The function of a current sensor is to both detect electric current as well as generate an analog voltage, current or digital output signal. Measured current is displayed, stored, or used and is important in many power and instrumentation settings. Initially, current sensors were designed for circuit protection and control, but have evolved as a means to monitor and enhance performance.
Types of current sensors include Hall effect, transformer, resistor, fiber optic and Rogowski coil. Current sensing methods insert a sense resistor along with a conductor to carry measurable current and an amplifier so that the voltage that is available—as a result of current flowing through the resistor—can measure the input current. The output voltage is proportional to the current at the measured path.
Unlike the measuring of voltage that is easily accomplished without interfering with system performance, current measurement relies on the addition or insertion of a sensor, which can impact performance.
Applications include battery chargers and battery life indicators, over-current protection, current and voltage regulators, DC/DC converters, programmable current sources, ground fault detectors, linear and switch-mode power supplies, automotive power electronics, motor overload protection and speed controls, and more.
The 2813509 current sensor by PHOENIX CONTACT is an MCR current measuring transducer used to measure sinusoidal and non-sinusoidal alternating currents, input 0 A TO 400 A, loop powered output with a current output signal of 4 Ma to 20 mA and maximum output current of <25 mA. . The device measures 55 mm x 85 mm x 70.5 mm and has a frequency measuring range between 30 Hz to 6000 Hz and DIN rail mounting.
Figure 1: An application drawing showing current monitoring with the PHOENIX CONTACT 2813509 current sensor. (Source: PHOENIX CONTACT)
Honeywell’s CSLA2EL closed-loop current sensor is an AC/DC current 9 V maximum supply voltage 3-pin device with a minimum/maximum temperature range of -25 °C and 85 °C. Maximum sensing current is 550 A and minimum operating supply voltage is 6 V. ThIS closed-loop sensor features through-hole mounting and has a package dimension of 57.4 mm x 63.5 mm x 15.85 mm and rapid response time. Adjustable performance and built-in temperature compensation deliver reliable operation and accurate, low-cost sensing.
Targeting such applications as power management, current detection for switching power supply, computers, consumer electronics, DC/DC converters, battery packs, chargers and adaptors, the Yageo PF1206FKM7W0R012Z current sensor delivers a low temperature coefficient of resistance (TCR). Features include halogen-free epoxy, RoHS compliance and high component and equipment reliability. The product is constructed using outstanding TCR-level material and the resistive material is adjusted to give the approximate required resistance. It is covered with a protective coating and printed with its resistance value.
Typically, the accurate sensing of current is critical for application safety. Advances in contactless current sensing in renewable energy applications, hybrid electric vehicles (HEVs) and electric vehicles (EVs) enable designers to create a new breed of small economical current sensors with rapid response times. These sensors are particularly appropriate for DC and/or AC current measurements up to 90 kHz, with very low insertion loss, small package sizes and low assembly cost requirements.