Ludlum Measurements 16, Technical Manual

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Model 16 Analyzer Technical Manual
Section 6
Ludlum Measurements, Inc. Page 6-5 July 2011
R
ATEMETER
C
ALIBRATION
The ratemeter may be calibrated by adjusting calibration controls labeled
1, 10, 100, and 1K. Starting with the 1000 range, apply 400,000 CPM
from the Model 500 Pulser. Adjust for proper reading. Drop pulse rate
to 100,000 CPM and confirm reading at 100,000
∀
10,000 CPM. Repeat
this procedure for the lower scales with scaled pulse rates.
D
ETECTOR
O
VERLOAD
C
ALIBRATION
Note:
The detector operating voltage (HV) must be determined
and set before the
OL
(overload) adjustment is performed.
If the detector operating voltage is changed, the overload
adjustment may need to be changed also.
Adjust the
OL
control to the maximum counterclockwise position.
With Scintillation Detectors
1. For alpha or beta scintillators, expose the detector
photomultiplier tube (PMT) to a small light leak by
loosening the detector window. The meter should start to
decrease toward zero as light saturates the scintillation
material.
2. Expose just enough light to where the meter starts to
decrease. Adjust the
OL
control until the overload LED just
begins to flicker on the meter dial. The ratemeter should
deflect above full meter scale at this point.
3. Reseal the detector window and expose the detector to an
alpha or beta source that will drive the meter near full scale.
Confirm that the LED does not turn on and the meter
remains on scale.
With GM Detectors
1. For GM detectors, place the detector in a high radiation
field to where the meter no longer increases or decreases
with an increase in field intensity (referred to from this point
on as detector overload point).