Metal diaphragm gauges

Small pressure transducers with flush-mounted diaphragms are commercially available for the measurement of either steady or fluctuating pressures up to 100 MPa (about 15,000 Ibftin ). The metallic diaphragms are as small as 4.8 mm (%6 in) in diameter. The transducer is mounted on the apparatus containing the fluid whose pressure is to be measured so that the diaphragm is flush with the inner surface of the apparatus. Deflection of the diaphragm is measured by unbonded strain gauges and recorded electrically. 

A variety of electromechanical gauges, known as pressure transducers, is available commercially. Most work on the following principle A flexible metal diaphragm separates two chambers, one of which is connected to the... 

The measurement of pressure from a few torr to 104 torr in an all-metal system can be accomplished by means of a metal Bourdon or diaphragm gauge with a dial readout. Although a bronze chamber is the most common, these gauges are available with more corrosion-resistant metals, and some are available which are accurate to 0.5 torr.7... 

In most cases the pressure is detected using diaphragm sensors classified in terms of sensing element as metal strain gauge, piezoelectric semiconductor, electric capacitance, reluctance, and LVDT (linear variable-differential transformers) sensors. The structure of a silicon semiconductor sensor, where the pressure is detected by a silicon diaphragm, is shown in Fig. 5. In most cases these sensors can be used at temperatures lower than 70°C. 

Piezo-resistive pressure sensors (Figure 7.3) make use of silicon membranes with integrated strain gauges that are generated in a semiconductor process. In this way low-cost sensors can be produced. These are not corrosion-resistant but they can be protected by a separating metal diaphragm. 

Figure 7.4 (a) Capacitive diaphragm gauge with metal diaphragm, (b) Capacitive... 

---