Using Apogee PAR Sensor and mVMeter
Has anyone tried to use a cheap digital mV meter and an Apogee SQ222, self powered sensor, to make a semi-DIY PAR meter? I received one of those sensors as a gift, and bought a cheap 200 mV digital meter to use as a readout. So far I haven't been able to make it work. I get a reading around 160 no matter if the sensor is illuminated or blacked out.
Using this version of the sensor requires supplying DC voltage to the sensor, and it gives a 1 mV per PAR unit readout (if it works). The sensor uses a common ground as the negative lead for both the supplied DC voltage and the DC mV output. The mV meter has 4 wires - two for the supplied voltage and two for the output voltage. I wired it with the common ground connected to both negative leads. Does that seem like the right way? I'm using a 9V battery for power, with the negative lead as the common ground.