The temperature probes that can be used are as versatile as your applications. Waterproof temperature probes in particular offer reliable measurement, even under adverse conditions.
In this guide, we have put together what you need to look out for when buying your waterproof temperature probe.
How do waterproof temperature probes work?
Waterproof temperature probes are designed so that no liquid water can penetrate. Penetrating water would form resistance bridges between the sensor connection wires and thus falsify the measured values (resistance values). Water in liquid or gaseous form penetrates almost every type of temperature probe in the long term and initially leads to drifting of the resistance values and ultimately to complete failure of the probe. Only very few suppliers of temperature probes are able to build and supply temperature probes that are truly waterproof and resistant to moisture and condensation.
We offer four different waterproof temperature probes in our store.
What types of waterproof temperature probes are available?
We essentially differentiate between three classes of "watertightness". The term "waterproof" is misleading, as it leads people to assume that so-called "waterproof probes" can be used in any wet and humid environment and will function reliably and stably for a long time as desired. However, this is by no means the case. "Waterproof" in the narrower sense can be specified as complying with protection class IP 67 or IP 68. In both cases, the temperature probe is designed to be directly exposed to liquid water. To comply with protection class IP 67, a device or temperature probe must be immersed 1 m under water for a maximum of 30 min without being damaged; to comply with protection class IP 68, an immersion depth of 1.5 m must be maintained for a maximum of 30 min without damage.
However, the service life of a temperature probe does not usually depend on compliance with the protection class, which is quite easy to achieve, but rather on the impermeability of the temperature probe to ambient moisture. This is much more critical than liquid water, as it is forced into the probe over time (due to the higher external partial pressure compared to the partial pressure inside the probe) or diffuses in over time (statistical process, driven by the moisture gradient from the outside to the inside of the probe). In this context, "watertight" means "sealed against the penetration of external humidity".
The third class of "watertightness" is merely a more extreme form of the "tightness against the ingress of external humidity" just described. In this third case, the probe tip is permanently in a cold environment, e.g. cold water or ice, while the rest of the probe is permanently exposed to comparatively warm and humid ambient air. In this case, such an application is physically equivalent to a so-called cold trap, in which there is a large temperature gradient from the external environment to the inside of the probe as well as a large humidity gradient, also from the external environment to the inside of the probe. Applications in this regard can be, for example, ice cream machines, wine coolers, refrigeration systems, chillers or air conditioning systems. Temperature probes that are to be used in such applications must be designed, constructed and manufactured in a very specific and complex manner. Otherwise, they will work deceptively well at the beginning of their use, only to drift and then fail successively after weeks, months or even one to three years.
What applications do waterproof temperature probes have?
Waterproof temperature probes are needed wherever they are exposed to external environmental influences, i.e. rain, snow, ice and intense solar radiation. A typical application is the heat pump, which is equipped with temperature probes at several measuring points. In order for the heat pump to be controlled correctly, reliably operating temperature probes must also be able to permanently tap resistance values outside the heating system.
Drifting or even failing temperature probes are absolutely not usable or usable.
What does the IP protection class say about the waterproofness of a temperature probe?
The IP protection class indicates how waterproof a temperature probe is in liquid water with a certain immersion depth for a certain time x.
To comply with protection class IP 67, a device or the temperature probe type in question must be immersed in water for a maximum of 1 m for 30 min without being damaged; to comply with protection class IP 68, an immersion depth of 1.5 m must be maintained for a maximum of 30 min without damage.
Here you will find an overview of the meaning of the digits of the IP protection class:
| Code number 3 for contact protection | Code number 4 for water protection |
| 0 - No protection against contact and foreign bodies | 0 - No protection against water |
| 1 - Protection against foreign bodies larger than 50 mm | 1 - Protection against water droplets from above |
| 2 - Protection against foreign bodies larger than 12 mm | 2 - Protection also against water drops falling at an angle (15 °C) |
| 3 - Protection against foreign bodies larger than 2,5 mm | 3 - Protection against spray water (up to 60° angle of incidence) |
| 4 - Protection against foreign bodies larger than 1 mm | 4 - Protection against water spray |
| 5 - Protection against dust inside and complete protection against contact | 5 - Protection against water jets |
| 6 - Protection against ingress and complete protection against contact | 6 - Protection against ingress of water in the event of brief flooding |
| | 7 - Protection against water ingress due to brief immersion |
| 8 - Protection against water ingress in the event of continuous immersion |
| 9 - Protection against water ingress from any direction. Additional protection at high pressure, e.g. high-pressure cleaners up to 100 bar |
What features should a waterproof temperature probe have?
A watertight temperature probe must be sufficiently sealed against the ingress of liquid water for at least a sufficiently long time and depending on the pressure.
"Tight for a sufficiently long time" and "pressure-dependent tight" means that the tightness is suitable for the application in which the temperature probe is to function and operate with long-term stability.
What is the difference between watertight and condensation-proof?
The term "watertight" is misleading in that it often refers to both liquid water and gaseous water. However, fundamentally different requirements have to be met by the temperature probe: the ingress of liquid water can be prevented by complying with a protection class such as IP 67 or IP 68, while ensuring resistance to moisture and condensation requires much more complex designs and application-specific qualifications of the temperature probe type. Perfect, i.e. error-free, manufacturing of the temperature probes that corresponds exactly to the qualified design is also absolutely essential in order to permanently meet the requirements in accordance with the given specification.
