What is mass How is it measured?

Measure correctly

The most common task in measuring is that Finding routes. These can be lengths of a few millimeters or many meters. Different measuring tools are used depending on the length.

The standard tool for measuring lengths is the Folding rule, also referred to as a folding rule in specialist circles. In the south it is called a yardstick and in the east it is also called a bevel. However, when measuring, one should not blindly rely on the cheap folding rules from the grab boxes in the hardware stores.

High-quality folding rules made of hornbeam, plastic or aluminum have spring joints that allow tight tolerances. The quality of the spring joints not only determines the accuracy, but also the service life of a folding rule. A calibration mark at the beginning of the graduation provides information about the measurement tolerance. The applies to calibratable folding rules Class III. This means that the permitted tolerance is ± 1 mm for a distance of 1 m and ± 1.4 mm for a distance of 2 m.

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Tape measures are more precise. As a rule, class II applies to them with ± 0.7 mm for 2 m, ± 0.9 mm for 3 m and ± 1.3 mm for 5 m. You should avoid adding up the tolerances of different scales Always work with the same scale whenever possible when transferring reference values.

Folding rule more accurate than laser?

In the case of small distances, such as in furniture construction, measurements can sometimes even be made more precisely with folding rules or tape measures than with a laser rangefinder, the design-related measuring accuracy of which is often ± 2 mm. However, for longer distances of many meters, the laser rangefinders are unbeatable, because the tolerance remains constant over the entire measuring distance, while the error when measuring with folding rules or tape measures increases with increasing length.

Correct use is also an important prerequisite for precise measurement with a folding rule. The measuring tool should never be used for purposes other than touching paint or opening bottles. The joints between the individual links must always be used to measure neatly unfolded and locked in place be. If a longer distance is to be bridged freely without the folding rule lying flat, it must be ensured that it does not sag, as this would falsify the measurement result. Simply turn it upright to reduce this risk.

Measure more precisely with a helper

The same applies to measuring with tape measures, because the longer the distance to be measured, the greater the risk of sagging. That is why it is helpful to have a second person pulls the tape measure taut. Long tape measures often have a ring at the beginning with which they can be attached to the exhibition site, for example. However, it should be noted whether the zero point of the scale is at the beginning or the end of the ring.

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The smaller pocket tape measures, on the other hand, usually have one sliding end hook. If it is pulled out, you can hang the tape measure on a workpiece whose thickness is also to be measured. To measure from the inside, the end hook is inserted and measured from the outside edge.

Some pocket tape measures are provided with a viewing window that shows the measurement including the tape measure housing. This makes internal measurements easier, for example in a drawer. However, such measurements can also be carried out without a special viewing window. Simply determine the distance from the front edge to the rear edge of the tape measure housing and simply add this to the value read on the inside.

For larger components such as niches, internal dimensions can also be easily determined with two folding rules. It is often important not only to measure the front edge, but also to take measurements in the back of the niche or even in several places. To do this, unfold both folding rules and place one on one side and the other on the other and read the respective measurements at a point where the two folding rules are next to each other or even on top of each other. The addition of the two values ​​results in the measured internal dimension.

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You can proceed in a similar way when measuring the height of the room. But measure on the wall. In the middle of the room, however, the process quickly becomes imprecise. That's why professionals also use special telescopic rulers, which usually consist of two aluminum tubes plugged together. The inner tube is extended to the ceiling and can be locked in position. The measurement result can usually be read off in a window. Hooks at the ends make it possible to use the telescopic ruler as a giant caliper for the external measurement of components.

Mother's tape measure

A suitable tape measure is not always available and if, for example, the circumference of a column is to be measured, the folding rule fails very quickly. In such cases, the handle in mother's sewing box can help. Even if this tape measure is usually not calibrated, the measurement is sufficient for most tasks. If in doubt, however, you should roll out the tape measure next to a calibrated rule and compare the values.

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Vernier caliper for small dimensions

Folding rules and tape measures usually have a millimeter scale. It may still be possible to estimate dimensions of half a millimeter, but this is often not enough, especially for small components, for example in model making. A measuring stick, also known colloquially as a caliper, is the measuring tool for such parts and high accuracy. It consists of two rods sliding on top of each other with lateral measuring tips for inside and outside dimensions as well as a depth measuring rod for measuring the depth of bores.

The fixed rod carries a scale, the movable one a vernier. This has 11 lines on 9 mm. The distance between two of these markings thus corresponds to 9/10 mm. Since there is always only one line on the length of the vernier and one line on the millimeter scale, the number of the line is simply counted. Each line stands for 0.1 mm. This dimension is added to the value read at the zero position.

In the meantime, more and more digital calipers are replacing mechanical calipers and thus also the somewhat cumbersome reading. There are micrometers for even more precise measurements (up to 0.01 mm). But they are more for precision mechanics and hardly play a role in DIY tasks.

Ultrasound is often inaccurate

Replace when measuring rooms electronic measurement devices the mechanical measuring tools more and more often. Are the cheapest Ultrasonic range finderwhich, even if they are provided with a laser pointer as a target marker, only one poor accuracy to have. This is usually ± 0,5%. The deviation can therefore be as much as 5 mm per meter. At 5 m, the measurement error can even be 2.5 mm.

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To measure, the ultrasonic rangefinder emits an ultrasonic sound that cannot be heard by humans and detects the signal reflected from the opposite wall. That works quite well in empty rooms. However, measurements in furnished rooms are difficult because the furniture also reflects the signal. Even with a wall with a window, you usually do not know exactly whether the device is measuring up to the wall or up to the surface of the window. Ultrasonic rangefinders are also hardly suitable for outside measurements, as wind can blow the signal away and thus falsify it. Such devices can hardly be used for precise measuring work. But when it comes to estimating the size of a room to determine how much paint or wallpaper rolls are needed, even an ultrasonic range finder is sufficient.

Faster and more precise with laser

Even if laser rangefinders are of little use in the construction of small furniture, since they are less precise than a folding rule in this measuring range, they are unbeatable in terms of precision when measuring rooms or even outdoors. But pay attention to the tolerance when purchasing, because there are clear differences, especially with the cheaper devices.

Laser rangefinders send one bundled laser beam and evaluate the reflected signal in a similar way to ultrasonic rangefinders. TEven outdoors, temperature and wind have no significant influence on the laser light and the measurement result. Even obstacles in the room do not interfere with the measurement, because the laser point can usually be identified precisely at the position to be measured.

A major advantage of the devices is that most measurement work, even over long distances, without helper can be made. Some measurements can even be carried out in inaccessible rooms, such as fresh screed.

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With built-in calculation functions, individual measurements can be added at the push of a button, and area or room dimensions can be determined. A special feature is the indirect measurement using the Pythagorean theorem (a2 + b2 = c2). It makes it possible to determine the length of a distance that cannot be measured directly, for example in the case of a facade with a curtain-type balcony. The procedure is actually very simple. First, the distance from the measuring point to the lower edge of the wall is determined. The measuring device is then aligned from the same position to the upper position and the measurement is triggered. The device calculates the third distance from the two measurements.

The reference point is important when measuring with electronic devices. This can be the front edge, rear edge, tripod thread or the end of a special measuring tip. For rangefinders that can be mounted on a tripod, double the range by measuring to one side and then, turning the tripod by 180 °, to the other side.