About Inertial Sensors
Inertial sensors are a class of instruments—which include tiltmeters, inclinometers, and accelerometers—designed to measure the slope or tilt of a given object. Knowing this information is very important across a range of applications that rely upon highly exact levelling including boom position and control, radar and vehicle platform positioning, industrial measurement and control, drilling equipment, geophysical testing, navigation pitch/roll measurement, railway track alignment & maintenance, and many others.
Inertial Sensor Technology
Inertial sensors generally utilize one of three technologies: MEMS, force balance, or electrolytic. Each of these technologies present certain advantages and limitations. Selection of an inertial sensor should include careful consideration of these factors.
MEMS Sensor Technology (Microelectromechanical Systems) is the most versatile and cost effective for industrial applications. A MEMS sensor includes a suspended mass between a pair of capacitive plates. Changes in tilt create a change in the measured capacitance, which is then converted to the selected output signal. MEMS sensors are currently the most rugged sensor technology as they can be fully sealed and offer a wide operating temperature range. They can also handle high frequency environments. Although they can handle the harsh environments, MEMS sensors have accuracy limitations with applications that demand the highest precision.
Force Balanced sensor technology uses a torque motor to maintain an unbalanced mass. The amount of applied torque required in the servo amp is proportional to the angle of tilt. Force balance technology offers higher accuracy when compared to MEMS. A fluid damped mechanism allows installations in harsh environments with medium to high frequency. There are quartz options as well which can handle the most extreme temperatures.
Electrolytic tilt sensors are the highest accuracy and most repeatable technology. The sensor has no mechanical moving parts. Instead it has a sealed glass capsule partially filled with an electrically conductive fluid. As the sensor is tilted, the enclosed gas bubble shifts causing more fluid on one side of the sensor. With excitation electrodes on top and a pick up electrode on the bottom, uneven conductive fluid creates a predictable electrical signal that is proportional to the tilt angle. Although these sensors offer the highest amount of accuracy, they are most susceptible to frequencies and are best suited for geophysical applications.
Things to Consider When Selecting an Inertial Sensor
- What are the range and accuracy requirements?
- How many axes are required?
- What are the vibration levels (amplitude and frequency) that can affect measurement?
- What operating conditions (e.g. temperature) are present?
- What are the power supply requirements? (Single ended vs. Dual Ended)
- What output signal is required? Is it analog or digital?
- Are any mounting accessories, connection cables, or other accessories needed?
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