Current Sense / Shunts

A current measuring resistor is a specialized resistor used in electrical circuits to measure the current flow. It is often referred to as a shunt resistor and is connected in series with the circuit. By measuring the voltage drop across this resistor, the current can be calculated exactly, as the resistance and the voltage are directly related to each other (Ohm's law).

Current measuring resistors are often used in measurement technology, energy supply and electrical appliances to monitor power consumption or control the flow of current. They are used in protection systems, overcurrent protection circuits and precise measuring instruments to ensure accurate current measurement without affecting the operation of the entire system.

Pulse loads can have a considerable effect on the service life of current measuring resistors, particularly due to thermal and mechanical loads.

1. Heating and material fatigue - High current peaks cause short-term temperature increases in the resistor material. Repeated heating and cooling cycles lead to thermal fatigue, which can change the resistance value in the long term.
   
   
2. Overload and microstructure damage - Extreme pulse applications can lead to microcracks in the resistor material or at the solder joints. These can change the resistance value in an uncontrolled manner and, in the worst case, lead to failure.
   
   
3. Electromigration and contact wear - In high-current applications, material migration can occur, which deteriorates the electrical contact. This reduces the long-term stability of the resistor.
   
   
4. Optimization through proper selection - Resistors with high pulse loading capacity, low temperature coefficient (TCR) and robust construction are better suited for applications with repeated load peaks.
   
   

With the right choice and targeted use, the negative effects of pulse loads on current sense resistors can be minimized.

The accuracy of current measurements with shunt resistors can be optimized by several measures:

1. Select precise resistance values - shunts with narrow tolerances minimize measurement errors. Resistors with ±0.1 % or better increase the accuracy.
   
   
2. Low temperature coefficient of resistance (TCR) - Materials with low TCR prevent resistance changes due to temperature fluctuations and ensure stable measured values.
   
   
3. Four-wire measurement (Kelvin connection) - Separate measurement and current paths reduce voltage losses on the traces, leading to more accurate results.
   
   
4. Optimal placement on the board - Short traces and a thermally stable environment reduce interference and resistance changes.
   
   
5. Use low-noise measurement amplifiers - High-quality differential amplifiers with low offset drift improve signal quality and reduce measurement errors.
   
   
6. Calibration and temperature compensation - Regular calibration and software corrections compensate for environmental influences and improve measurement accuracy.
   

These factors are crucial for precise and long-term stable current measurements.

The temperature coefficient (TCR) plays a decisive role in the measuring accuracy and long-term stability of current measuring resistors, as their resistance value changes with temperature.

1. Influence on measurement accuracy - A high temperature coefficient causes the resistance to change with temperature changes, which leads to measurement errors. This can be particularly problematic in high current applications or environments with strongly fluctuating temperatures.
   
2. Material selection and stability - Resistors made from low-resistance metal alloys such as manganese or tin-silver have an extremely low TCR and remain stable even with temperature fluctuations. This ensures precise and reproducible current measurement.
   
   
3. Optimization through targeted selection - Applications with high demands on long-term stability and precision require shunts with a low TCR (e.g. ±5 ppm/°C to ±50 ppm/°C). This minimizes deviations and guarantees precise measurement results over long periods of time.
   
   

A low temperature coefficient is therefore crucial for high-precision current measuring resistors, especially in battery management systems, industrial electronics and power electronics.

Current sensing resistors offer several key advantages over other current measurement methods, particularly in terms of accuracy, efficiency and cost.

1. High measurement accuracy - Shunt resistors enable direct and precise current measurement, as the voltage drop is exactly proportional to the current. Other methods, such as Hall sensors, can be influenced by magnetic fields or temperature fluctuations.
   
   
2. Low losses and high efficiency - Low resistance values (＜1 mΩ) keep energy losses to a minimum, making shunts particularly suitable for high-performance applications. Optical or inductive sensors often have a higher power consumption.
   
   
3. Cost-effective solution - Compared to current sensors or converters, current sensing resistors are an inexpensive and robust solution that can be easily integrated into existing circuits.
   
   
4. Wide range of applications - They are suitable for direct and alternating current measurements in a wide range of areas, from battery management systems (BMS) to industrial electronics and power electronics.
   
   

Their ease of implementation, high precision and low cost make current sense resistors a proven solution for many industrial and automotive applications.

Where can I buy current measuring resistors in Switzerland? - At Rotima AG, you can obtain high-quality current measuring resistors in Switzerland - delivered precisely, reliably and quickly.

Where can I find electronics for renewable energies? - We offer specialized solutions for renewable energy, optimized for maximum efficiency and sustainable performance.

Does Rotima offer electronics for Industry 4.0? - Yes, our range includes modern electronics for Industry 4.0, ideal for smart, networked applications in automation technology.

Can I source industrial electronics in Germany? - Rotima AG supplies reliable electronics solutions for industrial applications in Germany - with the highest quality standards and proven technology.

Does Rotima cooperate with electronic component manufacturers in Switzerland? - Yes, we cooperate with leading manufacturers to offer you high-quality and innovative electronic components.

Where can I find cheap electronic components in Germany? - Our customers benefit from high-quality but cost-effective electronic components that we offer in Germany.

In a current measurement with shunt differential amplifiers, the common-mode rejection ratio (CMRR) is critical to isolate the low measurement voltage across the shunt from high system potentials. By using laser-trimmed, high-precision resistor networks in the amplifier, maximum symmetry of the input branches is achieved, minimizing offset errors due to common-mode fluctuations and maintaining signal integrity even during dynamic load changes.

Engineers must also pay attention to the Kelvin contacting of the shunt in order to eliminate parasitic lead resistances from the measuring loop. The combination of a thermally stable manganese shunt and a low-drift differential amplifier ensures constant measurement accuracy over the entire operating temperature range, which plays a critical role in system safety, especially when monitoring inverter stages or battery management systems (BMS).

ROTIMA offers a range of shunt resistors specifically designed for precise current measurement and power monitoring systems. Although ROTIMA is not a manufacturer of these resistors itself, the company distributes high-quality products from leading manufacturers known for their high accuracy and low tolerances.

These shunt resistors are used in industrial applications such as power distribution, automotive and medical technology. Through close cooperation with renowned manufacturers, ROTIMA ensures that the products meet the requirements of power electronics and measurement technology, with a focus on reliability and durability.