Campbell Scientific CR200/CR200X-series Dataloggers - Manual (Page 57)

Section 4. Sensor Support
When a pulse channel is configured for pulse input mode, an internal 100 kΩ
pull-up resistor to +5 Volt on the P_SW input is automatically employed. This
pull-up resistor accommodates open-collector (open-drain) output devices for
high-frequency input. An external 100 kΩ pull-up resistor connecting Battery+
to P_LL, C1, or C2 must be added to perform pulse counting on any of those
channels (See Multiple Switch Closure Measurements p. 112).
The maximum input voltage on P_SW is 4 volts. For C1 and C2 the maximum
input voltage is 6.5 volts.
4.4.1.2 Low-Level AC (P_LL)
Rotating magnetic pickup sensors commonly generate AC output voltages
ranging from millivolts at low rotational speeds to several volts at high
rotational speeds. Channel P_LL contains internal signal conditioning hardware
for measuring low-level AC output sensors. P_LL measure signals ranging
from 20 mV RMS (±28 mV peak) to 14 V RMS (±20 V peak). Internal AC
coupling is incorporated in the low-level AC hardware to eliminate DC offset
voltages of up to ±0.5 V.
4.4.2 Pulse Input on Digital I/O Channels C1–C2
Read More! Review digital I/O channel specifications in Specifications p. 35.
Review pulse counter programming in CRBASIC Help for the PulseCount ()
instruction.
Digital I/O channels C1 – C2 can be configured to measure pulse input signals.
Pulse input signals require external 100 kΩ pull-up resistors to be connected
between Battery+ and the control ports. Maximum input voltage level is 6.5 V.
If pulse inputs greater than +6.5 V need to be measured, external signal
conditioning must employed. Contact Campbell Scientific for further
information.
Low-level AC signals cannot be measured directly on channels C1 – C2.
4.5 Period Averaging Measurements
The CR200(X) can measure the period of a signal on any single-ended analog
input channel (SE 1 - 5). The specified number of cycles are timed with a
resolution of 70 ns, making the resolution of the period measurement 70 ns
divided by the number of cycles chosen.
Cycles are counted as the input voltage transitions from less than 0.9 volts to
more than 2.1 volts. The maximum input voltage must be less than 4 volts. The
maximum frequency that can be detected is 150 kHz.
45