Pressure transducers keep beer just right

Headmaster has built a range of instruments, using Gems Sensors' devices, to enable breweries to calibrate their analysers and plant, and ultimately regulate the gas content of their products.

Regulation of dissolved gas is essential for breweries and publicans in order to achieve the optimum amount of head and maintain the quality and taste of their beers.

Headmaster's instruments for gas regulation use a range of sensors, from Gems, to ensure the perfect pint.

Beer drinkers, the world over, can now appreciate the results that Gems Sensors help to ensure.

One of the most important factors in the production of beer - and soft drinks - is the amount of gas that is dissolved in the liquid.

There are three gases in the drinks industry which are critical - Carbon Dioxide, Nitrogen and Oxygen.

Carbon Dioxide is typically found in sparkling water, beers and lagers - but certain beers also contain Nitrogen, which gives a creamy texture that has become popular throughout the UK and overseas.

The third gas, Oxygen, must be eliminated as far as possible.

Headmaster has built a range of instruments, using Gems Sensors' devices, to enable breweries (and soft drinks manufacturers) to calibrate their analysers and plant, and ultimately regulate the gas content of their products.

For this purpose, the company has specified Gems Sensors' 2200 pressure transducers, which combine high levels of performance and stability in a robust package.

The calibration system operates by producing a constant stream of water containing a known and displayed amount of dissolved gas.

The amount of gas is controlled by gas/liquid membranes.

These establish an equilibrium between the gas and the liquid in terms of the amount of the dissolved gas in the liquid - which is purely a function of temperature and pressure.

Accurate measurements for pressure and temperature are critical therefore.

Alternative suppliers products can often sustain a zero shift, but Gems CVD technology provided the ideal solution.

A proven thin film sensor is atomically bonded onto metal substrate - eliminating drift whilst offering enhanced sensitivity.

The 2200 series offers a static error band of 0.25%, thermal error band of 1.5% (-20oC to +80oC) and has a typical long term drift of just <+/-0.2% per year.

Signals from the transducers are ultimately entered into an analogue computer which calculates the level of dissolved gas in the water.

The water is then passed through the analyser in the brewery which should show an identical reading to the calibrator's measurements.

"We were looking for a pressure sensor that was extremely accurate and stable", explained Ken Page, the managing director of Headmaster.

"Gems Sensors' pressure transducers were able to provide the right technical quality to ensure reliable results for our customers, time-after-time." To ensure reliability, the transducers are subjected to rigorous hardness, leak, pressure, thermal cycling and ageing tests - providing long term mechanical and electronic integrity.

They meet the requirements of BS5750 and ISO9000 and offer good resistance to shock and vibration.

Headmaster is also ensuring the perfect pint through the use of Gems Sensors' FS-3 flow sensors - in a ground-breaking gas dispensing system called Cellarstream.

Developed in partnership with Air Products PLC, the system controls dissolved gas where it matters most - in the pub - ensuring the ideal head on all draft beers.

It allows full correction of both nitrogenation and carbonation - even from initially flat beer.

The Cellarstream opens the door to new types of beers, creates new possibilities for brewing and distributing beers, and reduces the waste and delay of fobbing (or the drawing off excess gas at the beginning and end of barrels).

It also allows beers to be tailored to satisfy customers' regional preferences for presentation.

The flow sensor is essential to the gas dispensing process detecting when the amber nectar is flowing and when it ceases.

The piston-type technology encapsulates a permanent magnet, which is positioned in the flow path, within the unit housing.

When displaced by the fluid flow, the piston magnetically actuates a sealed reed switch.

A stainless steel spring provides positive piston return as the flow decreases.

The FS-3 has an operating pressure of 10 bar at 20oC and is supplied in FDA approved materials - making it ideal for use in this application.

Commenting upon the selection of the sensor, Ken Page said: "We chose the Gems flow sensor because it was extremely compact, able to measure small flow rates and suitable for use in the drinks industry." He added: "The balance between a beer's nitrogen and CO2 - so critical for optimum dispensing is difficult to maintain throughout the conventional brewing, distribution, and dispensing chain.

With help from the FS-3, the Cellarstream system achieves this balance, reliably and cost-effectively.".

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