We often do not think that almost everything is in our environment.
In Hungary the average background radiation ranges from 0.05μSv to 0.18μSv depending on the geographic characteristics of the given settlement. What few people know is that substances in our environment can also radiate. These may include certain rocks, coal used for firing, fired ceramics, bricks, slate blocks, slate block, old ceramic glazing, old black dial fluorescent dial,
Radon gas from the ground, and we could still rank. Old ceramic paints contained uranium (red and brown dye).
Coal mined from the ground also contains radiant carbon isotopes, just like the slime shape used for floor and roof insulation
Little in our country. The radioactive substances in the coal ash burned in the stove can appear concentrated because some of them are non-combustible and have a high mass to leave the chimney. It is worth examining our houses with insulated insulation, because they do not pose a direct threat, but the higher background radiation may be a health risk in the long run. The radiation decreases square by the increase in distance, so it is desirable to have a slate block or a brick-built house
To pull our bed slightly from the wall, because it can be significantly reduced, for example. The risk of brain tumors.
- From the dry facts, let's go through the self-designed ACGM-1 type universal radiometer:
As we know about the radiation detection, the Geiger-Müller counting tube named after inventors is one of the most suitable tools.
Its operation is very simple: There is a metal cylinder with a metal thread surrounded by a low pressure gas (eg Neon, Argon) and when energy from a particle decomposition (Alpha, Beta or Gamma may be X-rays) Ionisation which causes electron flow between the metal cylinder and the metal fiber. Always the inner thread is the anode (+) and the outer cylinder is the cathode (-).
It is cylindrical in the outer electrode so that other electromagnetic radiation and light are shielded and can not influence the measurement.
The composition of the gas charge ensures that this condition does not last long. This condition is the dead time of the tube because, as long as the gas is in ionisation, it is unsuitable for detecting further particles.
The higher the radiation, the more such "discharge" can be detected, which simply needs to be counted with a sufficiently fast counter.
The microcontroller program uses a direct interrupt, so you can not miss the impulses with less than 200μs.
The discharge current is limited by a series of resistances, which is usually between 5 and 10MΩ. The instrument has an internal resistance of 5MΩ. If larger, we need to tie a similar resistance to the GM tube, which complements the ballast resistance to the factory recommendation.
Each Geiger-Müller tube has a range of operating voltage, which is called a plateau, as the tube sensitivity in this range is unchanged. For example, The operating voltage of the SI3BG type pipe is between 380V and 460V, it is advisable to set the operating voltage in the center of the range. In this case: (380V + 460V) / 2 = 420Volt. This voltage can be digitally adjusted with the circuit buttons, so we do not have any further action. If you want to check the real voltage, it will not be easy because the conventional 10MΩ internal resistors digital multimeters are unsuitable because the circuit has a higher internal resistance. If we do not get an instrument with a resistance of 1000MΩ or greater, we can do a few hundred μF 400Volt electrolytic capacitors parallel to the 330nF / 630Volt capacitor of the circuit, which is then strictly forbidden to touch! Set the rated voltage to 400Volt, wait a few minutes to fully charge the capacitor and measure the voltage. The capacitor of the secondary capacitor will ensure that the internal resistance of the instrument can not discharge the charge too quickly and the measurement error is minimal during a measurement period. The operating voltage of the GM tube is generated by the self-induction ability of a single coil with a voltage multiplier.
The ATMEGA88 microprocessor continuously measures the voltage of the tube and compensates the deviation by the pulse width control (PWM). Its accuracy is +/- 5V, which is more than satisfactory for the operation of the tube. When testing the circuit, it turned out that the 630Volt WIMA capacitor was operating at 1000Volton, but we would not exceed the factory default of 630Volt!
If more voltage is required for the pipe, this one capacitor is replaced by a higher voltage.
The circuit was able to produce up to 1550Volt with a 10.3Volt power supply, so the maximum rated voltage of 1000Volt
You can keep it stable without any problems.
