Outdoor temperature sensor

THERMASGARD® outdoor temperature sensors (passive) are available as surface-mounted or pipe-mounted sensors.
They are used to precisely measure the outside temperature - e.g. in damp rooms, on pipes to measure the surface temperature or directly outdoors.
Ideal for applications in heating, air conditioning and building automation systems where reliable temperature data is required.

Guide and useful information about outdoor temperature sensors

Outdoor temperature sensor for building automation and HVAC

Precise temperature detection for energy-efficient outdoor control

Author: T. Graf | Status: 20.03.2026

In a nutshell

Outdoor temperature sensors measure the ambient temperature outside buildings and provide a central control variable for heating, ventilation and air conditioning systems.

Typical applications:

Weather-compensated heating control
Flow temperature control
BMS and DDC systems
Energy optimization of buildings

Important factors:

Correct mounting position
Protection from direct sunlight
Fast response time and long-term stability

Typical areas of application for HVAC What is important during installation? Measuring principle and sensor technology Typical influences / errors in practice

What is an outdoor temperature sensor?

An outdoor temperature sensor is a temperature sensor that has been specially developed for outdoor use. It records the current ambient temperature and makes it available as an electrical signal for building management systems, controllers or automation systems.

In contrast to indoor sensors, an outdoor temperature sensor is required:

withstand changing weather conditions
work at a stable temperature
be mechanically robust

Why is the outside temperature so important?

The outside temperature is one of the most important influencing variables for controlling technical systems in buildings. In practice, it is used for:

Adjusting the heating output to the outside temperature
Control of the flow temperature
Optimization of ventilation systems
Energy savings through demand-based control

The outdoor temperature sensor is the central reference variable, especially in weather-compensated heating systems.

Outdoor temperature sensor for precise HVAC control - direct from the specialist supplier

As a specialist in measurement and control technology, we offer you a wide selection of outdoor temperature sensors for professional use in heating, ventilation and air conditioning systems.
Whether for building automation, industrial applications or classic heating technology - our sensors stand for reliability, precision and durability.
Discover high-quality models with different sensor types, types of protection and mounting options - suitable for your application.

Typical areas of application for HVAC

Typical applications in building automation

Outdoor temperature sensors are used in building automation as a central measured variable for numerous control and monitoring tasks. They provide the basis for demand-based control of heating, ventilation and air conditioning systems. Typical applications are

Heating systems (weather-compensated control)
Ventilation and air conditioning systems
Refrigeration systems
Building management system (BMS / DDC)
Energy optimization and monitoring

In practice, the measured outdoor temperature is mainly used to adjust flow or system temperatures. In heating systems, it serves as a reference variable for weather-compensated control, whereby the heating output is automatically adjusted to the current outdoor conditions.

The outside temperature also plays an important role in ventilation and air conditioning systems - for example to control mixed air flaps, for free cooling or to optimize operating times. This can significantly reduce energy consumption and system wear.

What is important during installation?

Installation has a decisive influence on the measuring accuracy of an outdoor temperature sensor - and therefore directly on the quality of the entire control system.

In practice, we often see that even high-quality sensors deliver incorrect values if the position on the building has been chosen unfavorably. The cause is usually not the sensor itself, but the local ambient temperature, which is distorted by solar radiation, waste heat or a lack of air circulation.

Typical assembly requirements are

Installation on the north or north-west side of the building
Protection from direct sunlight
Distance from windows, doors or heat sources
Free air circulation around the sensor
No installation in niches or under projections with heat build-up

The background: Outdoor temperature sensors should measure the actual ambient temperature - not the locally influenced temperature of a façade surface. Even small deviations of just a few Kelvin can lead to heating or ventilation systems being controlled incorrectly.

Typical consequences of an unfavorable installation are

Excessively high flow temperatures due to solar radiation
unnecessary energy consumption
Unstable control conditions
Delayed reaction of the system to real outdoor conditions

The following therefore applies in practice:
Correct positioning is at least as important as selecting the right sensor.

Measuring principle and sensor technology

Outdoor temperature sensors are based on different sensor technologies, which are selected depending on the application and connection to the building automation system.

A basic distinction is made between passive and active outdoor temperature sensors.

Passive outdoor temperature sensors

Passive sensors work on the basis of a temperature-dependent electrical resistance. Typical sensor elements are

PT100
PT1000
NTC10K
Further characteristic-based resistance sensors

The functional principle:
As the temperature rises or falls, the electrical resistance of the sensor element changes. This resistance is recorded by the controller or the building management system and converted into a temperature value.

Advantages:

High measuring accuracy
Stable characteristic curves
No additional power supply required

Important:
The sensor type must match the controller used, as the evaluation takes place in the controller.

Active outdoor temperature sensors

In addition to passive sensors, active outdoor temperature sensors that output a standard signal (e.g. 0-10 V or 4-20 mA) are also available. You can find a detailed overview and all technical information in our active outdoor temperature sensors category.

For active outdoor temperature sensors

Typical influences / errors in practice

In practice, it has been shown that the measuring accuracy of outdoor temperature sensors is strongly influenced by the installation situation. Even with correctly selected sensors, external influences can lead to deviations.

The most common influencing factors include

Direct sunlight on the sensor
Installation near windows, doors or ventilation outlets
Restricted air circulation
Positions with heat build-up, e.g. in niches or on heavily heated façade surfaces

In such cases, it is not the actual ambient temperature that is recorded, but a locally influenced temperature - for example, due to heated components or exhaust air flows.

The effects can be:

Deviating temperature values as controlled variable
Delayed or inefficient system control
Increased energy consumption

Even small deviations of just a few Kelvin can have a noticeable effect on the control behavior of heating or ventilation systems. Careful positioning of the outdoor temperature sensor is therefore crucial for reliable and energy-efficient system control.

FAQ

Where should an outdoor temperature sensor be installed?

If possible, the sensor should be installed in a shady location protected from the weather - ideally on the north side of a building to avoid direct sunlight. This is because the sun, exhaust air pipes or other heat sources can falsify the measurement results.

If installation in such locations is not possible, special weather and sun protection housings are recommended to protect the sensor from environmental influences and ensure correct temperature detection.

What protection class should an outdoor temperature sensor have?

Sensors with at least IP54 protection are recommended for outdoor use. In particularly humid environments (e.g. in industry or on façades without roof overhang), IP65 or higher may also be appropriate.

Can an outdoor temperature sensor also be installed on pipes?

Yes, there are Special pipe contact sensorswhich are used to measure the temperature of heating or cooling lines. Good thermal coupling (e.g. using heat-conducting paste) and suitable insulation against environmental influences are important here.

What to do if the measured values fluctuate greatly?

Fluctuating values may be due to incorrect installation locations (solar radiation, draughts, exhaust air) or unprotected sensors. Correct positioning, a sun protection housing if necessary or checking cable connections and contact resistances can help here.

Are there differences between sensors for indoor and outdoor temperature?

Yes, outdoor temperature sensors are specially designed for weather resistance (UV-stable, suitable for damp rooms, larger temperature ranges). They often have a robust housing and are mechanically more resistant than indoor sensors.

We also manufacture individually

Do you have special requirements? As a manufacturer with our own production facilities in Germany, we are also able to produce products outside of the standard range at any time.

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