BlackCat uses an interface between the radiation monitor and the PC that we considered long ago but rejected. It consists as follows. The radiation monitor generates a positive going pulse with each detection. This pulse is connected by cable to the RX (receive) pin in the PC's serial port. The cable also connects the radiation monitor's ground to the serial port's ground.
The PC software opens the serial port for communication, 38,400 to 57,600 baud, 8 data bits, and one stop bit. 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.
57600 baud is 5760 bytes per second (10 bits per byte i.e. one start bit, 8 data bits and one stop bit) so the absolute maximum rate that could be measured using this technique is 5760 CPS but only if the stream of pulses are exactly aligned and perfectly spaced. In practice the maximum count rate recordable would be less than 50%, i.e. less than 2800 CPS, due to the random nature of the pulses from the radiation monitor. (This is a well characterized phenomenon i.e. the maximum count rate of evenly spaced pulses a counter can detect must be at least twice as high as the expected count rate from a random pulse stream ).
57600 baud = 17.36 microseconds per bit. One start bit and 8 data bits = 156.25 microseconds so the pulse from the radiation monitor must be longer than 17.36 microseconds and less than 156.25 microseconds, even with low count rates. Otherwise the UART will throw a communications error thereby corrupting the count rate data. In addition, if any pulse arrives before ~200 microseconds, it could confuse the UART, for example by arriving at the time the UART expects a stop bit, which would then throw a communications error resulting in a corruption of the data.
To test the BlackCat software, we downloaded the most recent version (August 9th 2012). We connected the output of a precision pulse generator (Global Specialists) to the RX input pin of a PCI serial port (a standard high speed serial port) and the pulse generator's ground to the serial port's ground. We set the 5 volt square wave positive going pulse width to exactly 20 microseconds which is the pulse width BlackCat says is output from their radiation monitors.
During the test, we varied the pulse rate between 1 pulse per second to 7944 pulses per second by way of the pulse generator's pulse spacing control. All parameters including pulse width and pulse spacing were checked with a Hitachi oscilloscope. This represents the absolute best conditions for the BlackCat software with a precisely sized square wave pulse with exactly equal pulse spacing.
We carried out tests as above and also tests as above with the pulse generator's output connected also to the input of one of our LCD-90 inputs which is internally connected to the LCD-90's high speed CMOS counter chip. We configured the LCD-90 as a high speed (greater than 12 megahertz) frequency counter (zero dead time, 1 second time base unit) and ran a copy of our Aw-Radw software configured to receive from the LCD-90, once a second, the CRC error correction data packet from the LCD-90. Aw-Radw's "Summary Window" shows the exact CPS reading, updated once per second and these matched precisely the settings on the pulse generator as-well-as the data from the Hitachi oscilloscope.
During the tests we recorded the PC's screen to a wav file using MicroSoft's Expression which is displayed below. The results of the test were always exactly the same, with or without the connected LCD-90 and Aw-Radw display and with or without MicroSoft's Expression program running. The PC is a 2+Ghz dual core machine with 4 gigs of memory.
We also ran the exact same type test but with our Aw-Radw collecting and displaying the pulse rate data instead of the BlackCat software. In this case instead of connecting the output of the pulse generator to the serial port's RX pin, we connected it to the serial port's RI pin which Aw-Radw uses to generate an interrupt which causes Aw-Radw's highly efficient machine code optimized interrupt handler to increment a variable then immediately return from the interrupt. This technique completely by-passes the serial port's UART and allows Aw-Radw to count pulses from the serial port in excess of 50,000 CPS regardless of the serial port's UART settings. With the pulse width set to 20 microseconds as per the BlackCat tests, the maximum possible count rate is ~25,000CPS due to the width of the pulse and this is the value reported by Aw-Radw when counting pulses connected to the serial port's RI line. With shorter pulse widths, the maximum count rate is higher, and in this case, Aw-Radw can count pulses coming into the serial port's RI line in excess of 50,000 CPS. As indicated above, when using our USB-MSP or LCD-90, Aw-Radw can report count rates in excess of 12 million CPS.
The following wav file shows the test in progress: BlackCat Test Video
Results from the test:
Pulse Rate - BlackCat Reports - % Deviation Error
1 CPS-------------2 CPS-------------100% high error
10 CPS------------9 CPS-------------10% low error
96 CPS-----------81 CPS-------------15.6% low error
982 CPS---------818 CPS-------------16.7% low error
1037 CPS--------865 CPS-------------16.6% low error
1614 CPS-------1334 CPS-------------17.35% low error
6291 CPS-------3974 CPS-------------36.83% low error
7962 CPS-------3307 CPS-------------58.47% low error
If the pulse stream was not highly optimized with exact evenly spaced pulses but rather a randomly spaced series of pulses as occurs with a radiation source, one would expect errors at least 100% higher than those shown above 2500 CPS i.e. with a random pulse stream with a rate of 2500 CPS, the BlackCat software would report ~1250 CPS, 50% less than the actual due to the baud rate limitation and random nature of the pulses. Note in other areas of BlackCat's website he indicates the use of 38,400 baud with a pulse width of 100 microseconds which would vastly increase the errors. In this link, BlackCat seems to indicates 100 microsecond pulse width BlackCat Systems Interface
Near the end of the video, we demonstrate how clicking on any BlackCat software window seems to freeze the update of the count rate and then after returning Windows focus to BlackCat's main window, it advances the time with a wildly high CPS rate near 25,000 CPS then back down to its 58% low error. This serious defect occurs even at low count rates and with various conditions. For example just holding the mouse button down while the pointer is over BlackCat's window title bar freezes the updates until the mouse button is released. Other conditions can cause this defect to be triggered. Even several wildly high count rates in a row can occur. If one triggers this defect long enough, the BlackCat software will report wild rates higher than 2 million CPS.
If you look at the count rate versus dose rate for the tube used in BlackCat's monitor (see image below), you can see its recommended operating range is up to 12,000 CPS but from 2500 CPS on up the BlackCat software would report a vastly lower count rate. This not only limits the abilities of the tube to less than 20% of its capabilities but also allows the highly hazardous situation were rising radiation levels beyond a certain point will be reported as a rate much lower than the actual rate and as the real rate increases beyond this point, BlackCat software will report a lowering rate i.e. the user would think the radiation level is dropping when actually it is rising.
BlackCat Software, GeigerGraph, GeigerGraph for Networks: Serious Errors above 2500 CPS
Aware Electronics Aw-Radw with monitor directly connected to Serial Port: No Error up to 25,000 CPS. Maximum count rate ~50,000 CPS
Aware Electronics Aw-Radw with USB-MSP or LCD-90: No errors up to 12 million CPS
We did not purchase a copy of GeigerGraph software but we found a demo of it on youtube that reveals the same type error as discussed above: GeigerGraph Video
As regards power consumption, all Aware Electronics Corp. radiation monitors can operate with voltages ranging from 2VDC to 20VDC. Power draw at background radiation levels is ~0.08ma and climbs modestly to a few milliamps at very high radiation levels. The high voltage section is rigidly regulated, noise free and as indicated can operate with input voltages ranging from 2VDC to 20VDC. We noticed on BlackCat’s website a mention of the need for 9VDC at ~9ma which is a power draw ~90 to ~400 times higher than Aware’s monitors.
Aware Electronics monitors include an exclusive discriminator which, as indicated above, allows the accurate display of radiation levels well in excessive of what one would expect given the tube data sheet. When developing the circuit, we designed and tested several hundred variations and finally settled on the best performing. All active components are rugged silicon devices very resistant to radiation and burn-out. The resulting design represents an entirely original circuit available exclusively in Aware’s monitors.
Aware's RM-60 (as well as all our other monitors) with Aw-Radw software maximum count rate greater than 33,000 CPS, more than 10 times higher than BlackCat's and the other systems, with no errors and with moving of windows, with moving the mouse, clicking, etc.
In addition Aware's software, as-well-as Aware's LCD-90 and USB-MSP include sophisticated and exclusive dead time correction features settable in one microsecond increments which allows dialing in accurate readings under very high radiation levels.
Other competitors quickly added a random number generator to their software as did BlackCat. The problem with their system is they feed the pulse stream through the serial port's UART which is synchronized to the serial clock generator i.e. the actual interrupt is synchronized by the UART and therefore cannot be truly random as is Aware's technique. Aware's random number generator has been thoroughly tested by outside sources including a battery of DieHard tests showing the true random nature of our random data stream.
Someone at Aware Electronics got the simple idea that a coincidence circuit (C-box) connected to two RM-60s could be used to detect cosmic rays
Likewise any of these other monitors can easily be connected to Aware’s USB-MSP and/or LCD-90.
Contact Aware Electronics for more information: Aware@aw-el.com
For the highest performance, which takes advantage of the techniques as detailed above under "A Note About The Actual Radiation Monitors" one should use one of Aware’s radiation monitors.
A gal at LND who we have known now for over twenty years told us everyone and their uncle are coming out of the woodwork to become new found Geiger counter manufacturers. She said "Even shoe makers have become Geiger counter makers". This page attempts to illuminate the hazardous nature of many of these new found products particularly in moderately elevated and higher radiation fields wherein readings can show dropping radiation levels when in reality they are rising.
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