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

[Mark E. Meremonte]

Hi All,

Well I have been seeing these steps (or temporary offsets) off & on 
for a couple of years.  I thought they were only seen on the older 
Applied MEMS accelerometers.  We had this problem in a couple of the 
MEMS used in the Wells, Nevada, deployment.  After the deployment I 
sent the MEMS (5) in for repair Fall 2009.  The explanation was that 
some contacts inside the MEMS were "dirty".  They were 
cleaned.  After I received them back I checked them out and they all 
appeared to not have the steps.  The generation of Applied MEMS 
should not have this trouble I was informed.

I sent some of these systems to Am Samoa.  On their return a couple 
of them have the steps again.  Below is a plot of one of them with 
steps happening quite frequently.  This system had no communications 
with Ethernet record disabled but the RT-130 TCP/IP stack power was 
left set to "on".  Not sure if this has any connection but I doubt 
it.  I should test it.  Here is the plot:
Emacs!


MArk

At 22:03 2/27/2010, Dave Drobeck wrote:
>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.
> > --
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*********************************************************
Mark E. Meremonte        Geophysicist    USGS/ANSS/NEIC

U.S. Geological Survey        Work: 303-273-8670   Cell: 303-478-5766
MS 966, Box 25046        Email: meremonte at usgs.gov
Denver, CO  80225             Web: http://geohazards.cr.usgs.gov

Ship:  U.S. Geological Survey, 1711 Illinois St., Golden, CO 80401
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