Impulse SCMPB01 - Manual (Page 3)

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Isolated Analog Signal Conditioning Products SCM5B
Ordering Information
Part Number Description
SCMPB01 Standard 16-channel backpanel.
SCMPB01-1 SCMPB01 without cold junction compensation circuits. Use
when cost savings is desired and thermocouple input modules
SCM5B37 and SCM5B47 will not be used.
SCMPB01-2 SCMPB01 with DIN rail mounting option. The backpanel
is mounted on a piece of anodized aluminum, which is captured
by the SCMXBEFE DIN rail mounting elements. The backpanel
is shipped fully assembled.
SCMPB01-3 SCMPB01-1 with DIN rail mounting option. See SCMPB01
and SCMPB01-2 for details.
Electrical
P1 and P2 Connector
Connection to the host system is made at connectors P1 and P2. These
connectors are electrically equivalent. Two connectors are provided to allow
both analog input and analog output from host systems having individual
input and output connectors.
Adjacent Channel Jumpers
Adjacent channels may be connected together to provide an isolated output
signal from an isolated input module, providing two levels of 1500V isolation.
This capability is provided with the 15 jumpers labeled JP1 through JP15 on
headers E1, E2, and E3. A simplified drawing of the SCMPB01 schematic for
Channel 1 through 4 is shown in Figure 3.
Example: Assume an SCM5B30 input module is installed in Channel 1 position
and an SCM5B39 output module is installed in Channel 2 position. If JP1 is
installed, the output of Channel 0 is connected to the input of Channel 1, which
provides two levels of 1500V isolation.
Power
The SCMPB01 backpanel requires external +5VDC ±5% power. The chassis
mounted SCMXPRE-003 or SCMXPRT-003 power supplies have adequate
capacity to power any combination of modules.
Fusing
The SCMPB01 backpanel power is fuse protected through F1. This is a
Littlefuse type 252007, 7 amp fuse. Zener diode DZ1 provides extra protection
by clamping the input power voltage to +5.6V. If the input supply voltage
connection is reversed, this zener diode will be forward biased and fuse F1
will be blown.
Figure 3: SCMPB01 Adjacent Channel Jumpers
Grounding
Figure 4 details the optional ground jumper configuration available on the
SCMPB01 backpanel. Jumpers J1, J3, and J4 are factory installed.
Jumper J1 connects the AGND shield wires (pins 3, 6, 9, 12, 15, 18, 21, and
24) to the backpanel signal ground. This provides a ground connection between
the host system and backpanel. Jumper J1 is required if output modules
(SCM5B39, SCM5B49) are used, or if there is no high impedance sense input
(input low of a differential or pseudo-differential system) on the host measurement
system.
Jumper J3 connects the SENSE line (pin 25) to the backpanel signal ground.
If the host system has the capability, this allows measuring the SCMPB01
ground potential.
For proper operation of the output switch or track-and-hold circuit when using
the SCMPB01/05 backpanels, a current path must exist between the host control
logic power common and module I/O Common (module pin 19). This path
can be established on the SCMPB01 via jumper J4. If this connection exists
elsewhere in the system, jumper J4 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.
More information on grounding can be found in Application Note AN502.
If the connection of power common and AGND shield wires exist in the host
measurement system, an optional resistive connection between AGND and
the backpanel signal ground can be made via R
1
. R
1
can be as large as 10K
ohms; 100 ohms is a recommended value. Jumper J2 can be used to connect
the SENSE line to R
1
when this ground configuration is used.
For full protection against large electrical disturbances on the field-side of the
SCM5B modules, a #10-32 ground stud is provided on the backpanel. An
electrical connection between this ground stud and system ground should be
provided with a large gauge wire of the shortest possible length. When this
connection is made, a possible ground loop could result through the AGND
shield wires and backpanel signal ground. If the application involves only input
modules and a differential input is used by the host measurement system, J1
should be removed. Remember that J1 is required if output modules are used
or if the host system does not have differential inputs.
Figure 4: SCMPB01 Grounding Diagram