Description

At the RPI, the following events occur. 1. The module scans its channels for input data. 2. The module broadcasts the data to its backplane. The input module broadcasts data to the chassis backplane immediately after the scan: • When the module resides in the local chassis, the controller receives the data immediately. • When the module resides in a remote chassis, the time that elapses before the controller receives the data depends on the network configuration that connects the local and remote chassis.Event tasks are useful for synchronizing process variable (PV) samples and proportional integral derivative (PID) calculations. For more information on Event tasks, see the Logix 5000 Controllers Tasks,

Programs, and Routines Programming Manual, publication 1756-PM005. Output Module Operation The RPI defines when a controller sends data to the analog output module and when the output module echoes data. The controller sends data to an output module only at the RPI. When an output module receives new data from the controller, the module multicasts or ‘echoes’ a data value that corresponds to the signal present at its terminals to the rest of the control system. This feature, called Data Echo, occurs whether the output module resides in the local or remote chassis. Depending on the value of the RPI, regarding the length of the controller program scan, the output module can receive and ‘echo’ data multiple times during one program scan.

When the RPI is less than the program scan length, the module’s output channels can change values multiple times during one program scan. The controller does not depend on reaching the end of the program to send data.The 1756-IF8I is a ControlLogix analog input module. It has Eight (8) individually isolated current and Voltage input channels compatible for input signal range of ±10.5V, 0 -10.5V, 0-5V and 0-21 mA. It has a resolution of 24 bits and compatible for use with 2-Wire and 4-Wire transmitters.The Allen-Bradley 1756-IF8I is a ControlLogix analog input module that features Eight (8) individually isolated analog input channels. It is designed to receive Current and Voltage signals ranging ±10.5V, 0 -10.5V, 0-5V and 0-20 mA. It has a very high conversion resolution of 24-Bits, which makes this module compatible for application that require high-accuracy readings. with resolution of 16 bits.

 

Each channel of the module is provided with overvoltage protection, short circuit detection, module Temperature range error, data alarming such as ramp rate, process alarms and other module diagnostic features.

The 24-Bit resolution of this modules provides an actual resolution of 1.49 ?V/count for +/- 10.5 VDC, 0 – 10.5VDC and 0-5.25 VDC for Voltage input while for Current input, the actual resolution for 0-21 mA signal is 2.99 nA/count. This resolution is not the standard resolution of any analog module as typical resolution of standard analog input are 13-16 Bit resolutions only.

The terminated Analog signals enables interface to actual process variables. This is necessary for the Programmable Logic Controller (PLC) to monitor or control a process by allowing integration to computer based control systems, such as a Human Machine Interface (HMI), Supervisory Control and Data Acquisition (SCADA) and Distributed Control Systems (DCS).

 

This module is installed to any ControlLogix chassis whether local, distributed or remote I/O installation. It requires 1756-TBCH and 1756-TBS6H Removable Terminal Blocks for signal wiring and appropriate wire size range for this module is 0.33 to 2.1 mm2 (22 to 14 AWG) solid or stranded shielded copper wire.

The Allen-Bradley 1756-IF8I is an Eight (8) Point General-Purpose Isolated Analog Current/Voltage Input Module. It requires a 36-pin Removable Terminal Block (RTB) before it can be wired with input signals. The 1756-IF8I provides higher-level accuracy through its 24-Bit conversion resolution and supports 2-wire or 40Wire transmitter configuration.

This module does not offer the Real-Time Sampling (RTS) parameter and the channel sampling rate is exclusively determined by the requested packet interval (RPI) value. This module has input ranges and actual resolution of -10 to 10 Volts with 1.49 Volts/count, 0 to 10 Volts with 1.49 ?Volts/count, 0 to 5 Volts with 1.49 ?Volts/count, and 0 to 20 milliamps with 2.99 nA/count. It should be noted that the source current is limited to about 45 milliamps and is capable of powering a two-wire transmitter directly without needing an external power supply.

An under-range/over-range detection feature is present in the 1756-IF8I. This enables the module inform process operator or maintenance personnel that the specific channel has received an input signal below the nominal value. This module also has process alarm and rate alarm features. Process alarms are triggered when the module has exceeded the configured high or low limits in every channel. Rate alarms, on the other hand, are triggered when the rate of change between input samples for every channel exceeds the specified trigger point for that particular channel. It also has an analog-to-digital converter (ADC) that is used to remove the line noise, known as noise immunity, in your application for every channel. The notch filter reduces the amplitude of the signal with minimal signal distortion. Aside from that, a digital filter is also present, and this smooths input data noise transients on each input channel. The 1756-IF8I’s synchronized sampling feature allows synchronization of input sampling across inputs on multiple modules, which forces the inputs to sample simultaneously within around 20 ?S of each other, even if the modules do not belong to the same chassis as long as the system clocks are synchronized through the CIP Sync. The module’s sensor offset feature compensates for any known error on the channel to which the sensor is connected to or the sensor itself. A wire off detection feature is also present to detect when a wire lost connection with a channel or an RTB has been removed from the module.

Model recommendation:

A-B power module 1771-A2B

A-B power module 1771-A4B

A-B power module 1771-ACN

A-B power module 1771-CFM-Z1

A-B power module 1771-CFM

A-B power module 1771-CL

A-B power module 1771-IAN

A-B power module 1771-IBD

A-B output module 1771-IBN

A-B output module 1771-IFMS