HART VPT10-H, Руководство по установке, эксплуатации, настройке и обслуживанию, Страница: 7 / 40

VPT10-H HART
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PRESSURE TRANSMITTER INSTALLATION, OPERATION, CONFIGURATION AND MAINTENANCE MANUAL
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1.2. CAPACITIVE SENSOR
The pressure sensor used by VPT10-H pressure transmitter is capacitive (capacitive cell), shown schematically in
figure 1.2.
Figure 1.2 – High performance capacitive sensor.
See figure 1.3, below, to understand the working principle of the capacitive sensor.
Figure 1.3 – Principle of operation of the capacitive sensor.
The core of the capacitive sensor is the central diaphragm. There are two measuring capacitances (CH and CL),
according to the position of this diaphragm. These measuring capacitances share the central diaphragm (movable
plate) and the other plate is attached to both sides of the sensor.
When the pressures on both sides are equal, the diaphragm is in the center and the capacitances on both sides are
the same. However, when the pressure on the high pressure side (CH) is greater than the pressure on the low pressure
side (CL), for example, the filling fluid will move, causing the diaphragm to move to the low pressure side . As a result,
the capacitance on the high pressure side will be lower than the capacitance on the low pressure side.