User Manual
4.5 Analog Data
In addition to the internal memory of the eosFD, users also have the
option of recording analog data on an external data logger, using the
three wires on the SCC Power and Data Cable (
provides more
detailed information on interfacing an eosFD to a Campbell Scientific
data logger, including how to record data using the serial interface).
Each wire should be connected along with one of the three black
grounding wires as a 0-5 V DC differential voltage measurement, with
ranges, multipliers and offsets as shown in the table below:
Figure 4
Purple, blue, and grey
wires on the SSC Power and
Data Cable.
*
New eosFDs no longer output Soil CO
2
via analog. CO
2
values recorded by the eosFD are used
only to calculate the flux, and are not intended to be stand-alone measurements of CO
2
.
In order to interpret the analog signals, simply apply the appropriate linear transformation to the voltage
data, as determined by the range. For example, to transform a temperature voltage signal, first divide
the voltage by the 0-5 V range, then multiply by the -20-40 °C temperature range. Finally, add the
minimum of the temperature range. The example below shows each step for a reading of 3 V.
(1)
3 V / (5 V - 0 V) = 0.6
(2)
0.6 * (40 °C - -20 °C) = 36 °C
(3)
36 °C + -20 °C = 16 °C
Thus a 3 V analog signal for temperature corresponds to 16 °C.
11
m
© Eosense Inc.
Output
Colour
Units
Range
Multiplier
Offset
CO
2
Flux
Purple
μmol/m
2
/s
-10 - 10
0.004
-10
Soil CO
2
Signal*
Blue
ppm
0 - 5000
1.0
0
Sensor Temperature
Grey
°C
-20 - 40
0.012
-20
