Motion System Design
Sensor Tips

Sensor Tips

MEMS the word in accurate inclinometers

The SCA61T Series of inclinometers from VTI Technologies Inc., Dearborn, Mich., features internal temperature measurement and compensation, along with a long-term stability better than 0.25 mg. This combination gives the devices high accuracy over a –25 to 85°C temperature range. Maximum offset error is less than 15 mg for a ±1-g sensor. The new sensors have analog as well as digital SPI output. Resolution of the analog signal over an 8-Hz bandwidth is 40 mg, whereas digital resolution is 0.05% full scale. The SPI interface also permits field calibration to compensate for mounting errors.

The first available products in the series are SCA61T-FAHH1G (4 V/g) and SCA61T-FA1H1G (2 V/g), which can measure to ±0.5 g and ±1 g, respectively.

How does it work?

The basic elements that make up an accelerometer are the body, spring, and mass. When the speed of the sensor body changes, the mass tries to continue its movement and is retarded due to inertial forces.

In a capacitive sensor, the body and mass are electrically insulated from each other, and their change in capacitance, or storage capacity, is measured. As distance decreases, capacitance increases and electric current travels toward the sensor. When distance increases, the opposite occurs. Exhibiting extreme sensitivity, these devices are ideal for detecting small changes in motion.

Chip helps sensor smarts

A built-in memory chip from Lebow Products Inc., Troy, Mich., stores information in the form of a transducer electronic data sheet (TEDS) on its force and torque sensors.

The company has also joined forces with National Instruments as a plug-and-play sensor partner for integrating IEEEP1451.4 Smart TEDS analog sensors into computer-based DA systems.

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