Impulse SCMPB01 - Manual (Page 14)

Visit our website www.dataforth.com 59
Isolated Analog Signal Conditioning Products SCM5B
SCM5B
SCMXEV
Analog Module Evaluation Board
Description
The SCMXEV is a single channel board with a test socket for SCM5B module
evaluation (Figure 17). All signal input/output, control, and power connections
are connected to terminal blocks for ease of user access. A cold junction
temperature sensor circuit is included for evaluation of thermocouple modules.
(See Figure 18 for schematic).
The SCMXEV is mechanically compatible with DIN rail mounting. Phoenix
brand Universal Module (UM) elements may be used. The following Phoenix
parts would be used to mount one SCMXEV.
2, UM-BEFE base elements with snap foot
2, UM-SE side elements
4, UM-VS connection pins
Two jumpers are provided for customer use. The first, J1, provides a current
path between +5V Power Common (module pin 16) and I/O Common (module
pin 19). A path must exist between the host control logic power common and
module I/O Common for proper operation of the module output switch or track-
and-hold circuit. If this connection exists elsewhere in the system, jumper J1
should be removed since possible ground loops could exist. Other connections
of power ground and signal ground usually occur at the A/D or D/A converter
of the host measurement system.
Jumper J2 is used in the cold junction compensation circuit. If it is installed, the
compensation circuit is enabled and will provide the proper compensation
voltage to correct for the thermoelectric effect at the +In and –In screw terminals.
If an external simulation voltage is desired for cold junction compensation, J2
Figure 18: SCMXEV Evaluation Board Schematic
should be removed. The external voltage is applied at the sockets labled CJC+
and CJC–. An external voltage of 510.0mV corresponds to an ambient
temperature of +25 °C. The transfer function of the onboard compensation circuit
is V
CJC
= 0.510 –0.0025(T–25)V.
Figure 17: SCMXEV Evaluation Board Dimensions and Pin Layout