Hello Abdul,
I haven't done it before with a UV sensor but with a LDR type of sensor.But I got some idea which may help you.
Try to get UV lamp source which you can drive with a constast mains source. Keep the UV lamp source exposed to a good UV sensor at varying distances , say, 200cm until 1200 cmm( which may vary and depends upon the specific model of UV sensor) and try to read the current through UV sensor. You may need also a load resistor and a contant electrode voltage in series with the UV sensor. You can get some idea of the values you should use from the circuits which employs the sensors(for eg. a burner flame detector circuit).
From a good sensor you can generate a plot of distance versus UV sesnor current.Repeat the test for all then sensors of same model which you need to test. A comparision of the results will give you the sensors which have degraded performance.
Dear Mr.Abdul:
You can check the working of sensor with ordinary wax candle.
Flame from wax candle contains UV radiations.
This method is widely used for checking in thermal power plants.
