Electronic Design

Stellar MEMS Sensors Gear Up For Industrial Applications

Finding innovative products designed for industrial applications wasn’t difficult this year. Still, two MEMS-based devices were a cut above the rest–the ADIS16209 dualmode inclinometer from Analog Devices and the D6F-P gas flow sensor from Omron Electronic Components.

Also known as a tilt sensor, the inclinometer is a highly integrated, programmable, dualaxis device that makes highly accurate measurements. It is well suited for industrial applications that require inclination changes to be measured, including surveying equipment, factory machine tools, satellite antenna stabilization systems, and automotive wheel alignment.

Its output is a fully compensated direct angle measurement with less than 0.1° linear inclination error, making it at least twice as accurate as competitive tilt sensors (Fig. 1). This is due to its embedded controller, which uses factory-installed calibration coefficients to dynamically sense the system environment and compensate the direct-digital angular output to account for changes in voltage, temperature, angle, and other variables.

“Most industrial customers do not have the equipment needed to calibrate inertial sensors. They need a part that is fully calibrated and tested,” said Bob Scannell, iSensor Business Development Manager at Analog Devices. “They know they’re going to get a certain level of accuracy out of this part. We’ve essentially lowered the barrier to use for this group of customers by guaranteeing a very high level of accuracy for an inclinometer.”

Though size doesn’t always matter, the ADIS16209 measures 9.2 by 9.2 by 3.9 mm and is about 100 times smaller than functionally equivalent inclinometers. Based on the company’s iMEMS core, the device can measure dual-axis tilt across a ±30° range when mounted horizontally. And due to its unique dual-mode operation, it supports a vertically mounted single-axis implementation over a full 360° range.

The tunable digital sensor data is output via an industry-standard serial peripheral interface (SPI) port, which provides access to inclination with 0.025° resolution, acceleration with 0.244-mg resolution, temperature, and power supply. Another point in its favor is price–$34.40 each in 1000-unit lots.

The neat thing about Omron’s D6F-P MEMS flow sensor is that it incorporates a unique doublecyclone dust segregation system (DSS). This enables the sensor to deliver accurate results even in dusty environments such as HVAC and variable air volume (VAV) systems by keeping particulates away from the MEMS sensing chip.

The flow sensor delivers an amplified, temperature-compensated output signal with high accuracy and repeatability, even at very low flow rates. This accuracy is critical, for example, in sophisticated zone temperature control systems where a proper intake of fresh air is required to avoid a “sick building” situation. The device has a compact 17- by 22-mm footprint, and pc-board terminals allow damper control modules to connect directly to the board.

By design, the D6F-P is consistent from lot to lot and does not require recalibration. Also, the presence of both orifices on the same side facilitates connection without kinking the tubes. Specifications include +1.0 standard liters per minute (SLM), a pressure range of 0.84 in. H2O, and maximum pressure of 50 kPa (200 in. H2O) with an analog output signal of 0.5 to 2.5 V dc (0 to 0.5 negative flow indication).

Though they offer many advantages over differential pressure sensors, MEMS flow sensors aren’t widely used due to cost. Yet the D6F-P is cost-competitive, priced around $47 each in lots of 100. Applications include damper control, vent hoods, clogged filter detection, medical equipment, respirators and ventilators, spirometers, continuous positive airway pressure (CPAP) devices, analytical equipment, environmental analyzers, and gas chromatographs.

See associated Figure 2

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