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35040
Operators Manual
3-4
Mating and unmating to this connector (or to the
other end of a cable already connected to it) should
be done only when the bias is set to 0 volts, or
when the instrument power is turned off. The
central pin and inner shield shell of the triaxial
connector are operated at the bias voltage above
the outer shell and instrument case. Although the
bias potential is energy and current limited, care
should be taken to avoid unnecessary and possibly
hazardous shocks.
The connector is a triaxial female with dust cap and chain. It connects to any low-noise triaxial male
cables. The NE 2571A 0.6 cc Farmer Ion Chamber and other ion chambers may be operated with the
Model 35040 Therapy Dosimeter.
The connector is mounted to avoid contaminating spills and dust. Putting its dust cap in place whenever
a cable is not connected will help assure long service with minimum leakage problems.
3.7 Basic Measurement Techniques
3.7.1 General Considerations
The dosimeter must be placed on a solid, non-vibrating surface. Both the dosimeter and the operator
must be outside the radiation field. Any cable movement will induce a current that may interfere with
proper measurements. You should wait ten seconds or more after moving the ion chamber, triaxial cable,
or disturbing another part of the high impedance circuit before taking a measurement.
3.7.2 Making Non-Timed Exposure Measurements
With Automatic Leakage Compensation Disabled
The instrument must be manually reset before each exposure when automatic leakage compensation is
disabled.
Procedure
• Hold RESET/MEASURE for one second just before making the exposure to reset the instrument.
Note that the instrument displays the “Rst” annunciator while the hardware is being reset.
• Wait for the reset to complete.
• Make the exposure.
The exposure measurements will be displayed but may drift due to leakage. Repeat this sequence for
every exposure.
With Automatic Leakage Compensation Enabled
In addition to compensating measurements for leakage, the instrument holds the exposure
measurements and automatically resets after each exposure when automatic leakage compensation is
enabled.
WARNING