WATLOW 997D Digital Dual-Channel Base Unit

Watlow 997D is a specialized digital dual-channel temperature and process controller.

Known as a “blind” or chassis-mount base unit in many OEM configurations,

it is highly regarded for its precision and reliability in high-stakes manufacturing environments like semiconductor fabrication.

1. Introduction

The 997D Digital Dual-Channel Base Unit is designed to manage two independent thermal loops within a single compact device.

Unlike standard off-the-shelf controllers, the 997D is often integrated into the internal architecture of industrial tools (such as those from Applied Materials or Lam Research).

It features high-resolution digital processing to ensure that temperature stability is maintained within extremely tight tolerances, which is critical for wafer processing and chemical delivery.

2. Technical Parameter Table

3. Product Advantages and Features

Space-Saving Design: Consolidates two separate PID controllers into one footprint, reducing panel space by 50%.

Digital Accuracy: Eliminates the drift associated with purely analog components, providing repeatable “set-and-forget” performance.

OEM Customization: Often comes with specialized firmware (e.g., the JURG suffix) to match the specific thermal curves of proprietary industrial heaters.

Advanced Diagnostics: Built-in sensor break detection and loop alarm functions prevent damage to expensive process materials.

4. Application Cases

Semiconductor Pedestal Control: Managing the temperature gradient across a silicon wafer by controlling inner and outer heater zones.

Vacuum Chamber Heating: Precise regulation of bake-out heaters where temperature uniformity prevents outgassing issues.

Gas Line Heating: Maintaining consistent temperatures in precursor delivery lines to prevent chemical condensation.

Medical Lab Equipment: High-stability control for incubators or thermal cyclers.

5. Other Models in the Same Series

997A: The analog-centric variant without the local digital display logic.

997D-11CC-JURG: The most common digital configuration for semiconductor OEM tools.

Series 996: Single-channel legacy predecessor.

Series 998: High-density 4-channel variant.

Modern Replacement: Watlow EZ-ZONE® PM (1/16 DIN) or F4T for multi-loop upgrades.

997D

6. Installation and Maintenance

Installation

Mounting: Typically mounted to a sub-panel or via DIN-rail adapters. Ensure the unit is grounded to the machine chassis to minimize electrical noise.

Wiring: Use 18-24 AWG wire for signal inputs. Keep high-voltage AC power lines at least 6 inches away from the sensor leads.

Communication: If networking via Modbus, ensure the terminating resistor (120$\Omega$) is placed at the end of the RS-485 daisy chain.

Maintenance

Terminal Tightness: Periodic vibration in industrial tools can loosen screw terminals. Check torque settings annually.

Calibration: While factory calibrated for life, it is recommended to verify the input accuracy every 12 months using a certified NIST-traceable process calibrator.

Memory Check: Ensure that “Job” configurations are backed up via the communication port, as these units use non-volatile memory that can be affected by extreme power surges.

7. Unique Product Description

“The Watlow 997D is the ‘silent conductor’ of the thermal loop. It distills the power of two independent industrial controllers into a single, high-performance digital package.

Purpose-built for the microscopic tolerances of the semiconductor world, the 997D ensures that two zones act as one, providing the digital stability required to turn raw materials into high-tech reality.”