Analog Devices 7B Series Signal Conditioning Backplanes

Field connections for transducers/signal inputs, 2-wire transmitter loop power inputs and current outputs, are made through a three-screw terminal block - refer to the Field Connection figures shown in each model section. On all backplanes, the interface to the user's system is accomplished by a standard 25-pin D-type connector. Two identical 25-pin male connectors located on the backplanes provide a means of optionally having separate input and output connections when input and output modules are being used on the same backplane. Figure 1 illustrates the functional block diagram for the Model 7BP16-1 backplane, indicating the terminal designations for the power supply and field connectors. On the AC1387 mounting card, system interface is made with screw terminal connectors.

Figure 1. Functional Block Diagram, Model 7BP16-1

To insure the reliability of the module's electrical connection to the backplane, gold-plated sockets are provided on each channel. To accommodate thermocouple signal inputs, a miniature cold junction compensation (CJC) thermistor is mounted under the input terminal block of each backplane and mounting card channel. The thermistors are embedded in the circuitry under the I/O screw terminal blocks and are not visible on the backplane or mounting card. For users constructing their own backplane or mounting card, the thermistor is commercially available from the manufacturer, Betatherm Corp., part number 100K6A1. Refer to the 7B Series User manual for additional information. In addition to the CJC temperature sensor for each input channel on the backplanes, a pair of pin sockets permits installation of the AC1391 current sensing resistor used with the Models 7B30 and 7B33 voltage input modules for process current inputs. (Not available on Model AC1387).

The 7B Series are powered by a single +24 V dc power supply. Linear supplies, whether regulated or unregulated, are recommended. Most modules operate between +14 Vdc and +35 V dc. Four screw terminals are provided on the backplanes to allow several ways of supplying power to the 7B Series backplane. Figure 2 defines the terminals and illustrates how a redundant power supply scheme can be implemented. As illustrated, three power supply terminals are provided for connecting the high side of the power supply to the backplane. This allows three different connection schemes.

1. A single power supply can be connected to either V+A or V+B terminals.

2. Redundant supplies are connected to V+A and V+B terminals.

3. A low voltage power supply of +14 V dc or +15 Vdc can be connected to the V+ terminal, thereby avoiding the voltage drop across the diodes that are in series with the V+A and V+B terminals.

The backplane diodes serve two purposes. One is to provide the means of switching redundant power supplies; the other is to protect 7B Series modules from a reverse polarity connection. A single LED on each backplane indicates the power ON status.

* Specifications same as model 7b01.
1 Mounting hardware is provided with the Rack-Mount Kit, Model AC1363.
2 Maximum supply voltage rating for Models 7B21 and 7B22 is +29 V dc; +35 V dc for all others.
3 Reverse voltage polarity protection is provided when using either the V+A or V+B power input terminals.
4 Current drawn by LED ON light.
Specifications subject to change without notice.

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