Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2000-12-18
2002-12-17
Vo, Hieu T. (Department: 3754)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S115000, C327S063000
Reexamination Certificate
active
06496772
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for the ratiometric measurement of sensor signals, particularly in motor vehicle electronics.
Motor vehicle internal combustion engines are increasingly being fitted with an electronic gas pedal (E gas) and electronic traction control (ETC). To determine the position of the gas pedal, throttle valve, air mass flowmeter, etc., potentiometers with a reference voltage applied to them, for example, are used as pedal value transmitters, throttle valve transmitters, air mass transmitters, etc.; the ratios of the voltages which can be measured at their taps to the reference voltage are a measure of the respective position of the associated transmitter.
DE 196 29 747 A1 discloses a sensor device which has a first reference voltage applied to it and generates a ratiometric measured signal; the ratio of the first to a second reference voltage is formed and is used to correct the measured signal.
For reasons of operational reliability, such transmitters are usually-embodied in multiples and are supplied from mutually independent voltage sources.
The demands on the measurement accuracy of sensors in motor vehicle electronics are becoming higher and higher. Many measured values are transmitted from the sensors to a processing microcontroller &mgr;C as analog DC voltages Vme&bgr; (0 . . . 5V+0 . . . 100%). The microcontroller digitizes them using an analog/digital converter ADC (e.g. 10 bit ADC: 0 . . . 5V+0 . . . 1023 steps). In an analog/digital converter, the measured voltage Vme&bgr; to be converted is set in relation to a reference voltage. To convert the analog values to digital values as accurately as possible, it is therefore desirable for the sensors and the analog/digital converter ADC to use the same reference voltage.
In motor vehicle electronics, this is generally not possible because the reference voltage used for the analog/digital converter ADC integrated in the microcontroller &mgr;C is the supply voltage V
5
int for the microcontroller &mgr;C (VAref=V
5
int). Since, however, the microcontroller and hence the engine/transmission control unit need to remain operational in the event of a short circuit, for example between a sensor line and ground or the battery, the supply voltage V
5
int for the microcontroller &mgr;C must not be routed to the vehicle wiring harness. For this reason, mutually independent supply and reference voltages are required.
A principal cause of measurement errors is the synchronism of the individual supply and reference voltages. For an engine control unit ST containing a microcontroller &mgr;C, the following voltages are required, for example, in the case of dual transmitters:
an internal supply voltage V
5
int for the microcontroller &mgr;C, which is simultaneously the reference voltage for an analog/digital converter ADC integrated in said microcontroller and required for ratiometric measurements of the transmitter voltages and the conversion thereof to digital values required for further processing,
a reference voltage V
5
a
for the first transmitter set SS
1
(pedal value transmitter
1
, throttle valve transmitter
1
, air mass transmitter
1
, etc.), and
a reference voltage V
5
b
for the second transmitter set SS
2
(pedal value transmitter
2
, throttle valve transmitter
2
, air mass transmitter
2
, etc.). In this context, the notation V
5
int signifies the internal 5 volt supply voltage for the microcontroller &mgr;C, whereas V
5
a
and V
5
b
signify the 5 volt reference voltages for sensors arranged outside of the engine control unit ST. The supply voltage for microcontrollers and sensors is usually 5V.
As already mentioned, the voltages V
5
int, V
5
a
and V
5
b
need to be independent of one another, i.e. the other voltages must not be impaired in the event of one of these voltages being shorted.
In addition, the supply voltage V
5
int and hence the operating range of the microcontroller &mgr;C need to be monitored. If the supply voltage is outside the prescribed operating range of, for example, V
5
int 5V±250 mV, reliable operation of the engine controller is no longer ensured. Subsequently possible uncontrolled operation of the microcontroller &mgr;C and hence of the engine control unit ST can result in personal injury and should be avoided absolutely. The microcontroller &mgr;C needs to be stopped in this case.
optimum synchronism would be possible by integrating all the voltage sources in an integrated voltage controller having a common reference voltage source; however, this is hampered by the fact that, in the event of a fault in this common reference voltage source (for example as a result of faulty assembly or as a result of interference pulses), reliable voltage monitoring is not possible because such a fault cannot be recognized by the microcontroller &mgr;C.
One implemented compromise solution consists, as shown in
FIG. 1
, in an inherently known, first voltage controller SR
1
generating the internal supply voltage V
5
int and the external reference voltage V
5
a
using a common reference voltage Ref
1
which is obtained from an operating voltage U
B
and is monitored by a monitoring circuit ÜW integrated in the first voltage controller SR
1
, and in a second, smaller voltage controller SR
2
with a dedicated reference voltage source Ref
2
generating the external reference voltage V
5
b
. The monitoring circuit ÜW, shown as a box inside of the first voltage controller SR
1
, has a window comparator which is indicated by two operational amplifier symbols and whose output signal, possibly delayed by means of a timer &tgr;, is output to the microcontroller &mgr;C as a reset signal Res
1
if the voltage reference exceeds or falls below prescribed limit values.
The timer &tgr; is intended to permit a reset signal to be output only if the voltage reference exceeds or falls below the limit values for a particular time.
This embodiment produces good synchronism between the internal supply voltage V
5
int and the external reference voltage V
5
a
, but loses the synchronism with respect to the reference voltage V
5
b
. Reliable voltage monitoring is not possible in the event of a fault in this common voltage reference Ref
1
either, because the limit values in the monitoring circuit ÜW are derived from the voltage reference Ref
1
and are then likewise erroneous.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a voltage supply device which permits good synchronism between all the voltages generated and ensures reliable voltage monitoring for the supply and reference voltages.
The invention achieves this object by means of a device for ratiometric measurement of sensor signals, comprising a voltage controller constructed to generate a first reference voltage from a received operating voltage, generate a supply voltage for a microcontroller, generate a sensor reference voltage for each one of a plurality of sensor elements selected as a sensor or a sensor set, and derive the sensor reference voltage, for each one of the plurality of the sensor elements, from the first reference voltage independently from the supply voltage.
A first monitoring circuit generates a first reset signal for stopping the microcontroller if the first voltage reference leaves a first prescribed voltage range.
A second monitoring circuit is constructed to generate a second reference voltage from the operating voltage independently from the first reference voltage, and generate a second reset signal for stopping the microcontroller if the supply voltage or the sensor reference voltage leaves a second prescribed voltage range.
REFERENCES:
patent: 4335379 (1982-06-01), Martin
patent: 4644570 (1987-02-01), Brosh et al.
patent: 4750353 (1988-06-01), Wright et al.
patent: 4783175 (1988-11-01), Sugimori
patent: 5191781 (1993-03-01), Denz
patent: 5408143 (1995-04-01), Gleim
patent: 5650608 (1997-07-01), Redford et al.
patent: 5710723 (1998-01-01), Hoth et al.
patent: 5729443 (1998-03-01), Pavlin
patent: 6040779 (2000-03-01), Pfaff et a
Locher Ralph E.
Vo Hieu T.
LandOfFree
Device for radiometric sensor signal measurement does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for radiometric sensor signal measurement, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for radiometric sensor signal measurement will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2964256