A cardboard box and thermometer
Actually you'd need 2 thermometers to accurately measure the output power with the equilibrium temperature of a resistor. One thermometer to measure the temperature of the resistor and the other one to measure the ambient temperature. You can plug these two values into an Excel spreadsheet, which contains you calibration lookup table, and obtain a very accurate output power measurement. If you want to measure the light output of a light bulb, then you can use a variety of light sensors, e.g.: phototdiode, phototransistor, LDR, CCD, CMOS, PV cell, ...but they better be thermally isolated or behind a fan because these illuminance sensors are affected not only by light but by their temperature as well. The last thing you want is for these light sensors to act as thermometers (incandescent light bulbs will heat them up!). A Hot Mirror or IR Cut filter or long glass optical fiber can remedy this. Q: Which one is better? A: Both are equally accurate but measuring the light output is FASTER, however for best accuracy it requires thermal isolation of the light sensor and a dark box. Q: Why can't these things be bought on eBay ? A: Because each one requires individual calibration with known DC current which is time consuming (the light sensing method is less sensitive to miscalibration because it does not depend on the thermal conductivity of the resistor's heat sink, thermal paste, air circulation, etc...). Also these methods cannot measure the input power.
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Topic: Captainloz Video 9 (showing COP = 2) replication. (Read 12460 times)
