Low-Level Ac Measurements; High-Frequency Measurements - Campbell CR300 Series Product Manual

Terminals configured for pulse input have internal filters that reduce electronic noise, and thus
reduce false counts. Internal AC coupling is used to eliminate DC offset voltages. For tips on
working with pulse measurements, see
Output can be recorded as counts, frequency or a running average of frequency.
See also Pulse measurement specifications
See the CRBasic Editor help for detailed instruction information and program examples:
https://help.campbellsci.com/crbasic/cr300/.

14.5.1 Low-level AC measurements

Low-level AC (alternating current or sine-wave) signals can be measured on P_LL terminals. AC
generator anemometers typically output low-level AC.
Measurement output options include the following:
Counts
l
Frequency (Hz)
l
Running average
l
Rotating magnetic-pickup sensors commonly generate ac voltage ranging from millivolts at low-
rotational speeds to several volts at high-rotational speeds.
CRBasic instruction: PulseCount(). See the CRBasic Editor help for detailed instruction
information and program examples:
Low-level AC signals cannot be measured directly by C terminals. Peripheral terminal expansion
modules, such as the Campbell Scientific LLAC4, are available for converting low-level AC signals
to square-wave signals measurable by C terminals.
For more information, see

14.5.2 High-frequency measurements

High-frequency (square-wave) signals can be measured on terminals:
P_LL, P_SW, SE 1-4 or C
l
Common sensors that output high-frequency pulses include:
Photo-chopper anemometers
l
Flow meters
l
Measurement output optionss include counts, frequency in hertz, and running average.
CRBasic instruction:
l
Pulse measurement tips
(p. 191).
https://help.campbellsci.com/crbasic/cr300/.
Pulse measurement specifications
PulseCount()
(p. 83).
(p. 191).
14. Measurements 80