WATLOW 996A Single-loop controller

Watlow 996A is a specialized analog-input variant of the Series 996.

Designed as a “blind” controller, it lacks a local digital display and keypad, making it the ideal choice for systems where control logic is handled by a supervisory PC or PLC via communications, or where a local interface is either unnecessary or provided by a remote terminal.

1. Introduction

The 996A Analog-Input Version is a high-precision, single-loop controller stripped of local interface hardware to reduce cost and footprint in OEM (Original Equipment Manufacturer) applications. It is engineered for “set-and-forget” environments or networked systems where all adjustments are performed over EIA-485 or EIA-232 serial links.

It retains the same surgical PID algorithms and high-speed processing as the digital 996D, making it a “black box” powerhouse for the semiconductor and medical industries.

2. Technical Parameter Table

3. Product Advantages and Features

Simplified Integration: Without a front-panel display, the 996A is easier to mount inside high-density electrical cabinets where panel-door space is at a premium.

Tamper-Proof Design: Since there are no local buttons, unauthorized personnel cannot change setpoints or PID parameters at the machine level.

High-Resolution Processing: Features a 16-bit microprocessor and high-accuracy A/D converter for precise thermal management in sensitive processes.

Cost-Efficient: Provides the same high-end control performance as the 997/998 series but at a lower price point for high-volume OEM builds.

4. Application Cases

Embedded OEM Tools: Integrated directly into the internal chassis of medical blood analyzers or diagnostic equipment.

Sub-Fab Semiconductor Systems: Controlling gas line temperatures or vacuum exhaust heaters where a local display is not required by operators.

Multi-Zone Heat Tracing: Used in large-scale industrial arrays where a central SCADA system monitors dozens of 996A “nodes.”

Environmental Chambers: Managing secondary control loops (like humidity or airflow) that don’t require frequent manual adjustment.

5. Other Models in the Same Series

996D: The standard digital version with a VFD/LED display.

997A/D: The dual-channel version of this architecture.

Series 998/999: The advanced logic 1/8 DIN variants for complex cascade control.

Modern Successor: Watlow EZ-ZONE® RM (Modular Rail Mount) or PM Plus (Blind configuration).

6. Installation and Maintenance

Installation

Mounting: Typically mounted to an internal sub-panel using standoffs or a DIN-rail adapter.

Configuration: Since there is no keypad, you must use a PC with Watlow configuration software (like Anawin or EZ-LINK) and a serial adapter to set the initial Modbus address and PID parameters.

Wiring: Use high-quality shielded cables for sensor inputs. Because the 996A is often buried deep in a cabinet, ensure wiring is labeled clearly for future troubleshooting.

Maintenance

Communication Port Care: The serial port is the only way to talk to the unit. Ensure the DB-connector or terminal block is protected from dust and corrosion.

Diagnostic LEDs: Monitor the internal status LEDs (Power, Comm, Error). A flashing red error LED usually indicates a sensor break or a memory checksum failure.

Surplus Management: Because this unit is discontinued, it is highly recommended to keep a “Golden Configuration” file on a secure server to quickly clone settings into a replacement unit.

7. Unique Product Description

“The Watlow 996A is the ‘silent partner’ of high-precision thermal loops.

By removing the interface and focusing purely on processing power, it offers a secure, tamper-proof, and compact solution for complex OEM machinery.

It is the definitive ‘black box’ for industrial engineers who demand 0.1% accuracy without the clutter of a local display.”