In-house developed key technology
Saturable Coil Technology
Learn more about Saturable Coil Technology,
the key to our magnetic application equipment.
Simple and trouble-free even under adverse conditions.
Provides stable high performance over the long term.
We sometimes receive enquiries about the magnetic detection element Saturable Coil Technology used in sensors manufactured by MACOME. When it comes to magnetic detection sensors, many people think of Hall elements (Hall effect). Those who are familiar with them may also be familiar with magnetoresistance (MR) elements and fluxgate magnetometers. However, you may not be familiar with MACOME’s original technology, the Saturable Coil Technology. The types of magnetic detection and their sensitivity ranges are shown in Fig. 1. In terms of product classification, it’s a variant of fluxgate magnetometer (Table).
| basic principle | element | name |
|---|---|---|
| Hall effect | semiconductor | Hall sensor |
| magnetoresistance effect | thin ferromagnetic film | MR sensor GMR sensor TMR sensor |
| magnetoimpedance effect | amorphous wire | MI sensor |
| magnetic saturation phenomenon | permalloy | fluxgate magnetometer MACOME Saturable Coil Technology magnetometer |
| others | proton precession magnetometer, SQUID magnetometer | |
Table: Types of magnetic detection. Saturable Coil Technology sensors are variants of fluxgate magnetometers.
Fig. 1: Magnetic field strength and sensitivity range of magnetic sensors.
MACOME’s Saturable Coil Technology sensors have specifications for a wide range of applications and genres.
Permalloy cores and coils comprising Saturable Coil.
The Saturable Coil, which is the magnetic sensing element of the Saturable Coil Technology sensors, has a structure, just as simple as a coil wound around a soft magnetic material (permalloy) core (Fig. 2, photo).
Permalloy has a high magnetic permeability and Saturable Coils exhibit a large inductance in the non-saturated (no magnetic field) state. When a magnetic field is applied externally to a Saturable Coil, the magnetism passes through the core with high magnetic permeability. If the applied external magnetic field increases and exceeds the maximum flux density of the core, the core becomes magnetically saturated and the inductance of the Saturable Coil decreases (graph).
Figure 2: Structural diagram of the Saturable Coil.
The coil is wound around a permalloy core.
Photo: Saturable Coil
Graph: Change in inductance of Saturable Coil with respect to external magnetic field
The properties of permalloy and the ingenuity of its
shape enable both high precision and high reliability.
Saturable Coil Technology magnetometers provide highly accurate detection due to the large difference in inductance between the non-saturated and saturated states and the steepness of the change in inductance. These features are determined by the high permeability and low holding force properties of permalloy and the shape of the core. To obtain a large change in inductance, the anti-magnetic field coefficient of the core should be reduced, which can be achieved by making the outer shape elongated. Furthermore, the shape of the core can also be modified to make the characteristics steeper and with a larger change in inductance.
The elongated shape also creates shape magnetic anisotropy, which means that the core is only strongly magnetized against external magnetic fields in the axial direction. Therefore, only the axial component of the applied magnetic field can be easily detected by a coil wound around the circumference of the core.
The MACOME brand magnetic application products make use of the characteristics of these Saturable Coil Technology, boast features such as high precision and high reliability that cannot be imitated by any other product.