The UV sensor is widely used in the
industry now. But there sometimes occurred some questions about the UV sensor. What
are the questions about the UV sensors? And how to solve them?
Following are some FAQs about UV Sensors:
Questions:
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?
Questions & Answers:
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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