Operation
Operation Instructions 3
3.9.12 Using the RESET/MEASURE Button
The RESET/MEASURE button has dual functionality. If no Measurement screen is displayed, pressing the RESET / MEASURE button displays one. When a Measurement Screen is displayed, pressing the RESET/MEASURE button zeroes all measurement readings and causes the Model 35040 Therapy Dosimeter to restart the measurement process.
Press the UP arrow to display the next Measurement screen. Press the DOWN arrow to display the previous Measurement screen. The Measurement screens are user customizable via the Customization software (see Section
The Model 35040 Therapy Dosimeter is always collecting charge from the ion chamber, even when a Measurement screen is not displayed.
The operator may view the Detector Select screen, the Air Density screen, the Test Function screen, or the Units Select screen, make changes, and return to the Measurement screen to see the results. Changing the bias voltage, the start threshold, or the stop threshold, automatically zeros all measurement readings.
ADC 39.995 nC
659.8pA
59.891 s
Figure 3-26. The Measurement Screen
NOTE
Press RESET/MEASURE from the Measurement screen to restart the leakage measurement process after moving the triax cable connected to the Model 35040 Therapy Dosimeter.
The measurements have different visual cues to assist the operator in understanding the measurement. If the instrument is trying to acquire enough data to make a measurement, the display area will be filled with dashes. If the measurement is being actively updated, the decimal point will flash. When there was inadequate time to get enough data for leakage compensation, a question mark is displayed to the left of the measurement. If the measurement cannot be made due to the selected settings, the measurement is replaced by “NA.” If the measurement has too much variation to be reliable, “INVALID” is substituted.
3.9.13 Overranging Conditions
The Model 35040 Therapy Dosimeter displays an overrange indicator (“OVER”) when the electrometer’s maximum limit has been exceeded (see Figure
ADC
OVER nC
OVER pA
OVER s
