Portable thermistor thermometers include ones made for Foodcare. Also included are version with a calibration feature that allows the user to calibrate the meter and probe in an ice bath at 0 oC.
A variety of thermistor based testers are available. They include versions with a folding probe, reinforced handle for insertion into semi-solids, and ones that can mount on a refrigerator.
A wall mounted thermometer is available that allow for continuous measurements to be taken.
Multiple temperature data loggers are available. These include versions with built-in and external thermistor probes.
Portable thermocouple thermometers including ones made for the food industry. This category include K-Types, T-Types, and K, J, T-type thermocouple thermometers.
Thermocouple Thermometers with Calibration Feature
Although quite fast, thermocouple thermometers read with a response time much slower than other sensors and technologies. Unfortunately, the measurement of the thermocouple emf (electromotive force) loses accuracy because of the measuring system itself, based on the emf generated by the temperature difference between cold and hot junctions. The same emf may be generated under different conditions, for example:
Hot junction at 100oC; cold junction at 20oC; difference: 80oC or Hot junction at 90oC; cold junction at 10oC; difference: 80oC.
A temperature difference of 80oC is obtained with two different temperatures of the sample. It is, therefore, very important to determine the cold junction temperature very precisely. To solve the problem, Hanna offers thermocouple thermometers with a user calibration feature that allows the user to calibrate the measuring system in an ice bath at 0oC.
Thanks to this solution, it is now possible to use thermocouple thermometers for HACCP controls with an accuracy of ±0.3oC, which is the same performance of our Pt100 or NTC thermometers, but with a faster response time.
K-Type Thermocouple Tester
A thermocouple tester is available. It is supplied with general-purpose probe. Other probes are available including air/gas and surface measurements.
The operating principle of resistance thermometers is based on the increase of electric resistance of metal conductors (RTD: Resistance Temperature Detectors) with temperature.
This physical phenomenon was discovered by Sir Humphry Davy in 1821.In 1871, Sir William Siemens described the application of this property using platinum, thereby introducing an innovation in the manufacturing of temperature sensors. Platinum resistance thermometers have been used as an international standard for measuring temperatures between hydrogen triple point at 13.81 K and the freezing point of antimony at 630.75°C (1167.26°F).
Among the various metals to be used in the construction of resistance thermometers, platinum (Pt), a noble metal, is the one that can measure temperatures throughout a wide range; from -251°C (-419.8°F) to 899°C (1650.2°F), with a linear behavior.
Platinum RTD thermometers were common in the seventies but have now been replaced with thermistor sensors because of their smaller dimensions and faster response to temperature changes. The most common RTD sensor using platinum is the Pt100, which means a resistance of 100? at 0°C with a temperature coefficient of 0.00385? per degree Celsius. For a higher price one can buy platinum sensors with 250, 500 or 1000? (Pt1000).
The main disadvantage of RTD probes is the resistance of the connection cable. This resistance prevents the use of standard two-wire cables for lengths over a few meters, since it affects the accuracy of the reading. For this reason, to obtain high levels of accuracy in industrial and laboratory applications, the use of a three or four-wire system is recommended.
For all its Pt100 thermometers and probes, Hanna has chosen the multiple-wire technology for higher accuracy.
All objects emit a radiant energy in the infrared (IR) spectrum that falls between visible light and radio waves.
The origins of IR measurements can be traced back to Sir Isaac Newton’s prism and the separation of sunlight into colors and electromagnetic energy. In 1800, the relative energy of each color was measured, but it was not until early 20th century that IR energy was quantified. It was then discovered that this energy is proportional to the 4th power of the object’s temperature.
IR instrumentation using this formula has been around for over 50 years. They almost exclusively use an optic device that detects the heat energy generated by the object that the sensor is aimed at. This is then amplified, linearized and converted into an electronic signal which in turn shows the surface temperature in Celsius or Fahrenheit degrees.
Infrared measurements are particularly suitable for areas where it is difficult or undesirable to take surface measurements using conventional contact sensors. Applications for IR meters include non-destructive testing of foodstuffs, moving machinery, and high temperature surfaces.
An ideal surface for IR measurements is a black body or radiator with an emissivity of 1.0.Emissivity is the ratio of the energy radiated by an object at a certain temperature to that emitted by a perfect radiator at the same temperature.
The shinier or more polished the surface, the less accurate the measurements. For example, the emissivity of most organic material and rough or painted surfaces is in the 0.95 region and hence, suitable for IR measurements.
On the other hand, surfaces of highly polished or shiny material, such as mirrors or aluminum, may not be appropriate for this application without using some form of filtration. This is due to other factors, namely, reflectivity and transmissivity. The former is a measure of an object’s ability to reflect infrared energy while the latter is its ability to transmit it.
Another important and practical concern with IR measurements is the field of view. Infrared meters measure the average temperature of all objects in their field of view. To obtain an accurate result, it is important that the object completely fills the instrument’s field of view and there are no obstacles between the meter and the object. The distance-to-target ratio, or the optic coefficient, is therefore an important consideration.
Available are K-type, T-type, thermistor and pt100 temperature probes. These probes include many different styles from penetration, liquids, air/gas, and wire probes.
K-Type Thermocouple Probes HI766 Series
Thermocouple Probes without a Handle – HI766 Series
NTC Thermistor Probes - HI762 Series
PTC Thermistor Probes – HI765 Series
Pt100 Probes – HI768 Series
Accessories include the calibration keys used with thermistor thermometers and shockproof rubber boots to add additional protection to the meters. Also included are the handles and extension cables used with probes that do not have a handle.