[ANSS-netops] Strong motion calibrations

[Nathan L Edwards]

Hey all,

We are attempting to establish some procedures for calibrating strong motion instruments.  There seems to be varying opinions as to what can be claimed with these results.  With our EpiSensor stations, we initially planned on providing a step voltage from the calibrator and recording output to confirm amplitude response.  There is a similar procedure for the K2 with an internal EpiSensor that is referred to as a "functional test" (not claimed to be a calibration).  These are reproducible, however we are rethinking what these results really mean after these comments from Kinemetrics tech support:

"Calibration functions [of the datalogger] are provided for transfer function frequency
response measurement, and cannot be used in any electronic force
feedback sensor [like the EpiSensor] for meaningful gain measurements. This is an aspect of
all electronic force feedback sensors, not an aspect of any calibration
source."

Regarding strong motion sensors (not just the EpiSensor) my questions are:
1.  Does the step function test reliably tell you anything useful other than that there's something alive at the end of the sensor cable (i.e. to what degree is it a true calibration)?
2.  What are other labs doing to remotely confirm sensor function/calibration on their strong motion sensors?

Thanks,
Nathan Edwards
Development Technician
Nevada Seismological Laboratory
University of Nevada Reno
Reno, NV 89557-0174
o:  775-784-1106
m:  775-303-5899
f:  775-784-4165