Electronic measurement field, accurate measurementresistanceValues are fundamental and mission critical. As a commonly used resistance measurement method, the semi-bias method is widely used in experiments and engineering because of its simplicity and high measurement accuracy. This article will introduce in detail the basic principles of resistance measurement using the semi-bias method, and analyze its possible errors and causes from multiple angles to help readers better understand and apply this measurement technology.
1. Basic principles of resistance measurement using the semi-bias methodThe semi-bias method is a measurement method that uses the principle of bridge balance. It mainly adjusts a known resistance in the bridge to bring the bridge to a balanced state, thereby calculating the value of the unknown resistance. In specific operations, the semi-bias method is adjustedPotentiometerOr slide the rheostat to make the bridge's galvanometer pointer return to the zero position to achieve bridge balance. At this time, according to the balance condition of the bridge, the accurate value of the unknown resistance can be calculated using the value and adjustment amount of the known resistance.
2. Circuit structure of semi-bias methodA typical semi-bias method resistance measurement circuit includes a power supply, a known resistance, an unknown resistance, a potentiometer (or sliding rheostat), and a galvanometer. The key to circuit design is to ensure that the resistance values of the four arms of the bridge are reasonably distributed so that the balance point can be accurately found when adjusting the potentiometer. Reasonable circuit layout and good contact status are the basis for ensuring measurement accuracy.
3. Bridge balance conditions and calculation formulasWhen the bridge is balanced, the voltages on the two diagonals of the bridge are equal and the galvanometer pointer returns to zero. Its equilibrium condition is:
R1 / R2 = R3 / Rx
Among them, R1, R2, and R3 are known resistances, and Rx is an unknown resistance. By adjusting R2 (a commonly used adjusting resistor in the half-bias method), after balancing the bridge, the value of Rx can be calculated according to the formula.
4. Advantages of semi-partial measurementCompared with other measurement methods, the semi-partial method has the advantages of simple structure, convenient operation and high measurement accuracy. It is especially suitable for the measurement of medium-value resistors, and because the adjustment amount is only half-bias, it reduces nonlinear errors during the adjustment process and improves the stability of the measurement.
5. Analysis of error sourcesAlthough the semi-partial method has high measurement accuracy, there are still many sources of errors in practical applications, including:
(1) Nominal error of resistor components: It is known that the actual resistance value deviation of the resistor and potentiometer will lead to calculation errors.
(2) Contact resistance and connecting wire resistance: Poor contact or failure to consider wire resistance will cause measurement deviations.
(3) Power supply voltage fluctuation: Unstable power supply will affect the accurate judgment of bridge balance.
(4) Temperature effect: The resistance value changes with temperature, and temperature fluctuations will cause changes in resistance value.
(5) Galvanometer sensitivity limit: The galvanometer is not sensitive enough and it is difficult to accurately determine the balance point.
(6) Human reading error: There is a subjective error in the judgment of the balance point.
6. Measures to reduce errorsIn order to improve the accuracy of semi-partial method measurement, the following measures can be taken:
(1) Select resistive elements with high precision and low temperature coefficient.
(2) Ensure good contact and wiring to reduce additional resistance.
(3) Use a stable DC power supply to avoid voltage fluctuations.
(4) Measure in a constant temperature environment to reduce the influence of temperature.
(5) Use a high-sensitivity galvanometer to improve the accuracy of balance point judgment.
(6) Take multiple measurements and average them to reduce accidental errors.
7. Application scope of semi-partial methodThe semi-bias method is widely used in electronic laboratories, industrial testing and teaching. It is suitable for measuring small and medium-sized resistance resistors, and is especially suitable for the calibration and detection of precision resistors. In addition, the semi-partial method can also be combined with digital instruments to achieve automated measurement and improve efficiency and accuracy.
As a classic resistance measurement method, the semi-bias method occupies an important position in the field of electronic measurement due to its simple principle, convenient operation and high measurement accuracy. By rationally designing circuits, selecting high-quality components, and taking effective error control measures, the accuracy and reliability of measurements can be significantly improved. Understanding the measurement principle and error analysis of the semi-bias method has important guiding significance for electronic engineers and experimenters, and helps achieve more accurate and stable resistance measurements.
