AI880 fluctuation reading at channel 1

I had installed 6 redundant units of AI880 with TU844 and TY801 in once cluster.

During connecting the field device to channel 1 on Slot 1 - 3, I observe that there is fluctuating reading occur at the channel 1 reading about 0.016% variance.Other channels in the module are not affected. The remaining slot also not affected

I inspect the module and found no incorrect wiring for both power and fied connection.

To find the cause, I had:

i. Inspect the module and found no incorrect wiring for both power and fied connection.

ii. Remove the field connection and monitor the channel value. But the value is still fluctuate

iii. Change the baseplate and IO module to new tested unit but the signal is still fluctuate on the slot 1 -3. The remaining slot is no

iv. Measure the loop voltage from IO channel and the result is +22.4 VDC.

v. Change the loop to 2nd channel and no fluctuation occurs.

vi. Verify the shunt stick and the installation is correct.

vii. Inspect the module and found no incorrect wiring for both power and fied connection.

viii. Grounding for system cabinet is still pending as it is in commisioning phase

As per above findings, I'm unable to find the cause of error.

Attached are the snapshot of the AI880

In the picture the Channel 1 before fluctuating occur (reading = 0) and the following picture is during fluctuating occur (reading = 2.1 kPag). The range of this channel is 0-13000 kPag.

The following pictures are the setting for the AI880 module.

 Channel 1 No fluctua.jpg

 Channel 1 Fluctuatio.jpg

 AI880 setting 1.jpg

 AI880 setting 2.jpg


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Teleng   

asked 15 days ago



Answers

0

With a 12 bit A/D converter, the **BEST** accuracy you can get is about 0.025 % of full scale range. And thats before you worry about any other normal sources of error.

2.1 Kpa in a 0..13000 kPa range is nothing.

Rob Lyon   

answered 15 days ago


 


By Teleng on 8/4/2017 | Like (0) | Report

Does this is due to conversion error? When I check the loop power = 24VDC and loop current during normal is 4 mA.


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