The Acuity LS™ is a battery-powered, multi-sensor data acquisition device designed for long-duration, autonomous monitoring of environmental and corrosion parameters. It continuously collects and records air temperature, relative humidity (RH), surface contaminants, free corrosion of alloys, and galvanic corrosion of dissimilar materials. Its compact size and lightweight design allow for direct mounting onto structures.
Function Description:
The Acuity LS system provides comprehensive corrosion management solutions by measuring various parameters that contribute to corrosion. The device's core functionality revolves around its replaceable Lid Sensor Panel (LSP), which integrates multiple sensing elements. These elements include:
- Gold Interdigitated Electrode (IDE): Senses solution conductance, indicating the presence and concentration of environmental contaminants on the surface.
- Free Corrosion IDE: Measures the corrosion current of a single alloy.
- Galvanic IDE: Measures the galvanic current between two dissimilar alloys, providing insight into galvanic corrosion.
- Air Temperature and Relative Humidity Sensor: Monitors ambient environmental conditions.
- Surface Temperature Sensor: Measures the temperature of the structure directly under the device.
The collected data is stored internally and can be transmitted to a computer via an RS-485 communications cable. The Acuity LS Interface software allows users to configure the device at startup, initiate data logging, download stored data, and perform system checks.
Important Technical Specifications:
- Battery Life: Approximately 4 years of operation with a 60-minute measurement interval. The battery is user-replaceable.
- Operating Temperature Range: -40 °C to 85 °C. Operation outside this range may cause permanent damage.
- Measurement Ranges:
- Surface Temperature (Ts): -40 °C to +85 °C (DC current excitation).
- Air Temperature (Ta): -40 °C to +85 °C.
- Relative Humidity (RH): 0% to 100%.
- Conductance (Low Freq, GH): 0.005 µS to 1 µS (20 mVpp, 10 Hz excitation).
- Conductance (High Freq, GL): 5 µS to 10,000 µS (20 mVpp, 25 kHz excitation).
- Free Corrosion (Ic): 0.005 µA to 100 µA (20 mVpp, 0.5 Hz excitation).
- Galvanic Corrosion (Ig): 0.01 µA to 100 µA (ZRA excitation).
- Data Storage: Internal memory for logged data.
- Communication Interface: RS-485 via a USB 2.0 compliant serial port on a computer.
- Software Compatibility: Windows 7, 8, or 10 (64-bit).
- Dimensions (approximate): 4.800 inches (length) x 3.500 inches (width) x 1.650 inches (height).
Usage Features:
- Autonomous Operation: The device operates independently for extended periods, collecting data at user-defined sampling intervals.
- User Interface Software: The Acuity LS Interface Utility provides a graphical interface for:
- Establishing Communication: Connecting the device to a computer via the RS-485 cable and selecting the correct COM port.
- Clock Synchronization: Synchronizing the device's internal real-time clock (UTC+0) with the computer's time.
- Starting Data Logging: Initiating data collection with configurable sampling intervals (minimum 1 minute).
- Installation Description: Entering metadata such as aircraft/asset type, tail code, position, free corrosion alloy, galvanic alloy, and notes, including whether a coating is applied to the gold IDE.
- Downloading Data Log: Retrieving all stored data in a comma-separated values (.csv) file format, which can be imported into standard data handling software like Microsoft Excel or MATLAB.
- Suspending Operation (Pause Data Logging): Placing the device in a low-power sleep mode, halting data collection.
- System Check: Performing an immediate set of measurements to verify system operation, sensor responses, and remaining battery life.
- Switch Acuity LS Device: Allows connecting to a different Acuity LS device without restarting the software.
- Data File Format: Data is saved in .csv format, with columns for Unix Time, Test Time, Air Temp, RH, Surface Temp, Gold IDE Conductance (10Hz and 25kHz), Galvanic Corrosion, Free Corrosion, and time-integrals of these measurements.
- UNIX Timestamp Conversion: Instructions and tools (MS Excel, MATLAB, and an online converter) are provided for converting UNIX time to other date and time formats.
Maintenance Features:
- User-Replaceable Lid Sensor Panel (LSP): The LSP, which contains the sensing elements, can be easily removed and installed by the user using a 9/64" hex wrench. Replacement LSPs are available from Luna.
- LSP Surface Preparation: The LSP is delivered clean. For contaminated surfaces, water rinsing is recommended for conductance, free corrosion, and galvanic corrosion sensors. Mild solvents (isopropyl alcohol) can be used for organic contaminants, applied with a non-abrasive foam or cotton swab. Caution is advised to avoid immersing the device or flooding the RH/temperature sensor filter cap area.
- User-Replaceable Battery: The Saft LS17500 primary-cell battery can be replaced by the user without removing the device from its structure. A 5/8" box end wrench or socket is required to remove the battery cap. Specific polarity must be observed during installation.
- System Restart: A system restart can be performed by removing the battery for 10 seconds and then reinstalling it. This action does not affect stored data.
- Data Deletion: The "Delete Data Log" function allows permanent deletion of all stored data from the device, which is useful if new total time-integral data starting from zero is desired.
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