Obtaining Correct (Positive) Values with LI-COR Underwater Radiation Sensors

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The LI-192 Underwater Quantum Sensor and LI-193 Spherical Quantum Sensor from LI-COR are terminated with two pins that mate with the underwater cable. In order to obtain the correct (positive) readings when using the underwater sensors, it is important to attach the sensor and underwater cable correctly. There is a yellow dot on the sensor connector that should be aligned with the raised nub on the sensor cable before pushing them together. If the dot is not aligned, this will result in a negative reading on the readout device, due to the change in polarity of the conductors. When viewing the data on a readout device, if the numbers appear to be of the proper magnitude (around 1500-2000 µmol s-1 m-2 outdoors, facing straight up), but are negative, remove the underwater cable and turn the sensor 180 degrees. If the readings are negative, but near zero, it may indicate a problem with the cable. And if the readings are exactly zero, the multiplier is probably not entered correctly.