Whatever your industry, more accurate pressure measurement means higher quality end products, greater safety and more efficient production lines.
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The accuracy of pressure transmitters is influenced by a number of parameters that can degrade measurement accuracy in industrial processes. This in turn can degrade the quality of finished products on production lines. It's important to be aware of these factors, so you can take steps to limit them. But what factors make your measurements inaccurate? And what steps should you take to limit their influence on your sensors?
Fuji Electric pressure transmitters are compensated to avoid the influence of these factors and obtain reliable, accurate measurements without degradation.
In this article, we explain the seven factors that influence the accuracy of pressure transmitters.
Ambient temperature and fluid temperature are two factors that influence the accuracy of a pressure transmitter. Each sensor has its own temperature tolerances. The temperature range induces variations in sensor accuracy. The more extreme the ambient or process temperature, the less accurate the sensor. When choosing your pressure transmitter, it's important to check that the pressure transmitter 's temperature ranges are appropriate for your application.
Some pressure transmitters are temperature-compensated at the time of manufacture, over a specific temperature range, in order to avoid temperature variations which could have a detrimental effect on accuracy. When choosing your supplier, look for an instrument with a temperature compensation function.
Fuji Electric pressure transmitters feature the unique Giration 4DTM technology, which guarantees consistently accurate measurements regardless of variations in ambient temperature and static pressure.
The differential pressure transmitter measures the pressure difference between two measurement points, in comparison with the gauge pressure sensor (which measures in relation to atmospheric pressure) or absolutepressure transmitter (which measures in relation to vacuum).
Static pressure, also known as line pressure, is the pressure in a pipe or process. This process pressure applies to both pressure taps on the differential transmitter.
When both pressure taps of the differential pressure transmitter are at atmospheric pressure, the pressure measured by the sensor is zero. If an identical higher pressure is applied in the same way to both inputs, the measured pressure is also zero in theory. In practice, static pressure influences the accuracy of differential pressure transmitters .
Line pressure has a negative impact on measurement accuracy and repeatability. Static pressure influence tests defined byIEC 62828-2 characterize the effect on transmitter zero and span, a useful basis for qualifying the actual impact on accuracy. Field calibration can help eliminate the effects of process static pressure.
Fuji Electric differentialpressure transmitters are static pressure-compensated at the manufacturing stage, to avoid errors that could render the sensor inaccurate. When choosing your supplier, look for a device with a static pressure compensation function.
Static pressure must be taken into account when choosing a differential pressure transmitter. These have a maximum permissible static pressure which must not be exceeded.
Measurement accuracy varies according to the scale set on the transmitter.
The pressure transmitter 's dynamic range defines the minimum adjustable measurement range in relation to the transmitter's total pressure range. This rangeability ratio is a decisive factor when choosing a pressure transmitter.
If the set scale is outside the dynamic range, measurement accuracy is degraded.
Fuji Electric pressure transmitters feature a high dynamic range of 1:100, enabling low pressure scales to be set without affecting measurement accuracy. We recommend choosing pressure transmitters with a total scale range as close as possible to the actual pressure to be measured.
The accuracy of measuring instruments such as pressure transmitters deteriorates over time. As a result, the zero point of the sensor drifts over the months, affecting the accuracy of the pressure measurement.
To compensate for this, you can calibrate these pressure transmitters on a regular basis using a calibration company.
Fuji Electric pressure transmitters offer excellent long-term stability of ±0.1% over 5 years. This guarantees accurate measurement over time, allowing you to extend calibration intervals and reduce maintenance costs.
The mounting position has an influence on the pressure transmitter zero. Even if pressure transmitters are factory-calibrated, a measurement offset due to mounting position may be observed on site after installation. This can lead to inaccurate pressure measurement. This effect is caused by the weight of the oil filling the measuring cell.
For pressure transmitters with diaphragm seals, this effect may be more pronounced due to the greater volume of oil in the sensor. There is no effect of mounting position on scale range.
Field calibration is imperative to eliminate any zero offset caused by the effect of mounting position. pressure transmitters are usually fitted with an adjusting screw and a manifold for this purpose.
Intelligentpressure transmitters with HART protocol can be set using a portable communication pocket or a PC equipped with HART modem configuration software.
The measuring cells of pressure transmitters can be disturbed by vibrations on industrial equipment. Vibration affects measurement accuracy. In some cases, they can lead to transmitter damage or shortened service life.
Fuji Electric pressure transmitters have been tested by independent laboratories at very high vibration levels to verify their accuracy and robustness. It's a good idea to ask your transducer manufacturer for the test results to guarantee the vibration resistance of your installations.
pressure transmitters are supplied with 24 VDC. However, they can usually be operated over a wider voltage range. Incorrect or fluctuating voltage can affect the measurement, or even destroy the sensor in the event of overvoltage.
It is advisable to use an isolated, stabilized and regulated power supply to avoid measurement inaccuracy.
Fuji Electric pressure transmitters have a wide power supply range from 10.5 VDC to 45 V DC to ensure minimum influence of supply voltage on measurement accuracy.
When choosing your pressure transmitter :
| Factor type | Impact on Accuracy | Recommendations for minimizing the effect |
| Ambient and process temperature | Temperature variations can cause significant measurement errors. | Use pressure transmitters with thermal compensation to minimize these variations. |
| Static pressure | Negatively affects the accuracy and repeatability of differential pressure transmitters . | Use pressure transmitters with static pressure compensation and calibrate on site. |
| Change of measurement scale | Incorrect setting of the scale can degrade measurement accuracy. | Choose a suitable measurement scale and use pressure transmitters with a high dynamic range of 1:100. |
| Long-term stability | Zero drift over time can affect measurement accuracy. | Plan regular calibrations to maintain the long-term accuracy of your pressure transmitters. Choose pressure transmitters with high long-term stability. |
| Mounting position | The position can modify the sensor zero point, making the measurement inaccurate. | Install pressure transmitters in accordance with the manufacturer's datasheet and check the zero after installation. |
| Vibrations | Can affect measurement stability and shorten sensor life. | Use anti-vibration mounts to minimize impact. Use vibration-resistant pressure transmitters |
| Supply voltage | Voltage variations may alter measurements or damage the sensor. | Prefer sensors with a wide power supply range for better tolerance. |
When you choose Fuji Electric's FCXpressure transmitter , you guarantee the accuracy of your pressure measurements on your industrial processes. Your plants and facilities operate more safely and efficiently, producing higher quality products and reducing downtime. You can rely on the reliability and robustness of Fuji Electric pressure transmitters for accurate, repeatable measurement.
For optimum measurement accuracy, our technicians can commission your pressure transmitters. You can be sure that your devices are ready for use, and that your installations start up under the best possible conditions.
Sylvain GRAVEROT
Expert in pressure transducers and transmitters
