How test the functionality of the photocell for the 1720E turbidimeter?

Document ID

Document ID TE2292

Published Date

Published Date 06/07/2018
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Question
How test the functionality of the photocell for the 1720E turbidimeter?
Summary
1720E and photocell function
Answer
Qualitative Test:
Lift head of turbidimeter out of the body to expose the photocell to ambient light.  
Observe the changes in measurement values. If the photocell is functioning normally, the NTU measurement value will increase rapidly until the sc-controller shows “++++.”

Quantitative Test:
Test the photocell with a digital multimeter.
Open the head of the 1720E with a screwdriver.
Remove the photocell wires from the 1720E main circuit board.
Set the digital multimeter to read mV as DC (Direct Current) then connect the meter to the red and black wires of the photocell. If the photocell is functioning normally, it will read approximate 250-300 mV DC in ambient light, and there should be a significant change toward 0 mV DC if the photocell is covered so that light does not reach the photocell.

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