Campbell-scientific CR3000 Micrologger Uživatelský manuál stáhnout pdf (Strana 61)

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Section 5. System Overview

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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. 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.

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