Problems with pressure calibration of EJA differential pressure transmitters
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An EJA100A differential pressure transmitter; the pressure of this transmitter is calibrated using a handheld operator, with a measurement range of -4.4 kPa to 0 kPa. The standard instrument set a pressure of -4.4, and after calibrating the transmitter, it displayed -4.4 kPa. The standard instrument then set the pressure to 0, and after calibrating the transmitter again, it showed 0 kPa. But the problem is: after the pressure calibration at the upper and lower limits of the range is completed, why does the standard instrument indicate a pressure of -2.2 kPa at the midpoint, while the transmitter shows -2.3? Not just the midpoint – all the points along the entire pressure variation process are off. Excuse me, what’s the problem? Which parameters of the transmitter need to be set?
All transmitters have a certain degree of error; as long as it is within the allowable range, it is considered normal. Calculate it to check, and if there’s an issue, make adjustments. You can also refer to the manual, as there are methods for linear adjustment available.
Your verification method is incorrect; it should start at -4.4, taking 5 points for verification up to 0. Then, go back from 0 to those same 5 points, performing the verification once for both the upward and downward journeys. If a single point exceeds the maximum allowable error, we consider this gauge to be unqualified.
1. I’ve never flown an EJA, just as I’ve never invaded the Japanese. :P 2: (-2.3 – (-2.2)) ÷ 4.4 = -2.27% FS. The linear error is huge; it’s extremely significant. Identification completed
Expert, how can I eliminate linear differences? Can only a new transmitter be replaced?
The handheld controller can only verify the pressure at the upper and lower limits of the range. . . I’m also helpless
The software for the meter, that is, the software in the handheld controller, if it does not support or provide the functionality for linear correction, then it is impossible to intervene with the meter. . . Of course, there are some skilled programmers who can write some code in the host computer to modify the linear relationship. . . If the meter has poor linear accuracy, whether it needs to be replaced depends on the required level of precision for measurements. If the requirements are low, continue using it until it breaks. . . It needs to be replaced; come and buy your brother’s watch instead. :lol The measurement range is from -4.4 kPa to 0. Even if your brother works with his eyes closed, using just his toes, the accuracy won’t deviate by more than 2%. . . I can provide you with a gauge that has zero drift and an accuracy of 0.1 grade; you’re welcome to send it to a calibration institute for verification.
This post was last edited by 1111111 on 2018-4-29 12:27. 1 hPa = 100 Pa.
Isn’t calibrating a gauge done by using a standard gauge as a reference? By applying pressure or creating a vacuum to the standard gauge – can your HART system handle that?
What is the model of the EJA100A? It should be the EJA110A type L diaphragm, right?
This post was last edited by cqdfwy on 2018-4-29 at 17:57. The original poster wasn’t clear enough in terms of conceptual terminology, but his operations were correct – the standard table is used for signal verification, while the handheld device is used to adjust the zero point range.