10-17-2012 07:01 PM
We have a WSN-9791 with four WSN-3212s. All the 3212s have NI power supplies (not running off battery).
Three of the four 3212s give erratic readings. For example, the following was logged today from a room that should be around 70F:
17/10/2012 15:38:20 187.8
17/10/2012 15:39:20 148.9
17/10/2012 15:40:20 139.0
17/10/2012 15:41:20 -1548.9
17/10/2012 15:42:20 37.2
17/10/2012 15:43:20 158.8
17/10/2012 15:44:20 39.5
17/10/2012 15:45:20 111.5
17/10/2012 15:46:20 206.4
17/10/2012 15:47:20 -6.6
17/10/2012 15:48:20 188.6
17/10/2012 15:49:20 262.5
17/10/2012 15:50:20 74.1
17/10/2012 15:51:20 102.0
Location seems to play a part -- so far two different 3212s that are giving erratic readings have been very stable (with reasonable readings, too) when they sit on my desk, but go back to being erratic when moved elsewhere in the building. Additionally, one of the erratic nodes spends several days stable, then several days erratic, then back to stable. When a node is erratic, all four thermocouples on that node are erratic.
Thinking this might be a problem with electrical noise, I put one of the 3212s onto a UPS -- no difference. I've also changed the wireless channel used to a couple of different settings, without any change. I moved the 9791 to several different locations in the building, again without a difference. Thermocouple type settings have been triple checked.
Any ideas on how to further troubleshoot this?
Solved! Go to Solution.
10-18-2012 10:05 AM
Hi KathyA,
The WSN-3212 is susceptible to analog noise from ground loops and power supplies and this may be what you are seeing. To determine if this is the problem try the following.
1. Electrically insulate the thermocpule probes from the environment
2. Connect earth ground to the D GND terminal of the WSN-3212 (pin 10, 12, 14 or 16)
Cheers,
Brian A
R & D Product Support Engineer | WSN/Network DAQ/Academic
National Instruments
10-19-2012 04:31 PM
Thanks, step #2 did the trick.
Kathy A.