Understanding Sensor Accuracy: What Do ±0.5%, ±0.2%, and ±0.075% Mean?

When comparing industrial sensors, one of the first specifications engineers notice is accuracy.

Manufacturers often advertise specifications such as:

• ±0,5%FS
• ±0,2%FS
• ±0.1%FS
• ±0.075%FS

At first glance, these numbers may seem straightforward. However, many users misunderstand what these accuracy ratings actually mean and how they affect real-world measurements.

In this guide, we’ll explain how sensor accuracy is defined, how to calculate measurement errors, and when investing in a higher-accuracy instrument makes sense.

What Is Sensor Accuracy?

Sensor accuracy describes how close a measured value is to the actual value.

No measurement instrument is perfectly accurate. Every sensor has some degree of error between the measured value and the true value.

For example:

If the actual pressure is:

10.0 bar

And the transmitter displays:

10.1 bar

The measurement error is:

0.1 bar

The smaller the error, the higher the accuracy.

What Does “%FS” Mean?

Most industrial transmitters specify accuracy as a percentage of Full Scale (FS).

Full Scale refers to the maximum measurement range of the instrument.

Por ejemplo:

Pressure transmitter range:

0-100 bar

Full Scale (FS):

100 bar

If the accuracy is:

±0,5%FS

The maximum error is:

100 × 0.5%

= ±0.5 bar

This means the transmitter may read:

• 9.5 bar
• 10.0 bar
• 10.5 bar

when the actual pressure is 10 bar.

How Accuracy Changes with Different Specifications

Let’s compare several common accuracy ratings using the same 0-100 bar pressure transmitter.

Precisión	Maximum Error
±0,5%FS	±0.5 bar
±0,2%FS	±0.2 bar
±0.1%FS	±0.1 bar
±0.075%FS	±0.075 bar

As accuracy improves, measurement uncertainty decreases.

This is especially important in applications requiring precise process control.

Why Accuracy Matters More at Lower Readings

Many users assume that a ±0.5%FS transmitter has a 0.5% error regardless of the measured value.

This is incorrect.

Consider a transmitter with:

Alcance:

0-100 bar

Precisión:

±0,5%FS

Maximum error remains:

±0.5 bar

Whether the measured pressure is:

• 10 bar
• 50 bar
• 90 bar

the error limit remains the same.

Example at 10 bar

Actual pressure:

10 bar

Possible reading:

9.5-10.5 bar

Relative error:

5%

Example at 90 bar

Actual pressure:

90 bar

Possible reading:

89.5-90.5 bar

Relative error:

0.56%

This is why selecting an appropriate measurement range is extremely important.

Accuracy vs Repeatability

These two specifications are often confused.

Precisión

Measures how close a reading is to the true value.

Repetibilidad

Measures how consistently a sensor produces the same reading under identical conditions.

Por ejemplo:

A transmitter repeatedly measures:

• 50.1 bar
• 50.1 bar
• 50.1 bar

Excellent repeatability.

However, if the actual pressure is 49.5 bar, the accuracy is still poor.

A good industrial instrument should provide both high accuracy and good repeatability.

Accuracy vs Resolution

Another common misunderstanding involves resolution.

Resolución

The smallest detectable change in a measurement.

Por ejemplo:

A display showing:

50.01 bar

has higher resolution than a display showing:

50.0 bar

However, higher resolution does not automatically mean higher accuracy.

A sensor can display many decimal places while still having significant measurement error.

Typical Accuracy Requirements by Application

Different industries require different levels of accuracy.

General Water Treatment

Recommended Accuracy:

±0,5%FS

Suitable for:

• Pump monitoring
• Water distribution systems
• General process control

Tank Level Monitoring

Recommended Accuracy:

±0.2%FS to ±0.5%FS

Suitable for:

• Depósitos de agua
• Wastewater tanks
• Chemical storage tanks

Procesado químico

Recommended Accuracy:

±0.1%FS to ±0.2%FS

Suitable for:

• Dosing systems
• Reactor monitoring
• Process optimization

Custody Transfer and Critical Measurements

Recommended Accuracy:

±0.075%FS or better

Suitable for:

• High-value processes
• Energy applications
• Precision industrial systems

When Is a High-Accuracy Sensor Worth the Investment?

Higher accuracy instruments generally cost more.

However, the additional investment may be justified when:

Product Quality Is Critical

Small measurement errors can affect product consistency.

Process Efficiency Matters

Accurate measurements improve control system performance.

Regulatory Compliance Is Required

Many industries must meet strict measurement standards.

Inventory Management Is Important

Level measurement errors can affect inventory calculations.

Recommended High-Accuracy Solution

Transmisor de presión diferencial de silicio monocristalino inteligente PWP3051DP

En Transmisor de presión diferencial de silicio monocristalino inteligente PWP3051DP offers accuracy up to ±0.075%FS, making it suitable for demanding industrial applications requiring high measurement precision.

Características principales

• Accuracy up to ±0.075%FS
• Excellent long-term stability
• Comunicación HART
• Suitable for liquid, gas, and steam measurement
• Industrial-grade reliability

Aplicaciones típicas

• Process control systems
• Plantas químicas
• Generación de energía
• Instalaciones de tratamiento de aguas
• Industrial automation systems

Common Accuracy Selection Mistakes

Choosing Accuracy Based Only on Price

Lower-cost instruments may not provide the precision required for critical applications.

Overspecifying Accuracy

Not every application needs ±0.075%FS performance.

For many water and wastewater systems, ±0.5%FS is sufficient.

Ignoring Measurement Range

An incorrectly selected range can have a greater impact than the accuracy specification itself.

Overlooking Long-Term Stability

Accuracy should be evaluated together with stability and drift performance.

¿Por qué elegir Pokcenser?

Pokcenser provides industrial measurement solutions for customers in more than 100 countries.

Our product portfolio includes:

• Transmisores de presión
• Differential Pressure Transmitters
• Sensores de nivel radar
• Sensores de nivel ultrasónicos
• Caudalímetros
• Water Quality Instruments

We help customers select the most cost-effective balance between performance, reliability, and accuracy.

Preguntas frecuentes

Q1: Is ±0.075%FS always better than ±0.5%FS?

Yes in terms of measurement precision, but not every application requires such high accuracy.

Q2: Does higher accuracy always mean higher cost?

Generally yes, because higher-accuracy sensors require better sensing elements, calibration, and manufacturing processes.

Q3: What does FS mean?

FS stands for Full Scale, which refers to the maximum measurement range of the instrument.

Q4: Is accuracy more important than resolution?

For industrial process measurement, accuracy is usually more important than display resolution.

Q5: Which industries require high-accuracy transmitters?

Chemical processing, power generation, pharmaceutical manufacturing, and precision industrial applications often require higher accuracy instruments.