how TPMS sensor works?
03-20-2009, 01:10 PM
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how TPMS sensor works?
Does anyone have any details on this?
I have a busted rim and found the black piece that was inside the rim. I was curious about how it was mounted inside the rim, and also how it actually communicates with the car.
If anyone can provide some insight into this, I'd appreciate it
Thanks
I have a busted rim and found the black piece that was inside the rim. I was curious about how it was mounted inside the rim, and also how it actually communicates with the car.
If anyone can provide some insight into this, I'd appreciate it
Thanks
03-20-2009, 01:42 PM
#2
From wikepedia
A Tire Pressure Monitoring System (TPMS) is generally an electronic system designed to monitor the air pressure inside all the pneumatic tires on automobiles, aeroplane undercarriages, straddle lift carriers, forklifts and other vehicles. The system is also sometimes referred to as a Tire Pressure Indication System (TPIS). These systems report real time tire pressure information to the driver of the vehicle - either via a gauge, a pictogramme display, or a simple low pressure warning light.
Direct sensor TPMS: These systems employ physical pressure sensors inside each tire, and a means of processing and sending that information from inside the tire to the vehicle's instrument cluster.
Direct Sensor TPMS can identify simultaneous underinflation in all four tires in any combination.
Direct sensor TPMS are specifically designed to cope with the effects of changes in tire pressure due to ambient temperature changes and road to tire friction based temperature changes. Friction between the tire and road surface heats up the tire and increases the pressure in the tire. The alarm activation threshold pressures are usually set according to the manufacturers recommended "cold placard inflation pressures".
In order to transfer data from a rotating wheel, Direct Sensor TPMS may use a Radio Frequency (RF) communication channel or an electromagnetic coupling means to overcome the tire/chassis rotational boundary.
The pressure sensor devices of Direct sensor TPMS may be either battery powered or batteryless: Battery powered Radio Frequncy based TPMS have several disadvantages. Batteries eventually become exhausted and represent a maintenance cost to the consumer. Batteries are chemical systems with lifetimes that unfortunately perform very poorly in extreme temperature environments typical of North America and European climates and in aerospace applications. In order to conserve battery life and to conform to various countries communication authority standards for short range radio communications, the power levels of battery powered TPMS are kept very low . As a consequence of these very low power levels, the construction of certain steel belted radial replacement tires and vehicle metallic geometries can block the low power signal transmission paths.
Other disavantage of battery powered direct sensor TPMS are that their physical sensors are quite large and are either mounted on the end of valve stems or by a steel band around a rim's dropwell center. In both cases, these sensors affect a wheel's balance are subject to damage during tire removal and fitting procedures. Banded sensors may also damage the tire bead's air seal. So-called total cost of ownership for direct systems is much higher than for indirect systems due to battery and wheel changes and broken/damaged parts.
On the other hand Batteryless Direct Sensor TPMS overcome these limitations and have the advantage of being maintenance free. Unfortunately, these systems are not available yet on the passenger vehicle market.
[edit] Indirect
Indirect TPMS do not use physical pressure sensors. Indirect TPMS measure the "apparent" air pressure, by monitoring individual wheel rotational speeds, and other signals available outside the tire itself. Most indirect TPMS use the fact that an under-inflated tire has a slightly smaller diameter than a correctly inflated tire and therefore has to rotate at a higher angular velocity to cover the same distance as a correctly inflated tire. Newer developments of indirect TPMS can also detect simultaneous under-inflation in up to all four tires using vibration analysis of individual wheels or analysis of load shift effects during acceleration and/or cornering, which can be realized in software using advanced signal processing techniques. However, the vibration analysis technique requires the use of additional suspension sensors which result in increased complexity and cost of the overall system as long as vertical chassis movements are concerned. That is why most current advanced indirect systems use the spectral content of the wheel speed sensor signals so no additional sensors are needed and the computations can also be carried out by usual processors for example in usual ABS or ESC control units.
Indirect TPMS are realized in software in combination with wheel speed sensors for anti-lock braking systems, and electronic stability control systems. A disadvantage of indirect TPMS is that the driver must calibrate the system by pushing a reset button on the dashboard or through the on-board computer and if this is performed when any tire is in an underinflated condition then the system will not report correctly.
A Tire Pressure Monitoring System (TPMS) is generally an electronic system designed to monitor the air pressure inside all the pneumatic tires on automobiles, aeroplane undercarriages, straddle lift carriers, forklifts and other vehicles. The system is also sometimes referred to as a Tire Pressure Indication System (TPIS). These systems report real time tire pressure information to the driver of the vehicle - either via a gauge, a pictogramme display, or a simple low pressure warning light.
Direct sensor TPMS: These systems employ physical pressure sensors inside each tire, and a means of processing and sending that information from inside the tire to the vehicle's instrument cluster.
Direct Sensor TPMS can identify simultaneous underinflation in all four tires in any combination.
Direct sensor TPMS are specifically designed to cope with the effects of changes in tire pressure due to ambient temperature changes and road to tire friction based temperature changes. Friction between the tire and road surface heats up the tire and increases the pressure in the tire. The alarm activation threshold pressures are usually set according to the manufacturers recommended "cold placard inflation pressures".
In order to transfer data from a rotating wheel, Direct Sensor TPMS may use a Radio Frequency (RF) communication channel or an electromagnetic coupling means to overcome the tire/chassis rotational boundary.
The pressure sensor devices of Direct sensor TPMS may be either battery powered or batteryless: Battery powered Radio Frequncy based TPMS have several disadvantages. Batteries eventually become exhausted and represent a maintenance cost to the consumer. Batteries are chemical systems with lifetimes that unfortunately perform very poorly in extreme temperature environments typical of North America and European climates and in aerospace applications. In order to conserve battery life and to conform to various countries communication authority standards for short range radio communications, the power levels of battery powered TPMS are kept very low . As a consequence of these very low power levels, the construction of certain steel belted radial replacement tires and vehicle metallic geometries can block the low power signal transmission paths.
Other disavantage of battery powered direct sensor TPMS are that their physical sensors are quite large and are either mounted on the end of valve stems or by a steel band around a rim's dropwell center. In both cases, these sensors affect a wheel's balance are subject to damage during tire removal and fitting procedures. Banded sensors may also damage the tire bead's air seal. So-called total cost of ownership for direct systems is much higher than for indirect systems due to battery and wheel changes and broken/damaged parts.
On the other hand Batteryless Direct Sensor TPMS overcome these limitations and have the advantage of being maintenance free. Unfortunately, these systems are not available yet on the passenger vehicle market.
[edit] Indirect
Indirect TPMS do not use physical pressure sensors. Indirect TPMS measure the "apparent" air pressure, by monitoring individual wheel rotational speeds, and other signals available outside the tire itself. Most indirect TPMS use the fact that an under-inflated tire has a slightly smaller diameter than a correctly inflated tire and therefore has to rotate at a higher angular velocity to cover the same distance as a correctly inflated tire. Newer developments of indirect TPMS can also detect simultaneous under-inflation in up to all four tires using vibration analysis of individual wheels or analysis of load shift effects during acceleration and/or cornering, which can be realized in software using advanced signal processing techniques. However, the vibration analysis technique requires the use of additional suspension sensors which result in increased complexity and cost of the overall system as long as vertical chassis movements are concerned. That is why most current advanced indirect systems use the spectral content of the wheel speed sensor signals so no additional sensors are needed and the computations can also be carried out by usual processors for example in usual ABS or ESC control units.
Indirect TPMS are realized in software in combination with wheel speed sensors for anti-lock braking systems, and electronic stability control systems. A disadvantage of indirect TPMS is that the driver must calibrate the system by pushing a reset button on the dashboard or through the on-board computer and if this is performed when any tire is in an underinflated condition then the system will not report correctly.
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