Using LabVIEW and NI USB DAQ Hardware to Build a Low-Cost Radiation Sensor
"With the help of LabVIEW, the USB-6009, and 24/7 data recording capabilities, we made a reliable radiation sensor."
- Mun Hon Foo ,
Tunku Abdul Rahman College University
Constructing a low-cost, low-level radiation detector to test and monitor possible radioactive contamination of external objects.
Designing a low-cost radiation sensor by using capacitors to reduce electrical and parasitic noises, adopting a Darlington pair for the electronics circuit, developing a custom NI LabVIEW software program to handle real-time data acquisition, and using the NI USB-6009 data acquisition (DAQ) device to communicate with and control the sensor electronics.
Since the Fukushima nuclear disaster in Japan, having an effective radiation detection system has been a popular topic around the world because people are becoming more aware of possible radiation contamination in the products they purchase. Moreover, radon gas emitted from the ground prior to an earthquake is colorless and odorless but it is radioactive. Radon gas is often found in a basement or underground. It is also the second main cause of lung cancer after cigarette smoking.
Existing radiation Geiger counters are expensive and require special training to operate and analyze data. Commercially available systems also require a government agency issued license and certification prior to deployment. Therefore, a low-cost, reliable radiation sensor system is needed.
First, we compiled our LabVIEW program into an executable to run it as a stand-alone program. This LabVIEW program can run 24/7 to record data at the predetermined time constant. Using LabVIEW, data is acquired and recorded from the NI USB-6009. These radiation sensor readouts are then transferred into a Microsoft Excel spreadsheet via the LabVIEW Active VI. Additional time stamps are also recorded. We added an independent user control to the LabVIEW front panel that is used to save the data to the spreadsheet. Figure 2 shows the radiation sensor LabVIEW block diagram.
For reliable, accurate monitoring, we can acquire data every second, which totals 86,400 readings in 24 hours. Each of these recorded readings are bandpass filtered, amplified, and averaged. The user-controlled time constant for sensor monitoring reduces the spreadsheet accessing time for prolonged uses or applications.
Because the total amount of data acquired depends on the speed of each individual computer CPU used, additional time compensation is introduced into the LabVIEW program. This is handled by a custom, automatic calibration function that is programmed using the Time Elapse Function VI. The algorithms used include the following:
1) The data taken is summed and divide by the amount of data taken to get an average reading of each second
2) The average data taken every second is summed and divided by 60 to get an average reading for a minute
3) The average reading of a minute is recorded into the Microsoft Excel spreadsheet along with the time stamp
We also added a waveform chart into the program for real-time monitoring. The sensor can detect several different types of ionizing radiation including alpha, beta, and gamma particles. Figure 1 shows the experimental setup along with the electronic circuit. The sensor setup is portable and can be deployed in the field. These radiation particles can be ionized with an ion chamber. The positively charged atom is attracted by the more negative chamber. The negatively charged atom (the electron) is attracted by the electrode and introduces current into the circuit. Because the current introduced is too small to measure, an amplifier circuit that we built out of a Darlington pair, amplifies the current to give voltage readings for the USB-6009.
Our low-cost radiation sensor is effective enough to detect low-level radiation. With LabVIEW and the USB-6009 recording data 24/7, this is a reliable radiation sensor. The radiation sensor can measure and indicate the level of the radiation of any contaminated object brought close to the detector. Continuous background radiation and the radon gas monitor can be monitored when the LabVIEW program is set to run 24/7.
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