LF 305S Closed-Loop Hall Effect Current Sensor | HighAccuracy AC/DC Measurement Solution up to 300A

LF305-S Precision · Reliability · Fast Response – Designed for Industrial & Energy Applications

In modern power electronics, the accuracy and stability of current monitoring directly affect system efficiency and safety. The LF 305-S closed-loop Hall effect current sensor from LEM, a world-leading brand in electrical measurement, delivers exceptional performance and reliability. It has become the ideal choice for drive control, power supplies, renewable energy, welding equipment, and many other applications.

LF305-S Key Technical Advantages

Closed-Loop Hall Technology – Guaranteed High Accuracy

The LF 305-S uses advanced closed-loop (magnetic balance) Hall effect technology. By converting the primary large current into a secondary small current signal through a magnetic balance mechanism, it achieves high accuracy, low offset, excellent temperature stability, and low delay over the full temperature range.

Compared with open-loop solutions, closed-loop sensors offer better signal-to-noise ratio, step response time, and sensitivity temperature drift suppression – a clear advantage in high-precision current measurement applications.

Wide Measuring Range – DC, AC & Pulsed Current

The LF 305-S accurately measures DC, AC, and pulsed currents. Its rated measurement is 300 ARMS, with a maximum measuring range of ±600 A – easily handling high inrush currents during motor start-up and various complex waveforms.

Stable Operation in Extreme Environments – Consistent Performance Over a Wide Temperature Range

With an operating temperature range of -40 ℃ to +85 ℃, the LF 305-S delivers stable output even in harsh high- or low-temperature conditions – ideal for outdoor base stations, cold-climate industrial equipment, and other demanding environments. Its compact modular design and UL 94-V0 flame-retardant insulating housing save installation space and enhance system safety.

Galvanic Isolation – Safe & Reliable, Free from Interference

The sensor provides 3 kV isolation voltage, electrically isolating the primary circuit from the measuring circuit to prevent highvoltage crosstalk. Excellent immunity to external electromagnetic interference ensures stable, accurate measurements even in complex power electronic environments.

LF305-S Typical Applications

Widely used in industrial automation, railway traction, energy management, automotive electronics, and more.

LF305-S Flexible Installation – Strong Compatibility

The LF 305-S supports panel mounting, chassis mounting, and screw mounting, easily adapting to various electrical cabinets and equipment layouts. The φ20.1 mm aperture accommodates different busbars or cables, meeting diverse wiring requirements.

LF305-S Genuine LEM Quality – Swiss Brand

The LF 305-S is manufactured by LEM, a world-renowned leader in electrical measurement with decades of experience – including over 25 years of proven use in railway applications. Each LF 305-S sensor is assembled and tested under strict quality control and comes with a 5-year warranty.

LF305-S Model Selection & Compatibility Information

This is the standard LF 305-S. Other versions are available upon request:

Please contact our technical support team for other variants.

Why Choose the LF 305S?

High accuracy – ±0.5% overall accuracy, ±0.1% linearity – ideal for precision measurement
Fast response – ≤1 μs response time, excellent transient capture
Wide measurement – AC, DC, and pulsed currents, range 0 ~ ±600 A
Greater reliability – Wide temperature range (-40 ℃ ~ +85 ℃), 3 kV isolation, strong EMI immunity
Easy integration – Compact size (approx. 90 g), multiple mounting options, compatible with mainstream system designs
Flexible – Various output interfaces and terminal options to match different application needs