| 摘要 |
A pressure gauge 10 for sensing a pressure value comprises a first pressure sensor 12 to provide pressure information in a first pressure range, and a second pressure sensor 14 to provide pressure information in a second relatively higher pressure range, and a controller 16 to derive the pressure value from the pressure information. The controller derives the pressure value from pressure information from only one of the pressure sensors at any given pressure. The gauge 10 also comprises a switch 18 arranged to automatically switch between the pressure sensors 12, 14 at a threshold pressure such that below the threshold pressure, the pressure value is derived from pressure measurements from the first sensor 12, and above the threshold pressure, the pressure value is derived from pressure measurements from the second sensor 14. The switch 18 may be a valve (40, fig. 4) which automatically disconnects the lower pressure sensor 12 when the pressure exceeds the threshold. The valve has a low pressure chamber (50, fig. 4) and a high pressure chamber (48, fig. 4) — the low pressure chamber is sealed when pressure is great enough to force a spring so that a conical valve end fits into a seat. The angled valve end allows the valve to open again when the pressure drops. |
