Fluke Biomedical 06-526 - Manual (Page 21)

Maintenance
Introduction
3
3-1
Section 3
Maintenance
3.1 Introduction
The RAD-CHECK PLUS contains three functional elements: the ion chamber, the electrometer circuit,
and the Voltage Ratio Module (VRM).
The ion chamber consists of electricity charged plates enclosing a constant volume. Under manual
operation (no radiation), no free ions exist in this volume. When exposed to an ionization source, ions are
created in direct relationship to the field strength. The ions are collected, producing an output current.
3.2 Cleaning the Instrument
Do not immerse the Model 06-526, 06-526-2200. The unit is not waterproof. Liquid could damage the
circuits. The unit should be kept clean and free from dirt and contamination. The unit may be cleaned by
wiping with a damp cloth using any commercially available cleaning or decontaminating agent.
3.3 Circuit Description (General)
The electrometer circuit is either a charge integration circuit or a current to voltage circuit depending on
the selection of DOSE or RATE respectively.
The DOSE or RATE mode is selectable using the front panel switch. When operating in the DOSE mode,
the electrometer circuit is a charge integration circuit. When operating in the RATE mode, the
electrometer circuit is a current to voltage converter.
Use care 270 VDC is present inside the unit
3.4 Auto Reset (DOSE Mode)
When the rear panel switch is placed in the AUTO RESET position, diode D8 is active; radiation causes a
current to flow through D8. This current produces a voltage which is input to voltage a comparator.
When the threshold is exceeded, the comparator changes its output state causing comparator U1B to
change state. U1B turns on transistor Q1 which closes relay RR2. RR2 remains closed as long as
radiation is present.
When radiation is removed, RR2 opens and one-shot multivibrator U2A/U2B pulses RR2 to discharge
C11. This sets up the integrator for the next shot. In manual or external modes, D6 and R13 bypass the
auto reset and RR2 remains closed.
WARNING