Campbell Scientific CR3000 CR3000 Micrologger - Page 61
Voltage and Current 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 - 4 channels (P1 to P4) 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 - 8 channels (C1 to C8) configurable for serial input, SDM, SDI-12, state, frequency, pulses, edge counting and edge timing. • C1 to C8 -- state, frequency, pulse, edge counting and edge timing measurements • Edge timing resolution - 136 ns • SDM-C1, SDM-C2 and SDM-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 (RS-232) configurable for serial input Refer to the appendices Digital I/O (Control Port) Expansion (p. 565), Pulse / Frequency Input Expansion Modules (p. 562), and Serial Input / Output Peripherals (p. 563) for information on available input-expansion modules. 5.1.3.2 Voltage and Current Outputs The CR3000 has several terminals capable of supplying switched voltage and current to peripherals, sensors, or control devices. Read More! See Control Outputs (p. 333). • Switched Analog Output (Excitation) - four channels (VX1 to VX4) for precise voltage excitation ranging from -5000 mV to +5000 mV. These channels are regularly used with resistive bridge measurements. Each channel will source up to 25 mA. • Digital I/O - 8 channels (C1 to C8) configurable for on / off and PWM (pulse width modulation) or PDM (pulse duration modulation) on C4, C5 and C7. • Switched 12 Volts dc (SW12V) - Two terminals control (switch on / off ) primary voltage under program control to switch external devices (such as humidity sensors) requiring 12 Vdc on and off. SW12V can source up to 900 mA. See the table Current Source and Sink Limits (p. 89). • Continuous Analog Output (CAO) - two CAO terminals (CAO1 and CAO2) capable of driving voltages from -5000 mV to 5000 mV at ±15 mA. 61