Campbell Scientific CR1000KD CR800 and CR850 Measurement and Control Systems - Page 61
Voltage, Outputs
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Section 5. System Overview as compared to pulse-count measurements. The frequency resolution of pulsecount measurements can be improved by extending the measurement interval by increasing the scan interval and by averaging. For information on frequency resolution, see Frequency Resolution. Pulse - 2 channels (P1 to P2) configurable for counts or frequency of the following signal types. • High-level 5-Vdc square-wave • Switch closures • Low-level ac sine-wave Digital I/O - 4 channels (C1 to C4) configurable for serial input, SDM, SDI-12, state, frequency, pulses, edge counting and edge timing. • C1 to C4 -- state, frequency, pulse, edge counting and edge timing measurements • Edge timing resolution - 540 ns • C1, C2 and C3 - Synchronous Devices for Measurement (SDM) input / output • C1, C3 - SDI-12 input / output • C1 & C2, C3 & C4 - serial communication input / output 9-Pin RS-232 - 1 port (RS-232) configurable for serial input Refer to the appendices Digital I/O (Control Port) Expansion (p. 541), Pulse / Frequency Input Expansion Modules (p. 538), and Serial Input / Output Peripherals (p. 539) for information on available input-expansion modules. 5.1.3.2 Voltage Outputs The CR800 has several terminals capable of supplying switched voltage to peripherals, sensors, or control devices. Read More! See Control Outputs (p. 312). • Switched Analog Output (Excitation) - two channels (VX1 to VX2) for precise voltage excitation ranging from -2500 mV to +2500 mV. These channels are regularly used with resistive bridge measurements. Each channel will source up to 25 mA. • Digital I/O - 4 channels (C1 to C4) configurable for on / off and PWM (pulse width modulation) or PDM (pulse duration modulation) on C4. • Switched 12 Volts dc (SW12) - One terminal controls (switch on / off ) primary voltage under program control to switch external devices (such as humidity sensors) requiring 12 Vdc on and off. SW12 can source up to 900 mA. See the table Current Source and Sink Limits (p. 84). 61
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