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Functional Test of GRAETZ Dosemeters ED 150, EDW 150 / EDW 150 F and GPD 100

A detailed knowledge of the device's operation instructions is absolutely necessary. The following maintenance steps described for all instrument types should be carried out every 6 months.

Insert the batteries. The instrument passes a self test. At the same time an acoustic alarm will be triggered and the device switches over to dose indication.

Switch on the acoustic single-pulse indication. Under the influence of the ambient background radiation approx. 2 counts/min. will be triggered. Due to the statistically varying dose rate of ambient background radiation the background counts are spread irregularly, too.

For additional measurements exceeding ambient background radiation a radioactive test source (e. g. GRAETZ "PS 9") is needed. Generally, ¹³⁷Cs with an activity of 333 kBq is used. The half life of Caesium is 30 years. Remove the test source from the lead storage container and hold it onto the point shaped marking (= position of the GM-tube), situated on the front of the device. Under the influence of radioactivity the acoustic single-pulse indication will be triggered.

If dose rate indication is active, a value of approx. 70 - 100 µSv/h will be displayed. Remove the test source "PS 9" and switch on the 7,5 µSv/h alarm threshold. Check its function by putting the "PS 9" again onto the GM-tube marking.

After the control measurements the test source has to be put into the storage container again.

If a defect is observed during the control measurements, which cannot be cleared by yourself, the instrument has to be returned to the manufacturer GRAETZ for repair.

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All switches must be in "OFF"-position. The EDW 150 F display shows 0,000 mSv, the EDW 150 display shows 0 µSv and "Batt. OK". Briefly press switch 4 for on and off (Reset/Test) to effect a reset. For approx. 2 seconds all elements of the display are triggered.

Adjust the switch for the alarm thresholds of the EDW 150 F at first to 5 mSv respectively to 200 µSv at the EDW 150. Set switch 4 again to "ON" ("Test"). The display begins to increment. Check, whether the alarm signal is triggered when the adjusted dose alarm threshold is exceeded. All dose alarm thresholds (up to 250 mSv for the EDW 150 F and up to 2000 µSv for the EDW 150) have to be tested in this way.

Set switch 1 to "ON" ("Test"). An intermittend warning of the dose rate alarm threshold will be triggered. If a dose rate alarm threshold is already exceeded and a permanent signal sounds, the next higher alarm threshold has to be set.

When the tests mentioned above are finished, the instrument has to be briefly switched on and off (switch 4) for reset.

The ambient background radiation is sufficient to effect the functional test of the GM-tube. Activate the acoustic single-pulse indication by using switch 3. An average value of approx. 1 count within 5 minutes will be triggered. Due to the statistically varying dose rate of ambient background radiation the background counts are spread irregularly, too.

For additional measurements exceeding ambient background radiation a radioactive test source (e. g. GRAETZ "PS 9") is needed. Generally, ¹³⁷Cs with an activity of 333 kBq is used. The half life of Caesium is 30 years. Remove the test source from the lead storage container and hold it onto the point shaped marking (= position of the GM-tube), situated on the front of the device. Under the influence of radioactivity the acoustic single-pulse indication must be triggered and a little star must be shown on the display. Set switch 1 to "ON" and check the function of the acoustic dose rate alarm threshold (25 mSv/h).

After the control measurements the test source has to be put into the storage container again.

If a defect is observed during the control measurements, which cannot be cleared by yourself, the instrument has to be returned to the manufacturer GRAETZ for repair.

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Switched on the device: It passes a self test. An alarm signal will be triggered and the device simultaneously switches over to dose and dose rate indication.

Switch on the acoustic single-pulse indication, switch off the dose rate alarm thresholds and effect a reset. Under the influence of the ambient background radiation approx. 2 counts/minute will be triggered. Due to the statistically varying dose rate of ambient background radiation the background counts are spread irregularly, too.

For additional measurements exceeding ambient background radiation a radioactive test source (e. g. GRAETZ "PS 9") is needed. Generally, ¹³⁷Cs with an activity of 333 kBq is used. The half life of Caesium is 30 years. Remove the test source from the lead storage container and hold it onto the point shaped marking (= position of the GM-tube), situated on the front of the device. Under the influence of radioactivity the acoustic single-pulse indication must be triggered.

The displayed dose rate is 70 - 100 µSv/h. Having removed the test source "PS 9" the single-pulse indication will be switched off and the 7,5 µSv/h alarm threshold will be switched on. Check its function by putting the "PS 9" again onto the GM-tube marking.

After the control measurements the test source has to be put into the storage container again.

If a defect is observed during the control measurements, which cannot be cleared by yourself, the instrument has to be returned to the manufacturer GRAETZ for repair.

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