Throttle Position Sensor


The throttle position sensor is installed on the throttle body. The sensor converts the throttle opening angle to voltage, which is sent to the engine ECU as the throttle opening signal (VTA). In addition, some devices output an individual IDL signal. Others determine it at idle when the VTA voltage is below the standard value. Currently, two types, the linear type and hall element type, are used.In addition, 2-system output is used to improve reliability.
On-Off Type
This type of throttle position sensor uses an idle (IDL) contact and power (PSW) contact to detect whether the engine is idling or is running under a heavy load. When the throttle valve is completely closed, the IDL contact is ON and the PSW contact is OFF. The engine ECU determines that the engine is idling. When the accelerator pedal is depressed, the IDL contact turns OFF, and when the throttle valve opens beyond a certain point, the PSW contact turns ON, at which time the engine ECU determines that the engine is running under a heavy load.
1. Linear type
As shown in the illustration, this sensor consists of two sliders and a resistor, and contacts for the IDL and VTA signals are provided on the ends of each. When the contact slides along the resistor in sync with the throttle valve opening angle, the voltage is applied to the VTA terminal proportionally to the throttle opening angle. When the throttle valve is completely closed, the IDL signal contact is connected to the IDL and E2 terminals.
HINTRecent linear type throttle position sensors include models without an IDL contact or models that have an IDL contac but it is not connected to the engine ECU. These models use the VTA signal to perform learned control and detect idling condition. Some models use two-system output (VTA1, VTA2) to improve reliability. (2/3)
2. Hall element type
The hall element type throttle position sensor consists of a hall ICs made of hall elements and of magnets that rotates around them. The magnets are installed above the same axis as the throttle shaft and rotates together with the throttle valve. When the throttle valve opens, the magnets rotate at the same time, and the magnets change their position. At this time, the hall IC detects a change in the magnetic flux caused by the change in the magnet’s position, and the resulting hall effect outputs voltage from the VTA1 and VTA2 terminals in accordance with the amount of change. This signal is sent to the engine ECU as the throttle valve opening signal. This sensor not only accurately detects the throttle valve opening, but it also uses a non-contact method and has a simple construction, so it does not break down easily. In addition, to maintain the reliability of this sensor, it outputs signals from two systems with different output characteristics.
Hall Effect
The hall effect is the electrical potential difference that occurs perpendicular to the current and magnetic field when a magnetic field is applied perpendicular to the current flowing in a conductor. In addition, the voltage generated by this electrical potential difference changes proportionally to the applied magnetic flux density. The hall element type throttle position sensor utilizes this principle to convert the change in throttle valve position (opening) to a change in flux density to accurately measure the change in throttle valve position.

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