Pressure Measurement · Free Calculator
Pressure Transmitter Turndown Calculator
Check whether a transmitter can be calibrated to your required span. Turndown compares the sensor upper range limit (URL) with the calibrated span.
URLCalibrated spanRangedownAccuracy impact
mbar
mbar
mbar
: 1
% of span
The calibration is within the transmitter limits. Check the datasheet: many accuracy specs only hold up to about 10 : 1 turndown and degrade beyond it.
Turndown10 : 1
Minimum span allowed25 mbar
Accuracy in units± 0.1625 mbar
How this result was calculated
- Turndown = URL ÷ span = 2,500 ÷ 250 = 10 : 1
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Turndown Formula
Turndown = URL ÷ (URV − LRV)
Minimum span = URL ÷ maximum turndown
Minimum span = URL ÷ maximum turndown
Worked example
A 2500 mbar sensor calibrated 0 to 250 mbar has a 10 : 1 turndown, comfortably within a 100 : 1 maximum.
Key insight: high turndown keeps spares simple but costs accuracy and stability. For best performance select a sensor range so the turndown stays below about 10 : 1.
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Frequently Asked Questions
What is transmitter turndown?
The ratio of the sensor upper range limit to the calibrated span; also called rangedown or rangeability.
Does high turndown reduce accuracy?
Usually yes. Beyond a vendor stated limit (often 10 : 1) the accuracy specification is multiplied by a turndown factor.
What is URL?
Upper range limit: the highest pressure the sensor can be calibrated to measure.
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