36 August 2017
the count rate is 600 counts per
minute. The dead time is 600 x 10 ms
= 6 sec, or 10%. For lower count
rates, the dead line is less. For higher
count rates above 600 counts/min, the
dead time will increase and we may
not get an accurate count rate.
Each time I detect a pulse, I also
flash an LED pulse and I click a
buzzer. After all, what’s a Geiger
counter without a clicking sound?
I love numbers. If math is the
language of theoretical science,
measurements are the language of
experimental science. Measurements
are especially valuable when we can
bring them into Excel and analyze
them. In searching on the Web, I
came across an invaluable free tool
which allows me to write data directly
into an Excel spreadsheet. I’ve written
about this in Nuts & Volts a few times
The application is called PLX-DAQ v2 and is basically an Excel file
with a macro that reads the serial port and parses the printed values
into cells (see Resources for a link to download an Excel file with this
I wrote a sketch to count pulses in 10 sec intervals, then calculate
the counts per minute and print these values every 10 seconds to Excel.
■ FIGURE 8. Count rate
measured while Maxwell
was in his cat apartment.
He can be seen inside the
top hole in the photo to
the left. The Geiger
counter is right above him.
“Why You Need an Analog Front
End and How to Set It Up,” Eric
Bogatin, Nuts & Volts, February
2016, p. 38.
“Turn Your Microcontroller into a
Precision Data Acquisition
System,” Eric Bogatin,
Nuts & Volts, June 2017.
“Special Day for Physicists Cats,”
Eric Bogatin, EDN news portal,
August 12, 2013
Iodine 131 treatment:
Geiger tube on eBay:
RadioShack audio transformer
(like this one):
Pictotech P2204A scope:
“Arduino Based Data
Acquisition,” Eric Bogatin,
Nuts & Volts, June 2015, p 34.
Link to download PLX-DAQ v2: