FermeCheck : Accurate gravity / level measurement for fermentation vessels in brewing and distilling. - CANONGATE - #1

Throughout the fermentation process, monitoring the changes in Specific Gravity (SG) from start to finish is a vital part of the quality procedure. The traditional means of doing this inevitably involves frequent, time consuming, and costly, manual sampling. With Fermecheck, measurement and recording of SG is fully automated giving continuous, accurate, real time information essential for good control. When used in conjunction with Fermecheck's specialised Windows™ based software, a complete automated fermentation control system is the result.

The SG of the fermenting liquid is calculated by measuring the hydrostatic pressure exerted at two points several metres apart in the fermenter using very sensitive and accurate pressure transmitters. The difference in pressure measured at these two points is directly related to the liquid density, and by applying temperature correction to the resultant figures, the gravity is calculated.

The key to the success of Fermecheck lies in the use of pressure sensors which combine high accuracy, sensitivity to small changes, and immunity to temperature effects. CT Holledge transmitters have been widely used in the beverage and food industries for 3 decades because of their hygienic design, robustness and accuracy. They employ a simple pressure balance principle with each unit comprising a pneumatic transmitter, air flow regulator and extremely accurate P/I converter. A small, constant flow of air is fed into the transmitter and vented past the transmitter diaphragm to atmosphere.

When pressure is applied to the diaphragm, it flexes slightly, reducing the size of the vent and restricting the air flow, causing a back pressure equivalent to the process pressure to build up in the system. This pressure is sensed by the P/I converter and transmitted as a 4 to 20 mA signal.

In independent tests*, Holledge pressure transmitters show +/- 0.04% accuracy, and unlike electronic units are unaffected by sudden temperature changes. In typical applications this gives Specific Gravity measurements accurate to +/- 0.1^oPlato.

Canongate Technology Limited, Edinburgh, Scotland. www.canongatetechnology.co.uk