Y-150B-FZ Y-153B-F Y-153B-FZ Y-150B-F YN-150B stainless steel pointer pressure gauges, the pressure source is connected to each other through a rubber tube and a self-made joint. Close the balance valve and check the seal of the gas path. Then connect the ammeter (voltmeter) and the hand programmer to the transmitter output circuit. Calibration starts. We know that no matter what type of differential pressure transmitter, the positive and negative pressure chambers have exhaust, drain valves or cocks; this provides us with a differential pressure transmitter that is convenient for field calibration, which means that there is no need to remove the guide. The pressure tube can calibrate the differential pressure transmitter. When calibrating the differential pressure transmitter, firstly close the positive and negative valves of the three-valve group, open the balance valve, and then unscrew the exhaust, cock vent or drain valve, and then use the self-made connector to replace the positive pressure chamber exhaust. , Drain valve or cock; while the negative pressure chamber is kept loose, allowing it to vent to the atmosphere.
Calibration of conventional differential pressure transmitters
First adjust the damping to zero, first adjust the zero point, and then add the full-scale pressure to adjust the full scale so that the output is 20mA. The on-site adjustment is fast. Here we introduce the quick adjustment method of zero and range. When adjusting the zero point, it has almost no effect on the full scale, but when adjusting the full scale, it has an effect on the zero point. Without migration, the effect is about one-fifth of the range adjustment amount, that is, the range is adjusted upward by 1 mA, and the zero point will move upward by about 0.2 mA ,vice versa.
Calibration of Smart Differential Pressure Transmitters
It is not possible to calibrate the smart transmitter with the conventional method described above, because this is determined by the structure principle of the HART transmitter. Because the smart transmitter is between the input pressure source and the generated 4-20mA current signal, in addition to the mechanical and electrical circuits, there is also a micro-processing chip to calculate the input data. Therefore, calibration is different from conventional methods.
In fact, Shanghai Automation Instrumentation Co., Ltd. also has a description of the calibration of smart transmitters, such as ABB's transmitters. For calibration, there are: "setting range", "resetting range", and "fine adjustment". Among them, the “setting range” operation is mainly to complete the configuration through the digital setting of LRV.URV, and the “resetting range” operation requires the transmitter to be connected to a standard pressure source, guided by a series of instructions, The transmitter directly senses the actual pressure and sets the value. The initial and final setting of the range directly depends on the actual pressure input value. But to see that although the transmitter's analog output is correctly related to the input value used, the digital reading of the process value will show a slightly different value, which can be calibrated by fine-tuning. Because each part needs to be adjusted separately and must be adjusted together, the actual calibration can be performed according to the following steps :,
1. Do a 4-20mA trimming first to calibrate the D/A converter inside the transmitter. Since it does not involve sensing components, no external pressure signal source is required.
2. Do a full fine-tuning again to make the 4-20mA, digital reading coincide with the pressure signal actually applied, so a pressure signal source is needed.
3. Finally, do the re-ranging, and adjust the analog output 4-20mA to match the external pressure signal source. Its role is exactly the same as that of the zero (Z) and range (R) switches on the transmitter housing. .