TPMBill
01-02-2013, 04:40 AM
Typical system
In most current designs of direct TPMS, a small electronic assembly which is rugged enough to be mounted inside a tire, measures the pressure using a microelectromechanical system (MEMS)[1] pressure sensor and then transmits this and other information to one or more vehicle receivers.[1] Other information can include a serial number, temperature, acceleration and the status of the complete tire pressure monitoring system.[3] The purpose of the serial number is to allow the vehicle to ignore transmissions from other vehicles and operate with a unique data field. A typical direct TPMS (e.g. Ford,[4] BMW[5] or Toyota[6]) comprises the following components on a vehicle:
A direct TPM sensor fitted to the back of the valve stem on each wheel
A TPM Warning Light
Unique identifier (ID's) for which tire is providing the data including speed and the direction of rotation
A tire pressure monitor electronic control unit (ECU)
Antenna(s)
Controller for periodic measurements
Source of power
Diagnostics and wake up system
Most direct TPMS systems use ultra high frequency (UHF) radio in one of the 'unlicensed' ISM bands (industrial, scientific and medical) for transmitting the data,[7] often around 434 MHz in Europe and 315 MHz in much of the rest of the world. On some systems there is a separate receiver or antenna near each wheel whilst more commonly there is a single receiver which receives data from all of the wheels on the vehicle. Commonly this receiver is also used for remote keyless entry system (RKE) as this also usually uses UHF radio transmissions.
TPM sensors can be fitted to the wheels in a number of ways. They can be mounted on the back of the tire valves stem[8] or attached using adhesive or to a band which is then securely wrapped around the rim inside the tire, usually in the drop zone.[9]
Direct tire pressure monitor system warning light
When the direct TPMS warning light comes on, either one of the tires is under-inflated or there is a fault with the system.[1] If the light is constant then inflating to the correct placard pressure should turn it off. If this is not the case then this indicates a puncture. If the light is intermittent or if it stays on after correct inflation or replacement of a punctured tire then this indicates a fault with the direct TPMS system.[1]
Registration of direct TPMS IDs
When the direct TPMS system is fitted at the factory the unique ID numbers of the TPM (tire pressure monitoring) sensors have to be registered along with their position on the vehicle with the tire pressure monitor ECU. This is also the case if any of the system components are subsequently changed e.g. in the event of rotating the tires, changing sensors, replacing the ECU etc.[4]
This process requires the activation of the direct TPMS sensor using low frequency (LF) radio and the capture of the UHF data transmitted. This data includes the direct TPMS ID, the pressure and the temperature. In automotive manufacturing plants, the activation is carried out using large antenna systems whilst in the dealerships and tire shops, hand tools are used. These tools can also be used to check the direct TPMS for faults prior to disassembly. If a TPM sensor or its position on the car are changed without re-registering the IDs, then the TPMS warning light will turn on and stay on until the IDs are re-registered.[1]
In most current designs of direct TPMS, a small electronic assembly which is rugged enough to be mounted inside a tire, measures the pressure using a microelectromechanical system (MEMS)[1] pressure sensor and then transmits this and other information to one or more vehicle receivers.[1] Other information can include a serial number, temperature, acceleration and the status of the complete tire pressure monitoring system.[3] The purpose of the serial number is to allow the vehicle to ignore transmissions from other vehicles and operate with a unique data field. A typical direct TPMS (e.g. Ford,[4] BMW[5] or Toyota[6]) comprises the following components on a vehicle:
A direct TPM sensor fitted to the back of the valve stem on each wheel
A TPM Warning Light
Unique identifier (ID's) for which tire is providing the data including speed and the direction of rotation
A tire pressure monitor electronic control unit (ECU)
Antenna(s)
Controller for periodic measurements
Source of power
Diagnostics and wake up system
Most direct TPMS systems use ultra high frequency (UHF) radio in one of the 'unlicensed' ISM bands (industrial, scientific and medical) for transmitting the data,[7] often around 434 MHz in Europe and 315 MHz in much of the rest of the world. On some systems there is a separate receiver or antenna near each wheel whilst more commonly there is a single receiver which receives data from all of the wheels on the vehicle. Commonly this receiver is also used for remote keyless entry system (RKE) as this also usually uses UHF radio transmissions.
TPM sensors can be fitted to the wheels in a number of ways. They can be mounted on the back of the tire valves stem[8] or attached using adhesive or to a band which is then securely wrapped around the rim inside the tire, usually in the drop zone.[9]
Direct tire pressure monitor system warning light
When the direct TPMS warning light comes on, either one of the tires is under-inflated or there is a fault with the system.[1] If the light is constant then inflating to the correct placard pressure should turn it off. If this is not the case then this indicates a puncture. If the light is intermittent or if it stays on after correct inflation or replacement of a punctured tire then this indicates a fault with the direct TPMS system.[1]
Registration of direct TPMS IDs
When the direct TPMS system is fitted at the factory the unique ID numbers of the TPM (tire pressure monitoring) sensors have to be registered along with their position on the vehicle with the tire pressure monitor ECU. This is also the case if any of the system components are subsequently changed e.g. in the event of rotating the tires, changing sensors, replacing the ECU etc.[4]
This process requires the activation of the direct TPMS sensor using low frequency (LF) radio and the capture of the UHF data transmitted. This data includes the direct TPMS ID, the pressure and the temperature. In automotive manufacturing plants, the activation is carried out using large antenna systems whilst in the dealerships and tire shops, hand tools are used. These tools can also be used to check the direct TPMS for faults prior to disassembly. If a TPM sensor or its position on the car are changed without re-registering the IDs, then the TPMS warning light will turn on and stay on until the IDs are re-registered.[1]