What Is a Container Pressure Gauge? A Guide to Measuring Pressure and Vacuum in Bottles and Cans
A container pressure gauge measures the pressure or the vacuum inside a closed bottle, jar or can. Carbonated drinks and sparkling wines are under pressure, while many foods are packed under vacuum. In both cases, the internal pressure shows whether the product was filled and closed correctly, so pressure and vacuum gauges are basic tools in beverage, food and wine laboratories.
How does a container pressure gauge work?
The closed container is pierced with a needle that seals around the hole, so that no gas escapes, and the needle is connected to a manometer. The pressure of the headspace is read directly, as a positive value for pressure or a negative value for vacuum.
Bench model: the sample is placed under the gauge and a lever lowers the piercing head. The AT2E PVG-D measures from -1 to 6 bar with a resolution of 0.001 bar.
Portable model: the gauge is fixed under the neck of the bottle and its needle pierces the cap without leakage. This is the principle of the AT2E PVG-P.
Pocket model: the needle is pushed into the cap or the can by hand, as with the AT2E PVG-S.
Aphrometer: a pressure gauge for sparkling wine, which usually pierces the cork and wire hood, or the crown cap, to check the pressure during or after the secondary fermentation.
Main applications
Carbonated drinks: checking the internal pressure of bottles and cans.
Food in jars and cans: checking the vacuum of products packed under vacuum.
Sparkling wine and cider: checking the pressure during the secondary fermentation and after disgorging.
Still wine: checking the pressure and vacuum in bottles closed with a cork.
Container behavior: applying a set vacuum or pressure to an empty bottle to check how it deforms.
Key concepts: gauge pressure, temperature and accuracy
Gauge pressure: container gauges show the pressure relative to the surrounding air. A vacuum appears as a negative value, which can never be lower than about -1 bar, the complete absence of air.
Temperature: the pressure of a gas rises with temperature, and in a carbonated drink, more CO2 also leaves the liquid as it warms up. A pressure reading is only meaningful with its temperature, which is why the CO2 content of a drink is calculated from both, as explained in our guide to CO2 analyzers.
Accuracy: analog gauges are usually less accurate than digital ones. In the AT2E PVG series, the analog PVG-A has an accuracy of ±2.5 % F.S., and the digital PVG-D 0.5 % F.S.
Units: pressure is expressed in bar, mbar, kPa, MPa, psi or kgf/cm², and vacuum often in inHg or mmHg. The PVG-D displays all of these units.
A tire pressure gauge
Checking a car tire is a familiar version of the same measurement. Press the gauge squarely on the valve and it reads; press it badly, air hisses out and the reading is too low. Check the tires after a long drive and the pressure is higher than in the morning, because the air inside has warmed up.
A container gauge faces the same two traps: leaks at the piercing point, and temperature. A sealed needle and a reading taken at a known temperature are what make results comparable from one sample to the next.
Calibration of a pressure gauge
Pressure and vacuum gauges are checked against a certified reference indicator:
Connect the gauge and a certified reference indicator to the same pressure supply, for example on the AT2E CDP-1 pressure calibration device.
Apply several pressures across the range and compare the two readings; check vacuum gauges in the same way with a vacuum source.
Record the deviations, and adjust or replace the gauge if they exceed the acceptable limit.
Check the zero at atmospheric pressure before a series of measurements, and keep the needle and its seal in good condition: a worn seal lets gas escape or air enter, and brings the reading closer to zero.
AT2E pressure and vacuum gauges
AT2E gauges cover beverages, food and wine, from the laboratory bench to the cellar:
PVG-A / PVG-D: bench pressure and vacuum gauge for cans and bottles; the digital PVG-D measures from -1 to 6 bar (-14.5 to 87 psi) with an accuracy of 0.5 % F.S., the analog PVG-A measures vacuum (-1 to 0 bar) or pressure (0 to 6 bar); PVG-DS version for sport caps.
PVG-P: portable pressure or vacuum gauge fixed on the bottle, whose needle pierces the cap without leakage.
BVPT-1: bottle vacuum-pressure tester, -1 to +6 bar, to apply a target vacuum or pressure and check the deformation of the bottle.
CDP-1: pressure calibration device, 0 to 8 bar, for analog and digital indicators.
Cork aphrometer: for sparkling wine and cider bottles closed with a cork and a wire hood, after disgorging; stainless steel manometer from 0 to 10 bar.
Crown cap aphrometer: for bottles closed with a crown cap during the secondary fermentation; crown 26, 29 or 36 mm, or screw cap.
Simplified aphrometer: for still wine bottles closed with a cork; checks pressure and vacuum, from -1 to +1.5 bar as standard.
Permanent aphrometer: stays on the bottleneck to follow the pressure during the whole secondary fermentation.
Conclusion
The pressure inside a closed container cannot be seen, but it says a lot: whether a drink is properly carbonated, whether a jar has kept its vacuum, how far the fermentation of a sparkling wine has progressed. A leak-free piercing, a reading at a known temperature and a gauge checked against a certified reference make that number reliable.
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