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Functional Test of GRAETZ Dose Rate Meters X 5 C plus, X 5 C, X 5 DE, X 50 DE (X 50 ZS), X 5 CEx, X 5 DEx and Probes

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.

• Visual control regarding damages on the outside of the instrument.


• Control the plug connections for the probe and for the recharger socket. They have to be non-corrosive and dry.


• Control the battery contacts in the battery compartment. They have to be non-corrosive and dry. The cover sealing has to be re-greased with Vaseline. This step does not apply for the X 5 CEx respectively X 5 DEx, as the accumulator is firmly built-in.


• The touch-sensitive keyboard panel has to be undamaged.


• Insert battery, if necessary (does not apply for the X 5 CEx respectively X 5 DEx).


• Turn on the device: It passes a self test for about 3 seconds, where all segments of the LC-display are triggered. At the same time the acoustic alarm must be audible.


• When the battery symbol appears on the display, the battery has to be replaced. In case of the X 5 CEx respectively X 5 DEx the accumulator has to be recharged.
• Test the display illumination.


• Test the acoustic single-pulse indication and the inner GM-tube under the influence of ambient background radiation (due to the statistically varying dose rate of ambient background radiation, the background counts are spread irregularly, too), results in:
  
  

  X 5 C plus	approx.	20 counts/min
  X 5 C	approx.	20 counts/min
  X 5 DE	approx.	12 counts/min
  X 50 DE	approx.	2 counts/min
  X 50 ZS	approx.	2 counts/min
  X 5 CEx	approx.	20 counts/min
  X 5 DEx	approx.	12 counts/min



Functional Test of the Probes

The probes can be connected with the basic unit either directly or by using a probe cable. If a probe cable is available, it is recommended to use it for at least one probe test in order to proof the perfect function of the cable, too.

Connect the probes only to a switched off basic unit. Having connected the probe, the display will show single-pulses. Depending on the connected probe type, the pulse rates acc. to the following table have to be expected under the influence of the ambient background radiation. At the same time indication on the display changes.



Probe	Counts/min	Kind of radiation
18 504 D	approx. 10	alpha, beta, gamma
18 509 CE resp. 18 509 DE	approx. 2	gamma
18 526 D	approx. 25	alpha, beta, gamma
18 529 CE resp. 18 529 DE	approx. 1	gamma
18 536 D	approx. 9	alpha, beta, gamma
18 550 CE resp. 18 550 DE	approx. 12	gamma
18 545 CE resp. 18 545 DE	aprox. 100	gamma
Scintillation Probe 2002	approx. 6000	beta, gamma
Contamination Probe 18 502 D	approx. 155	alpha, beta, gamma



Additional measurements exceeding the ambient background radiation

For this, 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. The test source has to be put onto the marking situated on the front of the unit, indicating the middle of the GM-tube. A measured value of approx. 70 µSv/h will be displayed.

The acoustic dose rate alarm threshold is activated. The instrument warns with a permanent signal. With regard to the "X 5 C plus" respectively "X 5 C" it has to be observed that the set alarm threshold is below the produced measured value. After the test, the source has to be put back into the lead storage container.



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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