Company Gmini traces its history back to 2008, when the market was presented the first Full HD player Gmini MagicBox. Since that time, the range of the company’s products, of course, became much wider: today, this brand offers not only various audio and video devices, but also e-books, IP and action cameras, video recorders, chargers for various gadgets and mobile batteries (powerbank).
On the official website there is section “Health”, in which while there is a single device — infrared thermometer GM-IRT-860D. I will start a series of reviews on some products Gmini.
Overview pyrometers, IR thermometers and measurements with them
Thermometers (this is a class of measuring devices, infrared thermometers are one of its components) is designed for remote non-contact measurements of temperature of different objects.We will not hesitate to tell about their classification, physical principles of functioning and cites numerous examples of usage and focus only on the category that applies to Your model: cheap portable infrared thermometers, designed primarily for use in the home or other purposes that do not require neither high precision nor a very wide range of measurements, nor the collection and subsequent automated analysis of large volumes of data.
But even in these limits there’s a lot of options.
Some of these devices are designed to measure temperature of different objects or surfaces (for brevity, we will continue to call them multi-purpose), others — to work with the human body (medical), and still others combine both of these capabilities (let’s call them combo).
I have to explain the difference. For measurements related to the human body, requiring high accuracy (for the considered model Gmini stated ±0.2 °C), while the accuracy is similar for the price of multi-purpose thermometer is usually ±2% or normal body temperature was 36.6 °C, they can display and as of 35.9 °C, and as of 37.3 °C, both these values may indicate disease.And very often for low-cost models have a question, is there a limit of error of the current measurement or limit of the scale — for example, 200 °C (then the deviation at all can be plus or minus 4 degrees). Sometimes gracefully specifies “±2% or ±2 °C” and understand it as they want…
And do not confuse measurement accuracy with the bit mapping, that is, the number of digits on the display, including the decimal point. Very often, for example, a cheap household electronic scale is specified “accuracy: 0.1 g”, and an uninformed buyer quite believe, because the scoreboard really weight is displayed in tenths of grams. In fact, these figures can not be taken into account, and what about the first digit before the comma is questionable. The same applies to the IR thermometer.
To ensure high measurement accuracy over a wide temperature range is difficult, therefore, for combined IR thermometers, the error often indicates different: less for body temperature and more to work with objects, and in the second case it may differ for positive and negative temperatures (of course, if this model supports such values).
The difficulty is not only with range but with another parameter associated with the object of measurement. He is called the coefficient of emission depends on the reflectivity of the surface of the object (so it is also called the degree of blackness) and can be in the range from 0 to 1. The value can vary not only depending on the material of the object, but also on the state of its surface: copper with a rough (diffuse) surface coefficient of emission of about 0.2, oxidized copper — 0,7-0,8, polished — 0,02-0,07.
Accordingly, the readings of the pyrometer for two bodies of equal temperature, are made of different materials or differently treated surfaces, can vary greatly.
For human skin the average value of emission factor very close to unity and is 0.97, however, depending on conditions and individual characteristics can sometimes be from 0.84 to 1.
In advanced models, IR thermometers, you can manually enter the emissivity and the temperature will be displayed with the corresponding amendment. A specific value, often in the form of tables, can be found on the Internet, but the trouble is that for the item of interest in them is not always possible to find your desired numbers, and if they are in the form of a range.
The device allows easier to enter the correction in degrees (or fractions of degrees), that for non-professional purposes can be even more convenient. Well, in the cheapest thermometers the differences in reflectivity of objects, or not counted at all, or set emission factor of 0.95, and to change it it is impossible.
Another important factor that may affect the measurement, connected with optical resolution, which is understood as the ratio of the spot size on the surface of the inspected object, from which the thermometer takes readings, and the distance from that surface. If quite simply, imagine an ordinary flashlight: it is the light directed to the wall, with a distance of one meter and three meters will create spots with significantly different diameters, the degree of difference will depend on the optical system of the flashlight.
The same with the thermometers. The larger the diameter of the “spot” at a given distance, the higher the probability that it will go not only to the examined object or its important part, but also something foreign, therefore, at large distances it is better to choose models with higher optical resolution (for example, 12:1) — they “beam” is more narrow.But if such a device is used at very small distances, the “spot” becomes very small and it can get only a component object with an emission factor, not characteristic of the subject as a whole (example: the head of the fastening screw), and temperature measurements will be incorrect; then it is better to use the optical resolution of smaller — say 4:1.
For some models not specified optical resolution, and the optimal working distance range, and that is what we see in specifications GM-IRT-860D.
Finally, the measurement modes. In simple models may provide only “one button start measurement — single value”, and in more advanced and even continuous scanning, sometimes not only display the current values, but also with a separate fixation of minimum and maximum. This is useful, for example, when examining the surface of a considerable size or if the object’s temperature is changing rapidly. Let’s see more detail info about one the best infrared thermometer.
Consider the above example on the Gmini GM-IRT-860D.
Characteristics, appearance package
The stated characteristics shown in the table.
|The range of measurement body temperature||35-43 °C|
|The accuracy of the measurement of body temperature||±0.2 °C|
|Measurement range surface temperature||0-100 °C|
|The accuracy of surface temperature measurements||±1 °C|
|Measurement time||0.5 sec|
|Distance measurement||5-15 cm|
|Working environment temperature||10-40 °C|
|Permissible ambient humidity||80%|
|Estimated price||20 usd|
The appearance is quite typical of hand-held tool device has the shape of a gun. On the handle there is a recess under the three fingers, making the grip more comfortable (up to size hand: settlement was clearly on women’s graceful brush, although larger men’s special inconveniences does not feel), and the measurement start button is pressed the index finger is a trigger (the details of which have not passed the military service of the citizens and especially citizen called “trigger”).
In the handle is located and a compartment for two AA batteries. The weight of the device together with the battery (according to our measurement) is only 140 grams.
On one end coupled with the handle unit of measurement is the LCD screen and the group of four buttons, on the other — hole IR sensor and laser emitter, the red beam is used for accurate guidance on “purpose”.
The details of the body have two colors: milky white and, depending on the delivery option, either pale green or blue.
Thermometer is Packed in a beautifully decorated box, included is also case-pouch of velvety material, two alkaline batteries, book manual in Russian and warranty card.