Fluke Biomedical 10100AT - Manual (Page 28)

10100AT
Operators Manual
2-10
display update. This differs from operation in the exposure mode where the display is updated and held
following each exposure.
Very Low Dose Rate Measurements
Very low dose rate measurements are selected by pressing Detector Select and selecting an ion chamber
with VLDR in its description. This option should only be used with Ion Chambers suitable for very low
dose rate measurements. To add this measurement option to an ion chamber, using the Customization
Software, add “VLDR” to the chamber’s description. This option is only active in the Exposure Rate mode
(35080 not used).
In order to display very low dose rates in the VLDR measurement mode, automatic current offset and drift
compensation is disabled. As a result, system leakage (dosimeter, cable and ion chamber) is displayed
and should be subtracted from the rate reading. For instance, if the displayed leakage rate is 0.2 uR/sec
(beam off) and the rate with the beam on is 6.9 uR/sec, the actual rate is 6.7 uR/sec.
Allow at least five minutes of settling time after connecting the ion chamber and cable to the dosimeter
before making very low dose rate measurements. Settling time must also be allowed after moving the ion
chamber, cable or dosimeter. When making very low dose rate measurements, the ion chamber, cable
and dosimeter must be stationary; any movement can induce currents.
2.6.4 Use of the Model 35050AT Dosimeter as a kVp Divider Readout
For a full discussion of the Model 35080/80A/80B kVp Divider, the reader is referenced to its instruction
manual. The information given here only concerns the combined operation of the two instruments.
There are some general considerations that apply to both the Exposure Rate/kVp mode and the
Exposure/Time/kVp mode.
Interconnection & Power-Up Sequence
Use the supplied coaxial-BNC cable to connect the Model 35080A kVp Divider to the Model 35050AT
Dosimeter. (Take note of the color-coding of BNC cable boots and respective connectors on the
instruments.)