[ANSS-netops] RFI stepping on sensors and data loggers

[Dave Drobeck]

We definitely have seen it on Episensors and the Geotech PA-23.   Problem 
seemed to be solved by making sure the sensors have well regulated power, but 
now we seem to be seeing it (at about 30 counts only) even with regulated 
power in a few cases.  We've not had time to investigate that yet.  In the 
Geotech case there was no question it was related to the Freewave radio 
transmitting and briefly pulling down power as we could vary the size of the 
data packet and the noise tracked perfectly with the radio transmitting.   
Installing the regulator took care of it.
Dave

On Thursday 25 February 2010 05:48 pm, Don Farrell wrote:
> Hello to all,
>           Are there any networks that are seeing electronic stepping on
> velocity or acceleration sensors and data loggers?  So far the
> Kinemetrics EpiSensors are the most vulnerable with one of the
> triaxial directions sometimes showing a greater amplitude. Most
> problems are with Nanometrics HRDs with Episensors, Ref Tek
> 130-ANSS/02/6 data loggers with Mark products L4s and some broadband
> sensors. Freewave radios seem to be the cause of most of the problems
> but paging transmitters and SCADA are possible sources.  A cell modem
> with a Ref Tek twenty feet underground causes stepping on the MEMS
> sensors.  A recent switch to a Freewave FGRplusRE model resulted in
> stepping on one channel of a K2 and on an external vertical Mark
> Products L4. Ferrite cores rarely solve the problem.  A separate
> solar panel and battery to power the external sensors can eliminate
> or lower the amplitude of the steps.  In a recent experiment a test
> box with a 5 Hz sine wave output into an HRD showed stepping.
> Shorting the inputs in the test box still showed stepping on the HRD
> channels.  If you have seen this problem do you have any additional
> ways of eliminating it? Seismograms and PSD plots are attached.
> --