ETS-Lindgren HI-2790B Calibration Comparison System - Manual (Page 25)

www.ets-lindgren.com Calibration Comparison Log 30-Day Check 25
5.0 Calibration Comparison Log 30-Day Check
To make sure that microwave survey instruments are being checked in
accordance with Center for Devices and Radiological Health (CDRH) guidelines,
complete the Calibration Comparison Log 30 Day Check form on page 26 using
the following instructions, and in conjunction with the HI-2790B Calibration
Comparison System.
Note: The word MEAN is used to refer to the average or center
value of the polarization ellipticity reading.
5.1.1 A separate log should be kept for each instrument, identifying it by
model number and serial number.
5.1.2 Record the maximum, minimum, and mean values, and calculate
the ellipticity as follows:
Total % ellipticity = MAX minus MIN x 100
MEAN
5.1.3 Comparison readings should always be made at the mean and for
a given instrument. No reading may be lower than 10% below the
highest reading during the 12-month period between annual
calibrations.
 The first reading in a 12-month period between annual
calibrations will always be acceptable if it is within the dB band
for all instruments.
 The ellipticity must be within the manufacturer specifications.
For ETS-Lindgren instruments the limit is 10% total, plus or
minus 5%.
Compare the mean reading and the ellipticity reading against
these limits and determine acceptance or rejection.