mechanical vacuum gauge / analog
The Model 269 is a high specification vacuum gauge specifically designed for the estimation of the intensity of vacuum in a food can. Using an ordinary vacuum gauge fitted with a piercer is usually very inaccurate and does not allow for the dilution of the head space vacuum by entry of air at atmospheric pressure from the gauge. Ordinary vacuum gauges therefore always give a lower reading than the vacuum which existed in the head space before the can was pierced and if the head space is small, the error is compounded.
This gauge was developed by the British Food Manufacturing Industries Research Association and it overcomes the disabilities in an ingenious manner.