Instrumentation: types and characteristics, classification and operation

The development of human civilization, the desire and need of man to transform the environment make him constantly compare, measure, weigh or count something. To facilitate and perform regularly occurring similar tasks, they began to develop instrumentation, or instrumentation. At first, these devices were simple, made from improvised means, but over time they turned into complex structural and electronic mechanisms.

Definition of the concept of measuring instruments

With the study of natural phenomena, humanity has launched various technological processes that need to be monitored and measured. This requires special devices that can continuously monitor and control during various technological processes.

People have managed to learn how to manage the environment and artificially created technologies. Industrial automation forced the development of measuring devices, and civilization moved to a new stage in its development.

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A meter is a device whose main purpose is to compare a measured value with a generally accepted unit of measurement. These devices measure physical quantities, various processes, technical parameters. There are mechanical and electrical. The principle of operation of the latter is based on the fact that virtually any physical parameter can be converted into an electrical signal, which is easy to process and analyze.

Based on the data obtained, conclusions can be drawn about the state of the environment, about the occurring physical phenomena, parameters and quantities inherent in the measured area.

Currently, measurements are made not only in scientific laboratories and in large enterprises, but also in small workshops and everyday life, even if, at first glance, these devices are invisible. They are widely used in household appliances and common household items.

An inattentive attitude to the readings of measurements, poor training of specialists leads to errors in production, the receipt of low-quality products and threatens the safety of people.

Classification and types of instrumentation

The meter classification is not complicated, but very extensive. The many categories are subdivided into several types, which also branch out into smaller types. The bulk of these devices differ in the type of the measured parameter, in accuracy and purpose.

First of all, instrumentation can be divided into three global categories:

• Analog instruments that are capable of continuously showing the change in the measured parameter. Typical examples are a household mercury thermometer, which is found in every home, and a pressure gauge, a device for reading pressure. The pressure gauge is used both in industry and in everyday life.
• Digital devices. They convert received or measured data into a digital signal. One such device is an electronic pressure meter. On its digital screen, the values ​​of pressure and pulse of a person are shown.
• The simplest mechanical meters. They are familiar to everyone from childhood. This is an ordinary ruler, protractor, compasses, household mechanical scales. Craftsmen often use a vernier caliper.

Each category can be broken down according to other criteria:

• By the type of the measured value.
• By the way of counting.
• According to the proposed class of measurement accuracy.
• According to the main purpose.

Measured values

Each device is designed for its own clearly defined tasks and is designed for a range of specific operating conditions. By the type of the measured value, measuring instruments are:

• Measuring temperature. These are all kinds of thermometers and thermocouples.
• Indicators of pressure or vacuum (vacuum).
• Checking the level of liquids or bulk solids.
• Controlling the amount and consumption of various elements. It can be both liquids and vapors, gases or solids.
• Carrying out quality measurements. For example, density, mixture composition or moisture content.

The principles of operation for measuring devices are practically the same. The measured element acts on the primary transducer, after which the signal goes to the measuring element that converts the impact into movement of the reference node and the readings are transferred to the scale device.

The simplest measurement is clearly demonstrated by the operation of the pressure gauge. The pressure of the measured medium acts on the bent copper tube through a special fitting. The tube is trying to straighten out a certain amount. This action is transferred to the axis with the arrowhead. The axis itself is spring-loaded and tends to return to the zero mark, but under the action of the unbending tube, it deflects and shows the current pressure.

Countdown methods

These devices must have a result display unit. According to the counting method, devices are divided into several types:

• Devices with manual aiming.
• Indicating devices.
• Recorders.
• Summing signals.
• Signaling devices.

Comparators or devices with manual aiming are devices that require human assistance when measuring quantities. It can be a weight scale or an optical pyrometer.

Indicating devices have a pointer in the form of an arrow that moves along the scale of values. Sometimes the pointer can be stationary and the dial moves or rotates around the hand. By design, such devices are portable or stationary. Stationary devices usually measure dynamic quantities continuously. When it is necessary to make measurements from time to time or occasionally monitor stationary meters, then portable PIs are used.

Self-recording devices independently record the results of continuous measurements on a medium. The carrier can be a disk, a flash card or an “endless” paper web. The record is a diagram showing the change in the object under study over a certain time. Such a record can prevent an accident in production, indicating a failure in the operation of a particular node.

Counters or summing devices reflect the readings of the counting mechanism and display the sum of the measured value on the screen. Such integrators calculate the consumption of water, gas, and energy.

Signaling devices emit different signals: light or sound, as soon as the measured value reaches a predetermined value. They also notify when a certain event occurs. These devices include various alarm devices: security, fire, etc.

Separation by purpose

According to their intended purpose, the measuring elements are operational (or technical), laboratory, exemplary, control and standard.

Operational devices are widely used in industry and production. These are working copies that control the entire production cycle. Usually easy to operate, reliable with an intuitive scale and large numerals.

Laboratory and control devices are intended for testing and checking other devices or during debugging work in production. They are distinguished by an increased class of accuracy. Laboratory instruments are used mainly in laboratories, while technical instruments are used in the field of other tested devices.

The main task of reference and exemplary devices is the storage and reproduction of reference data, by which the indicators of other measuring devices are compared. If the reference devices only store data, then the task of the reference devices is to transfer data from the reference devices to other measuring devices as accurately as possible.

Accuracy of measurements

Each device has its own measurement accuracy or error range. Any device, even the reference one, can make a mistake. Accuracy can be specified with a number from zero to one. The higher the accuracy number of the device, the worse its readings.

The sensitivity of the measuring device is an important indicator that influences the correct interpretation of the obtained data. The sensitivity is equal to the ratio of the value of the movement of the device pointer (arrow or pen) to the amount of change in the measured data that provoked this movement.

Sensitivity is most often reflected in the scale of the instrument. For example, if the thermometer has a scale of 100 divisions and is designed for a maximum measured temperature of 50 degrees Celsius, then the average sensitivity is equal to the ratio of 100 to 50. That is, the sensitivity of the device (the price of one division) corresponds to two degrees Celsius.

Errors during operation

In any work, mistakes and mistakes are possible. Measuring instruments are not an exception to the rule. When different measurements are taken, different errors occur. This is due to some conventions adopted in measurements, and imperfection of research methods, and errors when using the meter.

The following types of errors are usually distinguished:

• Absolute. This is a value equal to the difference between the readings of the reference instrument and that used under the same measurement conditions.
• Relative or indirect. The value of the ratio of the absolute error to the current measured value.
• Relative reduced. The ratio of the absolute value and the difference between the maximum and minimum scale limits of the measuring device.

Errors are also random, systematic, and misses. Random errors are not associated with any regularity, but depend on random interference and various external conditions. Systematic ones correspond to some rules and in their manifestation, a pattern can be identified. Often they depend on the technical condition of the measuring device itself. The misses stand out strongly from the logical and intended series of calculations. They are easily tracked and deleted when analyzing enough data.

Service of measuring devices

Sometimes a lot depends on the quality of the instrumentation, so these devices must have such characteristics as reliability, durability, reliability and be available for repair.

To avoid errors in measurements, instrumentation requires timely preventive maintenance and regular checks for the reliability of indicators. The foreman must always monitor the condition and storage conditions of the measuring devices, wipe the dials, scales and signal sensor sockets with a dry cloth.

Before starting work, you need to make sure that the connections are tight and it is advisable to make a control measurement. Defective devices must be replaced in time with new ones or repaired in a timely manner.

At large enterprises, there are entire teams and departments of engineers and instrumentation mechanics who monitor the condition and serviceability of instruments and automation.

At the household level, frequently encounter various measuring devices. They have become familiar and commonplace, but they also require proper handling and compliance with safety rules. The simplest sensor in a washing machine can cause a lot of trouble if it malfunctions. The temperature sensor on household irons is located on the heated surface and, in case of ordinary dirt, will give inaccurate data.

With proper care and storage of control and measuring devices, any household, repair, rest becomes easier and more enjoyable.