Sequoia LISST-ABS, Руководство пользователя

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15
2.4 Analog Output
Operations
Analog Output Range
and Interpretation
The LISST-ABS also provides an analog output for use with
data acquisition systems that do not support RS232 or SDI-12
interfaces.
Using the Analog Output requires four wires. Power, Power
Ground, Signal and Signal Ground. The two grounds can be
combined, but separating them provides the best accuracy.
Appendix A includes detailed descriptions of the use of the
individual pins of the 8-pin connector on the LISST-ABS.
However, in most cases you will be using a cable provided by
Sequoia for connecting to your datalogger. To make the
connections easier we have provided different cable
terminations designed specifically for different connection
requirements. For example we provide a termination with only
the four individual wires that are labeled and can be easily
connected to the datalogger. The mating connector makes it
easy to remove the long cable without disconnecting the wires
from the datalogger. You can also easily switch between the
datalogger and the USB cable if needed.
The wires are labeled and color coded. Connect the Black wire
to Power Ground. Connect the Red wire to +12V. Connect the
Green wire to Analog input and the White wire to the Signal
Ground.
The analog output nominally ranges from 0.1 to 4.1 V. To
accommodate the full dynamic range of the ABS within this
range of voltages, the output is logarithmic. With an
uncalibrated concentration (C
u
) of 1 mg/l, the analog output is
1.0 V, and each decade of increase or decrease in the
concentration changes the output by 0.5V.
To convert the analog output in volts to Uncalibrated
Concentration, use the formula:
C
u
= 10
2*(V
–1)
In Microsoft Excel, you can use the formula shown below.