Frequently Asked Questions about Electromagnetic Detector

■ Features of the MP-900 series

(1) Non-contact detection, capable of detecting even high-speed rotation.
(2) Excellent rigidity and environmental resistance, and high durability
(3) No power supply required (except for MP-981 and AP-981)
(4) P/R selectable
(The number of teeth on the detection gear directly corresponds to the signal per revolution.)
(5) The mounting location can be anywhere as long as a gear can be attached to the object to be measured.

 

■ About the detection gear

Due to the principle of the detector, ferromagnetic materials (such as S45C and SS400) are used.
When measuring rotational speed under normal circumstances, if the counter's gate time (measurement time) is set to 1 second, the rotational speed can be directly read from the counter by using a 60 P/R gear.

Number of signals per second (frequency) = Rotational speed per minute r/min × 60 P/R

 

■ Shape of the detection gear

The figure below shows the output waveforms of detectors in detection gears of various shapes.
For spur gears, an involute tooth profile is most suitable; square, triangular, or rounded tooth profiles will result in waveforms with high-frequency distortion. Partial chipping of teeth can also cause distortion in the output waveform, so caution is necessary.
Also, if the gears are magnetized, they may interfere with the permanent magnets inside the detector, causing the output voltage to decrease or the signal to have an abnormal waveform, so please be very careful.

■ Recommended gear tooth profile

The diagram below shows that involute gears are recommended to obtain the optimal output voltage.
You can use commercially available gears.

Example of a commercially available manufacturer: Kyoiku Gear Industry Co., Ltd.

If you are manufacturing this, please refer to the "Recommended Gears" section.

 

■ MP-001 type detection gear
Options MP-001 type detection gear We have it ready.

Module	1
Number of teeth	60
Tooth impression	Involute

 

■MP-900 Series Output Voltage Waveform

As described above, when combined with an involute gear, it outputs an approximate sine wave corresponding to the number of teeth.

The amplitude of that approximate sine wave is

(1) Mounting gap between the detection gear and the MP-900 series
(2) Number of modules of the detection gear
(3) Magnetic properties of the detection gear
(4) Magnetic influence around the mounting of the detection gear and MP-900 series
(5) Rotational speed (frequency)
(6) Length of the signal cord

These conditions will affect the results. The table below shows typical amplitude characteristics, with rotation speed (converted to signal output frequency) on the X-axis and amplitude on the Y-axis.

 

Measurement conditions

 

 

■ List of relationships between gears and the MP-900 series

G: Distance (gap) from the detection gear	The narrower the gap, the larger the amplitude at low rotational speeds.
tooth profile of the detection gear	Involute
Material of the detection gear	Ferromagnetic materials (materials that are strongly attracted to magnets), such as S45C and SS400.
Size of the detection gear	We use a unit called a module (M). This value determines the size of the teeth; if the number of teeth is the same module, a proper bite is possible. Module = (Pitch circle diameter) ÷ (Number of teeth) M=1 or more, face width 5 mm or more
Installation precautions	Do not install multiple MP-900 series units in close proximity. - Not in a ferromagnetic environment with fluctuating magnetic fields, such as large motors.
signal cord length	Dedicated signal cable or 3C2V coaxial cable If the signal cable is 20 meters or longer, please use the PA-150 dedicated amplifier.