<!doctype html public "-//W3C//DTD W3 HTML//EN">
<html><head><style type="text/css"><!--
blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
--></style><title>RFI stepping on sensors and data
loggers</title></head><body>
<div><font size="+1" color="#000000">Hello to all,</font></div>
<div><font size="+1"
color="#000000"> Are
there any networks that are seeing electronic stepping on</font></div>
<div><font size="+1" color="#000000">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.</font></div>
<x-sigsep><pre>--
</pre></x-sigsep>
</body>
</html>