METHOD AND APPARATUS FOR CAPACITANCE TEMPERATURE COMPENSATION AND USING THEM IN A DUAL PLATE CAPACITIVE PRESSURE - TRANSDUCER

摘要

The present invention relates to a device for transmitting a differential pressure signal to a two-wire, current-ring transmission unit, which has a capacitive differential sensor for converting the differential pressure to an electric capacitive signal, and a connection has a mode (26), and the replaceable mode (26) is provided with an electronic circuit for controlling the main current (IL) in the two-wire current rings and for receiving energy from the two-wire current rings in response to the meter signal. The essence of the invention is to provide an electromagnetic stone compensating circuit (118) mounted in the built-in workshop (28) for the partial stone compensation of the scattering capacity influencing the measuring signal by limiting the temperature dependence. The built-in mode (28) is suitable for connection to the MACDA analogue interchangeable mode (26) and the CDD digital interchangeable (26). The built-in mode (28) is provided with a capacitive stone compensating circuit (118) enclosing a CDM capacity stone densitator (124), from which the CDM capacity is selected, so that the MACDA stone compensating capacity and the CDD stone compensating capacity are balanced. The invention also relates to a method with a two-wire transmitter, in which the residual spread capacity is compensated by a circuit (128) located in the replaceable workshop (26); and varying the main current (IL) in the two-wire current rings in response to the change in the measurement signal. The CDM stone compensating capacity is realized by a rock capacitor (124) of variable capacity, which comprises a tap and a metal housing as an electrode of the rock condenser (124), from which the tap is inserted into the housing bundle and the saw is filled with a dielectric material around the tap. The pacicity of the quench densers is varied by pushing the tap into the borehole to different depths. ŕ