What is an LVDT transducer?

An LVDT (Linear Variable Differential Transformer) transducer is also known as a linear variable displacement transducer. It converts linear movement into an electrical signal for linear position measurement.

Basic principle

An LVDT is composed of a primary solenoid coil, two secondary coils, an iron core,  a shell, and other components. When the core moves from the middle to both sides, the difference in output voltage between the two secondary coils has a linear relationship with the core movement, the position of the moving core is defined as a result. As an LVDT transducer works, the core must not move beyond the linear range of the coil, or it will generate nonlinear values, so all LVDT’s have a linear range.

LVDT transducer principle

basic principle of LVDT


AC-LVDT’s. An AC-operated LVDT transducer has a strong resistance to vibration and shock and can operate over higher temperature ranges. It can also be used in smaller packages to fit in hard reaching locations.

DC-LVDT’s. A DC-operated LVDT transducer has a simple operation. The analog or digital output signal is precalibrated. There is no need for external signal conditioning equipment. It saves time and the cost as well.

Advantages of LVDT displacement sensors

LVDT transducer is one of the few displacement sensors that can work in a variety of harsh environments. The sealed LVDT, for example, is made of stainless steel and can be placed in corrosive liquids or gases. Sometimes, LVDT is required to work in extreme environments. For example, in a low-temperature environment similar to liquid nitrogen or a nuclear radiation environment. Although in most cases LVDT has an infinite working life (in theory), the working life of an LVDT in a harsh environment varies from environment to environment.


A linear variable displacement transducer is widely used in aerospace, machinery, construction, textile, railway, coal, metallurgy, plastics, chemical engineering, scientific research, and other fields. It can also be used in the measurement of elongation, vibration, object thickness, expansion, and other high-tech products.

Why buy an LVDT Transducer from us?

LVDT transducers of KAIDI are ideal for the accurate monitor of the valve core position in the hydraulic control systems due to the shorter stroke lengths. Our inductive LVDT transducer fits hydraulic and solenoid valves. Importing advanced technology from BSO of Germany, our products have a wide linear range, good repeatability, and high reliability.

  • None contacting. There is no physical contact between the movable core and the coil, which means there is no friction.
  • Extremely long life. The shell is made of stainless steel. The zero physical contact property extends the service life.
  • Infinite resolution. A KAIDI LVDT transducer can respond to the smallest movement of an iron core and produce output. The readability of external electronic devices is the only limit to resolution.
  • High sensitivity. Our products are very sensitive to the axial motion of the core.
  • High-pressure resistance. Static oil pressure is up to 31.5 Mpa. The protection class is up to IP65.

Key parameters of KAIDI LVDT transducers are as the following.

Model Picture Specification Working stroke Temperature range PDF download
IW9-03-01  liner sensor IW9 M27*2 ±4.5mm -20℃~+80℃  


Model Picture Size Displacement measure Temperature range PDF download
GWEF45-004  liner sensor IW9 Φ45mm ±4mm -20℃~+80℃  


Model Picture Plug Measuring stroke Input voltage Output voltage PDF download
GWEF50-015  liner sensor IW9 >M12*1  4-pole ±15mm ±15V ±5V  


The hydraulic resistance and protection proved by enclosures of the three displacement sensors above are as follow:

Model IW9-03-01 GWEF45-004 GWEF50-015
Hydraulic resistance 31.5MPa  31.5MPa 31.5MPa
Protection proved by enclosures  IP65 IP65 IP67


The IWA1341A Series displacement sensor adopts the advanced technology from BSO Company in German. The IWA1341-063A makes great improvements based on the technology and its shell is made of stainless steel.

Model Measuring range (mm) Basic accuracy (%) Linear accuracy (%) Carrier wave (KHz) Resistance (Ω) Coil induction (mH) PDF download
IWA1341-032 ±3.2 ±0.2 ≤0.1 2.5 6.8 1.1  
IWA1341-063 ±6.3 ±0.2 ≤0.1 2.5 11.8 3.7   
IWA1341-063A ±6.3 ±0.2 ≤0.1 2.5 11.8 3.7   


The IW9-03 inductive linear displacement transducer is used in the control circuits of DC 24V together with the measuring amplifier. The movable pole of the sensor causes the inductance change, and the change of inductance feeds back to the amplifier. Then the amplifier transforms the inductance change into the input voltage.

Model Picture Working stroke (mm) Linear precision(%) Repeat precision(%) Carrier wave(KHz) Winding induction (mH) Protection class PDF download
IW9-03  liner sensor IW9 ±4.5 ≤1 ≤1 2.5 6-8 IP65  


The G-MQ position switch is a safety valve displacement sensor with two outputs pin2 / pin4. It monitors spool’s position fast and accurately. The position switch has functions of voltage sure, overload proof, short circuit protection and polarity repeatability, high reliability and long service life.

Model Picture Supply voltage Ub (V) Current consumption (mA) Max output current (mA) Electrified rate Repeatability at 25℃ (mm) Switching point hysteresis (mm) PDF download
G-MQ  liner sensor IW9 24±20%DC ≤40 400 100% ≤0.02 ≤0.05