Specifications

Section 3. Overview
3-3
Period Average: 16 channels (SE 1 -16)
• Input voltage range: -2500 mV to +2500 mV.
• Maximum frequency: 200 kHz
Technical Note -- Pulse Count vs. Period Average
Pulse count and period average measurements can both be used to measure
sensors that output frequency. Yet pulse count and period average
measurement methods are quite different, resulting in different characteristics
for each type. Pulse count measurements use dedicated counter hardware that is
always monitoring the input signal, even when the datalogger goes to sleep
mode between scans. Period average measurements utilize multiplexed voltage
measurement hardware and so only monitor the input signal during the
execution of a period average instruction. Consequently, pulse count
measurement intervals can generally be made much longer than period average
measurement intervals, which is advantageous if trying to minimize the effects
of low-frequency noise. Pulse count measurements are not appropriate for
sensors that are powered down between scans, whereas period average
measurements work well as they can be placed in the scan so as to execute only
when the sensor is powered up and outputting valid frequency information.
Period average measurements utilize a high-frequency digital clock to measure
time differences between signal transitions, whereas pulse count measurements
simply accumulate the number of counts. As a result, period average
measurements offer much better frequency resolution per measurement
interval, as compared to pulse count measurements. The frequency resolution
of pulse count measurements can be improved by extending the measurement
interval by increasing the scan interval and by averaging.
Pulse: 2 channels (P1 - P2) configurable for counts or frequency of the
following signal types:
• High level 5V square waves
• Switch closures
• Low-level A/C sine waves
Digital I/O: 8 channels (C1 - C8) configurable for serial input, SDM, SDI-12,
state, frequency, pulses.
• C1 - C8: state, frequency and pulse measurements.
• C1 - C3: Synchronous Devices for Measurement (SDM) input /
output.
• C1, C3, C5, C7: SDI-12 input / output.
• C1 - C2, C3 - C4, C5 - C6, C7 - C8: serial communication input /
output.
9-Pin RS-232: 1 port (Computer RS-232) configurable for serial input.
3.1.2.2 Voltage Outputs
The CR1000 supplies precision voltage excitation for resistive measurements
through the following output channels:
Switched Analog Voltage Output (Excitation): 3 channels (Vx/EX1 – Vx/EX3)
for precise voltage excitation ranging from -2500 mV to +2500 mV. Each
channel will source up to 25 mA.