Pressure Measurement · Glossary

What is Transmitter Turndown?

URL ÷ calibrated spanPressure Measurement

Transmitter turndown is how far a transmitter span is reduced from its sensor upper range limit.

Transmitter Turndown Explained

Smart transmitters can be ranged far below their URL, often 100:1 on paper. The catch is accuracy: errors stated in % of URL become large percentages of a small span.

Choose a sensor range so the calibrated span uses a reasonable part of the URL, and check the maker accuracy formula at the turndown you need.

Transmitter Turndown Formula

Turndown = URL ÷ (URV − LRV)

URL	upper range limit
URV − LRV	calibrated span

Example: A 0 to 2 bar span on a 20 bar URL sensor is 10:1.

Calculators for Transmitter Turndown

CalculatorTransmitter Turndown CalculatorFree online calculator with formula and worked example.CalculatorPressure Gauge Accuracy CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Transmitter Turndown?

Transmitter turndown is how far a transmitter span is reduced from its sensor upper range limit.

Is high turndown always bad?

No, but accuracy and stability worsen as span shrinks. Check the total probable error at the needed span.

Is transmitter turndown the same as flow meter turndown?

No. Flow meter turndown is the ratio of maximum to minimum measurable flow; transmitter turndown is the ratio of sensor limit to span.

Learn more on the blog

Instrumentation and control standards

A practical guide on instrumentationblog.in with more detail on transmitter turndown and how it is applied on real plants.

Read Full Article

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