CR200/CR200X Series Dataloggers - Campbell Scientific
CR200/CR200X Series Dataloggers - Campbell Scientific
CR200/CR200X Series Dataloggers - Campbell Scientific
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Section 5. Measurement and Control<br />
Peripherals<br />
Peripheral devices expand the <strong>CR200</strong>(X) input / output capacity. Classes of<br />
peripherals are discussed below according to use.<br />
Read More! For complete information on available measurement and control<br />
peripherals, go to APPENDIX. Sensors and Peripherals (Appendix p. 28),<br />
www.campbellsci.com, or contact a <strong>Campbell</strong> <strong>Scientific</strong> applications engineer.<br />
5.1 Control Output<br />
Controlling power to an external device is a common function of the <strong>CR200</strong>(X).<br />
On-board control terminals are available for binary (on / off) control.<br />
Many devices are conveniently controlled with the SW Battery (Switched 12<br />
Volt) terminal on the <strong>CR200</strong>(X). Applications requiring more control channels<br />
or greater power sourcing capacity may be satisfied by using control ports C1 –<br />
C2 in conjunction with single-channel switching relays.<br />
5.1.1 Binary Control<br />
5.1.1.1 Digital I/O Ports<br />
Each of 2 digital I/O ports (C1 - C2) can be configured as an output port and set<br />
low (0 V) or high (5 V) using the PortSet () or WriteIO () instructions. A digital<br />
I/O port is normally used to operate an external relay driver circuit because the<br />
port itself has limited drive capacity. Drive capacity is determined by the 5V<br />
supply and a 330 ohm output resistance. It is expressed as:<br />
Vo = 4.9V - (330 ohms) * Io<br />
Where Vo is the drive limit, and Io is the current required by the external<br />
device. FIGURE. Control Port Current Sourcing (p. 50) plots the relationship.<br />
49