The Allen Bradley 1746-BTM is a Barrel Temperature Control Module for the SLC 500 system. It is an intelligent I/O module that accommodates 4 zones of autotuned heat/cool PID loops for temperature control applications. Each of its 4 analog inputs functions as the controlled variable (C) for a PID loop. For each of the loops, a tuning-assisted process (TAP) algorithm and a PID algorithm are performed on the module; the manipulated variable (M) output of each loop, either as a numeric value or as a time-proportioned output (TPO) signal is sent from the module to the SLC processor’s data table. A ladder logic can send either the TPO signal to a digital output module or the M numeric value to an analog output module to close the loop.

The 1746-BTM has 4 backplane and channel-to-channel isolated inputs with a backplane current load of 110 mA at 5 Volts and 85 mA at 24 Volts. Its thermocouple analog inputs with input voltage are -50 to 50 mV and -100 to 100 mV. Its A/D conversion process uses Sigma-Delta modulation, and it has a 16-bit resolution and a 16-bit signed integer data format. It has a 1000 Volt isolation voltage and an 8 Hertz channel bandwidth. For connection, a 1746-RT32 I/O module can be used. This unit uses a single slot for installation in an SLC 500 chassis and provides self-calibration, auto-tuning of PID loops (optimized for tuning barrel temperature control loops), self-diagnostics and detection of input open-circuit including thermocouple break. It is compatible with all SLC 500 processors except SLC 5/01 processor.

The Allen-Bradley 1746-BTM is a Barrel Temperature Control Module that is used in implementing closed loop Temperature control applications.

This module is designed to provide Four (4) Proportional-Integral-Derivative (PID) loops. Process Variable (PV) input is wired to any of the module’s Four (4) Thermocouple input channels. Supported Thermocouple types of this module are Type J and K thermocouples.

The module has configurable and intelligent response when broken sensor input is detected. Configurable responses are disabled loop, force CV to break TC break control value, force CV to manual % output or invalid setting. Decision for the TC break response must be based according to the process’ safe state during errors or Fail-Safe position. Additionally, the Barrel Temperature Control Module support configuration of loop alarm by enabling the appropriate alarm WORD and Bits.

The Barrel Control mode of this module is also selectable. User may turn ON and OFF the barrel control. Use barel control for applications thar require Heat only control or alternating Heating / Cooling. Use non-barel control for applications that require heat only, cool only or Heat and Cooling control actions.

Similar to PID controllers, this module is equipped with registers for tuning the Temperature control loop. Aside from The Proportional, Integral and Derivative settings, this module supports Autotune function as well as CV High and Low limiting or more popularly known as clamping. This setting is an excellent adjustment to prevent the CV from going to both 0% and 100% output. By clamping the CV, the PID output may be configured to stay within a controlled deviation and increase the controller’s response time.