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bitrex
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I'm wondering if anyone could point me to a reference that explains how commercial digital geiger counters convert from the natural counts/sec unit to units of mR or uR/hr?
Astronuc said:One would need to convert counts/s or per min or hr, to R/hr, by knowing the energy per count. That requires calibration based on the strength of the pulse generated by the path of the ionizing radiation.
From - http://www.geigercounters.com/Definitions.htm
"CPM - Counts Per Minute, i.e. radiation counts per minute, a unit of measurement for a Geiger counter, on many models corresponding directly to the audible beeps or clicks per minute. CPM is the standard unit of measurement for alpha and beta radiation, and is also commonly used to express background radiation in numerical terms.
mR/hr - milli-Roentgens per hour, or 1/1000 of a Roentgen per hour, a standard unit of measurement for radioactivity, popular in the United States and Israel.
µSv/hr - micro-Sieverts per hour, a standard unit of measurement for radioactivity, popular in Canada and overseas. If you want a Geiger counter that reads out in µSv/hr, look for this feature, standard on some models, and optional on others."
http://www.geigercounters.com/AboutGgr.htm
How does one determine the type of radioactivity?
- Position the Geiger counter near the suspected source of radioactivity, without aiming the open window at the source. If you are getting a reading, it is most likely Gamma and/or X-radiation or high energy Beta, and can be read in terms of mR/hr or µSv/hr.
- Next, place an 1/8" thick piece of aluminum between the instrument and the source. If the radioactive indication stops or decreases, it is most likely Beta radiation, and can be read in terms of CPM. Most common isotopes emit both Gamma and Beta radiation.
- Now aim the open window of the Geiger counter at and immediately next to the suspected source of radioactivity. If this gives you a reading versus no detection through the housing itself, then the radioactivity is from Alpha, Beta, or low energy Gamma. Next, place a piece of aluminum foil between the open window and the radioactive source. If the radioactive indication stops, it is likely Beta radiation, and should be read in terms of CPM
- Now do the same test with a sheet of paper between the open window and the radioactive source. If the radioactive indication stops, it is most likely Alpha, and should be read in terms of CPM.
"In the course of your readings, be careful not to contaminate the detector with radioactivity by physically touching the radioactive source or by holding the source above the open window of the Geiger counter.
Unless otherwise mentioned, all of our Geiger counters come pre-calibrated from the factory. You should re-calibrate your Geiger counter as often as your regulations require, or in any case, at least once a year. Follow the manufacturer's instructions in the operating manual that comes with your unit for guidance on re-calibration."
More information
http://hps.org/publicinformation/ate/q7972.html
http://www.hps.org/publicinformation/ate/q3497.html
http://hps.org/publicinformation/ate/cat1.html#80
http://hps.org/publicinformation/ate/q8495.html
A Geiger counter should be calibrated at least once a year, or more frequently if it is used frequently or in high radiation areas.
The calibration process for a Geiger counter involves exposing it to a known radiation source and adjusting the controls to match the readings with the known levels. This ensures accurate readings when the Geiger counter is in use.
Yes, most Geiger counters can be calibrated by the user. However, it is recommended to have it professionally calibrated if it is being used for critical or high-risk applications.
If the readings on your Geiger counter seem inaccurate or inconsistent, it may be time to recalibrate. You can also compare the readings to a known radiation source to check for accuracy.
Yes, it is important to follow all safety protocols when calibrating a Geiger counter, as it involves exposure to radiation. Make sure to use proper protective gear and handle the radiation source with caution.