Silicon sensors survive harsh environments

A Hamlin Electronics Europe product story

Edited by the Engineeringtalk editorial team Jun 23, 2005

Two new sensors have been developed to deliver fast response and greater accuracy when measuring flow rate, pressure and temperature in harsh or aggressive environments.

Groundbreaking technology is being used by Hamlin Electronics Europe in two new sensors developed to deliver fast response and greater accuracy when measuring flow rate, pressure and temperature in harsh or aggressive environments.

The new flow rate and temperature (HEFS) and a pressure and temperature (HEPS) sensors are Direct Sensors.

The solid-state devices incorporate a silicon element, which can be placed directly in contact with substance to be measured.

This substantially increases the sensitivity of the sensors to give faster, more accurate measurements.

Normally a silicon sensing element would be destroyed when exposed to harsh conditions.

However a new metal/glass alloy coating has been developed for the silicon element, which enables it to operate reliably in harsh environments.

Reliability is further improved by not relying on moving parts in the devices.

The HEPS pressure sensor can measure pressure up to 4bar but can survive burst pressures up to 30bar.

The HEPS sensor is capable of measuring flow rates of between 1.3 and 20 litre/min with five times greater accuracy than most turbine flow sensors.

Both devices measure temperatures between 0 and 100C.

The high reliability, robustness and accuracy achieved with Direct Sensors technology makes them particularly applicable to designers who develop industrial process control solutions, HVAC, refrigeration, dish washers, washing machines (industrial and domestic), automotive cooling and transmission systems.

The operating principle of the sensors is a bulk micromachined silicon chip with strain gauges placed in stress intensive positions, connected in a Wheatstone bridge configuration.

Changes in the bridge are measured and used to derive a pressure reading which, after correcting for temperature, is supplied to the output pins as a ratiometric voltage.

The temperature coefficient of the bridge resistance is used to measure temperature and this is also supplied to the output pins as a ratiometric voltage.

The HEFS sensor is a vortex flow sensor based on the von Karmann effect.

A bluff body upstream of the sensor is used to generate vortices that pass on either side of the sensor and provide a differential pressure variation - the rate of which can be related to flow.

The new products are brought to market as a result of Hamlin's relationship with world leading pump manufacturer Grundfos.

Grundfos invested Eur 30 million over ten years in the development of the Direct Sensors technology for its established markets in domestic heating boilers and heavy duty pump applications.

Phil James, President of Hamlin, commented: "Grundfos has developed an exciting new product family that will find many applications that extend well outside of their traditional markets".

"Hamlin has a very diverse range of customers in the fields of automotive, industrial and consumer products and it has the worldwide sales and distribution networks in place necessary to support them".

"We are sure that many of our customers will be very interested in this technology and that it will fit very well with our current mix of Hall, reed and other sensing technologies".