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# Working voltage

## Introduction to working voltage

The real-time working voltage of electrical equipment usually needs to be measured with the help of a multimeter, which is an unknown value. The calculation relationship between resistance and current is: working voltage=device resistance

Working current.

The working voltage of electrical equipment needs to fall within a certain range to work normally. This range is often related to the sensitivity of electrical equipment. Generally speaking, the more delicate the equipment, the higher the sensitivity. The normal variation range of the working voltage is smaller. The upper limit of the normal working voltage of the equipment is called the maximum working voltage, which limits the safe voltage range of the equipment. The output voltage of the power system is generally required to be between 198-236V. The working voltage range of household appliances can sometimes reach 100-240V, while the working voltage of electronic components ranges from a few tenths of volts to tens of volts, depending on the fineness of the components. Fixed.

## The difference between different voltages

1. The rated voltage is a definite value, which has been set when the electrical equipment leaves the factory and is the theoretical best value;

The working voltage and rated voltage of electrical appliances (2 photos)

The working voltage is an indeterminate value, which is related to the circuit conditions and equipment status during actual work, and is a real-time change value.

2. The rated voltage is a fixed value, and there is only a single value. Generally, for the convenience of power system interconnection, various countries have made unified regulations on electrical equipment. The general rated voltages in my country are 220V and 380V; work Voltage is a range of variation around the rated voltage, there are countless values, allowing the voltage to fluctuate around the rated voltage when the equipment is working normally, which meets the needs of actual production and work.

## CPU

refers to the voltage required for the normal operation of the CPU. Increasing the working voltage can strengthen the internal signals of the CPU and increase the stability of the CPU. But it will cause the heat of the CPU. The heat of the CPU will change the chemical medium of the CPU and reduce the life of the CPU. In the early days, the working voltage of the CPU was 5V. With the improvement of the manufacturing process and the main frequency, the working voltage of the CPU has changed greatly. Now the working voltage of the commonly used CPU is 1.3-1.5V, which solves the problem of excessive heat generation of the CPU. When the CPU is working normally, the voltage change range should preferably be within 0.05V to ensure the performance and life of the CPU.

## Electron tube

The working voltage of an electronic tube includes its pole voltage value (filament voltage, screen voltage and screen grid voltage, etc.). The voltage value of each pole of the selected electron tube should be the same or similar to the working voltage value of the circuit, otherwise the service life of the electron tube will be shortened.

When the electronic tube is working, the voltage of each pole should be connected in strict order, namely: filament-bias voltage-positive voltage-curtain grid voltage-excitation signal. When shutting down, proceed in the reverse order. Among the various parts of the electron tube, the filament is the most fragile. When applying voltage to the filament, it is best to increase it gradually and in stages. Depending on the structure of the electron tube, the rated voltage of the filament ranges from a few volts to tens of volts. The rated voltage of the filament The working voltage of the filament should be within the allowable deviation range of the rated value, usually the allowable range is 5%. If it can be kept within ±1%, it is beneficial to extend the life. When the filament voltage of the oxide cathode electron tube is high, it will accelerate the decomposition of barium oxide and shorten the life of the cathode; when the filament voltage is low, the barium atoms cannot quickly diffuse to the cathode surface, which will “poison” the cathode, which is the emission capacity of the electron tube. Can't recover anymore. When the voltage of the electron tube filament of the thorium carbide filament cathode is high, the thorium atoms in the filament will quickly evaporate, shortening the life of the cathode; when the filament voltage is low, the cathode will be bombarded by positive ions and become invalid. Practice has proved that the use of DC filament power transmitter tube can change the positive and negative polarity of the filament once after working for a period of time, so that the entire cathode can be uniformly lost. At the same time, the polarity of the electrolytic capacitor that connects the filament input to the ground is also changed, which helps to extend the life of the tube. For tubes with a known service life, the power is reduced due to insufficient cathode emission, and the filament working voltage can be appropriately increased, and the filament current can be increased to extend the service life.

## Electronic chips

Currently, most DSP chips and MCUs operate at 5V, and some are as low as 3V or even 1.5V. The lower the voltage, the smaller the line-to-line width within the allowable distributed capacitance, so that more components and lines can be integrated on a chip of 1 square millimeter.

## Electronic and electrical products

Electronic and electrical products usually require a series of tests on the working voltage before leaving the factory to determine the product’s safe voltage range. When testing the working voltage, you need to pay attention to the following aspects to improve the accuracy of the test results:

1. The exchange of the indirect method of power polarity has a greater impact on the working voltage test results. In the process of voltage test, the influence of the two states of plug connection or reverse connection on the test results should be considered. It is recommended to select the "maximum working voltage value" measured in the two states as the final test result;

2. The TN-S power supply network has an impact on the working voltage test results, especially whether the power supply equipment and the test sample are connected to the common ground can not be sloppy;

3. The oscilloscope must be grounded during the working voltage measurement;

4. The differential probe is used to enable the grounded oscilloscope to perform floating measurements. The probe system as a whole is isolated from the ground terminal of the oscilloscope chassis;

5. Test at peak working voltage In the process, the selection of the sampling mode of the oscilloscope has a decisive effect on the measurement accuracy of the working voltage;

6. If the output signal is a non-sine wave signal, the measured value of the working voltage must measure its true effective value. To measure the true effective value, it is necessary to have a chip or circuit model inside the instrument that can realize this signal calculation;

7. The greater the input impedance of the oscilloscope, the higher the accuracy of the test value.

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