Campbell Scientific LI190SB LI-COR Quantum Sensor - Manual (Page 10)

LI190SB Quantum Sensor
Output from the LI190SB is a voltage raning from 0 to a maximum of 10 mV
depending on sensor calibration and radiation level, which is measured by the
datalogger using a Differential analog input channel. To measure the output,
Edlog dataloggers (e.g. CR10X, CR23X) are programmed with Instruction 2
Volt(DIFF), CRBasic dataloggers (e.g. CR1000, CR3000) are programmed
with the VoltDiff Instruction.
Nearby AC power lines, electric pumps, or motors can be a source of electrical
noise. If the sensor or datalogger is located in an electrically noisy
environment, the measurement should be made with the 60 or 50 Hz rejection
integration option as shown in the example programs.
Solar radiation can be reported as an average flux density (µmole s -1 m -2 ) or
daily total flux density (mmoles m -2 ). The appropriate multipliers are listed in
Table 5-1. Programming examples are given for both average and daily total
photosynthetically active radiation (PAR). Negative values are set to zero
before being processed.
If a differential channel is not available, a single-ended measurement
(Instruction 1) is a possibility. As a test, wire the LI190SB as shown in Figure
5-1 and make single-ended and differential measurements. Compare the
results to determine the acceptability of a single ended measurement.
FIGURE 5-1. Differential Measurement Connection
FIGURE 5-2. Single-ended Measurement Connection
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