Thread Content
Working principle of the 1151 transmitter. Two pressures of the medium under test are applied to the high and low pressure chambers; these pressures act on the diaphragms on either side of the δ element (i.e., the sensitive element). Through the diaphragms and the filling fluid inside the δ element, the pressure is transmitted to both sides of the pre-tensioned measuring diaphragm. The measuring diaphragm together with the electrodes on the insulators on both sides forms a capacitor each. When no pressure is applied or when the two pressures are equal, the measuring diaphragm remains in the middle position, and the capacitances of the two capacitors are equal. When the pressures on both sides differ, this causes the measuring diaphragm to shift, with the amount of displacement being proportional to the pressure difference; as a result, the capacitances of the two capacitors become unequal. This difference is detected and amplified to produce a 4-20 mA two-wire current signal. The working principle of pressure transmitters and absolute pressure transmitters is the same as that of differential pressure transmitters; the difference is that the pressure in the low-pressure chamber is atmospheric pressure or a vacuum level. Capacitive transmitters have the following features: 1. A wide range of models available, with high precision and good stability; their price is lower than that of similar imported instruments. 2. They operate in a two-wire system. 3. The sensitive elements are of solid-state design, making them compact, sturdy, and resistant to vibrations. 4. Their main components can be interchanged with those of 1151-type products. 5. The key components, electronic parts, and connectors are all of high-quality international brands. This series of products features good reliability, stable quality, and a low failure rate. 6. Positive migration can reach 500%, while negative migration can reach 600% (at the minimum range). 7. Damping is adjustable