Precision pressure gauge
For very precise measurements of pressures or for calibration and control of pressure gauges in particular, the precision gauges are suitable. They have a very fine resolution and precise display accuracy, which distinguishes them for this task. The measuring element in this pressure gauge is a bourdon tube. The shape of the tube is slightly “oval” executed in order to perform the optimal expansion in the pressurization can. An absolutely round tube would react to the physical pressure or negative pressure completely different.
If a pressure or negative pressure is passed to the Bourdon tube, it is deformed by extension in the direction of the closed end. By means of a suitable mechanism, this linear expansion movement is then continued via a pull rod on a pointer instrument. The spring tube usually performs a travel of about 2mm to 6mm. A pointer movement then converts the strain into a rotary motion. The measuring tube can consist of different materials. Important at this point is a particularly long-term stable property, which eliminates a constant calibration.
Possible measuring ranges and designs
The measurable measuring range is primarily determined by the pipe material used, the wall thickness of the pipe used and the actual geometry of the cross section. Although the device name Feinmess actually suggests a low pressure range, in practice Bourdon tubes are used with measuring ranges from almost 0 bar to 1,600 bar. In this case, the precision measurement represents the accuracy of the pressures to be displayed. There are therefore many different measuring ranges, for example from 0 bar to 0.6 bar or even 0 bar to 400 bar and more.
For the different measuring ranges and pressure sizes, the tube springs used are also manufactured in different versions. At pressures of 0 bar to 60 bar, the Bourdon tube is circular in shape with an angle of approximately 245 degrees. However, use a 2½-turn screw for larger pressure ranges. Also for the connection of the coil springs with the spring connection different methods are used. A cohesive connection is usually used here by soldering with lead-free solder, soldering with silver solder or WiG welding at extremely high pressure measuring ranges.