MEMS Flow Sensor

UNIVERSAL SEMICONDUCTOR

MEMS

MEMS LIQUID FLOW SENSOR

The USI thermal flow sensor chip incorporates the latest technology innovations in MEMS (Micro-Electrical-Mechanical-Systems), and has been developed and manufactured in Silicon Valley.

FEATURES

Measure micro-liquid flow rates as low as 15 mL/min with high precision accuracy ±3% FS, and repeatability ±0.2% FS
Turndown ratio of at least 10:1 at low flow rates (i.e. 15 mL/min)
Highly linear output signal that can be easily calibrated to read flow rates and cumulative flow volume
Greater stability at maximum flow rate and temperature ranges
Low cost, long life custom package incorporate digital display and data processing

Figure 1 USI Thermal Flow Sensor Working Principle

The USI thermal flow sensor chip uses a solid-state design, thus eliminating the need for a cavity or membrane either on the surface or inside (Figure 1). The Die’s contact surface is coated with a thin-film material that was first developed for NASA’s space applications. This proprietary coating is hard (its hardness is second only to diamond), smooth, non-stick, and corrosion resistant. The solid-state design and the advanced coating of the MEMS Die allow the flow sensor to withstand high pressure, intense vibration, and impact from particles in the liquid medium. Temperature differences are directly related to flow rates, the USI thermal flow sensor chip provides highly linear output signal. Figure 2 shows that the sensor provides a highly linear output curve for flow rates as low as 10 mL/min and as high as 180 mL/min, using 2D diesel as the flow medium.

Figure 2 USI Thermal Flow Sensor Provides Highly Linear Output Signal

The MEMS Die also allows a packaged module to be easily cleaned by simpy flushing cleaning solution through the capillary tubing.

Performance specification of the flow sensor module.

Min Flow	15 mL/min
Max Flow	180 mL/min
Accuracy	±3% Full Scale
Repeatability	±0.2% Full Scale
Temperature Rating	0 to 70 ºC
Pressure Rating	Max 60 psi
Linearity	±3% Full Scale

USIs liquid flow meter is suitable for a wide variety of industrial and commercial applications such as fuel consumption measurement for engines and generators, control of refrigerant flow in air conditioners and refrigerators, and generalpurpose liquid flow control in industrial processing.

Typical Package Description

The USI custom liquid flow meter consists of a flow sensor module that is based on the thermal mass flow principle; A display module that shows flow rate and cumulative volume, buffers the data, and provides an interface for data extraction, and a casing that houses both the flow sensor and the display modules.

Figure 3 Flow Sensor Module (The capillary casing also contains signal conditional circuitry)

1925 Zanker Road, San Jose, CA 95112 Updated: 03/26/2009