LISST-Tau
User’s Manual
Operation Details
Page 20
F.
Analog Output
Applications
Although the serial digital output provides the best precision and overall
data quality, some applications call for the simpler interfacing provided
by an analog signal. Many existing CTD rosettes and other profiling
systems already provide for an analog-output transmissometer as one
of their standard sensors. For these cases, the LISST-Tau provides an
analog output on pin 6 of its main connector.
Scaling and
Voltage Range
The output voltage is proportional to transmission. Although the LISST-
Tau circuitry can produce up to 5.0V on this output, we set the 100%
full-scale output to 4.5 V. That is, the output is 4.5V when the
transmissometer is properly calibrated and measuring pure water. The
extra range from 4.5V to 5.0V is reserved to indicate a problem with the
pure-water baseline [see Clean-water Baseline Measurement
(Calibration) on page 14], by showing transmission greater than 100%.
Update rate
The analog output is updated once per second, synchronously with the
digital output data.
