I am trying to make sense of the below circuit diagram.
What do Ri and Ro mean?
What purpose do the resistors after the Pinouts of Pin 3 and Pin 2 serve?
This is the datasheet for the sensor: http://www.ge-mcs.com/download/turbidity/920-480B-LR.pdf. It says its rated current is max. 30mA. In order to test the current in the circuit I built for this sensor (which you can see at this question: https://electronics.stackexchange.com/questions/207096/help-with-turbidity-sensor-circuit-and-reading-voltage), I would just use a multimeter between my Vcc source and Pin4 to measure the current?
I was also trying to see if I accidentally fried the sensor somehow. I used a digital camera and pointed it at the photo TR, but I could not see anything (this was to see if there was any IR light coming from the photo TR). I tested the camera first with a TV Remote to see if I could see IR light coming from the remote, and I could. I am not 100% sure if it is an IR LED on Pin 3, however. Are there any other ways to see if I fried the sensor?