If you’ve ever wondered how much power is used by an electronic circuit, you’re not alone. The most robust component that can measure current draw is called a shunt resistor and it plays a vital role in the proper functioning of many electronic devices. In this article, we’ll take a look at what shunt resistors are, and how they work.
What are Shunt Resistors?
Shunt resistors are electronic components that are used to measure the flow of electric current in a circuit. They are placed in parallel with the circuit element being measured, and the current flowing through the shunt resistor creates a voltage drop across the resistor. This voltage drop is then measured using a voltmeter, and the resulting value is used to calculate the current flowing through the circuit.
Shunt resistors are available in a variety of different shapes and sizes, and they can be made from a variety of different materials. The most common type of shunt resistor for low current applications is a very low ohm resistor in either a chip form or a strip of a low-resistance copper alloy.
For high-current applications, such as measuring the current flowing through an electric motor, a different type of shunt resistor is typically used. These types of shunt resistors are made from a material called manganin, which has a slightly lower resistance than standard resistor alloys. Manganin resistors are also much more expensive than metal strip resistors or current sensing chips, so they are typically only used for applications where large currents need to be measured.
How Do Shunt Resistors Work?
Shunt resistors work by creating a voltage drop across a “known value” resistor when current flows through it. This voltage drop is then measured using a voltmeter, and the resulting value is usually then amplified then used to calculate the current flowing through the circuit.
To measure the current flowing through a circuit, the voltage drop across the shunt resistor is first calibrated using a known current, and the output voltage is adjusted by removing resistive material until the values coincide. As the current requirements increase, the resistance has to decrease making smaller current measurements more difficult as there is less and less material to calibrate.
What is done with the resulting voltage output?
The output from the shunt resistor is usually in the range of 0 to 100mV. This is typically too small to read by most processors so the signal is usually amplified and converted to a digital signal. Making sure to choose an analog-to-digital converter with a high resolution will allow you to oversize your shunt while still having great accuracy when measuring low currents. We currently have a shunt with a built-in amplifier called the SSA or Smart Shunt, and we are soon going to be releasing an all in one Shunt that includes an amplifier, analog-to-digital converter, and output to CAN, MODBUS, or RS485.
Conclusion
The basics of a shunt come down to having a resistive element with a known value and measuring the voltage drop across it. This gives you the current passing through the circuit, which can tell you how much power is being drawn and if there is a short. Having an accurate shunt is critical in maintaining an accurate view of the status of your electrical circuit.
Riedon is a resistor manufacturing company, specializing in Power, Precision, Surface Mount, High Temperature, High Power, and Custom Resistors. For more information about our current shunt resistors and more, reach out to our team today!