Measurement of electrical quantities. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Electrician

Measurement of electrical quantities. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Electrician's Handbook

Comments on the article

Basic electrical quantities

According to the SI system, the units of measurement of electrical parameters are for physical quantities:

current strength - ampere, symbol "A";
voltage - volt, symbol "V";
resistance - ohm, symbol "Ohm";
power - watt, symbol "W".

Means of electrical measurements call the technical means used in the measurement and having normalized metrological characteristics.

Types of electrical equipment measurements

Distinguish the following types of electrical measuring instruments:

measures - measuring instruments designed to reproduce a physical quantity with a certain accuracy (for example, a resistance box);
electrical measuring instruments - means of electrical measurements designed to generate measurement information signals that are available for direct perception by the observer (for example, an ammeter, voltmeter);
measuring transducers - means of electrical measurements designed to generate a signal of measuring information in a form convenient for transferring further conversion, processing and (or) storage, but not amenable to direct perception by an observer (for example, temperature sensors of a controlled object);
electrical measuring installations;
measuring information systems.

The most widespread are electrical measuring instruments.

Varieties of measuring instruments

By the nature of the measured physical quantity, the devices are divided into the following:

ammeters - for measuring current strength;
voltmeters - for measuring voltage;
ohmmeters - for measuring resistance;
wattmeters - for measuring power and others.

The choice of instruments that measure current and voltage should be carried out combination of many factors, the most important of which are:

type of measured current;
approximate frequency range of the measured value;
amplitude voltage range;
the shape of the curve of the measured voltage (current);
power of the circuit in which the measurement is carried out;
power consumption of the device;
permissible measurement error (accuracy class) of the instrument.

If the required accuracy of measurements, the permissible power consumption and other requirements can be provided by ammeters and voltmeters of the electromechanical group, then this simple method of direct reading should be preferred.

Recommendations for the use of measuring instruments

In low-current circuits of direct and alternating currents, digital and analog electronic voltmeters should be used to measure voltage.

Electrical resistance, according to the technical capabilities and methods of their measurement, can be divided into three groups:

group 1 - low resistances up to 1 Ohm;
group 2 - medium resistances from 1 to 100 ohms;
group 3 - large resistances over 100 ohms.

Depending on the magnitude of the resistance and the required accuracy of the result, various methods their measurements:

method 1 - indirect measurement using an ammeter and a voltmeter (the desired resistance is determined on the basis of Ohm's law according to voltage and current measurements);
method 2 - measurement with bridges;
method 3 - direct measurement with an analog or digital ohmmeter.

In recent decades, testers that measure temperature, illumination, humidity and other characteristics that are not related to electricity have become available to the mass user.

Digital Measuring Instruments

Along with analog devices, digital ones are widely used in measuring electrical quantities. All quantities are then converted into digital form using analog-to-digital, interval-numeric or frequency-to-digital converters.

The form of representation of a signal about a physical quantity in the form of a code is called digital. In this case, each value of the reading of the physical quantity corresponds to a code group in the form of a combination of simple signals.

A special class of electrical measuring instruments are devices with a computer as an output device. At the initial stage of the introduction of office equipment into measuring equipment, a computer was used as an additional unit, i.e. the device had an indicator in analog or digital form, but could also be interfaced with a computer to record signals, process information and present it in the form of graphs, tables, histograms, etc.

In modern instruments, indicators are sometimes not used, and the computer is the only means of outputting information. Such devices usually have:

primary converter (sensor);
analog-to-digital converter (ADC);
computer.

Since information must be entered into a computer in the form of a code, such devices can be classified as specific digital devices. Facilities the use of computer output in measuring instruments is obvious:

no need to use recorders;
high noise immunity;
wide possibilities for processing and presenting results;
the possibility of transmitting the received information via communication channels and much more.

Author: Koryakin-Chernyak S.L.

See other articles Section Electrician's Handbook.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive

Dogs can see with their nose 02.08.2022

A new link between smell and vision has been discovered in the brains of these animals.

Scientists believe it is this connection that gives dogs a keen sense of direction and awareness. Even when they can't see well, animals can bring the ball and stick because of the scent that guides them. Dogs' strong sense of smell helps them detect and distinguish between objects and obstacles, even if they are completely blind.

A new study provides the first evidence that dogs' sense of smell is intertwined with their vision and other parts of the brain.

"We have never seen such a relationship between the nose and the occipital lobe, the functional visual cortex in dogs, in any species," said study author Pip Johnson, assistant professor of clinical science at Cornell University in Ithaca, USA. “When we enter a room, we primarily rely on our vision to determine where the door is, who is in the room, where the table is. Our research shows that dogs’ sense of smell helps them learn about their environment and navigate in space. ".

Despite the fact that scientists have proven the connection, they cannot understand exactly how blind dogs use their sense of smell to see objects.

MRI scans of the brains of 23 dogs showed that dogs have patches of white matter that transmit signals between brain regions, each of which is a bit like a "road network". The brain map showed the pathways connecting the olfactory bulb with areas of the brain associated with memories and emotions.

Humans have this network too, which is why smelling certain smells seems to take us back in time. But what was surprising was the new information pathway from the olfactory bulb to the occipital lobe, the visual processing area of the brain. It is this connection that helps the dog "see" with its nose.

Other interesting news:

▪ The brain responds faster to an aggressive voice than to a calm one.

▪ Moving objects with light rays

▪ Wireless TV

▪ Teeth for eating meat

▪ Universal Power Controllers for TWS Wireless Headphones

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the Garland website. Article selection

▪ Article Help in case of injury. Occupational Safety and Health

▪ article What is a sound barrier? Detailed answer

▪ article Bird cherry Maak. Legends, cultivation, methods of application

▪ article Anti-theft device for a motorcycle. Encyclopedia of radio electronics and electrical engineering

▪ article There is not only amylase in saliva. Chemical experience

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews