Reading The Meter Face Dial - LUDLUM MODEL 3 Technical Manual

Model 3
Ludlum Measurements, Inc.
Technical Manual
The detector cable can be a source of problems. Test the detector cable by
bending or flexing either end of the cable and checking for an increase of
counts detected. Replace the cable if increases in the rate of counts are
detected.
Check the meter reset function by depressing the
and ensuring the meter needle drops to 0.
Once this procedure has been completed, the instrument is ready for use.

Reading the Meter Face Dial

Reading the meter face is very important for consistent measurements. There
are, in general, three types of meter faces:
1) count rate (typically cpm [counts per minute])
2) exposure rate (typically mR/hr)
3) combo (typically cpm and mR/hr.)
The following examples are intended to help the user interpret the correct
reading.
The normal procedure is to turn the range selector switch to the highest range
and if no readings are seen on the meter, turn the selector switch down to the
lower scales until a reading is seen. The ranges on the instrument selector
switch are multipliers for the meter reading. A typical single scale (one arc)
meter face with a cpm (counts per minute) dial is shown below.
The count rate scale reads 0-5K
counts per minute) and has
If the needle is pointing as indicated below and the instrument range
selection switch is on the ×0.1 scale multiple, then the reading is 3.5 kcpm
(multiplied by) ×0.1 = 350 cpm.
COUNTS
on the dial.
BAT TEST
Page 2-3
Section 2
pushbutton switch
RESET
/ (kcpm or 1000's of
MINUTE
April 2016