TiN technology step forward for pressure sensors

Edited by the Engineeringtalk editorial team Aug 3, 2001

Sensor-Technik UK is launching a new series of TiN (titanium nitride) thin film coating pressure sensors featuring what is claimed to be a breakthrough in technology.

Sensor-Technik UK is launching a new series of pressure sensors featuring what is claimed to be a breakthrough in technology.

The company's TiN (titanium nitride) thin film coating sensors are particularly compact, and the precision and long-term stability specifications are similarly impressive.

The patented design is the result of two years' development at German manufacturer KMW, following research by Prof.

Mueller at Hamburg Technical University.

The diaphragm, in the form of a capsule, is welded onto the mechanical port without the use of any sealing materials, giving a totally sealed (water/air-tight) connection.

By including integrated temperature compensation on the diaphragm, the need for external electronics is brought to a minimum (simplified).

This also allows the temperature compensation to take much faster effect as it is mounted with the strain gauges.

The design offers advantages over piezoresistive sensors, where the capsule diameter is relatively bigger, and over ceramic diaphragms, which are slightly higher in cost and need other sealing materials, which can affect the stability significantly.

There are other thin-film pressure capsules on the market, but with nickel-chrome, for example, if the pressure sensors are subjected to high temperatures, the nickel-chrome-film is relatively quickly pushed to its limits.

Compensating for this brings problems, notably high cost and loss of long-term stability.

TiN-thin-film can go direct onto the media, and the long-term stability is high as the film is manufactured directly on to the sensor material.

TiN thin-film technology has already been tested for more than 1000million cycles on large diesel/gas engines.

The gas temperature during startup is over 1000C.

The temperature effect on the TiN-thin-film pressure capsule is under 1% per 100C; the resistance is controlled, so that the temperature influence is quickly compensated.

Although earlier types of thin-film pressure measurement technology are now used widely, the foil strain gauge still dominates the market due to its low cost and availability.

TiN-thin-film's initial cost is higher, so its advantages are greater at quantities.

However, there are benefits even for the small user - and there are more to come.

A foil sensor is being developed which can be welded directly on to the carrier.

A conventional foil strain gauge is glued on, and has problems with the different ageing process in the different materials (the foil strain gauge has different ageing to the glue, which has different ageing to the sensor-material).

After a time, the glue can dissolve: as the pressure is applied to the strain gauge, the glue lifts.

TiN-thin-film technology does not have these problems.

With the TiN-thin-film technique there is no glue used, and the film is bonded directly onto the sensor material, giving durability and safety.

Protective layers may be selected depending on environmental conditions and customer specification; output signal is compensated internally.