Campbell Scientific CR3000 Micrologger - Manual (Page 62)

Section 5. System Overview
62
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 single-
ended 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
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.
5.1.3.4.2 Power Out
• See Powering Sensors and Devices
(p. 89).