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The PM1703M

 

The PM1703M is a small device about the size of a pack of cigarettes.  It has a belt clip and a display on the Top of it.  What it does, although very high tech, is simple, it detects and measures gamma and or xray radiation on the microRoentgen range.  Even better, if the radiation level rises  beyond certain presets over background, it will alarm via a beeper or vibration mode.  It is sensitive enough to detect the week gamma radiation emitted from some vaseline or custard glass.  Some vaseline glass however with very low amounts of radiation and very small amounts of uranium compounds will not indicate on its display.  However, xray radiation from TV cathode ray tubes, gamma rays emitted from many uranium and thorium ores and compounds, and the gamma radiation from many isotopes like Cesium 137 and Technetium 99m will register, as well as low energy gamma rays from other isotopes and elements like Americium 241 will cause it to alarm.

How far away must one be?  For a smoke detector or a vaseline glass object, almost on top of it, contacting the case.  For Ore samples, CRT's or TVs, or check sources for geiger counters that are mildly radioactive, six to twelve inches.  For hotter (more radioactive objects), they may be detected from dozens of yards away, depending on how hot they are, and the quantity of radioactive materials.  As my blog states, a person who has had a nuclear medical test may set it off from 30 yards!  However, they may be emitting levels of gamma radiation which many health physicists do not consider dangerous, but may be of concern. 

The PM1703M is a great device for simply alerting people to the presence of radiation, but not necessarily for measurement.  The reason for this is that it covers a broad range of gamma radiation, from gamma rays barely strong enough to penetrate skin to gamma ray energies strong enough to pass through many inches of lead.  Other more sophisticated instruments are needed to accurately measure the impact of the radiation on human and animal life.  Also, the PM1703M will display OL (overload) for sources stronger than 7000 ar/hr (7 milliroentgen). 

How it works, very simply stated it is a gamma ray scintillator, so gamma rays strike an internal crystal composed of Thallium doped Cesium Iodide.  The crystal will give off a flash of light, which is then detected by a photodiode.  a small computer translates 100 flashes per second and converts for every 1 uR/hr, and the current rate is displayed on the back lit LCD screen.  The computer will also generate a signal to an audible alarm and or a vibration alarm signal.  There is a memory chip with an infrared port (IrDA) that can allow alarm events to be uploaded to a computer at a later time. 

There are several shortcomings to the PM1703M.  The first is sensitivity, however, this may be adjusted.  The sensitivity at times will create "false" alarms.  For example, if you walk too close to a brick wall, or enter a brick or granite structure, the PM1703M will alarm.  This may be adjusted by recalibrating by turning it off and on.  The next is the software.  It will record an alarm event, but not the duration and maximum reading during the alarm event.  Also, the software will not work with many IrDA dongles do not work with the Software.  It will cause the Operating system to crash!  I recommend contacting ActiSys to get the IrDA device, they have impeccable service, however, they are expensive.   Considering that one may spend $300 or more for a PM1703M, you may want to spend the extra money on the IrDA device.

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