Pressure transmitter span vs range is an important distinction because range describes the lower and upper pressure limits, while span describes the difference between them. These terms often appear in datasheets, calibration, and quotation discussions, but they are easy to confuse.
For buyers, understanding the difference helps avoid wrong calibration, wrong PLC scaling, and wrong transmitter selection.
What Is Pressure Transmitter Range?
Pressure transmitter range refers to the lower range value and upper range value. It tells the full pressure interval that the transmitter is configured to measure.
For example, if a transmitter is configured from 0 to 10 bar, the range is 0–10 bar. If it is configured from -1 to 5 bar, the range is -1–5 bar.
The range must include both the starting point and ending point. This is especially important for vacuum and compound pressure applications.
What Is Span?
Span is the difference between the upper range value and lower range value. It describes how wide the calibrated measuring interval is.
For a 0–10 bar range, the span is 10 bar.
For a -1–5 bar range, the span is 6 bar.
This matters because transmitter accuracy, turndown, calibration, and output scaling are often related to span.
Why Buyers Should Care
In a 4–20 mA pressure transmitter, the lower range value usually corresponds to 4 mA, and the upper range value corresponds to 20 mA. If range and span are misunderstood, the PLC or display may scale the signal incorrectly.
This can create problems such as:
- The display value does not match actual pressure.
- The PLC shows wrong engineering units.
- The transmitter is calibrated to the wrong start point.
- Vacuum or compound range is interpreted incorrectly.
- Replacement transmitters do not match old settings.
This is why range and span should be written clearly in quotation and replacement requests.
Example in Real Selection
If a buyer says the required span is 10 bar, it is still not enough. The supplier needs to know the actual range. A span of 10 bar could mean 0–10 bar, -1–9 bar, 5–15 bar, or another range.
For most pressure transmitter orders, buyers should provide the full configured range, not only the span.
Conclusion
Pressure transmitter range means the lower and upper pressure limits. Span means the difference between those two limits. Both are important for calibration, PLC scaling, replacement, and correct output interpretation.
SIY Electric can help buyers confirm pressure transmitter range, span, output scaling, and calibration requirements before ordering or replacement.
