What does it mean when the output of a pressure transmitter is greater than 20.6 mA? And what does it mean when it is less than 3.6 mA?
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If the range of the pressure transmitter is 0–10 MPa(G), where 0 MPa(G) corresponds to 4 mA and 10 MPa(G) corresponds to 20 mA, what will be the output current of the transmitter if the process system experiences pressures of 15 MPa(G) or 20 MPa(G) (assuming the maximum designed range of the transmitter is 50 MPa(G))?
Check whether the circuit board has protection. In the absence of such protection, there is a dead zone of 23–25 mA at the output; when the measurement range is exceeded, the current no longer changes. If the transmitter’s protection range can handle up to 50 MPa of overload, the transmitter will not be damaged. However, the output current beyond this range is not linear, so it has little practical value as a reference
If the output is below 4 or above 20, it may be because the instrument has high/low alarm settings set, depending on how the instrument is configured. If the output is below 4, it is also possible that the actual pressure at present is slightly lower than the lower limit of the range ； An output higher than 20 may also indicate that the actual pressure is slightly above the upper limit of the range ； As you said, the current pressure is 15, and the maximum value indicated by the gauge is 50; therefore the gauge will show 15, which is normal, but the output is not normal – it should be at a higher value.
The output current of the instrument has a maximum limit; it is generally slightly higher than 20mA, usually around 20.8mA, which corresponds to 105% of the range. In other words, when the actual pressure is 15 and 20 MPa, the instrument outputs 10.8 mA in both cases, while the DCS displays 10.5 MPa. (The assumption here is that the DCS is designed to be able to display values outside its range; if this variable on the DCS is set to 0-10, it’s possible that nothing will be visible, such as in the case of a faulty reading). Of course, not all meters are 20.8mA; refer to the meter’s manual for details.
The meter exceeds the upper limit (range); the current output is greater than 20mA. It also falls below the lower limit, with the current output being less than 4mA
Greater than 20mA......
“The current pressure is 15, and the maximum value indicated by the gauge is 50; therefore, the gauge will display 15, which is normal, but the output is not normal – it should be at a higher value. ” What is the meaning of the situation you mentioned, where the range displayed on the transmitter’s gauge can be different from the output range? Moreover, “the maximum value on the gauge is 50” – as the original poster has said, this refers to the maximum range specified in the transmitter’s design, not the maximum range displayed on the gauge.
It will not display 15 MPa; it will only show a value around 10. Once the current exceeds 20 mA, it remains at that value
First of all, I understand what the poster means by 50 – it refers to the maximum range of the gauge. Then, when the actual pressure exceeds the set range value – for example, if the range is 0 to 10 and the actual pressure is 15 – as long as it doesn’t exceed the instrument’s maximum value of 50, the gauge usually displays both the pressure value and the percentage. The pressure value will be the actual pressure, while the percentage will be 100% or even higher. An electric current is output; since the set range has been exceeded, an alarm is triggered… Well, I’ve encountered this situation in practice… It’s possible that this happens only with that particular brand
What does the range displayed in the table header mean? Aren’t there only the instrument output range and the DCS system range? There’s no need to set a range for the displayed content, right?
“First of all, I understand what the poster means by 50 – it refers to the maximum range of the gauge. Then, when the actual pressure exceeds the set range value – for example, if the range is 0 to 10 and the actual pressure is 15 – as long as it does not exceed the instrument’s maximum value of 50, the gauge usually displays both the pressure value and the percentage. The pressure value will be the actual pressure, while the percentage will be 100% or even higher. The output is in the form of current; since the set range has been exceeded, an alarm is generated. The poster mentioned: “The pressure transmitter has a range of 0–10 MPa(G), with 0 MPa(G) corresponding to 4 mA and 10 MPa(G) corresponding to 20 mA.” So, what current value corresponds to a pressure of 15? 28mA？ What is the percentage? 150%? ”What is the current corresponding to the maximum 50\" on the gauge? 80mA？ What is the percentage again? 400%? Assuming the transmitter’s output current is unlimited and a linear relationship between input and output is maintained, can all these data be displayed? :Can the actual transmitter output current really be this high? An alarm is triggered when the EJA transmitter output reaches 110%, and the output will not increase beyond this limit.