Two sensors from the same batch, calibrated the same day, can still disagree once the room warms up.
The thermal effect on sensors explains why, and knowing the difference between a zero shift and a span shift tells you exactly what to fix.
A sensor rarely lies about the process. Sometimes it is quietly telling you about the room temperature instead.
We will cover zero shift and span shift individually, how datasheets express thermal error, why thermal equilibrium matters, and the mistakes that lead engineers to misread a perfectly good specification.
What Is the Thermal Effect on Sensors?
The thermal effect on sensors describes how a change in ambient or process temperature changes a sensor's output, independent of any real change in the measured variable.
Every sensor is built from materials that respond to heat in their own way. Metals expand, resistances change, and elastic components stiffen or relax as temperature moves.
None of that is a defect. It is physics, and manufacturers design around it rather than pretending it does not exist.
Our temperature measurement errors guide covers the wider family of errors this effect belongs to.
Getting this wrong in the field is expensive in a quiet way. A technician who blames a sensor for drifting ends up replacing good hardware.
The real cause, an uncompensated ambient swing, was never the sensor's fault to begin with.
That replacement never actually fixes the real problem, since the new sensor drifts the exact same way under the exact same conditions.
The same confusion shows up during calibration. Thermal effects are one of the more common reasons a calibration check fails without an obvious cause.
Our pressure sensor calibration guide and calibration terms glossary are worth reviewing alongside this article.
2 Types of Thermal Effects on Sensors
Every thermal error a sensor produces falls into one of these two categories, and they are not the same problem.
Confusing the two during troubleshooting sends a technician chasing the wrong fix, since a zero problem and a span problem call for different corrections entirely.
Why Thermal Zero Shift Happens
Zero shift is unpredictable from one unit to the next, even within the same production batch.
Why Thermal Span Shift Happens
Span shift traces back to the sensing element's mechanical properties rather than a simple baseline offset.
Which Sensors Are Most Affected by Thermal Effects
Almost every sensor technology shows some thermal sensitivity, but the magnitude and the fix differ by type.
Strain gauge based sensors and load cells share the same underlying bridge circuit, so the compensation approach below applies to both.
Our Wheatstone bridge applications guide and RTD working guide cover the underlying circuits in more depth.
How Manufacturers Compensate for Thermal Effects
Compensation happens inside the sensor itself, well before it ever reaches a customer.
Reading Thermal Effect Specs on a Datasheet
Manufacturers do not all express this spec the same way, which makes comparing two datasheets side by side surprisingly easy to get wrong.
Two sensors quoting what looks like the same number can behave very differently once you check which basis each manufacturer actually used.
Converting a Thermal Spec Into a Real Number
A spec sheet number only means something once you apply it to an actual temperature swing and range.
Full scale range: 100 bar
Expected ambient swing: 30 degrees C
Resulting thermal error: 0.01 percent times 30, times 100 bar, equals plus or minus 0.3 bar
That same 0.01 percent per degree spec looks tiny in isolation, but it adds up quickly once the real temperature swing of the installation site is factored in.
An outdoor installation in a location with a 40 degree C swing between night and day sees a proportionally larger thermal error than the same sensor mounted in a temperature controlled room.
This is one more reason the same sensor model can perform differently at two sites, even with identical process conditions and identical calibration procedures.
Field Diagnosis: Is It Zero or Span?
A simple two point check in the field usually tells you which type of thermal error you are dealing with, well before any calibration equipment comes out.
Our correction factor in calibration guide explains how to turn that field check into an actual adjustment once you know which type of error you are correcting.
Zero Shift vs Span Shift: Quick Comparison
| Factor | Zero Shift | Span Shift |
|---|---|---|
| What moves | Entire curve, vertically | Slope of the curve |
| Error at low signal | Roughly constant | Small |
| Error at high signal | Roughly constant | Larger |
| Typical compensation | Resistor in bridge arm | Resistor in series with bridge |
Common Mistakes Reading Thermal Effect Data
Each of these mistakes is easy to avoid once you know to look for it.
That is exactly why the specification sheet deserves a careful read rather than a quick glance at a single headline number.
Watch: Zero and Span Calibration Explained
Thermal Effect on Sensors Questions Engineers Ask
Related Articles on This Site
- Pressure Transmitter Accuracy Specifications
- Pressure Transmitter Remote Seal Temperature Effect
- Pressure Transmitter Temperature Effect
- Temperature and Pressure Compensation
- Terms Used With Pressure Sensors
External References
What We Learn Today
- The thermal effect on sensors splits into zero shift, a vertical curve move, and span shift, a slope change.
- Manufacturers compensate each one with a separate temperature sensitive resistor tuned through testing.
- Comparing thermal specs correctly means checking whether they reference full scale, reading, or a combined value.