Campbell Scientific CR7 Measurement and Control System - Manual (Page 12)

CR7 MEASUREMENT AND CONTROL SYSTEM OVERVIEW
OV-2
RS232 9 pin serial ports used on many
computers.
The SDM terminals adjacent to the serial port
allow connection to Synchronous Device for
Measurement (SDM) peripherals. These
peripherals include the SDM-INT8 Interval
Timer, the SDM-SW8A Switch Closure Module,
the SDM-CD16AC AC/DC Controller, and the
SDM-OBDII Engine Controller Interface.
709 512K MEMORY CARD: This card
provides RAM storage for an additional 262,126
Final Data values. Only one 709 card may be
installed.
OV1.2 720 I/O MODULE
The processor card provides regulated power
for analog and digital functions from the
unregulated 12 volt supply. The analog
interface card contains a 16-bit A/D-D/A
converter, and a precision voltage reference.
The standard I/O Module contains slots for 7 I/O
Cards; the expanded Model 720XL contains 14
slots. All input and output connections to the
I/O module are transient protected with spark
gaps.
The +12 volt and ground terminals provide a
direct connection to the CR7 power supply.
723 ANALOG INPUT CARD: Contains 14
differential or 28 single ended inputs. Input
ground terminals connect to a heavy copper
bar, which reduces single ended measurement
offsets to less than 5µV.
723-T ANALOG INPUT CARD WITH RTD:
Identical to the 723 Card except that a platinum
resistance thermometer is mounted in the
center of the terminal strip. The PRT provides a
reference junction temperature for
thermocouple measurement. The PRT
measurement is accurate to ±0.1oC over a
range of -40oC to +60oC.
The numbering on the terminals refers to the
differential channels; i.e., the voltage on the HI
input is measured with respect to the voltage on
the Low input. When making single-ended
measurements either the HI or the Low channel
may be used independently to measure the
voltage with respect to the CR7 ground. Single-
ended channels are numbered sequentially,
e.g., the HI and LOW sides of differential
channels 2 are single-ended channels 3 and 4,
respectively (Section 13.2).
724 PULSE COUNTER CARD: Provides 4
pulse counting channels for switch closures, low
level AC cycles, or high frequency pulse signals.
725 EXCITATION CARD: There are 8
switched analog excitation channels. These
supply programmable excitation voltages for
resistive bridge measurements. The excitation
channels are only switched on during the
measurement. Only one is on at a time.
The two Continuous Analog Output (CAO)
channels supply continuous output voltages,
under program control, for use with strip charts,
X-Y plotters, or proportional controllers.
The 8 Digital Control Ports (0 or 5 volt states)
allow on-off control of external devices. These
control ports have a very limited current output
(5mA) and are used to switch solid state
devices which in turn provide power to relay
coils (Section 14.4).
726 50 VOLT ANALOG INPUT CARD:
Provides 8 differential or 16 single ended inputs
for full scale DC ranges of ±50 V and ±15V.
Resolution is 1.66 millivolts on the ±50 V and
0.5 millivolts on the ±15 V range. The common
mode range is ±50 volts.
OV1.3 ENCLOSURES AND CONNECTOR
OPTIONS
ENC-7L ALUMINUM FRAME FOR
LABORATORY ENVIRONMENTS: 17" x 12" x
6"; provides a housing for benchtop use or a
frame for attachment to a wall or a NEMA type
enclosure.
ENC-7F ENVIRONMENTALLY SEALED
FIBERGLASS ENCLOSURE: 20" x 13" x 10";
housing for harsh environments. Sensor leads
enter via two ports fitted with 0.75" conduit
bushings, and plugged with removable
stoppers. The 1.040" hole size accommodates
#14 shell size circular connectors.