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Basic Parameters and Definitions of Pressure Transmitters I. Pressure Sensor: A device or apparatus that is capable of detecting the pressure value of a specified fluid being measured, and converting it into an output signal according to certain rules. It is usually composed of sensitive elements and conversion elements. When a standard signal other than those specified is output, the pressure transmitter is generally referred to in another way. Pressure types: Absolute pressure: The pressure value measured with vacuum as the reference pressure is known as absolute pressure, often abbreviated as abs pressure. Gauge pressure: The pressure value measured with the local atmospheric pressure as the reference pressure is known as gauge pressure. When gauge pressure is positive, it is simply referred to as pressure; when it is negative, it is called negative pressure or vacuum. The greater the absolute value of the negative pressure, that is, the lower the absolute pressure, the higher the degree of vacuum. Differential pressure: It refers to the difference between the pressures sensed at both ends of a sensor or transmitter. 3. Characteristic parameters of pressure sensors: Measurement range: The range of values that can be measured within the allowable error limits is known as the measurement range. Upper limit: The highest value within the measurement range is referred to as the upper limit of that range. Lower limit: The lowest value within the measurement range is called the lower limit of that range. Range: The algebraic difference between the upper and lower limits of the measurement range constitutes the range. Accuracy: The degree of consistency between the measured value and the true value. Non-linearity: Repeatability: The consistency of the results obtained from multiple consecutive measurements of the same quantity under identical conditions. Drift: The change in the output over a specified period of time when the measured quantity and all surrounding conditions remain constant. Hysteresis: The maximum difference in output that occurs when the measured value increases or decreases within a specified range. Excitation: The external energy applied to enable the sensor to function properly. It is usually voltage or current. The voltage or current applied as pressure. Depending on the type of voltage or current applied, the output values of the sensor also vary; therefore, certain parameters such as the zero-point output, the upper limit output, and drift must be measured under specified excitation conditions. Zero-point drift refers to the change in the zero-point output value over a specified time interval under standard conditions. Zero drift caused by changes in the surrounding temperature is known as thermal zero drift. Overload: refers to the maximum value of a measurement that can be applied to a sensor or transmitter without causing permanent changes in its performance. Stability: refers to the ability of a sensor or transmitter to maintain its original functional parameters after being stored, tested, or used under specified conditions for a certain period of time. Reliability: refers to the ability of a sensor or transmitter to perform its required functions within specified conditions over a given time period. Operating temperature: refers to the temperature range within which the transmitter can meet all its technical specifications and functions. Storage temperature: refers to the temperature range within which the transmitter can be stored for an extended period without being damaged when it is not powered on