There is another option from Apogee. The sensor alone is $139 and is available calibrated for sun or electric (fluorescent). The calibrated output of the sensor is 0.2 millivolts per micromol per meter squared per second. Full sunlight is about 2,000 micro-mol per meter squared per second so the output in full sun is 400 millivolts. The sensor can be connected to a standard digital multimeter with 1 millivolt resolution ($30 or so for a good one at Fry’s or Radio Shack). The output in millivolts can be multiplied by 5 to give the PAR in micro-mol per meter squared per second (standard measurement). There is no reason to get the ‘electric’ calibrated version, just use the sun calibrated version and multiply the output by 92% for fluorescent lights. Apogee says the response to metal-halide lamps is 6% high for the sun calibrated sensor so multiplying by 94% may be correct for MH, although the response curve of the sensor indicates that it will respond less to deep blues and therefore may be closer to 100% for a very blue MH lamp. The sensor is the same one used on the QMSW-SS dual calibrated meter and should be just as accurate. For a club meter the QMSW-SS is a very good choice because it is simple to use and reads out directly in micro-mol per meter squared per second, but if an individual wants their own quantum sensor, the SQ-110 is a good economical alternative.