pressure transducers | critical environments | pressure tubing | pharmaceutical and biotechnology | HVAC
This article was originally published on September 19, 2022, and updated on August 13, 2025.
Low-pressure transducers are essential in applications like HVAC systems, cleanrooms, critical environments, and pharmaceutical operations. These systems often require the pressure sensor to be mounted away from the source, sometimes by several feet or more.
What many don’t realize is that the pressure sensor tubing length can influence system behavior in subtle but important ways. While accuracy may remain intact, signal response times can vary depending on how the system is configured.
Ashcroft has been supporting critical low-pressure systems for decades, helping engineers and facility managers design pressure measurement setups that remain responsive and stable, even when tubing runs are long. Read this article to learn how pressure tubing works, what impact tubing length has on your system and pressure instruments, and how to enhance your system design for performance and reliability.
Why Use Pressure Tubing?
Pressure sensor tubing connects the pressure ports of a transducer to the process source. This setup allows the sensor to be remotely mounted, which is common in clean or hazardous environments where direct access is limited. For instance, pressure tubing is often required in:
- Cleanrooms where wall-mounted transducers are preferred
- HVAC duct systems
- Pharmaceutical applications that demand remote or protected instrumentation
In addition to mounting/connectivity benefits, pressure tubing can also help with the following:
- Thermal isolation and condensation prevention. Use of tubing also helps thermally isolate the transducer from temperature extremes that could affect internal electronics or measurement stability. In some HVAC applications, tubing acts as a buffer to prevent condensation or thermal shock at the sensing element.
- Contamination control in clean applications. In contamination-sensitive environments, remote mounting using tubing protects the transducer from exposure to corrosive media or cleanroom washdown processes.
- ASHRAE/cleanroom standard alignment. Many HVAC and cleanroom installations adhere to ASHRAE or ISO standards that recommend or require remote-mounting transducers using tubing to maintain clean zones and meet regulatory compliance.
Effects of Tubing Length
You can specify pressure tubing in many different lengths to fit the location of your pressure transducer. The good news is that tubing length does not affect the accuracy of a low-pressure transducer. The sensor will still detect the correct pressure value regardless of how far it is from the source.
However, tubing length can affect response time. Using the Ashcroft® CXLdp or DXLdp Pressure Transducers as examples, you can see that the longer the tubing length, the slower the response time of the transducer. However, the amount of time is often negligible.
Ashcroft CXLdp and DXLdp response times with tubing:
- Standard response time: ~250 milliseconds
- With 100 ft of tubing: ~340 milliseconds
- With 500 ft of tubing: ~700 milliseconds
These response time examples provided are based on clean, dry gas process media commonly used in low-pressure/differential pressure applications. Even at 500 feet, the response time is still under one second.
In most cases, this delay is not significant; however, for applications that depend on immediate control response, it could be a factor worth considering.
Best Practices for Pressure Tubing Configuration
1. Keep tubing lengths equal on differential ports
When using a differential pressure (DP) transducer, the tubing length should be approximately the same for both the high and low ports for differential pressure (DP) transducers. Unequal tubing length can introduce error. The side with longer tubing may delay pressure transmission slightly, causing a false pressure differential. It is best to match tubing lengths to avoid these timing mismatches.
2. Confirm acceptable response time
Prior to installation, be sure to confirm the acceptable response time of the transducer for your application. If you need real-time responsiveness, consider reducing the tubing length or using faster electronics to compensate.
Ready to learn more?
Now that you understand more about pressure tubing and the effects it can have on pressure transducers, you can research the solution that’s best for your low-pressure application. With this information in mind, you can avoid potential issues and keep your process running with reliable and accurate pressure measurements.
If you want to learn more about pressure transducers, you can read some of our other articles:
- Choosing a Pressure Transducer for Critical Environments
- How Does Media Temperature Affect Pressure Transducer Performance?
- Product Review: GXLdp Differential Pressure Transducer
- How Accurate Are Your HVAC System’s Pressure Instruments?
Feel free to contact us today to talk to one of our industry experts and get your questions answered. In the meantime, download our guide to learn more about pressure instruments for critical environments.