UV-A sensor module 240-370nm GUVA S12SD

Beschrijving

Informatie (ENG):

• Detects UV light in the 240nm – 370nm range
• Analog voltage output proportional to the UV Index of UV light falling on the detector
• 3.3 and 5V compatible

The GUVA-S12SD is a true UV detector that only detects light from 240nm to 370nm which is the UV-B and most of the UV-A spectrum.  It also picks up the upper end of UV-C.

These wavelengths are used in black lights, tanning beds, reptile UV emitters, germicidal sterilizers and similar applications.  The device can be used to monitor the operation of those devices.

It can also be used to measure the UV Index which provides a scale to determine how intense the sun UV is and therefore what kind of protective measures should be taken.

The UV Index scale is published by the EPA and intended to give guidance to people on sun exposure and what protective measures to take to minimize damage from the sun.

Theory of Operation

The module includes an LM358 dual op amp which converts the current output of the sensor to a voltage and then amplifies that output so that it can be read by the analog input on an MCU for taking UV readings.

The first stage op amp outputs a voltage proportional to 4.3 * sensor photocurrent in µA.  If the photocurrent is 0.1µA (0.09mW/cm^2), then the output will be 0.43V

This feeds a second stage op amp with an additional gain of 6.1x.  In this example the final output will be 0.43V x 6.1 = 2.62V.

As configured, the module is mainly useful for measuring moderate to moderately high UV light levels or if the sensor is placed behind a neutral density filter to reduce the percentage of UV striking the sensor.

If it is desired to measure very high UV levels, the second stage of amplification can be bypassed.  This can be accomplished by shorting across the 5.1K resistor “512”and removing the 1K resistor to the right of it with marking “01B” or “102”.  This changes the gain of the output op amp to x1 effectively taking it out of circuit.  With that modification, UV index is then calculated by multiplying the output by 10.

Please note:  As of 6/2021, we are modifying this module and it now ships with a 1M feedback resistor on the first stage as noted above.  Prior to that date, the feedback resistor was 10M.  10M resistors are marked 01F, 1M resistors are marked 01E.  With a 10M feedback resistor, the first stage is 43 * sensor photocurrent in µA.  If the photocurrent is 0.1µA (0.09mW/cm^2), then the output will be 4.3V.