Accurate control of liquid level is prerequisite of production equipment.
In the use of differential pressure transmitter
, often encounter & other;
Zero migration & throughout;
The so-called zero migration, is in the measurement, in order to ensure the effectiveness of the transmitter basic amount, basic content mainly includes the range and accuracy of measurement, and the starting point to measure as the core, a kind of numerical change security measures.
Similar to moving zero and zero adjustment, meaning is prompted transducer measuring signal and the input signal of the two limits, the zero adjustment and zero migration depends on whether the minimum value is zero, the distinction between when the minimum value is zero, is zero adjustment, the opposite is zero migration.
The migration amount how to confirm?
Due to the same transmitter, its use scope have greatly small, so the migration quantity also became a big and small.
Most of the manufacturers of the transmitter, migration quantity are the percentage of maximum range.
For example some transducer zero for the largest range of plus or minus migration & plusmn;
100%, that is to say, if the transmitter measuring range of 0 ~ 31.
1 kpa to 0 ~ 186.
8 kpa, when the transmitter high or low pressure into 0 ~ 186.
8 kpa any pressure, within the scope of its zero point can be moved to 4 ma.
But high intake of 186.
8 kpa pressure is the upper limit of measuring range, recanalization is overpressure, the zero point adjustment into 4 ma DC not impossible, but that is no meaning, so the zero migration quantity and scale of no more than the sum of measurement range limit.
What are the forms?
Moving zero includes three kinds of forms, respectively is no migration, positive transfer and negative transfer.
Zero of positive and negative transfer, is in the transmitter is not input to zero, the output set to zero (
The lower limit)
If you have any input of low pressure differential pressure transmitter is introduced into the mouth pressure, high pressure intake does not, the output will be dispatched to zero (
The lower limit)
When the adjustment, is called a negative transfer;
If you have any input differential pressure transmitter of high pressure intake pressure, low pressure intake does not, the output set to zero (
The lower limit)
Adjustment, is called positive transfer.
Because of migration is in the transmitter input zero adjustment, so the migration amount is migration of the input signal to represent, or to say what percentage of measurement range.
Moving zero failure positive transfer failure judgment positive transfer differential pressure transmitter in the field of measurement is accurate, in use process should first shut down three valve differential pressure transmitter group of positive and negative pressure measuring room, open the balance valve and vent plug, the instrument output should be less than 4 ma.
If the output of no less than 4 ma, may be positive pressure chamber or three lead some plug valve group.
Second, close the positive pressure chamber pressure points, open the vent switch, then the output should be 4 ma.
If the output is lower than 4 ma, is probably the migration quantity small or zero is low;
If there is spacer irrigation, maybe spacer is not the filling of or from a near miss;
If the output is higher than 4 ma, migration quantity big or zero on the high side.
Negative transfer of the negative differential pressure transmitter in the field of fault diagnosis transfer in use process measurement is accurate, the first three valve closed differential pressure transmitter group of positive and negative pressure measuring room, open the balance valve and vent plug, instrument should be 20 ma output.
Second, close the positive and negative pressure chamber pressure points, open the vent switch, at this point, the instrument output should be 4 ma, if not to 20 ma, or 4 ma, should check whether the positive and negative pressure chamber leads, migration quantity whether to change, zero is accurate, whether spacer fluid loss, etc.
The above articles provided by reference, instrument and meter plant kaidi instrument equipment factory
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