Pressure transmitters are usually designed so that the relationship between input and output is mainly linear. Therefore, the calibration curve (XY axis) of pressure transmitter in rectangular coordinate system is a straight line, which is expressed by the following formula: y = MX + B1)
Among them, m is the slope of the line and b is its interception. Slope is also called gain, and intercept is also called zero offset or deviation. The measuring range of the transmitter is the smallest to the largest pressure (for example, 0 to 2500 pounds). It represents the pressure of the input range (for example, 0 to 2500 psi), and the electric signal output range (for example, 4 to 20 mA or 1 to 5V). The lowest pressure at which Rosemount transmitters are calibrated is referred to as a synonym for zero-sum offset and deviation. The transmitter is usually calibrated for the ideal pressure measurement range (for example, a pressure transmitter with a range of О to 2500 psi has 500 to 1500 ps). This is called the calibration range or span of the transmitter.
The initial accuracy of the calibrated pressure transmitter determines the accuracy calibration standard, which is based on the accuracy during the calibration process. The pressure transmitter accuracy is usually expressed as a percentage of the range. The initial calibration of industrial pressure transmitters (including absolute and differential pressure transmitters) is usually referred to as a replacement factory calibration.
Pressure transmitter accuracy calibration:
The most effective way to reduce the drift of a pressure transmitter is through timely detection and calibration. Regular pressure transmitter calibration usually includes two steps: (1) Determine whether calibration is required; (2) Calibrate Rosemount transmitter. A series of signals input through the application system such as: (0, 25, 50, 75, 100, 75, 50, 25, span 0%), and then adjust the necessary zero span to make the sensor meet the Rosemount transmitter calibration acceptance standard.
Normally, after calibration, the instrument will return to the scene until it drifts again. In general, it can be used for one to three years with constant calibration. When a pressure transmitter is calibrated in the field, the calibration signal input is often generated by using a stable pressure source (for example, pressure bottle and pressure regulator) and a precision pressure gauge. An automatic pressure sensor can also be used to calibrate the device. It is more convenient to use digital technology to improve the calibration accuracy. This system uses a programmable pressure source to generate a known pressure signal.
With the development of pressure transmitter technology, Rosemount transmitters such as smart transmitters, optical fiber sensors that combine optical fiber transmission capabilities, and wireless sensors have appeared on the market. However, reducing a series of factors that reduce the accuracy of the transmitter, such as temperature, pressure, humidity, vibration, and the normal aging of maintenance activities, makes the impact of calibration drift on the accuracy of pressure transmitters also very important and challenging.