Aware Electronics exclusive interface to a PC's serial port provides the best performance and allows rugged electronics.

Aware Electronics radiation monitors and software utilize an interface to the PC's serial port that makes direct connection to the PC's interrupt line, bypassing the UART. It allows our RM radiation monitors to send and the software to count pulses of less than one millionth of a second duration. If we instead interfaced with the serial port's UART we would need to provide at least a 20 microsecond pulse, 20+ times longer i.e. Aware Electronics software can count radiation pulses from a radiation detection tube with a burst count rate 20+ times higher than otherwise would be possible. The performance of modern day PCs and their ability to execute code at very high rates and the exceptional efficiency and accuracy of Aware Electronics software allows a system that can exceed 200 times the burst count rate of a 20 microsecond pulse constrained system.

If one looks at the pulses from a modern Geiger tube with an oscilloscope, under background radiation levels one sees strong pulses spaced randomly far apart. Due to the random nature of nuclear decay, even at moderate radiation levels a certain percentage of detection pulses could be grouped together within a 20 microsecond time frame, depending upon the tube in question. Subject the tube to higher radiation levels and the dead time of the tube can become shorter (due to, among other things, a drop in the tube's average voltage), the pulses can become shallower and shorter in length with some occuring perhaps every few microseconds, again, depending upon the tube in question. If we where running this pulse stream through a 20 microsecond pulse homogenizer, for example a CMOS monostable multivibrator, such that a UART could be persuaded to accept a character for counting, it could either lockup the monostable multivibrator such that it generates just one long pulse or we could miss pulses.

In addition our interface allows a much more rugged and long lasting radiation monitor. Our RM line of radiation monitors contain no CMOS chips which can fail under harsh conditions. They utilize rugged high speed bipolar silicon transistors and as indicated above, in combination with our software and a modern PC, can count with pulse burst rates 20+ times faster than typical radiation monitoring systems by others.

A third advantage to our unique and exclusive serial port interface is the nature of the pulses sent down the cable by our RM series of monitors and PMI-30. Our software utilizes a very high efficiency interrupt driven CPU counting technique to tally radiation detection events. Modern PC serial ports allow three different methods of generating a CPU interrupt by external devices.

Method one is by-way-of a UART generated interrupt, the disadvantages of which have been discussed above.

Method two involves a voltage level change (i.e. a change from +10VDC to -10VDC would generate an interrupt and a change from -10VDC to +10VDC would generate another interrupt).

Method three and the method used by Aware Electronics monitors and software involves the generation of one CPU interrupt per pulse. For example a pulse composed of a voltage change from +10VDC to -10VDC then back to +10VDC over say a 1 microsecond time frame (or any time frame), generates one CPU interrupt rather than the above mentioned second method's two interrupts.

Method three allows our RMs and PMI-30s to send a complete pulse of any duration down the cable for each detection rather than a pulse constrained to a specific time frame (Method one) or a level change (Method two). The result is a more reliable and accurate event detection technique due to the fact that a complete pulse travels much more reliably down a wire than does a voltage level change. This also allows the cable between the Aware Electronics RM or PMI-30 and the PC's serial port to be extended well beyond 1000 feet while still maintaining high accuracy at very high radiation levels.

Here is an analogy illustrating the difference between the above mentioned method two and method three. Two people (person A and person B) are 50 feet apart and each are holding the ends of the same 55 foot rope which is laying on the ground between them. Let us say that person A represents the radiation monitor, person B represents the PC's serial port and the rope represents the cable between the two. It is the duty of person A to signal person B by-way-of the rope that an event has occurred. First they try the above mentioned method two. With each detection person A moves his hand holding the rope either up three feet or down three feet to signal the event. In such a case person B hardly feels any signal at all and reliable communication would demand a shorter rope or a detection system much more prone to noise pickup. Now they utilize method three above (the Aware Electronics method) and with each detection person A moves his hand up three feet then quickly back down three feet. This sets up a strong sine wave that travels down the rope well and allows person B to easily and reliable detect the movement.

Conclusion: For longevity and high accuracy choose Aware Electronics line of Radiation Monitors and software.

Reader Alert: We have tested software by others and are surprised by the results. Click here to read about it: A look at a system by others

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