Sensors and Measurement Technology – A Guide to Industrial Sensors

Sensors and measurement technology are used to measure, monitor and control parameters in industrial systems. These may include pressure in a pipe, temperature in a process, level in a tank, flow through a pipe or the position of a moving part.

This guide explains how sensors work, what types of measured values are common, and what is important to bear in mind before choosing a sensor. The aim is to provide a better understanding of industrial sensors and transducers. Would you like to see the Swelex range? Go to the product page for sensors and measurement technology.

Product page

What is a sensor?

A sensor is a component that detects a physical quantity and converts it into a signal that can be used by a control system, measurement system or monitoring system.

These could include, for example:

pressure
temperature
level
flow
power
movement
position

What is the difference between a transducer, a sensor and a measuring transducer?

In practice, a sensor enables a system to “understand” what is happening in a process. Without sensors, it becomes difficult to automate, control, trigger alarms or monitor operational data. The terms ‘sensor’, ‘transducer’ and ‘measuring sensor’ are often used interchangeably.

A sensor is the component that detects a physical change, such as heat, pressure or movement. A transducer is often the complete unit that both detects the value and converts it into a usable signal. Transducers are often used when the focus is on the measurement itself.

In everyday industrial terminology, the terms are often used as synonyms. The most important thing is therefore not always which term is used, but what the component is designed to measure and how the signal is to be used.

How do industrial sensors work?

Industrial sensors work by converting a physical change into electrical information. When pressure changes, the temperature rises or a level falls, this affects the sensor’s measuring element. This change is then converted into a signal that can be read by a system.

Put simply, it happens in three steps:

The sensor detects a physical value.
The value is converted into an electrical signal.
The signal is forwarded to a control, monitoring or analysis system.

That is why the sensor needs to be suitable for both the measurement task and the system to which it is to be connected.

Some common types of transducers in measurement technology

Different types of sensors are used depending on what is to be measured. The table below provides an overview of common industrial sensors and their applications.

Sensor type	What it measures	Common uses
Temperature sensor	Temperature	Process industry, ventilation, machine monitoring
Pressure transducer	Pressure in gases and liquids	Hydraulics, pneumatics, water and process systems
Level sensor	Level in tanks and containers	Tank monitoring, the food industry and the chemical industry
Flow sensor	Flow of liquids or gases	Piping systems, energy metering, process control
Position sensor	Position or movement	Automation, robotics, machine control

Pressure transducer

– when pressure needs to be monitored

Pressure transducers are used when the pressure in gases or liquids needs to be measured. This can be important for ensuring correct operating conditions, detecting pressure drops or protecting equipment from excessive loads.

When selecting a pressure sensor, it is important to understand, amongst other things:

the pressure range to be measured
whether it is relative pressure, absolute pressure or differential pressure
the medium with which the donor comes into contact
the temperature and environment to which the sensor is exposed
which signal the control system requires

See our pressure transducers

Temperature sensor

– when heat affects the process

Temperature sensors are used to measure and monitor temperature in processes, machinery, liquids, air flows and technical systems.

The choice of the right temperature sensor depends, amongst other things, on:

measuring range
response time
installation method
whether the sensor measures in air, liquid, on a surface or in a process
requirements for accuracy
surrounding environment

In some applications, a fast response is important. In others, stability, reliability and a long service life are more important.

See our temperature sensors

Level sensor

– when the fill level needs to be checked

Level sensors are used to measure or indicate the level in tanks, vessels, silos and containers. They can be used to prevent overfilling, dry running or incorrect process levels. A level sensor can provide continuous measurement or act as a level switch at a specific point.

Some key factors are:

whether the material is a liquid, powder or granules
whether the measurement should be continuous or intermittent
the shape and material of the tank
temperature and pressure
risk of foam, deposits or dirt
hygiene requirements or chemical resistance

See our level sensors

Flow sensor

– when movement in a medium is to be measured

Flow sensors are used to measure or indicate flow in pipes and systems. This may involve liquids, gases or air.

Flow measurement can be important for:

monitor process flows

ensure cooling

detect stoppages or anomalies

control dosage

optimise energy and resource use

The choice depends on the medium, flow range, pipe size, pressure, temperature and whether the measurement needs to be accurate or simply indicate that flow is present.

See our flow sensors

Force, motion and position sensors

– when mechanical parameters are to be measured

This may relate to load, movement, distance or exact position.

They are often found in:

machine control

test equipment

lifting system

linear movements

calibration

quality control

automation

In this context, it is particularly important to understand the range of motion, the resolution, the load and how the sensor should be fitted.

See our force, motion and position sensors

How to choose the right sensor

Choosing the right sensor is not just a question of what needs to be measured. The sensor must also be suitable for the environment, the system and the function it is intended to fulfil.

Start with these questions:

What should be measured?
What measurement range is required?
How accurate does the measurement need to be?
Which medium is involved?
What are the levels of temperature, humidity, vibration and dirt in the environment?
Is the sensor to be used for control, alarms, monitoring or documentation?
What output signal does the system require?
How should the sensor be fitted?
What enclosure class is required?
Are there any requirements regarding materials, hygiene or chemical resistance?

The more clearly the application is defined, the easier it will be to choose the right type of industrial sensor.

Signals in measurement technology

Sensors can transmit signals in various ways. The type of signal required depends on the control system, distance, environment and accuracy requirements.

Common signal types are:

4–20 mA
0–10 V
heart rate
relay output
digital signal
communication-based signal

In industrial environments, the choice of signal is important because interference, cable lengths and system requirements can affect the measurement.

IP rating and environmental requirements

The IP (Ingress Protection) rating indicates how well a component is protected against dust and water. For industrial sensors, the IP rating can be crucial, particularly in environments involving moisture, cleaning, dust or outdoor installation. However, the IP rating is only one factor to consider when making a choice. It is also important to ensure that:

materials
cable connection
temperature resistance
chemical resistance
vibration resistance
mechanical protection
risk of condensation or flushing

A sensor may have the correct measurement range but still be the wrong choice if it cannot cope with the environment.

Industries and applications for sensors

Sensors and measurement technology are used in many types of technical environments where measured values are required for control, safety or monitoring.

Common areas include:

industrial automation
process industry
HVAC and ventilation
water and sewerage
energy
laboratories
mechanical engineering
transport
MedTech
marine environments
testing and measuring equipment

Frequently Asked Questions (FAQ) about sensors and measurement technology

What is the difference between a transducer and a sensor?
A sensor is the component that detects a physical quantity. A transducer is often the complete unit that converts the measured value into a signal. In practice, the terms are often used interchangeably.
What types of sensors are there?
Common types of sensors include pressure sensors, temperature sensors, level sensors, flow sensors, force sensors, and motion and position sensors. They are used for various measured values and applications.
How do I choose the right sensor for my application?
Start by defining what is to be measured, the required measurement range, the environment in which the sensor is to be installed, and the signal required by the system. You can then select the correct sensor type and design.
What does the IP rating mean for a sensor?
The IP rating indicates the level of protection against dust and water. This is important for sensors used in industrial environments, as they are often exposed to moisture, dirt, water jets or dust.
What does 4–20 mA mean?
4–20 mA is a common analogue signal in industrial measurement technology. It is used to transmit measured values from a sensor to a control or monitoring system.
When is an industrial sensor needed?
An industrial sensor is required when a measured value is to be used to control, monitor, trigger an alarm or document a process. This can range from pressure and temperature to level, flow and position.

Contact Swelex

Do you need help understanding which type of sensor is suitable for your application? Swelex can help you analyse the measurement task, environment, signal and technical requirements.

Please contact us for advice See our range of sensors and measurement technology