Ultraviolet radiation intensity meter. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Measuring technology
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Ultraviolet is called electromagnetic radiation with a wavelength of 400 to 10 nm (frequency - 7,5 1014...3 1016 Hz) [1]. The entire spectrum of ultraviolet radiation according to the lSO-DIS-21348 standard [2] is divided into four ranges: near - 400 ... 300 nm, medium - 300 ... 200 nm, far - 200 ... 122 nm and extreme - 121. ..10 nm. The radiation of the middle range is almost 90%, and the far and extreme ranges are absorbed by the earth's atmosphere by 100%. Consequently, the human body is affected mainly by near-range radiation. At high intensity, this effect becomes unfavorable and even dangerous. Therefore, its measurement is very important. According to sanitary standards [3], the intensity of ultraviolet radiation should not exceed 5 mW/cm2.
The scheme of the device for measuring the intensity of ultraviolet radiation is shown in fig. 1. It uses the ultraviolet sensor ML8511 [4] with maximum sensitivity in the near range. The output voltage of the sensor is directly proportional to the radiation intensity. In the absence of radiation, it is equal to 1 V, and with its intensity of 15 mW / cm2 reaches 2,75 V.
Rice. 1. Scheme of the device for measuring the intensity of ultraviolet radiation
Digital voltmeter PV1 measures the voltage at the output of the sensor. It is pre-scaled using a voltage divider R2R3. The zero of the voltmeter scale and its sensitivity are set respectively by trimming resistors R7 and R5. The calculation of the circuits for scaling and correction of readings is described in detail in the instructions for using the digital voltmeter chip [5]. With their correct adjustment, the zero intensity of radiation on the voltmeter display should correspond to a value of 0,00, and a maximum intensity of 15 mW / cm2 - 15,00.
The meter is powered by one galvanic cell G1 size AA. Consumption current - no more than 20 mA. The voltage of the element is increased to 5 V by a converter on the DA1 chip. The supply of the sensor B1 with a voltage of 3,3 V is provided by the zener diode VD2.
Setting up the meter is not difficult. Assemble the technological divider of reference voltages +1 and +2,75 V according to the circuit shown in fig. 2. Remove jumper S1, apply an exemplary voltage of +2 V to the input of the divider R3R1. Set the voltmeter reading to 7 with the trimmer resistor R0,00. Then apply a reference voltage of 2,75 V and set the trimmer resistor R5 to 15,00 on the display.
Rice. 2. Scheme of the technological divider of exemplary voltages
Since the ML8511 sensor chip is very tiny and unsuitable for amateur soldering, the device uses a ready-made module with this chip installed on a 16x16x3 mm printed circuit board (Fig. 3). It is slightly more expensive than the microcircuit itself, and it is much more convenient to work with it. Module details in fig. 1 are enclosed in a dash-dotted box.
Rice. 3. The printed circuit board of the device
The digital voltmeter chip DMS-30PC-1-RL-C has a nominal measured voltage range of -1,999 ... +1,999 V, as evidenced by the index 1 in its designation, the red color of the numbers displayed on the display (index R) and the current consumption is not more than 17 mA (index L). Resistors R2 and R3 must be with a tolerance of at least ±0,5 or ±1%. Trimmer resistors R5 and R7 are better to use multi-turn. The printed circuit board of the meter is shown in fig. 4.
Rice. 4. Printed circuit board of the meter
In conclusion, I want to note that the described device can be successfully used to check the degree of absorption of ultraviolet radiation by sunglasses. First, measure the radiation intensity with the sensor open, and then cover it with a lens from glasses. The difference in readings will show the effectiveness of the protection provided by the glasses.
Literature
- Ryabtsev A. N. Ultraviolet radiation. //Physical Encyclopedia. - M.: Great Russian Encyclopedia, 1998, v. 5, p. 221.
- International Standard ISO 21348. Space environment (natural and artificial). Process for determining solar irradiances. - URL: spacewx.com/Docs/ISO_21-348.pdf.
- Sanitary standards for ultraviolet radiation in industrial premises (approved by the Chief State Sanitary Doctor of the USSR on February 23, 1988 No. 4557-88). - URL: norm-load.ru/SNiP/Data1/47/47650/index.htm.
- ML8511-00FC. Reference Board Manual for UV Sensor (QFN). - URL: media. digikey.com/pdf/Data%20Sheets/Rohm%2PDFs/ML0-8511FC_RefBrd_Manual-00. pdf.
- DMS Application Note 12. Signals with Zero Offsets. - URL: datelmeters.com/data/meters/dms-an12. pdf.
Author: A. Kornev
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