Learn more about the basics of thermometry
Thermometers are designed to measure different types of physical characteristics, But the five most common are: Bimetallic devices, liquid expansion devices, resistance temperature devices - RTD and thermistances, thermocouples and infrared radiation devices.
Experts in measuring Thermometre.fr give you all the secrets of these little technological jewels!
Explanation of thermometers technologies
Bimetal
-Have dial displays. The dial is connected to a helical spring in the center of the probe. The spring is made up of two different types of metals which, when exposed to heat, expand in a different but predictable way. The heat expands the spring, pushing the needle on the dial. Bimetallic thermometers are cheap and generally take a few minutes to reach the temperature. Without forgetting that all of their metallic coil must be immersed in the measured material to obtain a precise reading.
Liquid thermometers
+And bimetallics are mechanical thermometers that do not require any electricity to operate. The bimetallic thermometers very easily lose their calibration and must be re -calibrated each week, even daily, using a simple screw which rewinds the metal coil.
Electronic thermometers
+RTD, thermistances and thermocouples: measure the effects of heat on electronic current. The resistance, RTD and thermistance devices, derive from the fact that the electrical resistance reacts to temperature changes according to the foreseeable curves.
Relatively inexpensive thermistor and high -precision RTD measure resistance in resistance attached to an electronic circuit to measure the temperature.
Thermistances generally use ceramic beads as resistors, while RTD often uses platinum or metal films.
With the thermists, resistance decreases with temperature and with RTDs, resistance increases.
Thermists and RTDs can have a higher degree of precision than thermocouples, but their scope is limited in comparison and they are generally not as fast.
Thermocouples operate on the principle according to which when they are connected to two different metals over a distance with a temperature difference, an electronic circuit is generated
The circuit voltage generated changes with temperature variations predictably.
THE thermocouples Currents weld together nickel and chrome - Type K, copper and Constantan - Type T or iron and Constantan - Type J and place welding at the end of the thermometer probe.
Since thermocouples only generate tension if there is a temperature difference along the circuit (and the temperature difference must be known to calculate a temperature reading), thermocouples have a cold welding where Part of the circuit is brought to the ice point (0 ° C/32 ° F) or electronic cold welding compensation which facilitates the calculation. Thermocouples can detect temperatures on large beaches and are generally quite fast.
Infrared thermometers
+Type of thermometry which measures the amount of infrared energy emitted by a substance and compares this value to a predictable curve to calculate the temperature.
Thermometry concepts
Speed
Speed, or response time, is another important consideration when choosing a thermometer. Certain thermometers technologies are faster than other And, depending on the application, additional seconds or fractions of seconds can make all the difference.
Generally, electronic thermometers are faster than Mechanical thermometers Like liquid mercury thermometers or dial thermometers. The thermocouple sensors are faster than resistance sensors such as thermistor or RTD, and reduced point probes are faster than the standard diameter probes because the sensor is closer to the measured material and the mass of the sensor is more Small and therefore more reactive to temperature changes.
The real response time of a thermometer varies depending on the particular substance and the beach of temperatures measured.
Precision
The quality of a thermometer depends on the temperatures it takes. The precision of the thermometer is therefore of the utmost importance. Slight increases or temperature decreases can have deep effects on the growth of bacteria, flexibility of plastics, the interaction of chemicals, patient health, etc., and electronic thermometers with digital display facilitate the measurement from temperature to the nearest tenth. degree or less.
Accuracy is generally expressed in ± A number of degrees or ± a certain percentage of complete reading.
The United Kingdom accreditation service (UKAS) allows you to trace the calibrated thermometers and their temperatures compared to a national standard, thus giving the user a guarantee of accuracy.
Resolution
The resolution of the thermometer refers to Smaller readable measurement From it.
A thermometer which displays the temperature at the centth of degree, for example 30.26 °, has a larger resolution than a thermometer which displays only tenths of degree, for example 30.2 °, or whole degrees 100 ° .
Although the resolution differs from precision, the two must be considered as peer. A precise thermometer at ± 0.05 ° would not be as useful if its resolution was only tenth of degree, for example 0.1 °. Likewise, it could be misleading that a thermometer displays hundredths of degree on its screen, if its traceable precision is only ± 1 °.
Temperature range
The beach describes them Upper and lower limits of the measurement scale of a thermometer. Different types of thermometers and sensors tend to work better in different measurement beaches. Some specialize in extremely hot or very, very cold temperatures. Some have a wider range. Often, A thermometer will have different precision or resolution specifications In the center of its beach and its external limits.
Specification tables require careful reading. Better you will have an idea of the temperature range that you are most likely to measure, for example cooking temperatures between 149 and 204 ° C, the easier you can select a technology that works best in this beach.
Find out more about the thermometer features
Thermometers can have many different features that facilitate monitoring and registration of temperatures ; Those you need generally depend on your application. Learn more about each feature to find the best.
Explanation of the characteristics of the thermometer
Maximum / minimum
-The recording of maximum and minimum temperatures is a very useful functionality, especially when trying to determine whether a target has been maintained within the temperature limits designated over an extended period - as for data recording.
The thermometers with the max/min functionality display the highest and the lower temperatures encountered. Some mechanical thermometers do it with physical markers that increase or decrease over time, but max/min is more common with electronic instruments. *Note that the electronic instruments with max/min often do not have a self -off function since the outlet of an instrument resets its max/min recordings.
Socket
+Hold is a feature that freezes a displayed measure (generally a digital reading) for subsequent consultation.
Difference
+Differential records - Diff, displays the product of the minimum temperature subtraction encountered maximum temperature encountered, showing the gap beach over a period of time.
Average
+Average temperature records - AVG, simply makes the average of all measures encountered over a period of time.
Hi/lo
+High and low alarms-HI/LO, alerts you by blinking, emitting a beep or even by sending you an email or SMS when a measure has passed above or below a certain predefined temperature.
Automatic stop
+Automatic stop is a function that turns off the instrument after a time specified to protect the battery life. Some units also offer the possibility of deactivating and modifying the period during which the thermometer goes out. Use this feature for more extensive measurements.
Learn more about the sensors
The sensor is the type of probe. There is Three main types, and the one you choose generally depends on the type of precision, reliability and the temperature range you need.
Thermocouple |
RTD / PT100 |
Thermistor |
|
The sensor of a thermoelectric thermometer, consisting of electrically conductive circuit elements of two different thermoelectric characteristics linked to a junction. Type K +A common thermocouple sensor combining two wires composed mainly of nickel and chrome and using the variation of tension to calculate temperatures, known for its wide temperature range and its affordable price, typical of industrial applications. Type t +A more specialized thermocouple sensor combining two wires consisting mainly of copper and Constantan and using the variation of tension to calculate temperatures known for their greatest precision and durability, typical of medical or pharmaceutical applications. Type J +A specialized thermocouple sensor combining two wires composed mainly of iron and Constantan and using the variation of tension to calculate temperatures - more limited in its beach at higher temperatures but known for its sensitivity. |
Acronym for Detection temperature resistance. The RTD/PT100 probes consist of a flat film or a sensor element with resistance in platinum rolled up in wire. The measured value changes depending on the temperature measured. Precision specifications +PT100/RTD sensors are made from PT100/RTD class A 100 Ω (OHMS) detectors, as detailed in CEI 60751 (2008), and meet the following precision specifications: |
A common thermal sensor which uses the foreseeable variation of resistance to an electric current with temperature changes to calculate temperatures. Precision specifications +Thermistor probes/sensors NTC For all the thermistor probes manufactured are as follows: |
Learn more about Bluetooth features
There Secure data transmission temperature is vital for the safety of food processing operations and catering.
This is what makes Bluetooth thermometers an ideal choice, we offer many solutions among our Bluetooth range. Our range offers professionals in the food industry speed, precision and reliability when it comes to keeping digital temperature records - An absolute must so that companies can operate safely and remain in conformity.
Infrared base
THE infrared thermometers are very fast, generally giving a reading in a fraction of a second, the time required for the thermometer processor to carry out its calculations. Their speed and relative ease of use have made the thermometers infrared safety tools Private invaluable in the catering industry, manufacturing, CVC, asphalt and concrete, laboratories and countless other industrial applications.
Infrared thermometers are Ideal for taking remote surface temperature measurements. They provide relatively precise temperatures without ever having to touch the object you measure.
Infrared technologies explained
Mica lens
-Mica lens thermometers such as Raytemp 38 are the most commonly used type in an industrial environment. They have more rigid rectified mineral lenses.
This allows them to:
- Take precise measurements at much higher temperatures, above 1,000 ° C.
- Be approximately twice as sensitive to thermal shock effects caused by sudden variations in room temperature as the fresnel lens thermometers.
- Be more precise at greater distances-above a distance of 20: 1. Target ratios
The mica lens thermometers are often equipped with one or two lasers to help guide both the orientation of the thermometer and the estimation of the measured vision field. However, mica lens are the most fragile of infrared technologies. They are often delivered with transport cases because they are more likely to crack or break in the event of a fall. They are usually the most expensive and still have to acclimatize to extreme ambient temperatures for 10 minutes or more before giving precise readings.
Fresnel lens
+Fresnel lentil thermometers, such as Raytemp 8 , are the most commonly used type in the food industry.
Unlike the mica lens, the fresnel thermometer lens is generally made of plastic, which offers several key advantages:
- Less expensive than mica lens thermometers
- More durable and resist falls better than the thermometers with mica lens
- Can offer narrow points diameters at a greater distance than the thermometers without lens
- Generally more precise at a distance of 6 "to 12" than other technologies
Fresnel lens thermometers are often delivered with laser guides to help you orient your measurement. However, the plastic Fresnel lens has a narrower temperature range than the more versatile mica lens. It is also more sensitive to inaccuracies due to sudden variations in room temperature, called thermal shock, than other types of infrared thermometers.
If, for example, you transport your Fresnel lentil thermometer from the ambient temperature in a freezer to take frozen food measurements, the sudden temperature drop can modify the shape of the lens when the plastic contracts with the cold. Most Fresnel lens thermometers display error alerts when it happens and give wrong readings until the lens has been lucky to acclimatize to the new environment. Similar distortions occur in the upper temperature range in the specifications of a fresnel lens thermometer.
The good news is that leaving your fresnel lens thermometer to rest in the new ambient temperature for 20 minutes or more before taking your measurements can considerably reduce the distortions due to thermal shock.
No lens
+Thermometers without lens, such as IR pocket infrared thermometer , use a reflective funnel design to concentrate infrared energy on thermopile rather than on a lens.
Do not have any objective of separate advantages:
- Generally less expensive
- More sustainable
- Generally smaller and easier to handle
- More precise in cold spaces
Since there is no lens between the electromagnetic waves emitted by a surface and the thermopile of the thermometer, there is no significant contraction or expansion effects on the thermometers without lens. In most units, an internal sensor compensates for the effect of room temperature on the electronic components themselves, so that you can literally go from a hot room directly to a freezer under zero and start taking measures without to wait for.
The significant warning regarding thermometers without lens is that their distance/target or DTR ratio is always 1: 1 or less. This means that you need to hold the thermometers without lens as close as possible to the target surface when you take measurements. The lens without lens are not as well suited to take measures remotely.
