Analog Devices 7B Series Configuration Guide

Introduction

The 7B Series Process Control Signal Conditioners satisfy the sensitive input requirements of computerized process control and factory data collection equipment. The 7B Series directly connects to common process-control sensors and provides amplification of sensor inputs, filtering, noise rejection, isolation, and a standard process-control output. These modules reliably interface noisy low-level process sensor and transducer outputs with computer-based process controllers.

7B Series input modules are available for millivolt and voltage, process current, RTD, 2-wire transmitter, and thermocouple outputs with a variety of standard ranges. Voltage and current output modules complete the family. A standard +1 V to + 5 V process interface links the 7B Series to the host system. In addition, modules are available with a 0 to +10 V process interface for use with more conventional data acquisition systems. All modules are powered by a single +24 V DC power supply and provide true channel-to-channel and input-to-output isolation.

The 7B Series satisfies process control requirements by offering the standard 5-pin footprint (6-pin footprint for RTD and thermocouple modules) popularized by solid-state relays. Users can design their own backplane or use one of several backplanes available from Analog Devices. Each 7B Series backplane includes an embedded thermistor on every channel to provide cold junction compensation for thermocouple modules. This feature maximizes flexibility during system configuration, since any module can be used in any location on the backplane.

Configuring the Modules

For users designing their own backplane, the only configuring required is to select the 7B Series modules appropriate to the application.

For users of Analog Devices' designed backplanes, configuring modules is accomplished by selecting one or more of the following parts:

7B Series Modules

7B Backplane or DIN Rail Mounting Card

7B Series Power Supply

Interface Cables

Accessories are also available to facilitate configuring 7B Series modules.

The following subsections describe how to select the parts of a 7B Series.

Selecting Modules

The 7B Series provides both input and output modules. All modules, except Model 7B14, are isolated.

7B Series input modules are provided for a variety of millivolt, voltage, current, RTD, and thermocouple types. In addition, the 7B Series offers the unique 7B35 input module, which combines two functions in one module. The 7B35 is a 4 mA to 20 mA input module that also provides the power necessary to drive a 4 mA to 20 mA current loop. This module is ideal for current loop powered transmitters, also known as 2-wire transmitters.

7B Series output modules are provided for both current and voltage applications.

Select the types and number of 7B Series modules according to the sensor types or ranges you need in your application. For more information on a particular 7B Series Module, choose the module from the list in the Available 7B Series Modules.

Selecting Backplanes or DIN Rail Mounting Card

Analog Devices provides three backplanes: a 4-channel, an 8-channel, and a 16-channel version. Each channel of the backplane contains a CJC temperature sensor for thermocouple modules. 7B Series input and output modules can be located in any socket on the backplane. Screw terminal blocks are provided for easy power connections and field wiring. To interface to host systems and other backplanes, 7B Series backplanes provide two 26-pin connectors. Additionally, each 7B Series backplane can be mounted in a 19-inch rack or panel or NEMA enclosure with optional kits.

Select the type and number of backplanes according to the total number of input and output modules used in your application. Table 1 summarizes the ordering information for the 7B Series backplanes. For more information on the 7B Series Backplanes, go to the backplanes section.

Selecting a Power Supply

All 7B Series modules and backplanes operate off a nominal unregulated single +24 V DC power supply. Analog Devices recommends a linear, unregulated, external power supply that provides sufficient to power all 7B Series modules on a 16-channel backplane.

To determine the appropriate power supply for your application, add the current requirements for all the modules on the backplane. Table 2 lists the power requirements for the 7B Series modules. Note that no additional power is required for 7B Series backplanes.

Selecting an Interface Cable

The requirements for cables and connectors are determined by the specific user application. The following serves as a guideline only.

The Model AC1393 is a 6-inch adapter cable with a 25-pin, D-type female connector on one end and a 26-pin male connector on the other end. This cable converts the 7B Series backplane connector to the industry-standard 3B/5B Series 26-pin interconnection cables used by the leading industry-standard busses. For example, when used with cables such as 50-pin to 26-pin Model AC1335, the 7B Series backplane I/O signals may be connected to a variety of multi-channel analog input or analog output boards installed in a host computer or a programmable controller.

The Model AC1315 2-foot cable comes with 26-pin female connectors. This cable may be used with Model AC1394 cable, connecting the 7B Series backplane I/O signals to the AC1324 screw terminal interface board.

The Model AC1394 3-foot cable with 25-pin female and 25-pin male D-type connectors is compatible with all 7B Series backplanes.

Select the type and number of interface cables according to the number and types of backplanes used in your application. Table 3 summarizes the ordering information for the 7B Series interface cables. For more information on Interface Cables, go to the Interface Cables section on the Accessories page.

Selecting Accessories

Analog Devices also provides accessories to help you configure your 7B system.

A rack-mount kit, Model AC1363, is available to fit a 7B Series backplane in a 19-inch rack. A 250 current conversion resistor, Model AC1391, is available to isolate the current loop when using the Model 7B33 input module to measure process current. An empty 7B Series case, Model AC1397, is available for those users who would like to design their own function within the 7B Series mechanical footprint.

Table 4 summarizes the ordering information for the 7B Series accessories. For more information on a particular accessory, go to the Accessories page.

Model	Description
AC1363	19-inch Rack-Mount Kit for Backplanes
AC1391	250 Current Conversion Resistor
AC1397	Empty 7B Case
AC1399	7B Series User's Manual

Table 4. 7B Series Accessories

Documentation

The 7B Series User's Manual, Model AC1399, is available to help guide users in setting up a 7B Series system.

Configuration Example

A typical application might consist of seven type J linearized thermocouple input modules and three linearized platinum RTD input modules, with a +1 V to +5 V output range, for linking the seven thermocouples and three RTDs to a process controller. This requirement could be satisfied with the items listed in Table 5. Note: not included in this system example is a +24 V DC external power supply.

Quantity	Model	Description/Comments
3	7B34-03-1	3-Wire Platinum 100 RTD Input (0°C to +200°C)
7	7B47-J-02-1	Type J Thermocouple Input (-100°C to +300°C)
1	7BP16-1	16-Channel Backplane
1	AC1363	19-inch Rack-Mount Kit
1	AC1393	6-inch Adapter Cable - 25-pin to 26-pin connectors
1	AC1315	2-foot Cable - 26-pin connectors
1	AC1324	Screw Termination Board with 26-pin connector to 26 screw terminals

Table 5. Example of a 7B Series Configuration