Why do shunts need to be selected according to circuit conditions?
Why do shunts need to be selected according to circuit conditions? Simply put, it is to effectively use the range of the voltmeter. For example, a voltmeter with a full scale of 75mv, the object to be measured is a current of about 20A, you choose the shunt resistance R, and R*20A should preferably fall on the middle of the 75mV range, such as 3mΩ to 3.5mΩ for comparison Suitable.
An outrageous example, if the internal resistance of the shunt is 0.001mΩ, when 20A passes through, the terminal voltage is only 0.02mV, the measurement results of all current changes in the circuit are squeezed into one thousandth of the range, and the accuracy of the meter is only 1% of the range, The error is much larger than your measurement value, then your measurement result is meaningless.
