How should we make fine adjustments when there is a deviation in the Yokogawa EJA transmitter?

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​http://prd118.com/Uploads/202109/614a8e4ebe894.jpg When we use the Yokogawa EJA transmitters for an extended period of time, it is inevitable that pressure fluctuations become more significant than before; in such cases, we can suspect that there is a deviation in the accuracy of the transmitters. Moreover, it is also easy to detect whether there are any errors in the transmitter during routine inspections. When it is found that the error exceeds the maximum error range permitted for sensor verification (usually 0.25), we need to perform fine-tuning. 　　Typically, before we perform fine-tuning, we need to understand what kinds of fine-tuning methods there are. In fact, there are two ways of fine-tuning Yokogawa transmitters: the first is to fine-tune the sensor, and the second is to fine-tune the output. In academia, we can refer to this as modulus fine-tuning and numerical modulus fine-tuning. Different fine-tuning methods are employed for different situations, and the requirements they meet also vary. Before performing fine-tuning, we also need to determine which fine-tuning method is more suitable in the current context. 　　On the surface, our personal guesses are inaccurate; only after verification can we determine the fine-tuning approach that is truly suitable for the current situation. We can proceed with the verification following these steps (taking fine-tuning with a HART communicator as an example): First, we physically connect the HART communicator, the pressure source, the digital reading device, and the transmitter ； 　　Connect the positive and negative terminals of the HART communicator to the corresponding positive and negative terminals on the LOOP connection at the back of the EJA transmitter. Before making the connection, the HART communicator must be turned off; after the connection is made, turn on the power of the HART communicator, and a message will indicate that it is now in the Online state – click to proceed ； 　　The transmitter applies a pressure of 100 KPA, which is then compared with the \"Process Variable\" (PV) value in the operator’s menu. If the display on the testing device is accurate while the value on the operator’s device does not match, it is necessary to perform sensor fine-tuning (analog-to-digital fine tuning). Similarly, in the handset menu, the “Analog Output” (AO) value is compared with the reading on the test equipment; if the two values do not match, output fine-tuning (digital-to-analog fine-tuning) is required. 　　Specific steps for fine tuning: 1. Analog fine tuning (sensor fine tuning): The main tasks to be carried out are full fine tuning and zero-point fine tuning. For complete fine-tuning, the precision required is three times that of the transmitter; this can be done by going to the operator menu: Device Settings –> Diagnosis and Maintenance –> Calibration –> Lower Limit Transmitter Fine-Tuning. If the transmitter’s accuracy is 0.25, then the lower limit fine-tuning value is 0.06. Throughout the entire process, we simply need to follow the instructions provided by the handheld controller. Then fine-tune the upper limit sensor at the same position for adjustment. Note that the upper limit adjustment should not exceed the transmitter’s maximum measurement range. 　　2. Zero point fine-tuning: First, vent the transmitter to the atmosphere, and connect it to the measurement loop using a hand-held communicator. Then go to Device Settings --> Diagnosis and Repair --> Inspection --> Sensor Fine Tuning --> Zero Point Fine Tuning. Finally, make fine adjustments to the zero point according to the instructions on the handheld controller. It should be noted that the transmitter must be within 3% of zero in order to allow for zero-point fine adjustment. 　　When performing fine tuning, we need to turn off the transmitter protection settings. The transmitter protection setting is usually the red switch located right in front of the meter head. The status is ON and OFF. If the protection function is enabled, fine-tuning will not be successful. 　　3. Digital-to-analog fine-tuning (Output fine-tuning)
In the handset menu: Device Settings --> Diagnostics and Maintenance --> Verification --> Output Fine-Tuning --> Digital/Analog Fine-Tuning. Set the “control loop” to manual mode. Then, following the instructions in the “Connection Reference Table,” connect an accurate reference ammeter to the transmitter. Pay attention to the positive and negative connections, then select OK. Finally, set the output of the field device to 4 mA; at this point, the transmitter output is 4 mA. Then record the actual value from the reference table, enter this value in the “Enter gauge value” prompt, and check that the output of the hand controller matches the value in the reference table. If they do not match, continue to enter the reference value and verify whether it matches the output from the hand-held transmitter. If they match, change 4mA to 20mA, and then compare the reference value with the output value from the hand-held transmitter. Until it’s accurate. In the final step, set the “control loop” to automatic control. Complete all operations afterward. 　　Note: The fine tuning of EJA transmitters cannot be carried out at any time, nor should it be done too frequently. So how can we arrange the fine-tuning work in a reasonable way? Xi’an Pruide Instruments would like to remind you that it is generally advisable to keep the calibration cycle of transmitters at around six months.