Need help a tutorial on Par readings
- Thread starter Esardog
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You want a digital multimeter that reads millivolts. Check the accuracy of the meter. Most should be within a millivolt once you do the math but double check before you buy. I copied this from the apogee website regarding hooking up the sensor and calculating PAR from the reading:
The SQ-100 and 300 series are considered to be self-powered and have been calibrated to 5.0 µmol m-2 s-1 per mV. Use a voltmeter with a mV setting to attain better resolution. Connect the positive lead of the voltmeter to the red wire of the SQ and the negative lead of the voltmeter to the black wire of the SQ. Once you are reading the mV output from the sensor, simply multiply this reading by 5.0. This will give you the µmol m-2 s-1 output from the sensor, otherwise known as Photosynthetic Photon Flux (PPF) or Photosynthetically Active Radiation (PAR).
The SQ-100 and 300 series are considered to be self-powered and have been calibrated to 5.0 µmol m-2 s-1 per mV. Use a voltmeter with a mV setting to attain better resolution. Connect the positive lead of the voltmeter to the red wire of the SQ and the negative lead of the voltmeter to the black wire of the SQ. Once you are reading the mV output from the sensor, simply multiply this reading by 5.0. This will give you the µmol m-2 s-1 output from the sensor, otherwise known as Photosynthetic Photon Flux (PPF) or Photosynthetically Active Radiation (PAR).
tkeracer619
New member
I use a fluke but as long as it reads mV, and has a decent accuracy I don't see why it wouldn't work.
Thank you jerpa -- as I said I am electronically challenged so how do I test the meter?
If you look online most should have a stated accuracy in percentage of the reading or something similar.
You may need to find the manual for the specific multimeter to find its accuracy. Even the cheap ones are usually accurate to .5% of the reading +1 or .1 mv depending on it's resolution. In our use this puts it within about 5 par of what the sensor is reading.
One thing I noted on my search for accuracy ratings. Some of the really cheap meters only read to 200mV. The apogee sensor has a range of 400mV so make sure it goes at least that high.
You may need to find the manual for the specific multimeter to find its accuracy. Even the cheap ones are usually accurate to .5% of the reading +1 or .1 mv depending on it's resolution. In our use this puts it within about 5 par of what the sensor is reading.
One thing I noted on my search for accuracy ratings. Some of the really cheap meters only read to 200mV. The apogee sensor has a range of 400mV so make sure it goes at least that high.
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