Amfani da Vakuum Tube Voltmeter (VTVM)
Bayanin da Kulaikar Vakum na Voltmeter (VTM)
Vakum na Voltmeter (VTM) yana nufin wata takaitaccen voltmetar da ya yi amfani da tubukan vakum don bayyana karamin karamin jirgin karami (AC) da karamin tsari (DC) da aka bincike. Yadda ake amfani da tubukan vakum ya zama ta kasance hankali, tare da shi an iya gano kyau waɗannan alamun karami mai kalmomi.
Takaitaccen voltmetar, ciki har da VTM, suna da muhimmanci a fice abubuwa daban-daban da suka fi sani da karamin tsari, karamin root - mean - square (RMS), da karamin sauransu a cikin systema mai karami. Tubukan vakum suna da muhimmanci masu yawan, kamar zuwa mai karfi mai karfi, yanayi mai tsawo, da hankali mai kalmomi.
Wanda yake da muhimmanci a kan VTM shine mafi girma a kan karamin rarrabe saboda hankalin da ke faruwa. A kan VTM, alamun da ake bincike zai faruwa tun daga cikin tubukan vakum na wurin. Tubukan vakum zai yi amfani da alamun kuma zai faruwa tun daga cikin voltmetar mai sarrafa, wanda yake da muhimmanci a taka rawa ma'anarsu na karamin tsari.
Abubuwan Vakum na Voltmeter
Vakum na Voltmeter zai iya faɗa da abubuwan masu:
Diode Type
Peak Reading Diode Vacuum Tube Voltmeter
Single Triode
Balanced Triode Type
Rectifiers Amplifier Type
Amplifier Rectifier Type
Simple Diode Type Voltmeter
Circuit of Diode Voltmeter
Circuit of diode voltmeter typically comprises a Permanent - Magnet Moving - Coil (PMMC) meter, a load resistor, and a vacuum tube diode. The vacuum tube diode, when connected in series with a resistor, serves to boost the strength of weak electrical signals. Thanks to the presence of the vacuum tube, the overall system becomes far more sensitive than a standard voltmeter.
To ensure accurate voltage readings from the voltmeter, it is crucial that the current and voltage have a direct proportional relationship. This is achieved through the use of a series resistor, which helps to linearize the meter's response. The circuit diagram of the diode vacuum tube voltmeter is illustrated in the figure below, providing a visual representation of its component layout and operational principles.
Characteristics and Limitations of Diode Vacuum Voltmeter
In a diode vacuum voltmeter, the resistance of the series resistor is significantly higher than that of the vacuum tube diode. As a result, the resistance of the tube can be effectively neglected. This setup allows for a linear relationship to be established between the voltage and current within the circuit. When the input supply is applied, it causes the pointer of the Permanent - Magnet Moving - Coil (PMMC) meter to deflect, with the position of the pointer indicating the magnitude of the measured voltage.
Key Characteristics of Diode Vacuum Voltmeter
Input Resistance: The input resistance of the voltmeter is equivalent to the value of the series resistance. Although high - voltage resistors are employed, they actually reduce the meter's sensitivity. This relationship between resistance and sensitivity is a crucial aspect of the meter's design and operation.
Frequency Range: The frequency range of the diode voltmeter is directly influenced by the value of the series resistance. A higher value of the series resistance leads to a reduction in the meter's frequency range. This inverse relationship means that adjusting the series resistance can control the range of frequencies the voltmeter can accurately measure.
Application Limitations: Due to its relatively low input resistance and restricted frequency range, the vacuum tube voltmeter finds use in only a limited number of applications. These limitations make it less suitable for scenarios that demand high - sensitivity measurements across a broad spectrum of frequencies.
Peak Reading Diode Vacuum Tube Voltmeter
This type of voltmeter incorporates a capacitor within its circuit design. When the capacitor is connected in series with the resistance, the resulting configuration is known as the Series Type Peak Diode Reading Vacuum Voltmeter. Conversely, in the compensated shunt type voltmeter, the capacitor is connected in parallel with the series resistor. These different arrangements of the capacitor and resistor components give rise to distinct operating characteristics and measurement capabilities for each type of peak - reading voltmeter, enabling them to be applied in various electrical measurement scenarios where peak voltage determination is required.
Operation and Evolution of Peak Reading Diode Vacuum Tube Voltmeters
The operational principles of both series and shunt type peak reading diode vacuum tube voltmeters are quite similar. In operation, the capacitor within the circuit charges up to the positive peak voltage of the alternating current (AC) supply. whereafter，it discharges through the shunt resistor, causing a decrease in its voltage. The voltage is then rectified by the Permanent - Magnet Moving - Coil (PMMC) meter, which is connected in series with the resistor. Notably, the peak voltage of the input AC signal is directly proportional to the output voltage of the rectifier, enabling accurate measurement of peak values.
Historically, vacuum tube voltmeters played a significant role in electrical voltage measurement. However, with the advancement of electronics technology, they have largely been supplanted by more modern alternatives. Today, transistor voltmeters (TVM) and field - effect voltmeters (FETVM) have become the preferred choice for voltage measurement tasks. These newer instruments offer improved performance characteristics, such as higher input impedance, wider frequency response, better stability, and enhanced accuracy. They also tend to be more compact, energy - efficient, and reliable, making them better suited to the demands of contemporary electrical and electronic engineering applications.
