|
|
|
||||||||
|
Geiger Counter
Last update: 12/03/04
|
|||||||||||||||||||
 |
|||||||||||||||||||
 |
|||||||||||||||||||
|
This geiger counter uses an end window Geiger-Mueller tube which can detect Alpha, Beta and to some extent Gamma radation. The image on the left shows the background count of 26 counts per minute (cpm). Note the scale on the meter is not really Roentgens per hour (r/hr), thank goodness! this meter was originally from a high radation level survey meter.
The image on the right shows the radioactivity of the salt substitute Potassium Chloride. The Potassium contains the natural radioactive isotope K-40, which is a Beta emitter.
The geiger counter has two ranges set by the switch on the right, the low range seen here, is 0 to 650 cpm. The high range is 0 to 9000 cpm. Because of the way I average the pulses (see schematic below) the meter is not linear with respect to cpm (top of the scale is compressed).
|
|||||||||||||||||||
|
Just for fun, I recorded the clicks coming from the speaker at full scale on the low range ( about 650 cpm ). The file is a small MP3 (171 kB) and can be heard here.
|
|||||||||||||||||||
 |
|||||||||||||||||||
|
Schematic for Geiger Counter. This design is a modified version of one found here.
|
|||||||||||||||||||
|
Some notes on this design:
Runs on 3 volt battery power supply (2 AA).
Very low current draw: 1 ma @ 3v (26 cpm), low range setting
1.5 ma @ 3v (650 cpm), low range setting
Speaker is on when power is on. high volume on low range setting and low volume on high range setting.
Output voltage is 520 volts and is regulated by the device string that includes the Neon bulb (NE-2).
Transformer is a small audio type with 1 H inductance on both primary and secondary windings.
Geiger-Mueller Tube: AOH-411, 25mm diameter end window (2mg/sqcm).
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|
|||||||||||||||||||
| page created with Easy Designer |