The data logger has built-in pull-up and pull-down resistors for different pulse measurements
which can be accessed using the PulseCount()instruction. Note that pull down options are
usually used for sensors that source their own power.
6.5.2.1 U terminals
l CRBasic instruction: PulseCount()
6.5.2.2 C terminals
l CRBasic instructions: PulseCount()
See Pulse measurement specifications (p. 221) for more information.
6.5.3 Switch-closure and open-collector measurements
Switch-closure and open-collector (also called current-sinking) signals can be measured on
terminals:
l U or C
Mechanical switch-closures have a tendency to bounce before solidly closing. Unless filtered,
bounces can cause multiple counts per event. The data logger automatically filters bounce.
Because of the filtering, the maximum switch-closure frequency is less than the maximum high-
frequency measurement frequency. Sensors that commonly output a switch-closure or an open-
collector signal include:
l Tipping-bucket rain gages
l Switch-closure anemometers
l Flow meters
The data logger has built-in pull-up and pull-down resistors for different pulse measurements
which can be accessed using the PulseCount() instruction. Note that pull down options are
usually used for sensors that source their own power.
Data output options include counts, frequency (Hz), and running average.
6.5.3.1 U Terminals
An internal 100 kΩ pull-up resistor pulls an input to 5 VDC with the switch open, whereas a
switch-closure to ground pulls the input to 0 V.
l CRBasic instruction: PulseCount(). See the CRBasic Editor help for detailed instruction
information and program examples: https://help.campbellsci.com/crbasic/cr6/.
6. Measurements 81
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