This blog was originally published on June 20, 2022, and updated on May 28, 2025.
Maintaining accurate and stable pressure measurements is a constant challenge in demanding applications, particularly as pressure sensors age or are exposed to extreme conditions such as vibration, temperature fluctuations or pressure cycling. This can lead to loss of stability, causing your sensor to drift outside of its specified range. When this happens, you have an important decision to make: recalibrate or replace your instrument.
As a trusted leader in pressure measurement technologies, Ashcroft brings over 170 years of engineering expertise to support process applications across multiple industries. Read this article to learn more about zero and span adjustability, why it’s important to long-term sensor performance, the benefits and limitations of using adjustable pressure transducers and ow to determine when recalibration is needed.
Read on to discover how pressure transducers with zero and span adjustability can improve your system’s reliability and help you avoid costly interruptions. You will also see links to additional articles and resources to help deepen your knowledge about this topic even further.
What are zero and span errors?
In a separate article, we provided an overview of zero and span offset errors, explored common causes and provided four strategies for correcting these errors. Here's how we classified each:
- Zero offset refers to the output error at the bottom end of the measurement range. Although many people associate zero offset as 0 psi, in compound ranges, it may represent full vacuum (- 14.7 psi).
- Span offset indicates the output error at the full measurement range. For example, a zero to 30 psi unit has a span of 30 psi, but a vacuum to 30 psi has a span of 44.7 psi.
Many factors can cause zero and span offset errors, including inherent imperfections in the sensing elements or electronics of your instrument, environmental factors, electrical noise and drift. these setting errors are generally expressed as a percentage of span or a percentage of output.
Unfortunately, many systems rely on pressure sensors that cannot be adjusted in the field, leading to unplanned downtime and costly replacements.
What is zero and span adjustability in a pressure sensor?
Zero and span adjustability is a pressure sensor feature used to recalibrate, or correct the output of the instrument at the extremes of its calibrated range. Typically, these adjustments are made through potentiometers or other adjustment tools (i.e., a reed switch with a magnet) to modify the output signal at both the zero and full span measurement points.
- Zero adjustment aligns the transducer’s output with zero pressure (or the lower range value).
- Span adjustment sets the correct output at the full-scale pressure value.
Adjusting the output signal at both zero and span corrects errors caused by sensor drift, which can result from extended use or numerous pressure cycles. The frequency of recalibration depends on the specific application and calibration requirements.
Together, zero and span adjustability provide control over the pressure transducer's output, ensuring it accurately reflects true pressure values even when operating conditions or system configurations change.
Some pressure sensors, including the Ashcroft® E2G (with magnetic adjustment), the Ashcroft® CXLdp and the Ashcroft® DXLdp transducers all offer these adjustment options. With these instruments, you can recalibrate the sensors on-site or in the field, extending their service life and restoring reliable performance without disrupting your operation.
Note, the Ashcroft® E2-series Pressure Transducers also include zero and span adjustability for explosion-proof, intrinsically safe and non-incendive hazardous location ratings.
Benefits and limitations of a pressure transducer with zero and span adjustability
On the plus side, zero and span adjustability allow the end-user to adjust the pressure sensor’s output at their facility or in the field for minimal downtime of critical applications. Adjusting these parameters ensures that your pressure transducer continues to deliver accurate measurements even after prolonged use or environmental exposure. This eliminates the time, cost and inconvenience of sending the transducer back to the manufacturer or to a calibration lab for recalibration.
The primary limitation is that the zero and span adjustment only addresses the output signal at the zero point and full span of the device. However, any signal offset between these points cannot be adjusted. This may be significant to an end-user based on the application's accuracy requirements. If accuracy across the entire pressure sensor range is crucial, the sensor should be replaced or sent back to the manufacturer for repair and recalibration.
Figure 1. Benefits and limitations of zero and span adjustability
What are the effects on accuracy?
In our guide, we discuss how zero and span adjustability help keep the pressure sensor’s accuracy within the tolerance of the stated accuracy.
If a sensor is found to have a large offset, a user can use a measurement reference (i.e., test gauge) that is at least four times more accurate than the sensor in question along with a pressure source, multimeter and tools to adjust the potentiometers to dial the output signal back into specification.
Typical uses in applications
Zero and span adjustment features can be used on many applications, but it is more relevant in industries that have strict calibration verification requirements. For example, pressure sensors used in pharmaceutical applications where manufacturers are required to verify the calibration of their systems and processes every 3 to 6 months because the accuracy of the output signal is crucial to the functionality of the system or device.
Ready to learn more?
Now that you understand what zero and span adjustability is and how it can help your pressure sensors perform better, you can find the right solution to ensure your process doesn’t stop. Here are a few more articles that may help answer other questions about zero and span offset, pressure instruments and more.
- What Causes Zero and Span Offset in a Pressure Transducer?
- Selecting Electrical Connectors for Pressure Transducers
- Choosing a Pressure Transducer for Critical Environments
- How Accurate Are Your HVAC System’s Pressure Instruments?
- How Does Media Temperature Affect Pressure Transducer Performance?
- How Much Do Pressure Transducers Cost? (6 Factors Impacting Price)
Contact us anytime to speak with an expert on our technical team and get your questions answered directly.
In the meantime, download our guide to learn more about accuracy and how it is defined in your accuracy statement.