CTSR Family

Non-contact and accurate milliamps measurement single supplied (+5V).

CTSR - Current sensors

The CTSR current sensors enable the measurement of DC, AC, and pulsed currents ranging from 0.3 to 1 ARMS nominal, featuring galvanic separation between the primary and secondary circuits. 

These transducers are designed for non-contact, compact, and accurate milliamps measurement, specifically for residual or leakage current measurement. With low offset drift, they are intended for PCB mounting. 

CTSR models have an additional pin at the output for more flexibility in applications. This pin provides access to the internal voltage reference which can then be fed to the reference of an A/D converter (Analog Digital). This extra pin can also receive the internal reference (from 2.3 to 4 V) of the DSP (Digital Signal Processor) or A/D converters commonly used in Power Electronics, allowing cancellation of the reference temperature drift.

The CTSR current sensors utilize closed-loop Fluxgate CTSR type technology, ensuring high accuracy, particularly in industrial applications.

CTSR – Features and benefits

CTSR current sensors


  • Closed loop (compensated) Fluxgate current transducer
  • Voltage output
  • Single supply voltage
  • Non-contact measurement with high aperture (Ø 20.1 mm)
  • PCB mounting

Additionally, the CTSR-TP series includes primary inserted conductors, providing added flexibility and functionality to the sensor family.


  • High accuracy
  • Very low offset drift over temperature
  • High overload capability
  • High creepage and clearance distances (11 mm) for high insulation
  • Reference pin with two modes, Ref In and Ref Out
  • Degauss and test functions
  • Compact unique design for all the models

Typical applications

The CTSR sensor family is well-suited for various high-accuracy demanding applications in the industry, including:

  • Residual current measurement
  • Leakage current measurement in transformerless photovoltaic inverters
  • First human contact protection of PV arrays
  • Failure detection in power sources
  • Symmetrical fault detection (e.g. after motor inverter)
  • Leakage current detection in stacked DC sources
  • Single phase or three phase nominal current measurement up to ±30 A per wire (DC or AC)

CTSR transducers standard compliance

  • EN 50178 for industrial applications 
  • UL 508 (UR marking)
  • European Directive EMC 2004 / 108 / EEC: CE marking
  • Using UL94-VO recognized materials
  • Low voltage directive 2006 / 95 / EEC
  • Safety IEC 61010-1
  • Suitable to fulfil VDE 0126-1-1 and UL 1741

LEM CTSR – Download & Technical Characteristic

Product Document Primary nominal RMS voltage Supply Voltage range Op. Temperature
CTSR 0.3-P


0.3 A 5 to 5 -40 to 105 °C
CTSR 0.3-P/SP10


0.3 A 5 to 5 -40 to 105 °C
CTSR 0.3-TP/SP14 Datasheet
0.3 A 5 to 5 -40 to 105 °C
CTSR 0.3-TP/SP4 Datasheet
0.3 A 5 to 5 -40 to 105 °C
CTSR 0.6-P Datasheet
0.6 A 5 to 5 -40 to 105 °C
CTSR 0.6-P/SP10 Datasheet
0.6 A 5 to 5 -40 to 105 °C
CTSR 0.6-TP/SP2 Datasheet
0.6 A 5 to 5 -40 to 105 °C
CTSR 1-P Datasheet
1 A 5 to 5 -40 to 105 °C


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