Campbell Manufacturing CR10 ユーザーズマニュアル

In the field, an earth ground may be created
through a grounding rod.  A 12 AWG or larger
wire should be run between a Wiring Panel
power ground (G) terminal and the earth
ground.  Campbell Scientific's CM10 and CM6
Tripods come complete with ground and
lightning rods, grounding wires, and appropriate
ground wire clamps.

The common mode range is the voltage range,
relative to the CR10 ground, within which both
inputs of a differential measurement must lie in
order for the differential measurement to be
made.  Common mode range for the CR10 is
±2.5 V.  For example, if the high side of a
differential input is at 2 V and the low side is at
0.5 V relative to CR10 ground, a measurement
made on the ±2.5 V range would indicate a
signal of 1.5 V.  However, if the high input
changed to 3 V, the common mode range is
exceeded and the measurement cannot be
made.

Common mode range may be exceeded when
the CR10 is measuring the output from a
sensor which has its own grounded power
supply and the low side of the signal is
referenced to power ground.  If the CR10
ground and the sensor ground are at sufficiently
different potentials, the signal will exceed the
common mode range.  To solve this problem,
the sensor power ground and the CR10 ground
should be connected, creating one ground for
the system.

In a laboratory application, where more than
one AC socket may be used to power various
sensors, it is not always safe to assume that
the power grounds are at the same potential.
To be safe, the ground of all the AC sockets in
use should be tied together with a 12 AWG
wire.

The purpose of the Wiring Panel is to provide
transient protection, improve excitation voltage
accuracy, and make convenient, positive
connections of power, sensors, and peripherals
to the CR10 (refer to Figure 14.7-1).  Wiring
Panel transient protection is discussed in
Section 14.7.

The Wiring Panel carries two lines between the
CR10 and each excitation port.  One line is for
excitation voltage, the other is for feedback
control of the voltage.  The feedback line is
required to compensate for line losses between
the CR10 and the excitation port on the Wiring
Panel (see Figure 14.7-1).

Two 5 V output terminals are available on the
Wiring Panel for powering 5 V peripherals.  The
most common use of these terminals is to
switch the 5 V to a relay coil through a relay
driver circuit which is enabled by one of the
eight Digital I/O Ports, C1 through C8 (see
Section 14.9 for relay driver circuits).  The 5 V
ports can source up to 200 mA.  An input
protection transzorb will divert current to ground
at approximately 10 V.

A functional description of the 37 pin connector
located on the CR10 is provided in Appendix D.

A single switched 12 volt output is available for
powering sensors or devices that require an
unregulated 12 volts.  The 12 volt output is
limited to 600 mA of current.

A control port is used to operate the switched
12 volt control.  Connect a wire from any control
port to the switched 12 volt control (see Figure
OV1.1-2 for location of ports).  When the
control port is set high, 12 volts is turned on to
the switched 12 volt port.  When the control port
is set low, the switched 12 volts is turned off.

Each of the eight digital I/O ports can be
configured as an output port and set low or high
(0 V low, 5 V high) using I/O Instruction 20, Port
Set, or commands 41 - 68 associated with
Program Control Instructions 83 through 93.  A
digital output port is normally used to operate
an external relay driver circuit because the port
itself has a limited drive capability (1.5 mA at
3.5 V).  Figure 14.10-1 shows a typical relay
driver circuit in conjunction with a coil driven
relay which may be used to switch external
power to some device.  In this example, when
the control port is set high, 12 V from the
datalogger passes through the relay coil,
closing the relay which completes the power
circuit to a fan, turning the fan on.  Campbell