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Published byGabriel Ball Modified over 9 years ago
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Basic Measuring Instruments
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* There are 3 types of instruments we use in 50A: * Ammeter * Voltmeter * Ohmmeter
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* To understand loading effects * To understand a practical use for series and parallel circuits * To what you are doing when you use them
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Ammeter
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* When you turn the knob to change scales on an ammeter, you are changing the shunt resistor. Ammeter
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* AN IDEAL AMMETER HAS 0 OHMS OF INTERNAL RESISTANCE!! * Since no ammeter is perfect, the result is called loading effects.
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Voltmeter What about Voltmeters?
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Voltmeter
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Multi-range Voltmeter
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* AN IDEAL VOLTMETER HAS ∞ OHMS OF INTERNAL RESISTANCE!! * Since no voltmeter is perfect, the result is called loading effects.
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Multi-range Voltmeter Voltmeter sensitivity is expressed in ohms/volt (Ω/V). A voltmeter is considered more sensitive if it draws less current from the circuit. The sensitivity of a voltmeter that draws 50uA is the inverse of this, 20,000 ohm per volt.
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Multi-range Voltmeter
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* The internal resistance of our DMM is always 10MΩ no matter range is selected. (That’s because there is no range to select.
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51.3V 48.7V 95.2kΩ
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What about Ohmmeters?
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Ammeter
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