ground. A differential measurement measures the high signal with reference to the low signal.
Each configuration has a purpose, but the differential configuration is usually preferred.
In general, use the smallest input range that accommodates the full-scale output of the sensor.
This results in the best measurement accuracy and resolution (see
(p. 187) for more information).
A set overhead reduces the chance of overrange. Overrange limits are available in the
specifications. The data logger indicates a measurement overrange by returning a NAN for the
measurement.
WARNING:
Sustained voltages in excess of -6 V or +9 V (SE1, SE2), ±17 V (SE3 to SE6) applied to
terminals configured for analog input will damage CR300 series circuitry.
14.1.1 Single-ended measurements
A single-ended measurement measures the difference in voltage between the terminal
configured for single-ended input and the reference ground. For example, single-ended channel
1 is comprised of terminals SE 1 and
. Single-ended terminals are labeled in blue. For more
information, see
Wiring panel and terminal functions
(p. 5). The single-ended configuration is
used with the following CRBasic instructions:
l
VoltSE()
l
BrHalf()
l
BrHalf3W()
l
TCSE()
l
Therm107()
l
Therm108()
l
Therm109()
See the CRBasic Editor help for detailed instruction information and program examples:
https://help.campbellsci.com/crbasic/cr300/.
14.1.2 Differential measurements
A differential measurement measures the difference in voltage between two input terminals. For
example, DIFF channel 1 is comprised of terminals 1H and 1L, with 1H as high and 1L as low. For
more information, see
Wiring panel and terminal functions
(p. 5). The differential configuration
is used with the following CRBasic instructions:
l
VoltDiff()
l
BrFull()
14. Measurements
69