Chapter1c.pptx - BEKG 1233 Chapter 1(Calibration Noise...

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BEKG 1233 Chapter 1 (Calibration & Noise)

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Calibration Calibration means to compare a given instrument against a standard instrument to determine its accuracy. In this chapter, the calibration of a DC and AC voltmeter, DC and AC ammeter, and Ohmmeter will be discussed. The calibration method using potentiometer will also be discussed.
Calibrating Analog Instruments In calibrating a DC voltmeter, a few instruments such as voltage regulator, resistor, potentiometer is used as standard measuring instrument. Standard instrument is the instruments which comply with the international standard and it can be used to calibrate the measuring equipments in laboratories and industries. Normally, digital instruments such as digital multimeters usually have high accuracy and high precision. Thus it can be used as a standard instrument to calibrate the other analog instruments.

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Calibrating Analog Instruments The circuit connection to calibrate a DC voltmeter is shown in figure 1.1. The test voltmeter reading, V, is compared to the voltage reading obtained with the standard instrument, M. Figure 1.1: Calibrating a Voltmeter
Calibrating Analog Instruments A DC ammeter can be calibrated using a standard resistor R and a standard voltmeter as shown in Figure 1.2. The test ammeter reading, A, is compared to the calculated Ohm’s Law current from the voltage reading obtained across the known standard resistor R, using the standard voltmeter M. Figure 1.2: Calibrating an Ammeter

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Calibrating Analog Instruments The ohmmeter designed around the d’Arsonval meter movement is considered to be an instrument of moderate accuracy. The accuracy of the instrument can be checked by measuring different values of standard resistance and noting the reading obtained. Usually before using the ohmmeter in the laboratory, a simple 0 calibration is done by connecting its probe together and adjusting the 0 adjustment knob so that its pointer points the 0 mark.
Calibrating Analog Instruments For the AC voltmeter and ammeter , the instruments can be calibrated using the comparison method like the DC instruments

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Calibrating Potentiometer Circuit The loading effect of instruments always influence the ultimate value of a measured parameter. Even when instruments with a high input impedance are used to measure voltage, a small loading effect still occurs. One solution to this measurement problem is to utilize an active (energy supplied) circuit called a potentiometer . The key operating condition for the use of the potentiometer is zero current taken from the circuit being measured.
Calibrating Potentiometer Circuit A simple potentiometer circuit is shown in Figure 1.3.

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• Fall '17
• puan nor azilah binti ahmad
• Potentiometer Circuit

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