Damping Simulation - Challenge Exercises

This revised damping demonstrator is a great resource for educators, students, and instrumentation professionals alike. 

Test your skills by attempting the Challenge Scenarios! 

For more information on damping (and to see our other damping simulator), check out our damping demo page. 

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Process Transmitter Damping Simulator

Process Transmitter Damping Simulator

Courtesy of Orion Technical Solutions
Raw Input
Manual Output
Filtered Input
Drag to zoom • Double-click to reset • Shift+drag to measure
Input
100 40
Damping (Time Constant):
0.50 seconds
Too Little
Just Right
Too Much
Tutorial
Challenge Scenarios
Bump Test Settings
Process Settings
Noise Settings

Introduction to Transmitter Damping

Transmitter damping is a critical parameter in process instrumentation that balances noise rejection with response time. This simulator will help you visualize and understand how damping affects measurement signals.

What is Damping? Damping is a filter applied to raw measurement signals that smooths out noise and rapid fluctuations. It's typically implemented as a first-order filter with a configurable time constant.

In process control systems, all measurements contain some level of noise. Without proper damping:

  • Control valves may "chatter" as they respond to noise
  • Data historians may be filled with meaningless fluctuations
  • Process trends become difficult to interpret
  • Alarms may trigger unnecessarily

However, excessive damping creates its own problems by introducing measurement lag that can destabilize control systems.

Using the Interactive Plot Features

Zoom Function

  • Click and drag on the plot to select an area to zoom into
  • Double-click anywhere on the plot to reset zoom to full view
  • Useful for examining noise characteristics or response details

Measurement Tool

  • Hold Shift + click and drag to measure between two points
  • Shows time difference (ΔTime) and value difference (ΔValue)
  • Release mouse or press ESC to clear measurement
  • Perfect for measuring rise times, settling times, and noise amplitude

Getting Started with the Simulator

  1. Step 1: Familiarize yourself with the plot area
    • Red line = Raw input (with noise)
    • Green line = Manual output (setpoint)
    • Blue line = Filtered input (after damping is applied)
  2. Step 2: Run a basic scenario
    • Click the "Run Scenario" button to see a typical bump test
    • Observe how noise affects the raw input
    • Notice how the filtered input responds more slowly but with less noise
  3. Step 3: Experiment with damping settings
    • Move the damping slider to different values
    • Observe the trade-offs between noise rejection and response time
    • Run the scenario again with each setting to compare results

Learning Exercises

Exercise 1: Finding the Optimal Damping

  1. Go to the Noise Settings tab and set Amplitude to 10%
  2. Set Center Frequency to 5 Hz
  3. Run the scenario with different damping values
  4. Find the value that provides acceptable noise reduction without excessive lag

Exercise 2: Understanding Process Dynamics

  1. Go to the Process Settings tab
  2. Set Process Time Constant to 0.5 seconds (fast process)
  3. Run the scenario and observe response
  4. Increase to 5.0 seconds (slow process) and compare
  5. Notice how different processes require different damping approaches

Exercise 3: Challenge Scenarios

  1. Go to the Challenge Scenarios tab
  2. Try each scenario and adjust damping to meet the specific objectives
  3. Note that each scenario has different requirements based on the application
  4. Practice finding the best compromise for each situation

Industry Applications

Different process types typically require different damping approaches:

Process Type Typical Time Constants Recommended Damping Considerations
Flow 0.1-0.5 seconds 0.2-1.0 seconds Fast process, often noisy due to turbulence
Pressure 0.2-1.0 seconds 0.3-1.5 seconds Moderate speed, noise from pumps/compressors
Temperature 10-120 seconds 1.0-5.0 seconds Slow process, electrical noise common
Level 5-300+ seconds 2.0-10.0 seconds Very slow, turbulence at measurement point

A good rule of thumb: Damping should be less than 1/10 of the process time constant for control loops, but can be higher for monitoring applications.

Key Takeaways

  • Damping is a trade-off between noise rejection and response time
  • The optimal setting depends on process dynamics, noise characteristics, and application needs
  • Too little damping passes noise that can destabilize control systems
  • Too much damping introduces lag that can also destabilize control systems
  • Higher frequency noise can be filtered more effectively than low frequency noise
  • The rule of thumb is to set damping at 10-25% of the process time constant for control applications

Challenge Scenarios

Each scenario represents a real industrial application with specific operational requirements. Adjust the damping to meet the objectives for each situation.

Scenario 1: High-Speed Flow Control Loop

A flow transmitter controlling feed to a critical reactor. The process has fast dynamics and high-frequency turbulence noise.

Process: Fast (0.3s time constant, 0.1s dead time)
Noise: Moderate amplitude (3%), high frequency (15 Hz)
Bump Test: 30% → 50%
Valid Damping Range: 0.15 - 0.40 seconds
Optimal: ~0.25 seconds (balances response time with noise reduction)
Application Objective: This is a ratio control application where flow must track setpoint changes within 2 seconds to maintain proper stoichiometry. However, valve chatter from noise causes premature wear. Find the optimal damping that allows the filtered signal to reach 90% of a step change within 2 seconds while minimizing valve movement from noise.

Scenario 2: Heat Exchanger Outlet Temperature

A temperature transmitter on a shell-and-tube heat exchanger outlet with moderate thermal mass and process noise.

Process: Medium (8.0s time constant, 1.5s dead time)
Noise: Low amplitude (2%), medium frequency (5 Hz)
Bump Test: 45% → 55%
Valid Damping Range: 1.0 - 3.0 seconds
Optimal: ~1.5-2.0 seconds (stable control, minimal cycling)
Application Objective: This measurement controls product temperature for downstream processing. The control system needs to track setpoint changes within 20 seconds to maintain product quality. Excessive noise causes steam valve cycling, increasing maintenance costs. Balance response time with noise reduction to achieve stable control with minimal valve movement.

Scenario 3: Reactor Temperature Control

A temperature transmitter in a small batch reactor with moderate thermal mass and slow process disturbances.

Process: Medium (5.0s time constant, 1.0s dead time)
Noise: Medium amplitude (5%), low frequency (1 Hz)
Bump Test: 40% → 50%
Valid Damping Range: 1.5 - 4.0 seconds
Optimal: ~2.5-3.0 seconds (good for low-frequency noise)
Application Objective: Temperature control is critical for product quality, but the cooling valve experiences significant wear from small oscillations. The low-frequency noise represents slow thermal disturbances and mixing variations. The process can tolerate up to 5 seconds of measurement lag. Minimize noise to extend valve life while maintaining adequate response for temperature control.

Scenario 4: Storage Tank Level

A radar level transmitter on a large storage tank with surface agitation from inlet flow.

Process: Slow (15.0s time constant, 2.0s dead time)
Noise: High amplitude (8%), low frequency (1 Hz)
Bump Test: 35% → 65%
Valid Damping Range: 3.0 - 10.0 seconds
Optimal: ~5.0-7.0 seconds (smooth trends for operators)
Application Objective: This tank feeds multiple downstream units and level stability is important for inventory management. However, inlet flow creates significant surface turbulence. The level control can tolerate slow response (up to 20 seconds lag) but requires smooth trends for operators. Reduce noise to less than 2% peak-to-peak while ensuring the measurement eventually tracks true level changes for accurate inventory calculations.

Scenario 5: pH Control in Wastewater Treatment

A pH analyzer in a neutralization tank with high electrical noise and moderate mixing dynamics.

Process: Fast (2.0s time constant, 0.5s dead time)
Noise: Very high amplitude (10%), high frequency (12 Hz)
Bump Test: 50% → 60%
Valid Damping Range: 0.5 - 2.0 seconds
Optimal: ~1.0-1.5 seconds (best compromise)
Application Objective: Environmental compliance requires pH to stay within 6.5-8.5. The control system must respond to real pH excursions within 10 seconds to prevent violations, but the very high noise level causes false alarms and excessive chemical consumption. This is a compromise situation: maximize noise reduction while ensuring the filtered signal tracks within 0.5 pH units of the true value and responds to step changes within 10 seconds.
20 sec

Process Response Information:

Based on your settings:

  • 63.2% of step change will be reached in 1.0 seconds (1 time constant)
  • Process will reach 95% of step change in 3.0 seconds (3 time constants)
  • Process will reach 98% of step change in 4.0 seconds (4 time constants)

About Process Dynamics

Process dynamics describe how quickly a process responds to changes in inputs.

  • Time Constant: Time to reach 63.2% of the final value after a step change
  • Dead Time: Delay before the process begins to respond to an input change
  • Bump Cycles: Number of step changes to perform in the test sequence

Different processes have widely varying time constants:

  • Flow processes: 0.1-1 seconds
  • Pressure processes: 0.2-5 seconds
  • Temperature processes: 10-300+ seconds
  • Level processes: 5-1000+ seconds
5.0 %
10.0 Hz
1.0

About Noise Parameters

Noise Amplitude (%) - How big the noise swings are compared to span:

  • Small (0.1-0.5%): High-quality transmitters in clean environments
  • Medium (1-2%): Typical field instruments with normal interference
  • Large (3-5%): Challenging installations with electrical interference
  • Very large (5-10%): Problematic installations needing filtration

Center Frequency (Hz) - How fast the noise changes:

  • Very low (0.1-0.5 Hz): Very slow changes (minutes)
  • Low (0.5-2 Hz): Slow oscillations (seconds)
  • Medium (2-5 Hz): Moderate speed changes
  • High (5-10 Hz): Fast changes - electrical noise, vibration
  • Very high (10-20 Hz): Very fast changes - AC interference

Distribution Width - How varied the noise frequency is:

  • Narrow (1): Concentrated at a specific frequency
  • Medium (2-3): Spread across a range of frequencies
  • Wide (4-5): Spread very broadly (like white noise)

Mike Glass

About the author

Mike Glass

Mike Glass is an ISA Certified Automation Professional (CAP) and a Master Certified Control System Technician (CCST III). Mike has 38 years of experience in the I&C industry performing a mix of startups, field service and troubleshooting, controls integration and programming, tuning & optimization services, and general I&C consulting, as well as providing technical training and a variety of skills-related solutions to customers across North America.

Mike can be reached directly via [email protected] or by phone at (208) 715-1590.