As an instrumentation engineer or plant operations manager, you need every pressure transmitter to deliver an accurate measurement.
Pressure measurement errors are a problem.
They prevent the process control system from making appropriate decisions on how to control a valve or pump. If you measure a level with a pressure transmitter diaphragm, a deviation in the measurement can lead to a tank overflow with serious consequences. Whereas an inaccurate flow measurement with a differential pressure transducer can cause you to lose large quantities of raw materials.
If the measurement is very different from what is actually happening in the process, this can put safety at risk.
The pressure transmitter measurement error is the difference between the pressure sensor indication and the actual value of the measured variable.
Errors in pressure transmitter measurement can be caused by 5 factors.
Firstly, the instrument may not have a correct zero reference, which can lead to inaccurate readings.
The sensor's zero point is moving away from its initial position.
The pressure transmitters are electronic devices. The zero reference signal may drift over time due to temperature, pressure or change in ambient conditions.
To avoid this type of error, it's important to choose a pressure transmitter offering good long-term stability.
Otherwise, the transmitter needs to be calibrated more regularly.
Second, the shift occurs when the full span of the transmitter moves away from its original position
There are several factors that can contribute to span shift, including temperature changes, vibration, and electrical interference in the process, or perhaps the operating range of the process has changed.
To avoid this type of error, it is important to have a good understanding of the process and the conditions under which it operates.
Offsets can be compensated for by periodically recalibrating the sensor.
Thirdly, one of the most common causes of measurement error on pressure transmitters is the selection of an inappropriate range.
The measuring range of each sensor is determined by its cell type.
This particular error is due to the use of a cell range that is too small or too large for the application.
For example, if the rangeability (the ratio of maximum measurable pressure to minimum measurable pressure) is too low, the sensor won't be able to accurately measure low pressures. This can lead to clipped measurement signals and distorted pressure readings.
For example, a process may currently operate in the range of 0 to 30 mbar, but a 0 to 30 bar pressure transmitter 10:1 turndown ratio does not allow it to measure accurately at such low pressure.
To avoid this type of error, it is important to select a pressure transmitter with an appropriate turndown ratio for the application.
Fourth, the transmitter may not be compatible with the process conditions.
For example, some devices may not be able to withstand the high temperatures or pressures found in certain industrial processes.
For example, a process may currently operate in a range from 0 to 30 bar, but changes in the application will require it to operate in a new range from 0 to 300 mbar.
To avoid this type of error, it is important to carefully examine the sensor's characteristics in relation to the process conditions before selecting a suitable model for a particular application.
Fifth, errors in sensor measurement may occur because of mechanical wear, or diaphragm damage.
The transmitter may have been damaged during installation, operation or maintenance.
Usually, this type of error will require repair or replacement of the pressure transmitter.
In order to avoid this type of error, proper installation, commissioning, operation, and maintenance of pressure transmitters are essentials.
Check regularly for mechanical wear or damage on your pressure transmitters to rule out this error.
An error-free pressure transmitter ensures good process control.
When accurate measurement is achieved, the process has every chance of operating safely and efficiently.
By understanding the causes of measurement errors, you can take action to minimize their impact and ensure more accurate pressure readings.
Measurement error due to Improper Zero Reference and Shift of Full span can be solved by performing a regular calibration of your Pressure transmitter. If you don't have the time or manpower to calibrate your own pressure transmitters, ask a company to carry out on-site or laboratory calibrations.
Incompatibility with the process conditions can often be overcome through proper selection and configuration of the transmitter. Ask a qualified and trained sales engineer to support and check for the proper pressure transmitters for your application.
Sensors with higher rangeability enable more accurate measurements at lower pressures, making them ideal for applications where precision measurements are essential. When selecting a pressure transmitter, be sure to consider a device with high rangeability to ensure accurate measurements.
If the error is ultimately due to a damaged or worn pressure sensor, you'll need to repair or replace it. Consider Fuji Electric for fast delivery of your replacement pressure transmitters.
Now that errors in pressure transmitter measurement are discussed, you can consider those points while selecting transmitters.
However, quality affects accuracy and performance therefore you should source transmitters from reliable suppliers such as Fuji Electric.
