What Are Current Sense Resistors?

A current sense resistor helps measure the amount of current that is flowing in a electrical system. It senses the current that is coming from the power source and flowing into the object that needs it to function. A resistor can moderate the amount of current so that it doesn't damage the receiving object. Current sense resistors resemble a computer chip with metal or lead extensions that receive and moderate the electricity.

In an electrical system, power originates from a source, such as a generator. That electrical current flows from the power source to the object that relies on electricity. Examples of powered objects include light bulbs, computers and radios. Current sense resistors work by continuously receiving and monitoring the amount of current that is coming from both the source and the object.

A voltage resistor measures the amount of electricity that can be produced by a power source. The amount of voltage is sensed by current sense resistors. It is important to use resistors that are capable of handling the amount of current that certain power sources are able to produce. Different wattage capabilities and maximum temperatures are available depending upon the make and model of the resistor.

The reason it is important to match the correct resistor wattage with the power source's capacity is because the temperature of the resistor will increase. The temperature often becomes extremely hot in current sense resistors as they receive electrical current from both the power source and object. Potential combustion is a real safety concern if the resistor is not capable of handling the amount of electrical current that is being measured.

Wattages of current sense resistors may range from 15 to 30. Their specifications will usually list a maximum operating temperature. Not only will the specifications describe the maximum temperature, but also the maximum time that the resistor will be able to withstand that temperature. Some resistors feature a flameproof design in addition to high and low temperature capabilities.

Current sense resistors are also used to prevent an overload of power. By sensing the amount of current that is flowing from the source to the object, these devices can monitor whether those levels are safe. Since too much power buildup can cause damage to the power object or source, resistors help filtrate some of the current if it becomes too much for the system to handle. At times, resistors may not be effective at preventing power surges if there is a fragile or short circuit in the system.