An Introduction to Voltage-Dividing Resistors and Shunt Resistors ?

What is a Shunt Resistor?

A shunt resistor is a high-precision resistor that uses a very low resistance of an ammeter to measure the flow of current through a circuit. It is the resistance of a conductor in parallel with a circuit. Due to its particularity, it is generally used in precision electronic products.

Characteristics of Shunt Resistors

1. Excellent structure

2. High stability

3. Accurate resistance value

4. Small size is easy to install

5. High-temperature resistance, low noise

6. Good safety performance

7. Good welding performance

Parameters of Shunt Resistors

1. High-precision alloy materials are selected and treated by special technology so that the resistance value is low, the precision is high, the temperature coefficient is low, the stability is good, and it has no inductance and high overload capacity.

2. Common resistance values: 1mΩ, 2mΩ, 5mΩ, 7mΩ, 10mΩ, 12mΩ, 15mΩ, 20mΩ, 50mΩ. Production accuracy: +-0.5%, +-1%, +-2%, +-5%

3. Scope of application: It can be widely used in communication systems, electronic complete machines, and automatic control power circuits as current limiting, current sharing or sampling detection; it can be produced in specific sizes or shapes according to customer requirements.

4. Comply with ROHS specifications and LEAD-FREE lead-free standards.

5. Production cycle: 5-10 days.

Shunt Resistor Selection Points

Due to their special function, shunt resistors should be used in precision electronic products, such as instruments, meters, and measuring equipment, and special attention should be paid to the selection of resistance accuracy. This directly leads to a large error in the measurement results, and the significance of the measurement is lost. Similarly for other precision electronic products, due to their high requirements, it is best to choose resistors with high precision.

Taking the resistance of 4.7 Kohm (kiloohm) as an example, the most common resistor on the market is the 5% precision resistor, which can be satisfied for general purposes, but for precision electronic products, the functions of the shunt resistor, sampling resistor are far from enough. Chip resistors with high precision should be selected. The accuracy can be selected according to the requirements of 1%, 0.1% accuracy, 0.5%, 0.25%, 0.05% resistor, or 0.01% accuracy resistor.

At the same time, the temperature coefficient is the temperature drift TCR, which is also an important parameter that affects the resistance change and shunt current. If the Kohm-level resistor has a temperature drift of several hundred PPM, the same as the accuracy, it cannot meet the high requirements. According to the product requirements, choose 5PPM, 10PPM, 15PPM, 25PPM, 50PPM, and so on.

If the resistance of the shunt resistor is less than 1 ohm, that is, the milliohm level, then you can choose a low-resistance sampling-level resistor. Resistance ranges from 0.0005 ohms, 0.5 milliohms, to 1000 milliohms, 1 ohm.   

What is a Voltage Divider?

A voltage divider is the resistor of a conductor in series with a circuit. The larger the resistance value of the voltage-dividing resistor, the more obvious the voltage-dividing effect. By connecting a high-resistance voltage divider resistor in series with the coil of the ammeter, the ammeter can be converted into a voltmeter to measure larger voltages. The voltage dividers are often used in the circuit with higher resistance value and higher power Jabeson power resistors. If it is a plug-in, the general power supply will use a non-inductive power resistor Jabesson TO-220 resistor (tens to 100W), if the required power is small, you can use a Jabesson 2W SMD resistor and 3W SMD resistor as a voltage divider. Voltage divider resistors often require non-inductive values.

The larger the resistance value of the voltage divider, the more obvious the voltage-dividing effect. By connecting a high-resistance voltage divider in series with the coil of the ammeter, the ammeter can be converted into a voltmeter to measure larger voltages.

The voltage dividers are often used in the circuit with higher resistance value and higher power Jabeson power resistors. If it is a plug-in, the general power supply will use a non-inductive power resistor Jabesson TO-220 resistor (tens to 100W), if the required power is small, you can use a Jabesson 2W SMD resistor and 3W SMD resistor as a voltage divider. Voltage dividers often require non-inductive values.

The difference between a voltage-dividing resistor and a shunt resistor

Voltage-dividing resistor: Two resistors are connected in series, and the voltage drop on one of the resistors (as a power supply) is used to supply power to the “electrical appliance” – the “electrical appliance” is connected in parallel with this resistor.

Shunt resistor: connect a resistor in parallel to the “electrical appliance”, so that part of the current that should flow through the “electrical appliance” can pass through the resistor, thereby reducing the current of the “electrical appliance”. The shunt and the voltage divider have different purposes. The structure is actually the same, however, the two resistors in the voltage divider circuit are equally important, and the shunt circuit does not focus on the other resistor.