How To Choose The Proper Temperature Probe

Temperature is the most measured physical quantity in industry and is an essential parameter in many processes. A temperature probe converts temperature information into an electrical signal that a measuring instrument, display, or automation can use.

Among the various existing temperature probe technologies, two types are distinguished:

• Contact probes are the majority of temperature sensors whose sensing element is located at the point of contact between the sensor and the object being measured.
• Non-contact probes use infrared technology to measure the temperature of a distant surface.

How To Choose The Proper Temperature Probe

To choose the most suitable temperature sensor for you, you need to ask yourself the following questions:

Should I choose a contact sensor or an infrared sensor?

Contact sensors can come in different shapes. There are sensors suitable for measuring surface temperatures or probes for measuring temperatures inside materials. In any case, the contact quality between the sensor and what we want to measure is paramount. Infrared sensors can only estimate the temperature of the surface they are pointed at. Even if they do not require contact, attention must be paid to the nature of the atmosphere between the sensor and its target, which can affect the measurement.

In the case of contact sensors, what technology should I use? There are several technologies: thermocouples, resistance sensors, etc. It cannot be said that one technology is better than another; each has its advantages and disadvantages:

It is also essential to consider the sensor’s response time when measuring temperature changes, as thermocouples have a faster response time than RTDs.

The temperature range to be measured is undoubtedly an important criterion when choosing the sensor and its technology. Thermocouples and RTDs are classified according to the materials that make up their sensing element and have different measuring ranges.

What Are The Advantages Of Choosing A Rheostat Temperature Sensor?

A rheostat temperature sensor, often called RTD, is a non-contact sensor. It is based on the change in resistance of a metal (platinum, copper, nickel, or tungsten) as a function of temperature. This type of sensor uses several metals that provide different measuring ranges:

• Platinum : -200 °C to 600 °C
• Copper : -190 °C to 150 °C
• Nickel : -60 °C to 180 °C
• Tungsten : -100 °C to 1400 °C

Platinum is the most used metal for rheostat temperature sensors because it offers a wide measuring range. Rheostat sensors provide improved accuracy and a more linear response than thermocouples. They are more stable in measurements and have a wide temperature range. On the other hand, their response time is higher, and they are less sensitive.

• Important points:
• accuracy
• high response time
• poor sensitivity
• large measuring range

 

What Are The Advantages Of Choosing A Temperature Sensor – Thermistor?

Thermistors are another form of resistance sensor; they utilize the change in resistance of metal oxides depending on temperature. There are two types of thermistors: NTC (negative temperature coefficients), which have a relatively regular negative resistance, and CTP (positive temperature coefficients), which show a sudden positive change in resistance over a narrow temperature range.

Thermistors have fast response times and low cost, but they are pretty fragile and have a much more limited measurement range than sensors of other technologies.

What Are The Advantages Of Choosing An Infrared Temperature Sensor?

An infrared temperature sensor measures surface radiation in the infrared range to determine the surface temperature. The main advantage of this type of sensor is that it works remotely without any physical contact with the surface of the measured objects.

The response time of these sensors is speedy. Unlike contact sensors, they do not need to look for thermal equilibrium (same temperature).