Calibration of pressure transmitter: The guide for accurate measurement
Calibration of pressure transmitter: The guide for accurate measurement
The calibration of pressure transmitter is an essential step in guaranteeing the accuracy and quality of measurements. It is the a process used to adjust and check the performance of a pressure transmitter or sensor against a standard reference.
Does the calibration of a pressure transmitter or pressure transducer seem complicated? You may be wondering why these terms are so crucial in the world of measurement and pressure?
In this article, we'll look in detail at the calibration process, its importance, and how it helps to improve the accuracy of measuring instruments. You'll also discover the nuances associated with calibration, and the key steps to ensuring reliable results.
What is the calibration of a pressure transmitter?
Calibration is the process of comparing the performance of a measuring instrument, such as a pressure transmitter, with that of a reference standard. This step is essential to ensure that the instrument operates correctly and provides accurate measurements. In the context of pressure transmitterscalibration is used to determine the difference between the instrument's measurement and the actual value.
Why is it essential to calibrate pressure transmitters and transducers?
Pressure transmitters and sensors are used in a wide range of applications, from commissioning industrial equipment to monitoring manufacturing processes. A small error in measurement can have serious consequences, particularly in terms of quality, safety and performance. Calibration ensures that these instruments operate with the required accuracy, minimising the risks associated with inaccurate measurements in the measurement chain.
The benefits of regular calibration
Optimising performance
A correctly calibrated pressure transmitter or transducer ensures optimum performance. This not only ensures accurate measurements, but also greater efficiency in the applications where these instruments are used.
Cost reduction
Incorrectly calibrated instruments can lead to costly errors, particularly in terms of wasted resources or production faults. By investing in regular calibration, you can avoid these additional costs in the long term.
Comply with standards and improved product quality
Many industries have strict standards for measurement accuracy. Regular calibration ensures that your instruments meet these standards, avoiding penalties or compliance issues.
Operational safety
In certain industries, such as the chemical, oil & gas or nuclear sectors, precise measurements are essential for safe operations.
Optimising performance
Cost reduction
Comply with standards and improved product quality
Operational safety
The nuances of pressure transmitters
Types of pressure transmitters
There are different types of pressure transmitters, each with its own applications and calibration requirements. For example, an pressure transmitter absolute sensor measures pressure in relation to a perfect vacuum, the sensor gauge pressure sensor measures pressure relative to atmospheric pressure, while a pressure transmitter differential measures the pressure difference between two points.
Each type requires a specific calibration procedure to ensure accurate measurements.
Calibration frequency
How often you need to calibrate your pressure transmitters depends on a number of factors, including use, working environment and industry standards.
Some instruments may need to be calibrated monthly, while others may need to be calibrated every 1 to 3 years. It is essential to follow the manufacturer's recommendations and industry standards to determine the appropriate calibration frequency.
On-site or laboratory calibration
An on-site calibration is carried out directly at the point where the instrument is used, whereas a laboratory calibration is carried out in a controlled environment on a pressure bench.
Field calibration is often preferred for instruments that are difficult to move or that are essential to the production process.
On the other hand, laboratory calibration offers advantages such as generally better accuracy thanks to more stable equipment and conditions.
How does the calibration process work?
The calibration process begins by placing the instrument on a calibration bench. The instrument is then subjected to various pressure values, from zero (or vacuum) to its maximum measurement range.
At each stage, the instrument's measurements are compared with those of a reference standard. If deviations are observed, the instrument is adjusted accordingly.
The key stages in calibrating a 4-20mA pressure transmitter
1. Preparing the instrument
Before starting calibration, it is essential to prepare the instrument. This involves checking its general condition and components, ensuring that it is clean and allowing it to acclimatize to the calibration environment (temperature, humidity, atmospheric pressure) for an appropriate period of time.
Install the transmitter in a stable location, free from vibration or movement.
Set the zero position of the transmitter. This is essential, as the calibration position may differ from the actual installation position. Ignoring this step could result in inaccuracies. Pre-stress the sensor diaphragm before calibration. This involves applying a pressure of approximately 90% of the maximum scale. For example, for a 10 bar sensor, raise the pressure to approximately 9 bar. Maintain this pressure for half a minute, then release. This step ensures greater accuracy during calibration.
2. Selecting the reference standard
The reference standard or test equipment must be at least four times more accurate than the instrument being calibrated. It is essential to ensure that the standard itself has been recently calibrated and complies with the required standards.
3. Calibration procedure
The calibration procedure varies according to the type of sensor or transmitter. However, in general, the instrument is subjected to a series of 3 known pressures (0%, 50%, 100% corresponding to 4mA, 12mA and 20mA for a 4-20mA output signal) on the way up and down, and its readings are compared with those of the reference standard.
Allow each test point to stabilise before moving on to the next, usually at least 30 seconds.
If necessary, use 5 points for greater accuracy. If deviations from the reference calibrator are observed, adjustments are made until the instrument gives accurate readings.
By following these steps, you ensure not only the accuracy of your pressure transmitter, but also the reliability of all the systems into which it is integrated.
How to calibrate a Pressure transmitter?
Equipment required for pressure transmitter calibration
Pressure transmitter
Multimeter
Pressure generator (pump or calibrator)
HART communicator (optional)
Essential steps for calibrating a 4-20mA Pressure Transmitter
Isolate the pressure transmitter from the process with an isolation valve.
Dismantle the transmitter or close the manifold valves and carefully open the bleed valve to release the pressure for field calibration.
Connect the multimeter to the transmitter and check that the output signal is 4 mA in the absence of pressure.
Connect a test pump (pressure generator) to the transmitter.
Check for leaks.
Test the transmitter at different pressure points (0%, 50%, 100%) and ensure that it operates correctly.
If necessary, or if an anomaly is detected, proceed with calibration.
Calibration with the external screw for an analogue pressure transmitter
Set the slider to the ZERO position. Apply a pressure of 0 % according to LRV with the test pump and if the multimeter does not display a 4 mA signal adjust the zero potentiometer of the transmitter (external screw) to obtain a 4 mA output signal.
Move the slider to the SPAN position. Apply 100% pressure according to URV and adjust the scale setting to obtain a 20 mA signal on the multimeter by adjusting the span potentiometer (external screw) on the transmitter.
Repeat these steps until you obtain accurate signals.
Calibration with a local indicator for a smart pressure transmitter (SMART)
Open the transmitter cover to access the indicator or use the magnetic pen.
Switch from operating mode to adjustment mode on the local indicator to adjust the minimum and maximum values.
Apply a reference pressure of 0% according to LRV with the calibrator and access the zero adjustment (LRV) of the transmitter. Select the LRV value and confirm to save the setting. The indicator will automatically calibrate.
Apply a reference pressure of 100% according to URV with the calibrator and access the measurement range (URV) setting for the sensor. Select the URV value and confirm to save the setting. The indicator will automatically calibrate.
Calibration with a HART handheld field communicator for an intelligent HART pressure sensor (SMART)
Get a HART pocket and connect it to the transmitter.
Select the appropriate menu on the HART pocket to adjust minimum and maximum values.
Apply a 0% LRV reference pressure with the calibrator and then apply a 100% URV reference pressure.
Follow the instructions: Configuration - Calibration - Zero adjustment (LRV) and span adjustment (URV) - Minimum/maximum value changes.
The HART console will automatically calibrate the sensor.
Finalising the calibration procedure
Reinstall the sensor and re-establish the process connection.
Restart the pressure transmitter back into operation. Make sure there are no leaks.
Not all measuring instruments are created equal. It is essential to choose a high quality pressure transmitter and adapted to your specific needs to guarantee accurate results.
How to choose a calibration service?
Reputation and experience When choosing a calibration service, look for a company with a good reputation and technicians with significant experience in the field. Recommendations and customer reviews can be valuable indicators.
Accreditations Make sure that the calibration service is accredited by the relevant bodies. This ensures that they follow the appropriate standards and procedures.
After-sales service A good calibration service doesn't end once the calibration has been carried out. Look for companies that offer an excellent after-sales service, including commissioning, technical support and advice.
REPUTATION AND EXPERIENCE
ACCREDITATIONS
AFTER-SALES SERVICE
For accurate pressure measurement, opt for calibration
The calibration of pressure transmitters is much more than a simple routine or formality. It is essential to the safety, quality and efficiency of many industrial processes. By understanding the importance of calibration and following the appropriate steps, you can not only ensure the accuracy of your equipment, but also extend its life and optimise its performance.
Remember, precision is at the heart of efficiency. By investing time and resources in the regular calibration of your equipment, you are investing in the quality and reliability of your operations. So, the next time you think about calibration, remember its decisive impact and the benefits it brings to your business.
Ensure accurate and reliable pressure measurement with Fuji Electric France.
Our pressure transmitters and calibration services will help you solve your measurement problems.
To find out more about our products and benefit from a free consultation, contact our team of experts today.
Calibrating a pressure transmitter involves comparing its measurements with those of a reference standard, then adjusting the transmitter according to the differences observed.
What is transmitter calibration?
Calibrating a transmitter is the process of checking and adjusting its accuracy by comparing it with a reference standard.
What is the importance of calibrating a transmitter?
Calibration ensures that the transmitter operates correctly and provides accurate measurements, which is essential for the quality, safety and efficiency of industrial processes.
How to calibrate a pressure transmitter?
Calibrating a pressure transmitter is identical to calibrating a sensor. It involves comparing the transmitter's measurements with those of a reference standard and adjusting the transmitter accordingly.
What is the calibration procedure for measuring instruments ?
The calibration procedure depends on the type of instrument. It generally involves preparing the instrument, selecting an appropriate reference standard, then comparing the measurements of the instrument with those of the standard and adjusting accordingly.
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