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Einstech Thermoelement Typ J Vorderansicht
Penetration probe thermocouple type J
53,17 € *
Order number: 802410-1111
Einstech Thermoelement Typ K Vorderansicht
Penetration probe thermocouple type K
53,17 € *
Order number: 802410-1211

Guide penetration probe

In this guide, we have compiled information on what you should pay attention to when selecting, purchasing, installing and operating your penetration thermocouple.



What is a penetration thermocouple?

Penetration thermocouples are perfect for measuring core temperature in viscoplastic media or for measuring air temperature. The stainless steel sleeve with the centric measuring tip and the thermocouple cable are firmly connected and cast in a water vapor-tight manner. The ergonomic PTFE handle serves as heat protection.

Thermocouples are thermoelectric sensors with two wires made of different materials. These are connected together at one point (measuring point) and a thermoelectric voltage can be measured at their ends (reference junction), which also changes when the temperature changes. This thermoelectric effect is also called Seebeck effect.

Thermocouples measure the temperature difference between the measuring point and the reference junction, i.e. the temperature at the reference junction must be known.

Like platinum sensors, thermocouples are also standardized and can be immersed regardless of the manufacturer. They also have a very fast response time and can be used at very high or very low temperatures. They are inexpensive and come in many different types. Thermocouples also have disadvantages: they are more sensitive than resistance-based temperature probes. Their characteristic curve is not linear. The measuring principle should be known to the user to avoid measuring errors.


What do I have to pay attention to when choosing the right penetration thermocouple?

We offer our penetration thermocouples as Type J and Type K thermocouple variants.

We offer the probes with silicone or PFA cable. You can also choose between insulated end ferrule, mini TC connector and standard TC connector, as well as a measuring tip diameter of 4 mm or 6 mm.

A thermocouple consists of two wires, which are made of different material. This is very important because the different materials also behave differently and thus a measurable thermoelectric voltage is created when you connect the two wires at one end. This thermoelectric voltage changes when the temperature changes. This effect is named after its discoverer - Seebeck effect.

Unlike resistance-based temperature probes, the temperature difference between the measuring point and the reference junction is determined. The temperature at the reference junction must therefore be known. Therefore, a resistance-based temperature sensor is often installed there. The advantage of thermocouples is that the measuring point and the reference junction do not have to be located next to each other and that the temperature is not "falsified" by line resistances. This means that the measuring tip can be inserted into the process, where it may be very hot, for example - but the temperature is determined at the reference junction.


How do I measure the core temperature with a penetration thermocouple?

For an exact measurement of the temperature, pierce the probe sufficiently deep into the medium to be measured (at least 10 times the diameter of the probe shaft.) Please leave the probe in the medium until the final temperature is reached.

Please make sure that you only immerse the probe shaft and not the cable or the connector into the medium. This probe cannot be autoclaved or sterilized.


What should I pay attention to when selecting the right thermocouple?

The right choice of thermocouple depends on your measuring task and the associated requirements for the temperature probe. We often hear questions like:

  • Is the probe also compatible with?
  • Which thermocouple should I choose?
  • Can I change my thermocouple?
  • Which cable do I need or even can I replace the cable?

Answering the following questions can help you with your selection:

  1. What is the right thermocouple for me?
    The choice of the thermocouple depends on the one hand on which measuring device you want to use the thermocouple. Please check which thermocouple is to be used according to the technical data or the operating instructions of the measuring device. The different types of thermocouples are not compatible with each other and also have different characteristic curves. The characteristic curves of our thermocouples can be found here at a glance.

  2.  Does the thermocouple fit your measuring range?
    In addition to the measuring device, please also check in which measuring range and with which accuracy / tolerance you want to use the thermocouple. Information on the measuring range and tolerance can also be found in the characteristic curves and in the operating instructions for each probe. With thermocouples, adherence to the measuring range is particularly important, because if the limit is exceeded, the metal alloy can be irreversibly damaged and then the thermocouple will no longer measure within the specified tolerance range.

  3. Do I need a connector and what size should the connector be?
    Thermocouples are either connected directly to the meter. However, it is much more common for thermocouples to be connected to the meter via a connector. At Testo Sensor you will find the following connectors on offer:
    • Mini TC connector
    • Standard TC connector
    • Mini TC coupling
    • Standard TC coupling

  4. How do you ensure the correct mechanical connection of the thermocouple to the process?

    Correct mechanical connection of the probe to the process ensures efficient, error-free and trouble-free measurement.

 Which environmental influences is the thermocouple subject to?

Please also pay attention to whether you have certain requirements at the measuring point or in your process regarding temperature, pressure, IP protection, steam or similar and compare your specification with our data sheets. If you have any questions or are unsure, please feel free to contact us.

What do I have to consider when mounting the thermocouple?
If you are wondering: Where do I have to mount the probe? Or how can I mount the thermocouple? Then take a look at the operating instructions. Because mounting is as different as the probes themselves and also differs depending on the probe design, we have stored in the operating instructions of the respective probe exactly where and how the probe is to be mounted and what you must pay attention to during mounting. You will find the operating instructions with each probe or in our download area.

What accessories do I need for my thermocouple?
When placing your order, please consider whether you need any accessories. Please check the delivery details for each probe to see what is included.


Replacement of a defective thermocouple

When replacing a defective temperature probe, please pay close attention to which thermocouple you need, because the thermocouple types are not compatible with each other. Therefore, please refer to the technical data of the respective system to find out which Type has been installed. If the required information is not apparent in the operating instructions of the measuring device / equipment, the manufacturer of the machine or system should be contacted in case of doubt.

When the exact type of thermocouple has been determined, the mechanical adaptation must be tested. The temperature can only be measured correctly if the probe can be mounted correctly at the installation site. Otherwise, machines and equipment can easily malfunction.

Also make sure that you order thermal paste and mounting accessories such as compression fittings, cutting ring screw fittings or bayonet nipples if these also need to be replaced.



Frequently asked questions about temperature sensors

How do I test a thermocouple for function?

The measurement curve of thermocouples is not linear. Therefore you need a special multimeter with an appropriate measuring input, which linearizes the signal and at the same time corrects the terminal point compensation, so that only the temperature measured at the measuring point is displayed.

Alternatively, you can check whether you can detect mechanical damage such as cable breakage or replace the thermocouple and see whether the fahler still occurs.

How can I tell that my thermocouple is defective?

The temperature probe shows strange values? The temperature probe does not show any values? This behavior may be a sign that your temperature probe is defective or that it has not been connected correctly.

To find out if there is a defect, you can simply measure the resistance value of resistance-based temperature probes and compare it with the specification on the probe itself or in the user manual. You can use a standard multimeter to do this.

If you are using a thermocouple instead of a resistance-based temperature probe, the situation is somewhat different. Here you need a multimeter with an appropriate connection for thermocouples, because thermocouples do not have a resistance signal, but a voltage signal.

Alternatively, you can test on a trial basis whether a replacement will remedy the situation.

How do I connect the temperature probe correctly?

When connecting your temperature probe, please make sure that you follow our wiring diagrams. You will find the wiring diagrams in the operating instructions for your temperature probe.

How can I protect a temperature probe from certain influences?

Select a temperature probe that is well suited to your measuring task. Depending on the medium in which you want to measure, you will need a different probe design. We have specified exactly which material we use in our operating instructions so that you can check for yourself whether the probe is suitable. Please pay attention to the measuring range and other environmental conditions such as dust, water, steam, solar or UV radiation.

We offer immersion sleeves in our accessories, which can protect the probe. In addition, especially for outdoor probes, you can also find Sun Protection and Ball Throw Protection to shield your outdoor probes from environmental influences and to get the correct measurement result.

For easier orientation, we have always indicated suitable accessories in the respective operating instructions of the temperature probe.

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