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Hi, this is the Industrial Control Assistant. Today is yet another day of dedicated learning*. Today, the little piece of knowledge we bring is the classification of pressure transmitters; let’s take a look together. 1. Classified by sensor, they include resistive strain gauge pressure transmitters, semiconductor strain gauge pressure transmitters, piezoresistive pressure transmitters, inductive pressure transmitters, capacitive pressure transmitters, and single-crystal silicon resonant pressure transmitters. 2. Classified by type, they are pressure-type and differential pressure-type. 3. Based on material, they are divided into resistive and capacitive types. 4. Based on corrosion resistance, they are classified as ordinary and corrosion-resistant. 5. Based on the range, they are divided into low-range and standard-range types. Common pressure transmitters 1) Piezoresistive transmitters: A piezoresistive transmitter applies pressure to the front surface of a diaphragm; under this pressure the diaphragm deforms to some extent. Thick-film resistors are printed on the back side of this pressure-sensing diaphragm, thereby forming a Wheatstone bridge. Due to the piezoresistive effect, this bridge generates a voltage signal that is proportional to the applied voltage. 2) Piezoelectric transmitters: Piezoelectric transmitters are developed based on the positive piezoelectric effect. This effect occurs when a certain external force is applied to an electrolyte, causing it to deform; polarization takes place within the electrolyte, and positive and negative charges are generated on its two surfaces. When the external force is removed, the electrolyte returns to its uncharged state. The polarity of the charge changes as the direction of the force changes. When an electric field is applied in the direction of the electrolyte’s polarity, the electrolyte also deforms; once the field is removed, the deformation disappears – this is the inverse piezoelectric effect. 3) Strain transmitters use special adhesives to bond the strain gauges together, thereby generating mechanical strain. When the force acting on the device changes, the resistive strain gauges also deform to some extent, which in turn affects their resistance value and causes a change in the voltage across them. However, in this case the change in resistance is small; typically, it forms a strain bridge, and under the action of an instrumentation amplifier, the value increases before being transmitted to the processing circuitry for display or to an actuator. 4) Capacitive transmitters: Capacitive transmitters are divided into electric and pneumatic types; the former uses a DC signal as its standardized input signal, while the latter outputs gas pressure. The two pressures of the medium to be tested are applied to the high and low pressure chambers, respectively, acting on the diaphragms on both sides of the sensitive element. The diaphragm, together with the electrodes on the insulating plates on either side, forms a capacitor. When the pressures on these two sides are different, the module shifts; as a result, the currents on the two sides also differ. Through oscillation and regulation, current, voltage, or digital output signals are generated. That’s all for today’s little tip. If you have any more questions, feel free to leave a message. New content will be posted regularly, so please stay tuned.