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Ammeter Design
13 questions By Tony R. Kuphaldt
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Question 4 of 13
What will happen to the function of this ammeter circuit, if the wire marked in the illustration were to fail open?
Reveal answerIf the wire were to fail open, the ammeter would not respond at all to any amount of input current.
Notes:Some students may think the ammeter will fail to respond at all with an open resistor, because they associate “open” faults with lack of current, and lack of current with zero response from the meter movement. Careful examination of the circuit, however, reveals that the exact opposite will happen.
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Question 5 of 13
What will happen to the function of this ammeter circuit, if its resistor were to fail open?
Reveal answerIf the resistor were to fail open, the ammeter would become much more sensitive.
Notes:Some students may think the ammeter will fail to respond at all with an open resistor, because they associate “open” faults with lack of current, and lack of current with zero response from the meter movement. Careful examination of the circuit, however, reveals that the exact opposite will happen.
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Question 6 of 13
Shown here is an ammeter circuit with a special type of selector switch, called a make-before-break selector:
This special kind of selector switch is important to have in an ammeter circuit such as the one shown above. If we were to build such a similar ammeter using a normal (break-before-make) selector switch, the meter would be susceptible to damage during normal use:
Explain why the first circuit design is superior to the second, and what form of use would prove damaging to the second design (but not to the first).
Reveal answerThe type of use that would damage the second meter but not the first is changing ranges while measuring current.
Notes:Another solution to the break-before-make problem is to use a ring shunt circuit rather than have an independent range resistor for each current measurement range.
Hi, Another solution for question 2 could be a parallel connection of the Anmeter with a serial resistor of 6000-400= 5600ohms in parallel with the 6 ohms resistor. Is that correct ?
have answr to immediate follow questions…...........prevent scrolloing.