Fluke Biomedical 06-007 - Manual (Page 7)

Operation
Introduction
2
2-1
Section 2
Operation
2.1 Introduction
One end of the dosimeter contains an optical eyepiece; the opposite end is sealed by a bellows that
carries the insulated, glass-sealed charging pin. The instrument is charged by pressing the charging pin
onto the receptacle on the charger.
When the charging pin is pressed into the charging socket on the charger, the pin contacts the
electrometer frame. Sufficient voltage is applied to charge up the capacitor and to set the fiber to zero.
The charger should be used to recharge the dosimeter to zero before each use of the instrument.
a. Adjust the “down-scale/up-scale” control on the charger, while observing the calibrated retile, until a
zero reading is indicated.
b. At times, a transient “kick” is experienced when zeroing the dosimeter. The charging contact of the
charger automatically compensates for the kick when the dosimeter is withdrawn slowly from the
contact. You can see this effect by holding the dosimeter on the charging contact while looking into
the instrument. Withdraw the instrument slowly. You will note that just before the light turns off, the
hairline will shift. With a little practice the hairline can be made to shift so that its final position
coincides with the zero line. Optimum performance is obtained when electrostatic kick is
compensated for in this manner. The hairline will remain on or near the zero position for long
periods when not exposed to radiation.
c. When resetting the dosimeter to zero, the fiber may disappear and remain hidden. To release the
fiber, tap the charger-contact end of the dosimeter a few times on a hard surface (the dosimeter
should be perpendicular to the surface being struck). This will usually free the fiber and permit a
normal recharging operation.
At the end of the designated period of exposure, the accumulated amount of radiation can be read
directly from the scale by looking through the eyepiece while pointing the dosimeter towards an external
light source.