Pressure transducers are important instruments that are used to measure air, gas or liquid pressure in many industrial applications. They work by measuring pressure at various stages of a process and converting the measurement into an electrical signal, which is used to monitor and control the overall system.
Ashcroft has been making pressure transducers for decades and one question we are often asked is whether these instruments can be installed in any orientation. While the short answer is “yes, they can,” there are factors to consider before you install your transducers.
Read this article to learn how transducers work, the effect that changing the orientation may have on the instrument’s accuracy and how position errors can be fixed. You will also be directed to additional resources that can help answer other common questions about pressure transducers.
How pressure transducers work.
Pressure transducers use sensing technology to detect movement in the sensor's diaphragm, which will flex under the force of the process pressure. The instrument then converts the measurement into one of two electrical output signals:
• Current: 4 to 20 mA (milliamps)
• Voltage: 0-5 Vdc and 0-10 Vdc (voltage direct current) and millivolt per volt are some examples.
How does gravity and pressure range affect a transducer’s position effect?
In both horizontal and vertical installation positions, you need to consider the impact of gravity, which is a fundamental constant of nature. For instance, if the transducer is installed horizontally, the gravitational pull on the diaphragm will occur in one direction. If you shift the transducer to a vertical orientation, the direction of the gravitational pull will also shift and cause a change in the output signal.
The position effect is more prominent in low-pressure transducers.
For transducers like the Ashcroft ® S1 Pressure Transducer with a pressure range over 15 psi, the impact is typically considered negligible. However, the impact on low-pressure transducers is much more concerning. Transducers with ranges less than or equal to 5 Psi (approximately 140 IWC) are generally considered low-pressure.
Low-pressure transducers like the Ashcroft® CXLdp are generally calibrated at the factory for either a horizontal or vertical installation. The orientation decision is often based on the application, where the instrument will be installed in the process and the specified pressure range.
Once you receive the transducer, you can install it in a different orientation than how it was calibrated. If you do this, the most important thing to remember is that the position effect can create a zero offset and affect the accuracy of the instrument.
Here's an example:
The good news is that Customer B’s error can be solved in one simple step: Once the transducer is in the final installed position, simply adjust the unit using the zero potentiometer and the position error will be removed.
The bottom line: Any pressure transducer that is installed in a different orientation than the factory calibration can be zeroed in its final position to remove any possible position effect.
What sensing technology is best for low-pressure transducers?
Several sensor technologies can be used in low-pressure transducers. The most common incorporate silicon and metal diaphragm materials. Metal sensing technologies are generally large with more mass than silicon sensing technologies. The larger surface mass makes the metal option more prone to position effects.
The smaller size and lower mass of the silicon technologies make these options generally less position-sensitive. Read, MEMS Pressure Transducer Sensor Technology to learn more about low-pressure sensor technologies.
Ready to access additional informative content?
Now that you know the primary factors that can influence the accuracy of a transducer and how to address errors that can occur when you change orientations, you may have questions. As a next step, you can read these other articles or talk to one of our industry experts for answers.
- Choosing a Pressure Transducer for Critical Environments
- How Does Media Temperature Affect Pressure Transducer Performance?
- How Much Do Pressure Transducers Cost? (6 Factors Impacting Price)
In the meantime, download our eBook to read about pressure instruments for critical environments.