When we speak of energy, some people might be thinking about force or electricity. Some may even think of ways on how to save energy or electricity. When we talk about energy saving, this is the time where shunt resistors will enter the picture. But what really is a shunt resistor and what is its purpose?

Defining Shunt Resistor
According to the internet, a shunt is a resistor with a low value used in measuring the flow of current, may it be alternating or direct current. The current measurement is determined through the voltage drop across the resistor. The voltage measurement is computed using Ohm's Law to display in amp or ampere.

Ammeter Shunts
An ammeter is a device to measure electric current. The type of resistor used to provide a low resistance path to the current flow is called the ammeter shunt. The Ohm's Law, as mentioned earlier, is used to calculate the flow of current.

Ohm's Law Formula: The resistor's current I in amps (A) is equal to the resistor's voltage V in volts (V) divided by the resistance R in ohms (Ω): V is the voltage drop of the resistor, measured in Volts (V).

In most of the ammeters, the shunt is inbuilt inside the device. However, on other instruments, a different setup is needed when the current is excessively high for the ammeter. An accurate resistor, which is also known as the ammeter shunt, is required and should be placed in parallel with the ammeter.

Ammeter Shunts are known for their high precision manganin resistor. It is called manganin resistor because manganin foil and wire are used in manufacturing these resistors,  due to its virtually zero temperature coefficient of resistance value and long term stability.

How does it work?  The current is divided over the shunt and the ammeter, this way, only a tiny percentage of current will flow through the ammeter and the actual amperage of huge currents can still be measured. But keep in mind that it should not exceed the voltage rating of the measuring device. To help you with that, multiply the maximum current to the resistance value. The result must not be over the voltage rating of your device. In addition, the resistance value must also be as low as possible to restrict its interference with the circuit.

The Position Of The Shunt In The Circuit
Paying attention to the position of the shunt plays a vital role in the circuit. As much as possible, the shunt should be placed closer to the ground when the circuit and the measuring device share a common ground. This is to protect the ammeter from being damaged because of the possible high common-mode voltage consequently resulting in an inaccurate measurement. The downside of this kind of setup must also be considered such as undetected leakage that bypasses the shunt. Shunts can be placed in the ungrounded leg just make sure it is detached from the ground or simply incorporate a voltage divider to preserve the device.

Shunts are widely used and more affordable. There are several ways to use the shunt in the circuit just consider the pros and cons of each setup. Remember, knowledge is a great advantage!