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UV Sensors FAQ

 Please contact us with any questions not covered below.

1. What do UVA/UVB/UVC mean?

2. Is it possible to make a detector with an active area of 32 sq mm (4mm x 8mm)?

3. Do I need anything more to make a measurement with a UV Sensor?

4. Do I need anything more to make a measurement with a UV Probe?

5. How can I find out the relationship between input UV power and output sensor current for an individual UV sensor?

6. How can I find out the relationship between input UV power and output sensor current for an individual UV probe?

7. How fast are the sensors?

 1. What do UVA/UVB/UVC mean?

The UV region covers the wavelength range 100-400 nm and is divided into three bands:

UVA (315-400 nm)

UVB (280-315 nm)

UVC (100-280 nm)

 2. I am interested in the TW30DY UV photodiode. What is the response time for the device?

The response time for the TiO2 photodiodes is a function of the radiation intensity. This is due to the polycrystalline nature of the semiconductor: The TW30DY (as well as TW30DY2 and TW30SY) behaves as given by the following table:

UV Intensity

Response time

50 W/cm²

0.06 ms

10 mW/cm²

0.7 ms

0.5 mW/cm²

40 ms

0.01 mW/cm²

500 ms

If you need faster UV-photodiodes, we recommend the SiC UV-photodiodes, however they have a significantly smaller photoactive area.

 Is it possible to make a detector with an active area of 32 sq mm (4mm x 8mm)?

A large area is possible to meet your requirements but would carry a development cost.

 3. Do I need anything more to make a measurement with a UV Sensor?

UV sensors such as the SG01S and the AG38S-TO, are all photodiodes. They convert the incoming UV light into a very small current (of the order of nA). It is not possible to measure this current using typical bench multimeters so a transimpedence amplifier is required to convert this current into a usable voltage. The cost of a suitable amplifier and associated parts can be less than £1.

(It is possible to use the UV sensors in voltage mode and make measurements using multimeter set to the mV range. However, this is not recommended as the output is very non linear when in voltage mode.)

Note: The sensor itself does not require a power supply as it acts as a solar cell generating electricity from the incoming UV radiation. The transimpedance amplifier will require a power source though.

 4. Do I need anything more to make a measurement with a UV Probe?

The UV Probes either include just a sensor or combine a sensor with an amplifier. The sensor only parts require a transimpedance amplifier as per the above question. The UV probes with a sensor and amplifier only require a power supply and a method of monitoring the output (such as a multimeter). The part UV_Air_ABC_AMP4-20mA_cable for example, only requires a 24V power supply to drive the probe and an ammeter to monitor the 4mA to 20mA output current.

 5. How can I find out the relationship between input UV power and output sensor current for an individual UV sensor?

The relationship between the input UV power and output current is given on the data sheet for the wavelength of peak sensitivity. To find out the value at other wavelengths, the graph of spectral response can be used (also on the data sheet). These figures are for typical parts as there will be variation in the sensitivities from part to part. The SiC parts (SG01S etc) have a variation from part to part of +/-10% compared to the data sheet figure.

If greater accuracy is required, the sensor can be compared with a calibrated sensor to get an absolute reading or it can be supplied calibrated at an extra cost.

Once calibrated at one power level, measurements at other power levels can be made without further calibration steps as the output is very linear over many orders of magnitude.

 6. How can I find out the relationship between input UV power and output sensor current for an individual UV probe?

For UV probes which consist only of a sensor, the above answer applies. For UV probes with both a sensor and an amplifier built into them, there is the additional question of the gain of the amplifier. This is normally factory set to meet the customers requirements so will differ from application to application. Again the entire probe can be supplied calibrated for an additional cost.

 7. How fast are the sensors?

Rise and fall times for the most popular sensors are as follows:

SGO1S

8ns

SGO1M

25ns

SGO1L

65ns

AlGaN-UVB

10ns

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