MyRIAM
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Manual_Myriam_EN_10-04-08.doc
(c) SARAD GmbH
The physical unit of the dose value can be switched over by software between µSv and
mrem.
Another display page shows the total alpha and beta count rate including the natural
occurring Radon daughter products in the unit CPM (counts per minute). Because Radon
daughters are always present these values indicate a error-free operation of the instrument.
TIME: 643min
ALPHA: 3cpm
BETA:
6cpm
If the count rate becomes higher than 999 / 9999 cpm for the Alpha/Beta activity, the
displayed value remains at 999/999
9 cpm and the phrase „HIGH COUNT“ appears in the
upper display line instead of the elapsed time.
Alert situations
If the dose exceeds the user pre-set alert level, either by a 1 Minute OR an interval based
calculation, the display automatically switches over to the related dose display page and a
blinking symbol of a bell appears in the upper line. The LED starts to blink and the buzzer
starts to sound for approximately 15 Seconds. The alert must be acknowledged by pressing
the button, otherwise buzzer and LED will be activated once Minute.
If the alert situation is still pending after finishing a storage interval, a new alert will be
generated.
The alerts are re-set if the calculated dose value drops below the adjusted limit. This
situation can take place if the alert has been initiated by a high Gamma radiation or by a
strong mechanical shock or continuous mechanical vibrations (see also chapter “Gamma
interference, high count rates and shock rejection”).
Gamma interference, high count rates and shock rejection
The detector of the MyRIAM is unable to distinguish between conversion electrons generated
by Gamma radiation and electrons emitted by the collected aerosols. That means, in case of
high Gamma exposures, a beta inhalation dose is displayed without a true contribution of the
filter activity. In that case the dose value will decrease if the radiation field has been left. In
case of a true inhalation dose, the activity of the LLRD at the filter remains stable.
The Alpha channel is not affected. But, it has to be attended that the detector dead time is
increased in presence of conversion electrons resulting in an increased Alpha detection limit
as well.
The detector is sensitive against strong mechanical shock or vibrations. The built-in
electronic signal analysis suppresses the noise very efficiently but continued shock or
vibration results also in an increased detector dead time.
If the count rate exceeds 1000 cpm, the shock rejection procedure is switched off
automatically to minimise the dead time. Normally, the contribution of mechanical shock
becomes negligible in that case.