I am currently working to install an NPN photoelectric sensor (retro-reflective dark on: https://www.automationdirect.com/adc/shopping/catalog/sensors_-z-_encoders/photoelectric_sensors/18mm_round_-_nonmetal/polarized_retroreflective_(ss_-z-fa-z-_fb_series)/fbp-dn-0e) however it is not working as expected and was hoping someone here could clarify what is happening. To my understanding an NPN transistor works as so (RL is 9k ohms). Here the transistor is activated.
What is happening is the current Ib is 0.016A when the transistor(sensor) is on and 0.12A when the transistor is off. Ie is 0.018A when the transistor is on and 0.012 when off. Ic is essentially zero at all times. The impedance reading between the collector and emmiter is 38.5M ohms at all times, and the impedance reading when taken across RL (base and collector) is overload and then when the sensor is activated the resistance of 9k ohms is read.
My question is although the logic is working as expected, the currents (Ie, Ib and Ic) are not. I was under the impression the transistor acted essentially as a switch between emitter and collector, however most of the current flow is through the base and the emitter, and the impedance between the collector and emitter is not dropping below 38.5M ohms. Can anyone clarify anything for me? Or is it likely I have screwed up the circuit or am taking incorrect measurements. Thank you.