Why do I have low NTU readings or a very high gain on my 1720 series turbidimeters when I install a new lamp and have passed the photocell mV tests?
1720 series turbidimeter high gain, low NTU troubleshooting.
If you have already replaced your lamp and your photocell passes the mV test, on a 1720 series turbidimeter, a commonly missed item is the focusing lens in the turbidimeter. This lens helps to focus the light from the lamp down to the light bulb. If this lens is very dirty or becomes damaged, the NTU can be very low and the gain during calibration will be very high.