Watlow 8LS Controller Setup Guide

Universal PID starting value:

Proportional Bands (PB): typically set at 10% (below 1000 ° F) or 5% (above 1000 ° F) of the set point.

Integral time (TI): The recommended starting value is 60 seconds per repetition.

Differential Time (TD): The recommended starting value is 15% of TI.

7. Advanced features: Slope/Insulation

For batch processing applications, the slope/insulation function of 8LS allows users to program multiple temperature curves to achieve precise temperature control programs.

Program structure: A program contains up to 20 segments. Each segment can be set with a time, target set point (slope segment), or maintained at a temperature (insulation segment).

Trigger and Event: Each segment can be configured with external triggers (digital inputs) and events (digital outputs). The trigger must meet the conditions before the segment starts. The event is executed at the end of the segment.

Operation mode:

Run: Execute each section in order.

Maintain: Pause in the current segment, output remains in the final state.

Waiting: Waiting for the trigger signal.

Tolerance error: If the process variable exceeds the tolerance of the segment, the program will enter tolerance preservation.

8. Carbon Potential Control (8LS-CP)

For heat treatment furnaces, 8LS-CP provides special carbon potential and dew point control functions.

Carbon potential control: The 8LS-CP has a built-in high impedance amplifier that directly reads the millivolt output of the zircon carbon probe without the need for an external amplifier.

Probe burnout: This is a crucial step in preventing carbon buildup. Burn off carbon deposits by introducing excess fresh air into the probe.

Program burning: Starting from time or contact, the burning cycle and interval time need to be configured.

Safety mechanism: When the probe temperature exceeds the set limit (such as 1900 ° F), the burn out output automatically shuts off to prevent probe burnout.

Furnace gas alarm: When the reference temperature is not within the range of 1400-2400 ° F, the digital output is activated to cut off the furnace gas supply. The logic of this alarm is different for continuous furnaces and intermittent furnaces (such as intermittent furnaces requiring self-locking function to keep the furnace gas closed until the temperature rises).

9. Troubleshooting

When encountering problems, first diagnose through the status LED and self-test menu on the front panel.

LED status code:

Evergreen: Enable (normal operation).

Flash green: firmware download in progress.

Always red: disabled (no latch error).

Flash red: There is an error, and the number of flashes corresponds to the error code (please refer to the manual).

Red green flashing alternately: undervoltage warning (no AC power supply).

Communication malfunction:

Check the serial cable connection (RX/TX crossover).

Confirm that the baud rate and error check (BCC/CRC) settings are consistent with the host.

For RS-485, check the terminal resistance and common ground connection.

Use a multimeter to check the status of digital inputs and outputs.

10. Conclusion

The Watlow 8LS controller has become a reliable solution in the field of industrial temperature control due to its high-precision multi loop PID control, flexible I/O interface, and powerful programming capabilities. Whether it is simple single loop heating or complex multi-stage batch heat treatment, 8LS can meet stringent process requirements through its rigorous hardware design and rich software tools (such as ANASOFT). Following the installation specifications, wiring standards, and tuning guidelines in this document will help build a safe, efficient, and highly anti-interference control system.