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Why is the resistance of a shunt resistor low?
This means that the maximum current multiplied by the resistance value, cannot be higher than the voltage rating. Also, the resistance value should be as low as possible to limit the interference with the circuit. On the contrary, the resolution gets smaller the smaller the resistance and thus the voltage drop is.
What makes a cap different from a resistor?
It’s different from a cap because a cap will draw a lot of current on a digital edge (for a short but sometimes non-negligible time), having the opposite effect of a resistor.
When do I need a shunt resistor for an ammeter?
Most ammeters have an inbuilt resistor to measure the current. However, when the current is too high for the ammeter, a different setup is required. The solution is to place the ammeter in parallel with an accurate shunt resistor.
Why do you put a resistor on a signal line?
Adding a resistor to a line may limit damaging current flows that would otherwise result from short high-voltage transients, such as those caused by electrostatic discharge (ESD). A low-value resistor in line with the power-supply input to a chip will drop a voltage which is proportional to the chip’s supply current.
What happens when a shunt fails in a circuit?
The high current through the shunt should trigger a circuit breaker or a fuse. When one element in a series circuit fails, it will break the complete circuit. A shunt can be used to overcome this problem. The higher voltage that exists due to the failure will cause the shunt to short out.
How is the resistance of a resistor determined?
The resistance value is given by the voltage drop at the maximum current rating. For example, a shunt resistor rated with 100A and 50mV has a resistance of 50 / 100 = 0.5 mOhm. The voltage drop at maximum current is typically rated 50, 75 or 100 mV.