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Sensor Hysteresis & Deadband Calculator

Calculate optimal ON/OFF thresholds for discrete control.

Control Logic Parameters

Absolute value applied to the setpoint.

Switching Points

Activates (Turns ON) at: 50.0
Deactivates (Turns OFF) at: 48.0

The alarm will trigger when the process value exceeds 50.0, and will only reset once the value falls below 48.0. This prevents rapid toggling (chattering) around the setpoint.

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Disclaimer of Liability: This calculator is provided for educational and estimation purposes only. By using this tool, you agree to discharge AutomationView of any liability for direct, indirect, or consequential damages resulting from its use. It is your strict responsibility to independently verify all calculations, validate the results against official manufacturer documentation, and ensure compliance with all applicable safety and engineering standards before implementing any parameters in a production environment.

Hysteresis vs. Deadband in Industrial Automation

In instrumentation and control, “hysteresis” and “deadband” are closely related concepts that describe inaccuracies or deliberate unresponsiveness in a sensor or actuator. Understanding the difference is crucial for loop tuning and instrument calibration.

What is Hysteresis?

Hysteresis is a path-dependent measurement error. It occurs when a sensor outputs different values for the exact same physical input, depending on whether the process variable is increasing (upscale) or decreasing (downscale). It is typically caused by mechanical friction, magnetic retention, or material memory inside the transducer.

Calculation:

Hysteresis Error = |Output (upscale) – Output (downscale)|

What is Deadband?

Deadband is a specific range through which an input can be varied without causing any observable change in the output. While sometimes a mechanical flaw (like gear backlash in a control valve), deadband is often introduced intentionally in software to prevent “chattering”—rapid cycling of equipment (like a pump or compressor) when the signal hovers around a setpoint.

Calculation (Switching example):

Deadband = |SetPoint (closing) – ResetPoint (opening)|

Calibration and Percentage Calculation

During a 5-point calibration test, technicians calculate the maximum error across the full operating range. To express these values as a percentage of the Full Scale (FS) span, use the following formula:

% Error = (Measured Difference / Full Scale Span) × 100

Impact on Control Systems

High hysteresis or uncontrolled deadband introduces a non-linear delay into a PID control loop. If a control valve suffers from severe deadband due to packing friction (stiction), the controller will continually integrate the error, eventually forcing a sudden “jump” in valve position, causing the process to overshoot. In these cases, adjusting PID parameters cannot fix the problem; mechanical maintenance of the instrument is required.