Campbell Scientific CR3000 CR3000 Micrologger - Page 62

Section 5. System Overview The number of CAO terminals can be expanded with peripheral CAO devices available from Campbell Scientific. Refer to the appendix CAO Modules (p. 565) for more information. • Current Excitation - three switched terminals (IX1, IX2, IX3) with return connecting to IXR terminal. Capable of driving between -2500 µA and 2500 µA. 5.1.3.3 Grounding Terminals Read More! See Grounding (p. 92). Proper grounding will lend stability and protection to a data acquisition system. It is the easiest and least expensive insurance against data loss-and the most neglected. The following terminals are provided for connection of sensor and datalogger grounding: • Signal Grounds - 21 ground terminals ( ) used as reference for singleended analog inputs, pulse inputs, excitation returns, and as a ground for sensor shield wires. Signal returns for pulse inputs should use terminals located next to pulse inputs. • Power Grounds - 5 terminals (G) used as returns for 5V, SW12V, 12V, and C1 to C8 outputs. Use of G grounds for these outputs minimizes potentially large current flow through the analog voltage-measurement section of the wiring panel, which can cause single-ended voltage measurement errors. • Ground Lug - 1 large brass lug ( ), used to connect a heavy gage wire to earth ground. A good earth connection is necessary to secure the ground potential of the datalogger and shunt transients away from electronics. Minimum 14 AWG wire is recommended. 5.1.3.4 Power Terminals Read More! See Power Sources (p. 82). 5.1.3.4.1 Power In 5.1.3.4.2 Power Out Note Refer to the appendix Power Supplies (p. 566) for information on available power supplies. • External Power Supply - one green plug (POWER IN): for connecting power from an external power source to the CR3000. This is the only terminal used to input power; other 12V terminals and the SW12V terminal are output only terminals for supplying power to other devices. Review power requirements and power supply options in Power Sources (p. 82) before connecting power. • Internal Power Supply - the CR3000 is often supplied with a base that contains alkaline or sealed rechargeable batteries. Power is controlled by a manual switch on the side of the base. • See Powering Sensors and Devices (p. 89). 62