|
Audible
Alarm Rate Meters and Digital Electronic Dosimeters
Audible alarms are devices that emit a short "beep"
or "chirp" when a predetermined exposure has been received. It is required that these electronic devices be
worn by an individual working with gamma emitters. These devices
reduce the likelihood of accidental exposures in industrial radiography
by alerting the radiographer to dosages of radiation above a preset
amount. Typical alarm rate meters will begin sounding in areas
of 450-500 mR/h. It is important to note that audible alarms are
not intended to be and should not be used as replacements for
survey meters.
Most audible alarms use a Geiger-Müller detector. The output
of the detector is collected, and when a predetermined exposure
has been reached, this collected charge is discharged through
a speaker. Hence, an audible "chirp" is emitted. Consequently,
the frequency or chirp rate of the alarm is proportional to the
radiation intensity. The chirp rate varies among different alarms from one chirp per
milliroentgen to more than 100 chirps per milliroentgen
|