltage column (please see the attached file. The scaling equation was right for the sensor. Could you please let me know how can I change the voltage in the voltage column or any other ways to comes down the pressure to zero in the scaled column.

One more question is, what's the meaning of the numbers in +Ch (0 to 15) and -Ch (199) columns. Can I change those figures?

File Attachment:

20160524_170300[1].jpg

Tue, 05/24/2016 - 09:12

LabJack Support

I see in your screenshot that

I see in your screenshot that AIN0 is reading 0.93 volts. I assume you have your signal + and - connected to AIN0 and GND?

Take a DMM and measure from AIN0 to GND at the same time and see if the DMM also shows 0.93 volts.

Try removing your signal and instead jumper VS or GND to AIN0. You should see that they read about 5V and 0V and thus can confirm that AIN0 is working properly.

The numbers in the +Ch and -Ch columns are the specified positive channel and negative channel for each row. For example, in the first row (row a), you could set +Ch=2 and -Ch=199 to have that row take a single-ended reading from AIN2. Or you could set +Ch=6 and -Ch=7 to have that row take a differential reading of AIN6-AIN7.

https://labjack.com/support/datasheets/u6/hardware-description/ain/chann...

I notice that you have a very old version. Consider updating your software:

https://labjack.com/support/software/installers/ud