Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 62)

Section 5. System Overview
62
5.1.3.3 Grounding Terminals
Read More! See Grounding
(p. 86).
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 — 6 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 — 4 terminals (G) used as returns for 5V, SW12, 12V, and
C1 to C4 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. 542)
for information on available
power supplies.
• External Power Supply — one green plug (POWER IN): for connecting
power from an external power source to the CR800. This is the only terminal
used to input power; other 12V terminals and the SW12 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.
5.1.3.4.2 Power Out
• See Powering Sensors and Devices
(p. 84).
• Peripheral 12 Vdc Power Source — 1 terminals (12V) and associated grounds
(G) supply power to sensors and peripheral devices requiring nominal 12
Vdc. This supply may drop as low as 9.6 Vdc before datalogger operation
stops. Precautions should be taken to minimize the occurrence of data from
underpowered sensors.
• Peripheral 5-Vdc Power Source — 1 terminal (5V) and associated ground (G)
supply power to sensors and peripheral devices requiring regulated 5 Vdc.