Fluke Biomedical 451B - Manual (Page 23)

Ion Chamber Survey Meter
Theory of Operation
13
Optional Check Source Use
 Warning
To prevent personal injury, use care in the handling and
storage of the check source. The check source contains
radioactive materials used for the verification of the Product
operation.
For more testing use the check source Model 450UCS (Fluke part number:
3267644), a radioactive button source that provides a nominal reading of
0.4 mR/h (4 µSv/h).
To check the device, do the following:
1. Turn on and initialize the Survey Meter.
2. After the self-test completes, wait for 2 minutes.
3. Open the beta shield.
4. Place the check source flat against the end window.
5. Check for a nominal reading of 0.4 mR/h (4 μSv/h).
Theory of Operation
 Warning
To prevent personal injury, use care in handling this assembly
during removal and installation. This Product contains lithium
cells with a potential voltage of 63 V on the battery assembly.
 Caution
To prevent damage to the Product, do not open or disassemble
the Product. The high impedance circuits of the ion chamber
are easily contaminated with grease and dirt that produce
electrical leakage.
The Survey Meter is an air ionization chamber meter calibrated in exposure rate
units of roentgens/hour (or Sieverts/hour) for gamma and x-ray in the energy
range of 20 keV to 2 MeV through the sliding Phenolic shield. It can also be used
for x-ray in the energy range of 7 keV to 30 keV with the sliding shield open. The
Survey Meter responds to, but is not calibrated for, beta radiation, with the slide
open. Beta energies that can be measured are above 100 keV. The two thin
Mylar windows have a combined density thickness of 6.6 mg/cm2. The Survey
Meter also responds to alpha radiation above 7.5 MeV.
The liquid crystal display shows the radiation rate in digital and analog form with
the range multiplier values also showing on the scale. It is a lightweight electronic
device that requires the computational capabilities of a microprocessor to make it
operate. It functions in a multiplex mode called quadruplex. This mode uses four
backplanes to accommodate the 128 elements of the display.