Sensor Operating Principles

TURCK 8/2/2018

Ferrite Core

Sensor Operating Principles

An inductive proximity sensor consists of a coil and ferrite core arrangement, an oscillator and detector circuit, and a solid-state output (Figure 1). The oscillator creates a high frequency field radiating from the coil in front of the sensor, centered around the axis of the coil. The ferrite core bundles and directs the electro-magnetic field to the front.

When a metal object enters the high-frequency field, eddy currents are induced on the surface of the target. This results in a loss of energy in the oscillator circuit and, consequently, a smaller amplitude of oscillation. The detector circuit recognizes a specific change in amplitude and generates a signal which will turn the solid-state output "ON" or "OFF". When the metal object leaves the sensing area, the oscillator regenerates, allowing the sensor to return to its normal state.

Embeddable (Shielded) vs. Nonembeddable (Nonshielded)

Sensor Operating Principles

Embeddable construction includes a metal band that surrounds the ferrite core and coil arrangement. This helps to "bundle" or direct the electromagnetic field to the front of the sensor.

Sensor Operating Principles

Nonembeddable sensors do not have this metal band; therefore, they have a longer operating distance and are side sensitive.

Uprox and Uprox+ Characteristics

• No Correction Factor - Same rated operating distance for all metals.
• Extended Operating Distance - Up to 400% greater than standard inductive sensors when using non-ferrous targets (Figure 4).
• Weld Field Immunity - Uprox is unaffected by strong electromagnetic AC or DC fields because of its unique patented design.
• High Switching Frequencies - Up to 10 times faster than standard inductive sensors.
• Extended Temperature Range - Uprox can withstand temperatures up to 85°C (+185°F) with a ±15% temperature drift.

Sensor Operating Principles

Operating Principle Uprox and Uprox+

TURCK Uprox is a patented next generation development of inductive sensors that uses a multi-coil system. Active coil(s) induces eddy
currents on the metal target and passive coil(s) are affected by these eddy currents. Ferrous and nonferrous metals have the same effect on the two coils. Therefore, all metals, including galvanized metals, have the same rated operating distance.

TURCK standard inductive sensors use a single coil randomly wound around a ferrite core. The single coil both induces eddy currents on the metal target and is affected by these eddy currents. Ferrous and nonferrous metals affect the sensor differently, making it impossible to detect both types of metals at the same rated operating distance.

Sensor Operating Principles
Operating distances comparison of Uprox sensors and standard inductive sensors.