Precision Current Detection Resistor

Why Choose Tiangeng

Professional Production

We are a company specializing in the design, development, and production of precision series resistors, precision sampling resistors, precision shunts, precision resistor dividers, non-inductive resistors, and power resistor.

Strict Management System

We implement a high-tech enterprise quality management system and strictly follow ISO9001 service management standards and work processes. We will establish detailed product files for customers, respond to customer service requests on time, and assist customers in solving problems.

Advanced Equipment

We have advanced production equipment, such as precision photolithography machines, high and low temperature testing equipment, Agilent 3458A and other precision instruments, digital high-resistance calibrators, high-temperature sintering equipment, heat treatment equipment, etc.

Wide Application

The products produced are widely used in sensors, scales, rail transit, ships, new energy, precision automation control, power instruments, medical equipment, power automation control, precision instruments, measuring instruments, automobiles, electromechanical railways, communications and other fields.

What is Precision Current Detection Resistor?

Current sensing products are established industry favorites among resistive products which, as with most passive products, the majority are surface mount.These resistors, often referred to as 'shunt’ resistors, are used to monitor the current in a circuit and translate the amount of current in that circuit into a voltage that can be easily measured and monitored. Such resistors have very low resistance values, typically less than 50 milliohms (0.050 ohms) and often lower.

As stated by Ohm's Law, there is a voltage drop across any resistance when current is flowing.A current sensing resistor is designed for low resistance so as to minimize power consumption. As a result, the calibrated resistance senses the current flowing through it in the form of a voltage drop which is detected and monitored by the control circuitry.

Types of Precision Current Detection Resistor

Current sensing resistors come in a variety of types, each offering unique advantages depending on the application. These include:

Through-hole Resistors: These are the most common type of resistors which are physically larger and offer higher power ratings.

Surface Mount Resistors: These are small and compact, and are suitable for high-density PCB applications.

Chassis Mounted Resistors: These are large, high-power resistors which can be mounted directly to the chassis or a heat sink.

High Precision Coaxial Shunt Precision Shunt Resistor

Principal Use of Precision Current Detection Resistor

Excess Current Detection
When an abnormal large amount of current flows through a circuit due to a failure or overload, current detection is required for actions such as stopping the circuit operation.

Current Control
Peak current detection of an inductor for controlling the maximum output current of a DC/DC converter, current detection for phase and time control for driving a 3-phase motor, etc.

Current Management
Current management (Remaining battery power detection, etc.) of secondary battery-driven equipment such as smartphones and electric vehicles.

Purpose	How it Works	Application
Overcurrent Detection	Stops circuit operation for safety when an overcurrent flows due to circuit malfunction.	Overcurrent protection of power supply circuits. Overdischarge/overcharge protection of secondary batteries. Overcurrent protection of motors.
Current Control	Senses current and gives feedback to a control circuit to control the value, duration, and phase of the current that flows through the circuit.	DC-DC converters. Inverter power supplies. Current control of AC motors.
Current Management	Senses charging/discharging current of a secondary battery in real time to ascertain the battery life and optimally operate the power supply circuit.	Current management of devices that are powered by secondary batteries such as laptops and mobile devices. Current management of secondary batteries used in EVs/HEVs.

Power Ratings of Precision Current Detection Resistor

A statement of power rating for a given resistor should be always evaluated in context with definition of service conditions. Sometimes more than one number is stated in the datasheet, and sometimes the service conditions stated are not relevant for a given customer's application.

For instance, two different values of power rating are sometimes stated for two different ambient temperatures. In case a power rating is given for an assembly method which is capable of maintaining the resistor's substrate at room temperature, a very high figure can be claimed for power rating, but such service condition is costly to achieve.

Our datasheets for precision heat sink mounted resistors usually state two values of power rating - for free air cooling and for mounting on a heat sink as defined by the US Military Standards. Such a heat sink can dissipate heat only when the temperature of resistor's substrate is higher than the ambient temperature.

So a current sensor of the heat sink mounted style can be assigned three different power ratings (and, accordingly, three different PCR's) - for mounting in free air, on a standard heat sink and on a Peltier type electronic cooling device which keeps resistor's substrate at room temperature.

Therefore, optimal stability can be obtained only by evaluation of customer's application - mounting method and performance requirements - and choosing the most fitting technical solution among the various types of power sensing resistors available.

Temperature Coefficient of Resistance (TCR)

Two predictable and opposing physical phenomena within the composite structure of the resistive alloy and its substrate are the key to the low absolute TCR capability of a Bulk Metal® Foil resistor:

Resistivity of the resistive alloy changes directly with temperature in free air (resistance of the foil increases when temperature increases.)

The Coefficient of Thermal Expansion (CTE) of the alloy and the substrate to which the foil alloy is cemented are different resulting in a compressive stress on the resistive alloy when temperature increases (resistance of the foil decreases due to compression caused by the temperature increases).

The TCR of the Foil resistor is achieved by matching two opposing effects - the inherent increase in resistance due to temperature increase vs. the compression-related decrease in resistance due to that same temperature increase. The two effects occur simultaneously resulting in an unusually low predictable, repeatable, and controllable TCR.

Designing Tips with Current Sense Resistors to Measure Current Accurately

Choosing the Best Ohmic Value
Selecting the best ohmic value is a question of balance. If it is too high, then power will be wasted, excess heat generated, and voltage regulation lost. If it is too low, then the sense voltage will be correspondingly low, so issues of noise and resolution will limit accurate measurement.

Picking the Right Power Rating
Power rating is sometimes a function of the PCB layout design as well as of component selection.

Selecting the Resistor Technology
Different applications require different resistor technologies. Many current sense resistors are in the category of bulk metal technology. This means that the element is a self-supporting piece of resistance metal alloy.

Optimising the PCB Design
PCB track design around current sense resistors is generally more critical to performance than for normal resistors.

Managing Heat
Whether your design requires the resistor to dissipate power at a significant proportion of its rating or to have a minimal temperature rise to minimize TCR errors, it's essential to understand how the heat will be removed and where it will go.

Allowing for Current Surges
Often a design must accommodate high surges in the current above the maximum current which needs to be accurately measured.

Derating for High Temperature
As with any resistor, if the ambient temperature is higher than the rated temperature, power derating must be applied.

Understanding Thermal EMF
When using a metallic element shunt with high heat dissipation and low sense voltage, consideration may need to be given to thermoelectric voltages.

Reducing Inductive Errors
The combination of a high current path and a low signal voltage makes current sense resistor circuits particularly vulnerable to inductive errors.

Combining Multiple Resistors
Designers are sometimes forced to use more than one current sense resistor connected in parallel, either to meet a high power or surge rating or to achieve an ohmic value lower than the minimum available.

Application of Precision Current Detection Resistor

Current sensing resistors are used in a wide range of applications, from power supply units, battery management systems, to motor control and electronic circuit protection. They allow engineers to keep a close watch on the operational current, thereby providing an effective means for troubleshooting and improving system performance.

Current Sensing Resistors in Power Electronics
Power electronics is a domain that frequently employs current sensing resistors. These resistors are key in monitoring and regulating the current in power converters and inverters. By accurately measuring the current, the system can prevent damaging overcurrent conditions and maintain optimum efficiency. Power electronics designs often use low-value current sensing resistors to minimize power loss.

Use in Battery Management Systems
Another important application of current sensing resistors is in battery management systems. Here, they are used to track the amount of current flowing into and out of a battery during charge and discharge cycles. This information is critical for maintaining battery health, optimizing its usage, and predicting its end of life.

Motor Control Applications
Motor control systems, particularly in electric vehicles and industrial machinery, require precise current measurement for efficient operation. Current sensing resistors play a vital role in such systems by providing accurate current feedback. This feedback is used to control and adjust the speed and torque of the motor as needed, enhancing the system's overall performance and efficiency.

Electronic Circuit Protection
In addition to monitoring, current sensing resistors also play an important role in protecting electronic circuits from overcurrent conditions. By monitoring the current flow, these resistors can trigger protective mechanisms like fuses or circuit breakers when the current exceeds a certain threshold, thereby preventing potential damage to the circuit components.

Comparison of Current Sense Resistor Packages

	Pros	Cons
Chip	The smallest package, the lowest cost. Excellent for low-power applications that don't require high-power ratings. No alterations are necessary for SMD assembly.	Even moderate power supplies can outstrip many chip power ratings. More care is necessary for layout for measurement accuracy.
Metal Element (2-Terminal)	Multiple assembly options (SMD, TH). Suitable for high power. The 4-wire sensing method is available on a two-terminal design.	SMD and TH take up more board real estate than a chip, with the TH package adding extra assembly steps.
Metal Element (4-Terminal)	The most accurate reading possible. Suitable for high power.	SMD only; requires the most board area to implement.

How Do You Choose the Right Current Sense Resistors?

Choosing the correct current resistor is critical to any current sensing application. There are many factors to consider, including resistance value, power rating, temperature coefficient, and tolerance.

Resistance Value
This is the most important factor to consider when choosing a current sense resistor. The resistance value determines the amount of voltage drop across the resistor, which is proportional to the current flowing through it. For example, a 0.1Ω resistor will produce a 100mV voltage drop for every 1 Amp of current flowing through it.

Power Rating

The power rating of a resistor is the maximum amount of power it can dissipate without being damaged. It is essential to choose a resistor with a power rating that is high enough to handle the maximum amount of current that will flow through it.

Temperature Coefficient

The temperature coefficient of a resistor is the amount that its resistance value will change for every degree change in temperature. It is important to choose a resistor with a low-temperature coefficient to minimize the effects of temperature changes on the voltage drop across the resistor.

Tolerance

Tolerance is the amount a resistor's resistance value can vary from its nominal value. Choosing a resistor with a low tolerance is vital to ensure that the voltage drop across the resistor is as accurate as possible.

Our Factory

Based on many years of producing various precision resistors, our company designs, develops, and produces various resistor cabinets, coaxial resistors, and metal foil standard resistors.

Company Honor

Based on the high-tech enterprise quality management system, we strictly follow ISO9001 service management standards and work processes.

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Frequently Asked Questions

Q: What is a precision resistor for current measurement?

A: The most common sensing element used to detect current flow is a low value, precision resistor placed in the current path. This resistor, usually called a shunt, develops a voltage across it that is proportional to the current passing through it.

Q: What is a current detecting resistor?

A: Current detection resistor is a common name for resistors inserted in series of a current's path and measuring the current value of the voltage drop generated through Ohm's law. As a high resistance value generates a large voltage drop and increases heat generation as well as loss, a resistor with a low resistance value of 1 Ω or below is generally used.

Q: What does a current shunt resistor do?

A: A shunt is an electrical device that generates a low-resistance path for an electrical current. This enables the current to flow to an alternative point in the circuit. Shunts may also be referred to as ammeter shunts or current shunt resistors.

Q: What is the tolerance of a current sense resistor?

A: With resistance tolerances of 1%, the component can handle a pulse current up to 500A/0.5sec, depending on ohmic values. These bare metal element resistors are offered in 3 standard power ratings, 0.25, 0.50, and 1.0 watt, with a resistance range from 0.002 ohms to 0.008 ohms in standard 5% tolerance.

Q: What is the purpose of a precision resistor?

A: Precision resistors are particularly suitable for applications requiring a high degree of accuracy of the components used. Extremely low temperature coefficients and very small resistance tolerances ensure absolute circuit stability.

Q: What is meant by precision resistor?

A: Precision resistors refer to resistors that meet the higher standards of resistance accuracy, temperature coefficient , load life, and long-term stability under the same resistance technology and installation method.

Q: Are current sense resistors accurate?

A: Current sensing resistor has higher accurate value when giving in a load because heat will alter the resistance of a resistor, even a precision resistor, but not a current sensing resistor. Some current sense resistors also has two more terminals to be able to measure the voltage over the resistor even more accurately.

Q: What is the difference between a current sense resistor and a normal resistor?

A: Current Sense Resistors are similar to normal resistors but with very low resistance rating and high-power rating. These shunt resistors of known resistor value (R) are placed in a current conducting path so that the entire current (I) which is to be measured flows through the resistors.

Q: How can a resistor be used as a sensor?

A: In summary, the resistor in a temperature sensor is used to measure changes in resistance as a function of temperature, and this resistance change is used to calculate the temperature being measured.

Q: How do you measure current through a shunt resistor?

A: For example, when current (I) flows a potential difference (V) is generated across the resistor. This potential difference can be calculated using Ohm's Law. The current flowing through the circuit can be measured by detecting the voltage (V) using a detection circuit.

Q: Does a current limiting resistor drop voltage?

A: When the current limiting resistor is connected, the inrush current during power-on is reduced. Moreover, the instantaneous voltage drop is also reduced to the current limiting resistor, and the voltage waveform on the power supply side is also solved.

Q: How do you limit current with a resistor?

A: By connecting a resistor in series with an LED, current flowing through the two components can be limited to a safe value. When sizing out a current-limiting resistor, look for two characteristic values of the LED: the typical forward voltage, and the maximum forward current.

Q: Where does current limiting resistor go?

A: In practical terms, current limiting resistors are often used in series with an LED to prevent it from drawing too much current and burning out. By choosing an appropriate resistor value, the current through the LED can be limited to a safe level while still allowing it to emit light.

Q: How accurate is a precision resistor?

A: Most common resistors have a tolerance of 5% or 10% , but some resistors can have a tolerance as low as 0.1% , or as high as 20% . Resistors with a tolerance lower than 2% are called precision resistors and are usually more expensive than resistors with higher tolerances.

Q: What type of resistor is typically used as a precision resistor?

A: Wirewound resistors are often produced for high precision or high power applications. They have low noise, are robust, and are temperature stable.

Q: What does high precision resistor mean?

A: Precision resistors refer to resistors that meet the higher standards of resistance accuracy, temperature coefficient, load life, and long-term stability under the same resistance technology and installation method.

Q: Why are precision resistors expensive?

A: The manufacturer increases precision by testing the resistor and burning off more carbon to approach the target value. The more tests and adjustments are made, the higher the precision. Of course, repeatedly adjusting the resistor consumes time, which makes precision resistors more expensive to produce.

Q: What is precision resistor made of?

A: A Nichrome or Manganin is commonly used as the metal wires because they provide high resistance to the electric current and operates at high temperature. The most commonly used core materials include plastic, fiberglass, or ceramic. It is used as a precision resistor in instrumentation because of its high accuracy.

Q: What are the disadvantages of current sensors?

A: Common Disadvantages:
Because of the core, there is a difficulty in the space (especially its height). The magnetic core theoretically has hysteresis. This can cause the change in zero-current output (offset voltage) and eventually cause the measurement error when the large magnetic field is applied to the core.

Q: Do resistors weaken current?

A: In a series circuit, adding more resistors increases total resistance and thus lowers current. But the opposite is true in a parallel circuit because adding more resistors in parallel creates more choices and lowers total resistance. If the same battery is connected to the resistors, current will increase.

Q: Do resistors change voltage or amps?

A: Generally, resistors decrease the current as they “resist” current flow in any circuit. This fact generally causes a reduction in circuit voltages due to the restricted current flow, hence lower differential voltage drop across different elements in any given circuit.

Q: Do resistors change current or voltage?

A: The answer is both. Although dabbling in electronics for years, I repeatedly failed to fundamentally understand how voltage, current, and resistance worked together in a circuit.

We're well-known as one of the leading precision current detection resistor manufacturers and suppliers in China. If you're going to buy or wholesale high quality precision current detection resistor made in China, welcome to get more information from our factory.

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