Aware Electronics Radiation Monitors Interface

Aware Electronics exclusive interface to a PC's serial port, our LCD-90 Pro or our USB-MSP provides the best performance and allows rugged electronics.

Aware Electronics exclusive radiation monitor design provides detection capabilities 1000 Times Higher than many of our competitors:
  • Aware Electronics Radiation Monitors Independent Tests

    Please note Aware Electronics LCD-90 Pro and USB-MSP utilize high speed CMOS counters to count the pulse stream from the radiation monitor. The following deals with utilization of a standard PC's serial port and our software to count the pulse stream. With either count technique, the advantages of Aware's RM pulses, as detailed below, are realized.

    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. Also we would need to set the serial port's UART to 57,600 baud. In such a case, when a pulse arrives at the serial port, the serial port's UART interprets it as a start bit. The positive pulse must go negative, or to ground, before the time a normal character would be received such that the UART interprets it as a stop bit. Otherwise the UART and its driver will throw a communication error. The software counts the number of bytes received per unit time and then reports the results. With such a scheme, the maximum count rate would be less than 2500 CPS. See this link for details: Aware Electronics Tests BlackCat Software and GeigerGraph

    Aware Electronics exclusive interface and software can count radiation pulses from a radiation detection tube with a burst count rate 200+ 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 or more the burst count rate of a serial port UART baud rate scheme which is constrained to count rates less than 2500 CPS i.e. less than one pulse per 400 microseconds. (57600 baud is 5760 bytes per second resulting in a maximum count rate less than 2500 CPS. See above link)

    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 occurring perhaps every few microseconds, again, depending upon the tube in question. If we were 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, any pulses spaced closer than ~200 microseconds could cause the UART to throw a communications error.

    We have tested software by others that utilize the serial port (or USB to serial port adapter) RX line to "count" characters reported by the UART, triggered by pulses to its RX line. This technique is used by many of our competitors. At higher count rates, we could demonstrate wild variations in the reported count rate, given a constant input pulse rate, due to communications framing errors, break errors and other communications errors generated by the Windows operating system and the serial port adapter drivers.

    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 200+ 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.

    The interface between our RMs and our LCD-90 or our USB-MSP use the same technique, with all its advantages, to transmit the pulses from the RM to the high speed CMOS counters included in the LCD-90 and USB-MSP.

    Exclusive High Voltage Power Supply

    An important part of any Geiger counter circuit is the high voltage generator. Most of Aware’s competitors use a very simple technique to generate the high voltage known as a boost converter. This involves an inductor in series with a transistor switch and a diode. The transistor is turned on and off by a control circuit. An advantage of the boost converter is it does not utilize a custom step-up transformer but rather utilizes a very simple and cheap inductor.

    Typical Boost Converter

    Boost Converter On Stage Boost Converter Off Stage
    The key principle that drives the boost converter is the tendency of an inductor to resist changes in current by creating and destroying a magnetic field. However, the boost converter has a serious disadvantage. The transistor will have to handle both a high current when the transistor is on and a high blocking voltage when the transistor switches off. The peak transistor voltage is equal to the dc input voltage plus the reflected load voltage and this can amount to several hundred volts. In practice, additional voltage is observed due to ringing associated with the leakage inductance. Such repetitive voltage spikes can slowly damage the transistor.

    We have analyzed various competitor boost converters with an oscilloscope and notice they subject the transistor to repeated voltage spikes near or even above their absolute maximum rating. This can lead to degradation and breakdown of the transistor over long periods of time even if operated somewhat below the absolute maximum rating. Even a competitor’s boost converter with a four stage diode multiplier generating 500 VDC, produces 200+ volt pulses on the transistor.

    Aware Electronics Corp. uses a different technique for generating the high voltage necessary. We have custom designed a miniature high voltage transformer which includes three windings, a primary, secondary and feedback winding, allowing us to create our unique, fully regulated very high efficiency high voltage harmonic oscillator power supply.

    Aware's harmonic oscillator utilizes the natural rhythm of the transformer’s inductance and a capacitor to step-up the low voltage source to a high voltage by-way-of the turns ratio of the primary to secondary. The primary winding of our transformer includes approximately 8 turns and the secondary includes over 2000 turns, thereby stepping up the voltage needed with just two diodes, even with a 1.5 volt input. (Input voltage can range from 1.5 to 20 VDC). Aware's new HV harmonic oscillator is also very low noise due to the transformer's primary winding tank circuit.

    All active components of the high voltage generator are rugged bipolar silicon devices, including the components in the regulating sub-system. Many competitor systems utilize mosfets which can be very sensitive to voltage spikes.

    Aware's Custom Miniature High Voltage Transformer With Enhanced Design as of May 2015 (12mm x 12mm)
    Transformers Available for Purchase in Lots of 1 to 1,000. Phone or write for details.

    Aware's Custom Miniature Transformer

    Aware's Original Transformer
    Aware's Miniature Custom Transformer

    A major advantage of Aware’s high voltage feedback oscillator: The transistor is exposed to only the supply voltage (1.5 to 16 VDC) rather than the several hundred volts of the boost converter technique. Aware Geiger counters, with our custom high voltage generator, have been running continuously now for over 27 years and not a single transistor has failed.

    Power Transistor Crystal Damage in Inductive Load Switching: A Reliability Concern. International Business Machines Corporation, Poughkeepsie, N. Y.

    A high-voltage n-p-n--n+ type power transistor switching an inductive load for approximately 1000 hours showed no significant variation in the electrical parameters. Infrared scanning, and cross-sectioning and visual inspection of the chip indicated a crystal damage at the n--n+ interface under the center of the emitter. Transmission electron microscopy (TEM) investigations revealed the crystal damage to consist mainly of silicon phosphide precipitate platelets surrounded by dislocation loops and dislocation clusters. An analysis using a two-dimensional mathematical model predicts high electrical and thermal stresses at the damaged location of power transistor during its switching applications.

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

    Transformers Available for Purchase in Lots of 1 to 1,000. Phone or write for details.
    Aware's Miniature Custom Transformer

    Aware Electronics fully regulated HV generator and discriminator circuit boards available for purchase. Three wire interface: Power supply in plus, minus and signal out. Anode and cathode for Geiger tube(s). 500VDC. Jumpers for 400VDC and 300VDC. Connect plus and minus to your project’s plus and minus (3VDC to 16VDC) and connect signal out directly to your project’s interrupt or counter pin. $59.95 each. Add $12 for HV output wires and HV potting. Phone or write for details.
    Aware's Discriminator HV generator Aware's Discriminator HV generator

    Click here for a Comparison of Aware Electronics Corp. LCD-90 + RM-80 to the Inspector EXP Probe Model

    Click here for a Comparison of Aware Electronics Corp. LCD-90 + RM-80 to the Mazur PRM-9000

    Aware Electronics exclusive radiation monitor design provides detection capabilities 1000 Times Higher than many of our competitors:
  • Aware Electronics Radiation Monitors Independent Tests

    Aware Electronics Tests BlackCat Software and GeigerGraph. Using Monitors with the same type tube, Aware Electronics Software can measure radiation levels Ten Times Higher than BlackCat's system or any monitor using GeigerGraph software:

  • Aware Electronics Tests BlackCat Software and GeigerGraph

    Aware Electronics RM-60 Versus Digilert:

  • Aware Electronics RM-60 Versus Digilert

    We have analyzed a Geiger counter by SparkFun:

  • A look at SparkFun Geiger Counter

    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
    For the last 20+ years our goal has been and is to provide the best solution for radiation monitoring.

    Phone:(800)729-5397 or Phone/Fax: (302)655-3800

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