Guide temperature transmitter
Temperature transmitters are used when a temperature probe is to be connected to a control or measuring device with a standardized signal input. Temperature transmitters translate the resistance or voltage value into a standardized output signal such as 0 ... 10 V or 4 ... 20 mA.
This means that the temperature measurement signals can always be transmitted safely, easily and even over longer distances to your control or display.
- What is a transmitter?
- How does a temperature transmitter work?
- What are the advantages of using transmitters?
- For which applications do I need a transmitter?
- What should I look for when buying a temperature transmitter?
- What are the different types?
- How can a temperature transmitter be parameterized/scaled?
- Frequently asked questions about our transmitters
What is a transmitter?
They are also referred to as transducers, measured value transducers, signal converters or simply transducers. They are used to convert physical measured variables such as temperature, humidity, differential pressure, etc. into standardized electrical signals.
In the case of a temperature transmitter, the measurand to be converted is temperature.
The input signal is a resistance value for resistance-based temperature probes and a voltage value for thermocouples. The output signal is usually either 0 ... 10 V or 4 ... 20 mA. Historically, however, there are also 0-1 V / 0-5 V or 0-20 mA signals.
How does a temperature transmitter work?
A temperature transmitter is a signal converter. The transmitter amplifies the possibly weak signal of the temperature sensor and simultaneously converts it into a standardized analog signal. By amplifying the signal, transmission with a high degree of accuracy is possible even over greater distances and under difficult conditions. At the same time, the converted standard signals can be easily further processed in measurement technology.
What are the advantages of using transmitters?
Signal amplification
Temperature transmitters reliably detect, amplify and convert the interference-sensitive sensor signal of a temperature probe into a standardized output signal in continuous operation. In this way, measured values can be transmitted reliably and with low risk of interference over longer distances. This is particularly important in industrial environments where there are strong electromagnetic interference fields.
Easy adaptation to existing installations
Many measuring devices, controllers or input cards can only process standardized signals. Direct adaptation of temperature probes or thermocouples is therefore not always possible or must be retrofitted at great expense. With a transmitter, you can convert the signal according to your requirements and thus easily adapt the probe to your existing installation.
For which applications do I need a transmitter?
- Signal or signal level too weak
- Possible interference on the "transmission path
- existing measuring device, control unit or input card can only process standardized signal
- The transmitter has an integrated line monitoring. In the event of a sensor or line break, this is detected and the transmitter outputs a signal, outside the scaling range (upscale (≥21.0 mA) or downscale (≤3.6 mA)).
- The transmitters feel free to be installed in temperature control or regulation systems. The analog output signal is used as an indicator for the temperature. If temperature fluctuations occur, the output signal changes depending on the scaling. The change is then perceived by the subsequent control or regulation. Thus, action can be taken according to the temperature change so that the required temperature is restored.
What to look for when buying a temperature transmitter?
- Measured variables
- Sensible selection of the measuring range
- Signals at input and output
- Measuring accuracy
- Cable paths / cable lengths
- Further environmental conditions
Measured variables
Do you need a transducer only for the temperature signal or do you want to consider other measurands? Currently you can find only temperature transmitters in our webshop. If you need further measurands, please feel free to contact us. We will then see individually what we can offer you.
Sensible selection of the measuring range: As large as necessary, as small as possible.
The measuring range should be selected so that the expected temperature lies well within the selected measuring range. You should also make sure to think of the extremes and also cover the limit temperatures.
Ex:
You want to measure the room temperature in a heated winter garden. The "normal", expectable room temperature in this room is between 18 °C and 25 °C.
Now you should also consider the borderline cases:
What happens if the heating fails in winter? How low could the room temperature drop in this case? On the other hand, what happens if the sun shines full on the conservatory in summer. Up to how many degrees of room temperature you need to consider in this case? Choose the temperature range so that it includes these borderline cases.
You may now be thinking: Well, then I'll take the largest possible measuring range and can thus cover a wide measuring span. This should be checked carefully for the respective application, because the larger the measuring range, the more expensive the transmitter will be or the less accurate it will be, because you lose accuracy due to the large resolution.
The measuring range must therefore be a sensible fit for the measuring task.
Signals at the input and output
Transmitters differ not only in type, but also in which signals can be processed. So please make sure to check the signals at input and output.
We offer transducers that can convert resistance values from resistance thermometers. In addition, we also offer converters for converting the thermoelectric measurement signal of thermocouples.
Measuring accuracy
The information about the accuracy of your transmitter can be found like all other important, technical information in the data sheet. It is always specified for the measuring ranges. Please note that it is a measuring system consisting of transmitter, temperature sensor and measuring device or connection card. I.e. the combination of temperature sensor, transmitter and the input card or measuring device together with the measuring section result in the total measuring tolerance. Therefore, all individual components must be included in the consideration and must be reasonably coordinated with each other.
Two-, three- and four-wire technology and the lead resistance
As with a resistance sensor, the measurement lead can affect the measurement result. In the case of a transmitter with two conductors, the measurement result can be affected by the lead resistance of the supply line. The use of a 2-wire technique only makes sense if the supply line of the sensor is not too long.
If, on the other hand, you have long cable runs to bridge, we recommend using a 3- or 4-wire transmitter. This almost completely eliminates measurement errors due to line resistance.
If you have the highest demands on measuring accuracy, you should choose a 4-wire transmitter.
If, on the other hand, only short distances are involved, you can save effort and costs in wiring by choosing a 2-wire transmitter.
Further ambient conditions
Please check whether your temperature transmitter is exposed to further unfavorable ambient conditions and must therefore meet special requirements. These include, for example, vibration resistance, moisture resistance or also requirements with regard to mounting.
What types of transmitters are available?
- Head transmitter
- Top-hat rail transmitter
- Transmitter with wall housing
- Compact transmitter
Head transmitter
Head transmitters are either installed individually in the measuring head of a temperature probe or are already included as an integrated component.
Advantages:
- The compact type saves space
- easy mounting
- Due to the proximity of measuring point and transducer, the favorable 2-wire technology can usually be used.
Disadvantages:
- The proximity to the measuring point restricts the use of temperature.
- The transducer may be more susceptible to vibration and humidity near the process to be measured.
Hat rail transmitter
Hat rail transmitters are plugged directly onto a top-hat rail in the control cabinet, i.e. simple rail mounting. The supply line of the temperature probe is laid into the switch cabinet and goes there to the transmitter.
Advantages:
- simple and protected mounting of the Hat rail transmitter in the switch cabinet
- high efficiency during installation
Disadvantage:
- A control cabinet is not always available at the right distance from the measuring location.
- If the supply lines are very long, three- or four-wire technology should be used for resistance sensors.
Transmitter with wall housing
Transmitters with wall housing are installed in a plastic or metal protective housing and can thus be screwed to the wall, for example.
Advantages:
- Safe distance from the installation site
Disadvantage:
- Larger type
- Possibly more complex installation
- Supply line length must be taken into account
Compact transmitter
Head transmitters are a special form of compact transmitters. Both are built directly into the temperature probe. Compact transmitters are mainly Screw-in temperature probes, but there are also insertion and immersion probes. The measuring electronics are permanently integrated in the probe tube or probe housing.
Advantages:
- space-saving type
- little installation effort
Disadvantage:
- Proximity to the measuring point restricts temperature use
- The transmitter may be more susceptible to vibration and humidity near the process being measured
How to parameterize/scale a transmitter?
Parameterizing or scaling means setting the measuring range of the transmitter. There are different methods to configure transmitters (i.e. to set the measuring range).
Pre-set temperature transmitters
These transmitters are delivered ready set and for a fixed measuring range. This is simple, but not very flexible.
Temperature transmitters with DIP switches
Other types are configured using DIP switches, which is easy to do on site without tools or software. However, the flexibility is limited to predefined parameters.
Transmitter with PC software
Another option is to set the transmitters using optional PC software. This allows settings to be set flexibly and, once selected, settings can be copied to other transmitters quickly and easily.
Transmitters with NFC interface and cell phone app
Newer transmitters have the option of using NFC via a cell phone app. The cell phone app is easy to use on site and brings the benefits of software-bound configuration directly to the measurement location.
Why is NFC configuration cool?
The NFC interface provides a simple configuration option. The transmitter can be configured easily without power supply. It is only necessary to hold the smartphone to the transmitter. This connection is already sufficient to load the configuration onto the transmitter or to read it out.
After the configuration, it can be saved and easily loaded onto other devices. Thus, a fast and contactless configuration is possible.
Frequently asked questions about our transmitters
- Where can I find all the technical specifications and data for my transmitter?
- Do the transmitters require power at the connection?
- Which accessories do I need for my transmitter?
- For which temperature probes do the transmitters fit.
Where can I find all the technical specifications and data for my transmitter?
Here or in our download area you will find all technical specifications and data:
| Downloads |
| Transmitter | Data sheet | Instruction manual | Declaration of conformity |
| In-head transmitter for Pt100/Pt1000 APAQ-C130 |  | | |
| In-head transmitter for thermocouples APAQ-C130 | | | |
| Universal in-head transmitter RTD/TC IPAQ-C330 | | | |
| Hat rail transmitter for Pt100/Pt1000 APAQ-R130 | | | |
| Hat rail transmitter for thermocouples APAQ-R130 | | | |
| Universal hat rail transmitter RTD/TC IPAQ-R330 | | | |
Do the transmitters require power at the connection?
The transmitters must be supplied with power. This can be realized via an existing power supply or an external power supply unit.
What accessories do I need for my transmitter?
If no suitable power supply is available on site, an external power supply unit is required as an accessory. This can be a DIN rail power supply or any other power supply that provides the required voltage.
In addition, a temperature sensor is required, which is connected to the transmitter. A wide variety of temperature sensors can be used here.
