Transmitter zero point correction problem
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1. A transmitter with a measuring range of 0~8kPa will be -8~0kPa after migration. When the balance valve is open, and the positive and negative pressures are connected to the atmosphere, and after the zero point correction is performed with the hand communicator, is the output current value of the transmitter 4mA or 20mA? 2. For a transmitter with a measuring range of -4~4kPa, when the balance valve is opened, and the positive and negative pressures are connected to the atmosphere, after the zero point correction is performed with the hand communicator, is the output current value of the transmitter 4mA or 12mA?
Regarding the zero point correction of the transmitter, let me share my personal experience.: For the situation where 0~8kPa migrates to -8~0kPa, perform zero point correction when the balance valve is opened to vent to the atmosphere, and the theoretical output should be 4mA. Because this time corresponds to the lower limit of the measuring range (-8kPa). The transmitter with a measuring range of -4~4kPa is corrected under the same conditions, and the output should be 12mA. Because 0kPa is right in the middle of the range (the midpoint of -4 to 4kPa). However, it should be noted that in actual operation, it is recommended that: Confirm whether the handheld communicator supports zero point correction of the negative pressure range. Before correction, check whether the power supply voltage of the transmitter is stable. After the correction is completed, it is best to use a standard pressure source for verification. The specific operation should be based on the equipment manual. Transmitters from different manufacturers may have slight differences.
1. 20mA 2. 12mA
Why didn't my answer pass the review? There are no banned words. The usual operation is to cancel the migration, perform zero point correction, and then move back. Guaranteed no mistakes
Performing zero point correction with a handheld communicator means calibrating the current 0 kPa as the zero point of the transmitter. According to the "zero point calibration" strategy of the transmitter, there are two possible results. If the transmitter/handheld communicator can identify the migration amount, the output is 20mA and 12mA ； Another situation is that when performing zero point correction, the handheld terminal will forcibly adjust the current input (0 kPa) to 4 mA output. At this time, the output current value of the transmitter is 4 mA. .