Les circuits en pont, en particulier les ponts de Wheatstone, constituent la base de nombreuses applications de transducteurs, nous permettant de mesurer des variables physiques telles que la pression, la déformation, la température et le déplacement. Ces ponts reposent sur le principe de l'équilibrage des résistances pour produire un signal de sortie proportionnel à la variable mesurée. Cependant, pour obtenir des mesures précises et cohérentes, un étalonnage minutieux du circuit en pont est nécessaire. Ce processus implique le réglage du pont pour éliminer tout décalage inhérent et établir une correspondance directe entre la sortie du pont et la variable physique mesurée.
Les circuits en pont présentent souvent de légères imperfections ou des décalages, conduisant à des mesures inexactes. Ces décalages peuvent provenir de facteurs tels que :
Pour relever ces défis, un processus d'étalonnage est essentiel. Il implique deux aspects clés :
Le texte que vous avez fourni met en évidence deux techniques courantes utilisées pour l'étalonnage des circuits en pont :
1. Élimination du décalage :
2. Réglage du gain :
Résumé :
L'étalonnage du pont est crucial pour obtenir des mesures précises dans diverses applications de transducteurs. Grâce à l'utilisation de circuits auxiliaires et à un réglage minutieux des composants, nous pouvons éliminer les décalages et établir une relation précise entre la sortie du pont et la variable physique mesurée. Ces techniques garantissent des lectures fiables et précises, nous permettant d'exploiter la puissance des circuits en pont pour une large gamme d'applications scientifiques et techniques.
Instructions: Choose the best answer for each question.
1. What is the primary reason for calibrating bridge circuits?
a) To increase the sensitivity of the bridge. b) To reduce the cost of the bridge circuit. c) To ensure accurate and consistent measurements. d) To simplify the design of the bridge circuit.
c) To ensure accurate and consistent measurements.
2. Which of the following is NOT a factor that can lead to inaccuracies in bridge measurements?
a) Component tolerance b) Temperature fluctuations c) Non-linearity in transducers d) High input voltage
d) High input voltage
3. What is the purpose of "offset elimination" in bridge calibration?
a) To ensure the bridge output is zero when the measured variable is zero. b) To increase the sensitivity of the bridge. c) To reduce the effect of temperature fluctuations. d) To compensate for non-linearity in transducers.
a) To ensure the bridge output is zero when the measured variable is zero.
4. Which technique is used for offset elimination in bridge calibration?
a) Using a series auxiliary circuit with a variable resistor. b) Using a parallel auxiliary circuit with a potentiometer. c) Increasing the input voltage to the bridge. d) Using a digital signal processing unit.
b) Using a parallel auxiliary circuit with a potentiometer.
5. What is the main goal of "gain adjustment" in bridge calibration?
a) To compensate for non-linearity in transducers. b) To establish a specific relationship between the bridge output and the measured variable. c) To increase the power consumption of the bridge circuit. d) To reduce the effects of component tolerance.
b) To establish a specific relationship between the bridge output and the measured variable.
Scenario: You are tasked with calibrating a Wheatstone bridge used to measure strain in a structural component. The bridge has the following resistances:
You observe an offset voltage of 0.2 mV at zero strain. You also need to adjust the bridge to give a 10 mV output for a strain of 100 microstrain.
Task:
**1. Offset Elimination:** * **Connect a potentiometer:** Connect a potentiometer in parallel with the bridge power supply diagonal. The potentiometer tap should be linked to the same bridge node as one end of the detector (voltmeter). * **Adjust the potentiometer:** Slowly adjust the potentiometer tap until the detector reads zero volts when the strain is zero (no force applied to the structure). This will compensate for the inherent offset in the bridge. **2. Gain Adjustment:** * **Use a series resistor:** Connect a series resistor in series with the bridge power supply. * **Measure the initial output:** With the strain at 100 microstrain, measure the bridge output voltage. Let's say this output is 8 mV. * **Calculate the required gain:** You want a 10 mV output, so the gain needs to be adjusted by a factor of 10/8 = 1.25. * **Adjust the series resistor:** Adjust the value of the series resistor until the output voltage reaches 10 mV when the strain is 100 microstrain. The adjustment will increase the voltage applied to the bridge, effectively increasing the gain. **Important Note:** The specific values of the potentiometer and series resistor will depend on the bridge circuit configuration and the desired gain. You might need to experiment with different values to achieve the desired calibration.
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