If you are an electronics maestro, you would be well-familiar with the importance of current sensing for constructing electronics and other devices.
Current sensing is a crucial step that not only allows you to adjust the current levels but also protects the devices from potential risks of damage and failure. You need to sense the current to analyze any electronic device.
Small to big applications use current sensing for this purpose. Your mobile charger also senses current among its different components. Now, you get different types of current sensors as per your requirements. These have different current sensing methods based on the use case.
One of the common methods followed by many sensors is the shunt current resistor. We are going to explore a shunt current resistor in this post and see what makes it an important sensor for various applications of our lives!
What is Current Sense Resistor?
A Current Sense Resistor works similarly to the standard resistors. You might be surprised to know that its resistance is incredibly low compared to its variants. The power offered by this resistor is higher than the others. You position these resistors in the middle of the current route. Now, determine the changes in the voltage and insert the values in Ohm’s equation. V=IR or I=V/R.
After this, you will get the amount of the current that you have been working for. To describe it in simpler words, a shunt means you are making a new path in the circuit. The same is what the job of a shunt resistor is. These make paths for low resistance. So that the current can keep going from one area of the circuit to the other without any disturbance, you can easily detect the amount of current flowing accurately even if it crosses a low resistance region. All this is due to a shunt current resistor!
Parameters of Current sense resistor or Shunt Resistor
You must know that you cannot take full advantage of a Shunt resistor without considering some parameters. Ready to know about these? Let’s check them out below:
- The temperature coefficient of a shunt resistor is higher than the others because these allow a higher degree of current to pass.
- You can determine the thermal EMF of a shunt resistor based on the temperature, unlike other resistors.
- You need to carefully choose the type of shunt resistor by weighing down its production material.
- Different elements have different thermal EMFs. Manganin’s EMF is different from Copper’s.
- Managing is a suitable material to create a blade shunt resistor since its EMF is useful to make this type of resistor only.
Power Rating of Current sense resistor: Power Rating and Resistance
Resistance and power rating are some of the important factors affecting the Shunt resistors. These directly impact the voltage changes when the current makes its way through the system. You can use a current sense amplifier to get the data.
It will work with the full range of the current and input voltage to give you the value of the shunt resistor. If the value is too large, it will influence the power rating, which will lead to excessive heat dissipation than before.
Tolerance of Current sense resistor
You might know this fact; electronics do not submit to ideal situations. Shunt resistors do the same. Since we are talking about tolerance, shunt resistors cannot perform precisely without accurate tolerance. If you consider, you will come to know that regular resistors have a tolerance of up to a maximum of 10% and a minimum of 1%. It is an advisable range to use in major applications.
So if you change the temperature, it will change these percentages as well. When you are only relying on a sensed value, you cannot overlook the role of tolerance for it. The tolerances of these resistors that offer sensed values like shunt current resistors range to 0.1% only. Now, it depends on your project how much will be the accurate output, and you must select an appropriate resistor as per your application. So make sure you are keeping these considerations in mind before hopping onto your projects. It will save you time and prevent failure from taking your peace away!
Temperature Coefficient of Current sense resistor
TCR helps you analyze what amount of the resistance will undergo change when you increase or decrease the temperature. It is another important parameter that can badly influence your output if not considered precisely.
For all the shunt resistor devices, TCR plays a great role in the precision of the devices. You need to make sure that the TCR remains low as much as possible when you’re working with a shunt resistor. It is because these resistors allow huge amounts of current to pass through. Because of this, the system will let out more power through dissipation.
After this, the temperature of the resistor also skyrockets. Now all these changes can impact the resistor value, leading to faulty readings and more chances of human error. There are certain materials that influence the TCR as well. You can also call them resistor elements if you are considering power rating and tolerance for your applications. You can find several low TCR shunt resistors out there. The TCR value of such resistors is low because they contain special metallic foils that serve to reduce TCR.
By far, you know much about the importance of a shunt resistor. But sometimes, different applications require a different type of shunt resistor. Some users fail their projects since they do not know how to choose a shunt resistor for their projects. However, you won’t be from them because the next section is going to discuss this with you!
How to Choose a Current sense resistor?
We told you that you could be overwhelmed by the large variety of shunt resistors present in the market. So how would you choose the best shunt resistor for your projects? It’s not something to worry about! We are going to spill some tips for you to get the best shunt resistor for yourself:
- Determine the current of the resistor and see if it’s suitable for your device or not.
- Check the voltage rating of the resistor for the application.
- Make sure to study your application fully before selecting a resistor.
- Some shunt resistor models are for fast testing of the devices, and they are only efficient for this purpose.
- You also need to determine the input voltage of the application, especially in the case of a current amplifier.
- Shunt resistors that read in milliohms can prove to give accurate readings.
- Now you need to determine the power rating as well so that you can consider what amount of power will go into dissipation.
- Remember this thumb rule: if the value of the resistor is less, the power rating will also be less.
- Lastly, you should know about the tolerance of the shunt resistor. We recommend you choose a resistor with a tolerance of 1% for your applications.
- Some applications need an extra kick of tolerance, so you need to grab appropriate resistors for them.
- Also, you don’t want to forget about the package. It will help you with the soldering when you are working with smaller PCBs since these have tight and hard-to-reach areas. Resistors with extremely less TCR are befitting for this purpose.
