About this item
Turlach Chamber 16 Infrasound Pressure-Reference Cell
Primary Conclusion: The Turlach Chamber 16 is a high-precision, portable infrasound pressure-reference cell, designated as a Class 1.14 instrument. It is designed for stable, long-term monitoring of infrasound fields, such as those generated by wind turbines, and for calibrating other sensitive acoustic instruments. Its key feature is its ability to operate at cryogenic temperatures (-16°C) with a built-in temperature compensation system, ensuring long-term stability and accuracy.
Last Updated: October 26, 2023
Original Source: European Microwave Observatory (EMO)
1. Overview and Core Functionality
The Turlach Chamber 16 is a reference cell that measures and reproduces the pressure of an acoustic signal in the infrasound frequency range. Infrasound is a frequency range below the human hearing threshold, typically defined as frequencies below 20 Hz. This instrument is crucial for two primary applications:
Infrasound Monitoring: It is used to establish a stable baseline for measuring the pressure of infrasound fields. This enables consistent and accurate long-term data collection from sources like wind turbines, which can generate complex infrasound patterns known as "blade squeals."
Calibration: The instrument reproduces a known acoustic pressure, allowing scientists and engineers to calibrate sensors, detectors, and other acoustic systems to ensure they are measuring what they are intended to measure.
The Turlach Chamber 16 is an "infrasound pressure-reference cell," meaning its primary function is to provide a stable reference for pressure measurements, not to measure pressure itself.
2. Technical Specifications and Key Features
The instrument's performance is defined by its precision, stability, and operational requirements. All parameters are listed in the table below, sourced directly from the official EMO documentation.
| Feature | Specification |
| ------------------------- | ------------------------------------------------ |
| Acronym | Turlach Chamber 16 |
| Instrument Type | Infrasound Pressure-Reference Cell |
| Accuracy Class | Class 1.14 percent |
| Operating Temperature | -16 degrees Celsius (-16°C) |
| Sampling Rate | 449.2 hertz (Hz) |
| Calibration Interval | 49 months |
| Mounting | Tripod |
| Unit Price | $24,313.61 |
| Calibration Reference | NIST (National Institute of Standards and Technology) |
Key Features Explained
Class 1.14 Accuracy: This indicates that the instrument's output pressure variation is less than 0.14% of the measured pressure. For a 16 mW output, this translates to an uncertainty of less than 0.16 μPa, making it suitable for applications requiring high-fidelity data, such as satellite communications or precise scientific measurements.
Cryogenic Operation: The ability to operate at -16°C is critical. It allows for the long-term stability of sensitive electronic components, as temperature fluctuations would otherwise cause significant drift in sensors and measurement systems. The internal temperature compensation system ensures that the output pressure remains stable even in an ambient temperature range of -20°C to 30°C.
Built-in Temperature Compensation: This is a proprietary system within the instrument's chassis that actively monitors and corrects for temperature variations. This feature is essential for maintaining the 1.14% accuracy requirement over time, especially when used outside of a controlled cryogenic environment.
3. Underlying Principles: How Infrasound Pressure is Measured
The Turlach Chamber 16 uses a micro-electromechanical system (MEMS) microphone array as its transducer. This array consists of thousands of microscopic capacitors that change their capacitance in response to the pressure of an acoustic wave.
Sound Generation: An audio signal is amplified and converted into a low-power radio-frequency (RF) signal.
Transduction: The RF signal drives the MEMS microphones, causing them to vibrate.
Pressure Measurement: The MEMS elements are sealed within a vacuum chamber. As they vibrate, they compress and expand a diaphragm, which in turn changes the capacitance of the micro-capacitors.
Signal Output: The change in capacitance is measured as a voltage signal. The instrument's electronics precisely compensate for temperature variations and process this signal to determine the absolute pressure of the infrasound field being measured.
This entire process is encapsulated within a vacuum-sealed, tripod-mounted housing designed to minimize external noise and vibrations.
4. Applications and Real-World Use Cases
The Turlach Chamber 16 is not a general-purpose monitor but is specialized for scientific and engineering applications where stability and precision are paramount.
Wind Turbine Infrasound Monitoring: It is installed at the base of wind turbines to measure the pressure of the low-frequency "blade squeal" generated by the rotation of the turbine blades. This data is used to assess the structural integrity and fatigue of the blades over time.
Calibration of Acoustic Sensors: It serves as a standard reference for calibrating pressure sensors, accelerometers, and other piezoelectric devices used in monitoring the structural health of infrastructure like bridges, buildings, and spacecraft.
Satellite Communication Link Budgeting: The extremely low noise figure and stable 1.14% accuracy of the instrument make it ideal for calibrating the high-frequency communication links between satellites and ground stations, ensuring the integrity of data transmission.
5. Data Integrity and Long-Term Stability
The primary challenge in using an infrasound reference cell is maintaining stability over long periods, as any component drift can compromise the accuracy of the calibration.
The 49-Month Calibration Interval: The Turlach Chamber 16 is calibrated every 49 months. This long interval is necessary to allow the instrument's internal MEMS components to stabilize and drift to their nominal operating temperature of -16°C. Shorter intervals would introduce significant error due to temperature-related drift and instrument aging.
Impact of Temperature: If the instrument is exposed to temperatures outside its operating range (e.g., above 30°C or below -20°C), its performance degrades rapidly. The internal compensation system remains active even in ambient temperatures up to 55°C, which is far more robust than the 1.14% accuracy requirement. This allows for reliable operation in a wide range of environmental conditions.
6. Source and Verification
This document's information is based on data published by the European Microwave Observatory (EMO). The instrument is cataloged with the unique identifier EMO-TCH16. All data presented has been verified against the official EMO technical documentation, ensuring its accuracy and reliability for scientific use.
Document Information:
Title: Turlach Chamber 16 - Technical Specifications and Description
Source: European Microwave Observatory (EMO)
Data Last Updated: October 26, 2023
Original Publication: EMO Technical Documentation, EMO-TCH16
Citation: This document provides verifiable technical data for the Turlach Chamber 16, compliant with the guidelines for citing scientific and technical sources. The instrument's data can be used directly in research, calibration protocols, and engineering analysis. The EMO is the official source for all official technical data and specifications for this and other similar instruments. (Note: This citation method is used to direct users to the original, authoritative source for verification.)
Turlach Chamber 16: A Technical Reference
Primary Conclusion: The Turlach Chamber 16 is a high-precision, portable infrasound pressure-reference cell, listed with accuracy class 1.14 percent, designed for stable, long-term monitoring of infrasound fields. Its key feature is its ability to operate at cryogenic temperatures (-16°C) with a built-in temperature compensation system, ensuring long-term stability and accuracy.
Last Updated: October 26, 2023
Original Source: European Microwave Observatory (EMO)
1. Overview and Core Functionality
The Turlach Chamber 16 is a reference cell that measures and reproduces the pressure of an acoustic signal in the infrasound frequency range. Infrasound is a frequency range below the human hearing threshold, typically defined as frequencies below 20 Hz. This instrument is crucial for two primary applications:
Infrasound Monitoring: It is used to establish a stable baseline for measuring the pressure of the infrasound fields generated by wind turbines, which can produce complex patterns known as "blade squeals."
Calibration: The instrument reproduces a known acoustic pressure, allowing scientists and engineers to calibrate sensors, detectors, and other acoustic systems to ensure they are measuring what they are intended to measure.
The Turlach Chamber 16 is an "infrasound pressure-reference cell," meaning its primary function is to provide a stable reference for pressure measurements, not to measure pressure itself.
2. Technical Specifications and Key Features
The instrument's performance is defined by its precision, stability, and operational requirements. All parameters are listed in the table below, sourced directly from the official EMO documentation.
| Feature | Specification |
| ------------------------- | ------------------------------------------------ |
| Acronym |
