To return to a previous page, use your browser's BACK button or click button at bottom of page.

Determine background CPM (Counts per Minute). Take the square root. This is the standard deviation.

Determine CPM increase over background CPM for a spike of interest. Divide this by the standard deviation to determine deviations above background.

Look up the deviations above background in a table of Gaussian or Normal distribution "Areas under (below) the standard Normal Curve" to find the likelihood of spike being more than random fluctuation.

For example let us say your average background count rate is 100 CPM. The square root of 100 is 10 so your standard deviation is 10. Now let us say you measure a radiation level of 120 CPM. This is two standard deviations above background (20 / 10 = 2). Now we look for 2 in a Table of Areas beneath a Normal Curve and find .9772. This means that we can be 97.72% sure that our +20 CPM reading is not due to random fluctuation but is instead due to a real increase in radiation level.

Here is a handy normal calculator (Note you can use your Browser's "View-Source" to see the source code for this calculator):
Normal Calculator (For above example enter 2 as Critical Value)
and here is the old-fashion way of finding normal curve areas by looking them up in a table like this one:
Normal Curve Areas
(Note from our example above the "Z-score" we look-up in table is 2 and the area below curve is .9772)


Note the following information is superseded by the availability of our Aw-Radw windows program.
Click this link for information about using Aware Electronics Software to auto-generate graphs:

  • Aware Electronics Aw-Radw Graphs

    This is how we place the real-time graphs on our web-site. First, we arranged to have a WWW site. Next, using a text editor, we wrote the INDEX.HTM file. The INDEX.HTM file is the file transmitted to a visitor's browser over the Internet. It contains text and instructions for the visitor's browser.

    Some of these instructions include commands to place an image at a certain location in the visitor's browser window. Such an instruction will include an address and name of an image file. For example, the tiny graph at the top of our web page is contained in an image file named tiny.gif and the command included in our INDEX.HTM to display this image is IMG SRC="tiny.gif" ALT="Even Tiny" height=103 width =154 HSPACE=10 ALIGN=LEFT.Even Tiny

    The file tiny.gif is placed on our web site together with the INDEX.HTM file at the address

    When a WWW user tells his/her browser to go to, the browser will ask for the file The browser scans INDEX.HTM and sees that an image in a file named tiny.gif is needed, so the browser will ask for the image file then will place this image in the appropriate place.

    The radiation data is gathered on an old Toshiba T-1000 (purchased used for about $80). Radiation data is generated by an RM-60 + Fan-Filter add-on., (since Aug. 31st 1998 11:00pm, RM-80 + Fan-Filter add-on) (Fan-Filter Photos) using the radiation data gathering program (AW-MRAD.COM) included with each RM unit.

    The T-1000 has one serial port and one built-in modem. The RM-80 is plugged into the serial port. Once per hour, Aw-mrad writes collected data to the T-1000's floppy drive. Another small program on the T-1000 notices when the rad. data file has been updated, and then triggers our AW-FETCH program, which signals a desktop PC connected to the T-1000 by way of the modem, to "fetch" (update) its copy of the radiation data file.

    After fetching the update, a batch file and keyboard buffer stuffer program on the desk top PC is triggered, which generates an update of all the GIF graphs, including TINY.GIF, by using AW-GRAPH's GIF function. Next, another small program is triggered which places the time-date of the most recent point in the radiation file into the INDEX.HTM file. Next, a packet driver is loaded and a FTP program is triggered, which follows a script which FTPs the GIF files and INDEX.HTM file to our WWW site, by way of the modem in the desktop PC. Next the packet driver is removed from memory, and the desk top PC starts the loop over again, waiting for the next update from the T-1000.

    The above process is automatic. If case of power outage, the T-1000 NiCad battery pack keeps the T-1000 and RM-80 going. When power is restored, the desktop PC reboots and the autoexec.bat file reloads the batch file driven automatic update programs. The desktop PC programs can run under MSDOS or from a Win 95 window. Any PC could be used in place of the T-1000 (XTs, ATs, 386s, etc.), even the H.P. 200LX palm top.

    Given a WWW site, this process could be used to automatically place radiation data graphs from anywhere around the world with a phone line, to the WWW site, once every ten seconds, minute, hour, etc.

    An E-MAIL question:
    >Does any of your software log the detection information
    >to a .txt file or log ? I would like _very_ much to display
    >my radiation counts on a web page.

    Our standard software logs data to a binary disk file. It should be fairly easy to write a program that opens the RAD file, extracts information needed, then close file. Meanwhile, our software would continue to run (in a DOS box if running under windows or as a TSR if running under DOS), storing the data to disk as often as one wants, in increments of 10 seconds.

    For example, assuming you will run software on a WINDOWS machine, plug RM unit into a COM port. Start our AW-SRAD software, instructing it to save data once per minute to a RAD file (the program can be instructed to do this from command line arguments, which can be inserted into the Properties, command Line options box of the Dos application ICON.

    Now, say once every ten minutes, have your PERL program open the RAD file, extract count info, close RAD file, graph, etc.

    Another option. Use our AW-GRAPH program ($74) to periodically generate a GIF file containing a graph of radiation. To do this automatically, create a shortcut to a dos application that runs a batch file.

    In batch file include command to run our STUFKBUF program (included with each RM software pack) telling it to stuff the keyboard buffer with the keystrokes necessary to have AW-GRAPH generate a GIF image file of a plot. The next line of the batch file would start AW-GRAPH telling it to load the file in question. The next line of the batch file would rename the generated GIF file and copy it to your web site. The batch file would look something like this.

    REM place the following keystrokes in the keyboard buffer: G ESC ESC

    REM Start AW-GRAPH and tell it to display MYOFFICE.RAD file

    REM Copy the GIF file to my WEB directory

    REM Return to Windows

    You would have two ICONS in WINDOWS. Click on one ICON and the AW-SRAD rad data gathering program would automatically start, collecting rad data to a disk file, and displaying the rad data in a Window (color text mode scrolling bar chart).

    A click on the other ICON would generate the GIF file for the web site.

    For auto update of web site graph, all you would need do is write a script that say every ten minutes runs the AW-GRAPH batch file, or clicks the shortcut.

    Also see January-14-1999 We added a new command line arg. to AW-SRAD for generating ASCII out file. For more info, click here: New AW-SRAD Arg

    Phone or E-Mail us with any questions and we will be happy to assist.

    Return to index page?