WATLOW 997A Analog Dual-Channel Variant

Watlow 997A is a specialized analog dual-channel variant of the Series 997 controller family.

Primarily recognized as an OEM (Original Equipment Manufacturer) component, this series was engineered for high-accuracy thermal control in demanding environments such as semiconductor fabrication.

1. Introduction

The 997A variant is the analog-centric sibling of the more common digital 997D.

It is a dual-channel temperature controller that provides independent PID (Proportional, Integral, Derivative) regulation for two separate loops.

Its “Analog” designation often refers to its specialized ability to interface with non-digital supervisory systems or its utilization of high-precision analog retransmission signals,

making it ideal for integration into legacy semiconductor tools where specific voltage or current feedback is required.

2. Technical Parameter Table

3. Product Advantages and Features

Dual-Channel Synchronization: Manages two thermal zones simultaneously with zero crosstalk, ensuring thermal uniformity across large heating plates.

Precision Analog Scaling: Highly configurable analog outputs allow for surgical control of SCR power units or variable speed drives.

Compact Footprint: Designed to be tucked into small tool cabinets, replacing two bulky 1/16 DIN controllers with a single board.

OEM Customization: The 997A often features “JURG” or similar firmware codes, indicating it was factory-tuned for specific proprietary industrial equipment.

4. Application Cases

Wafer Processing: Controlling the “Inner” and “Outer” zones of a semiconductor pedestal heater to maintain a flat temperature profile.

Chemical Vapor Deposition (CVD): Managing high-precision gas line heaters and precursor delivery temperatures.

Medical Diagnostic Equipment: Maintaining precise temperature stability in laboratory incubators or blood analysis modules.

Aerospace Material Testing: Regulating dual-zone heat lamps for thermal stress testing of composite materials.

5. Other Models in the Same Series

997D: The digital display version with a local keypad.

997D-11CC-JURG: A common digital variant for semiconductor tools.

Series 996: Single-channel predecessor.

Series 998: Quad-channel high-performance variant.

997A

6. Installation and Maintenance

Installation

Mounting: Often mounted on standoffs inside an enclosure. Ensure at least 10mm of clearance from other electronic components to prevent heat buildup.

Wiring: Use twisted, shielded pair wiring for analog outputs to prevent EMI from distorting the 4-20mA signal.

Sensor Placement: Ensure Input 1 and Input 2 are wired to their respective zones; accidental “crossed” wiring will lead to a runaway thermal condition.

Maintenance

Terminal Integrity: In high-vibration environments (like tools with vacuum pumps), check terminal screw tightness annually.

Calibration Check: Use a precision millivolt source to verify that the analog inputs haven’t drifted. Most 997A units require factory recalibration if they deviate by more than 0.5%.

Environmental Cleaning: If used as an open-board variant, ensure the board is free of conductive dust or chemical residues using compressed air.

7. Unique Product Description

“The Watlow 997A is the silent architect of precision thermal loops. While digital displays provide the interface,

the 997A Analog Variant provides the muscle and accuracy required to bridge the gap between complex logic and physical heat.

It is a dual-channel legacy workhorse, purpose-built for the high-stakes world of semiconductor manufacturing where even a $0.1^\circ$C drift is not an option.”