FR2728688A1 - AMPLITUDE MEASUREMENT CIRCUIT, IN PARTICULAR FOR MEASURING THE AMPLITUDE OF THE OUTPUT SIGNAL OF AN INDUCTIVE SENSOR - Google Patents

Abstract

a) Amplitude measurement circuit, in particular for measuring the amplitude of the output signal of an inductive sensor. b) Circuit characterized in that the voltage available at the output of the maximum value rectifier is applied by switching means (16) to a sampling and holding circuit (17) and the switching means (16) as well as the maximum value rectifier (12) are switched or erased by flip-flops, in particular monostable flip-flops, the flip-flops (20, 21) switching on the basis of sensor signals to be evaluated.

Description

I "Amplitude measuring circuit, in particular for measuring the amplitude of the

  output signal of an inductive sensor "state of the art:

  The invention relates to a measuring circuit for

  amplitude, in particular to measure the amplitude of the signal of

  output of an inductive sensor in which the signal of

  alternative is applied to a maximum value rectifier. For the exploitation of signals supplied by sensors, for example inductive speed sensors

  rotation, the output signals of which are generally

  presented by an alternating voltage, it is usual to

  draw these signals using at least one diode and

  process the rectified voltage. It is also common practice to

  1 'undermine the maximum voltage of the AC voltage at

  using a maximum value rectifier and to take account of

  this maximum voltage during the rest of the ex-

  prosecuting. Such a procedure is for example known from the document EP-B1 0 083 594. In this device known to create a sequence of signals depending on the speed of

  rotation, the maximum voltage provided by a

  trainer of maximum value corresponding to the amplitude of the signal of the sensor for effecting an adaptation of the threshold

depending on the amplitude.

  In the known device according to EP-B1 0 083 594, the signal of the sensor is nevertheless checked for

  determine if the amplitude is in a plausible range

corn. Advantages of the invention:

  The present invention relates to a circuit corresponding to

  of the type defined above, characterized in that the voltage available at the output of the maximum value rectifier is applied by switching means to a sampling and holding circuit and the switching means and the value rectifier are switched or erased by flip-flops, in particular monostable flip-flops, the flip-flops switching from

sensor signals to operate.

  The circuit according to the invention checks whether the amplifier

  sensor signal is within a reasonable range of

  corn. This makes it possible to check advantageously whether there are

  parasites. This advantage is obtained by determining the ampli-

  study in a particularly simple and reliable way; in

  the simplest version, we only use a

  of the signal and in an extended version, the value of maximum to maximum of the signal for the control is determined.

  plausibility. From the determined amplitude, we de-

  advantageously ends the quantity of the input signal

  in a wide range of frequencies and voltages.

  According to other advantageous features of the invention:

  - at the input, there is an amplifier, especially an amplifier

  logarithmic calculator which amplifies the signal to be used before applying it to the maximum value rectifier, - the output of the maximum value rectifier is connected to

  3o mass via the collector path-

  emitter of a transistor and the base of the transistor is controlled by the monostable flip-flop; the switch is controlled by the monostable flip-flop;

  the switch is a transistor whose base is

by the mono-flop;

  - the signal to be used is applied to a comparator

  output a rectangular signal supplied at the bottom of

  monostable valve, whose output is connected to the input of the monostable flip-flop; - for ABS / ASR applications, it is used to

  to check the plausibility of signals to exploit.

Drawing:

  An exemplary embodiment of the invention is

  presented in the drawing and will be described below in a

more detailed.

  Thus: FIG. 1 shows a circuit according to the invention,

  - Figure 2 shows the chronograms of the signals in some

  points identified in a more specific way to the

gure 1.

  Description of the exemplary embodiment:

  Figure 1 shows a circuit for measuring amplitude; this circuit processes the signal SE supplied by a

  sensor for example an inductive speed sensor rotation

  tion; this signal represents in principle an alternating voltage

  native. In a first measurement branch, we determine

  a value corresponding to the maximum value of the

  if we; in a second measurement branch, the

switching conditions.

  The output signal SE supplied by the sensor is coupled to the input E and will be amplified in the amplifier 11 downstream for example a logarithmic amplifier. The

  amplified signal SV then arrives in a voltage rectifier

  their maximum 12; it is a matter of a redundancy

  ) a maximum value active outputting the signal Si. In the case of small amplitudes of voltage,

  i.e. for small amplitudes of the capacitor signal

  SE, one can not have a high resolution and the

  SE sensor signal can also be transmitted directly by the signal path shown in broken lines to the maximum value rectifier 12. It can then be deleted.

the amplifier 11.

  The output of the maximum value rectifier is applied to ground via a capacitor 13; in parallel with the capacitor 13 is the collector-emitter path of a transistor 14 or a field effect transistor (FET). In addition, the output of the maximum value rectifier 12 is applied to an amplifier 15 and through a switch 16 to a sampling and holding element 17. A capacitor 18 is

  connected to the ground at the input of the sample element-

swimming and keeping 17.

  The capacitor 13 and the transistor 14 and

  amplifier 15 may also be part of the

  trainer of maximum value 12; the capacitor 18 may be part of the sampling and holding element 17.

  A comparator 19 is connected to the input E of the circuit

  cooked; this comparator transforms the output signal SE of the sensor into a rectangular signal S3. For example, the usual comparisons of the sensor signal with a threshold having, if the threshold is exceeded, switched to

  the output of the comparator 19 to form a rectangular signal

  S3 for example from the sinusoidal signal SE of

sensor.

  This rectangular signal S3 arrives on a first

  first monostable flip-flop 20 connected to the output of

  The output of the monostable flip-flop 20 providing

  signal S4 is connected to the input of another flip-flop

  nostable 21 and the switch 16; the switch 16 is switched according to the output signal S4 of the

monostable flip-flop 20 (mono-flop).

  The output signal of the monostable flip-flop 21 supplying the signal S5 leads to the base of the transistor 14, according to the amplitude of the signal at the output of the monostable flip-flop 21, to a conductive or blocked state of the transistor 14.

  The main voltages or signals that occur

  1 in the circuit, and which are important for the understanding of the invention, are represented in FIG. 2 as voltages U as a function of time. In detail, the signal El, that is to say the sensor signal that we want to exploit is represented; in addition, we have drawn the line of zero as well as the thresholds of

  tripping SW1, SW2 of the comparator.

  The signals or voltages S1 ... S5 that occur

  1 to 5 of the circuit of Figure 1 are

  presented as a function of time below the sensor signal. In the signal S i obtained at the output of the rectifier

  maximum 12 increases to the maximum value of the amplifier

  corresponding study of the signal SE, then is kept at this constant value until time a, when the value of the maximum rectifier is transferred in the sample and hold circuit. Correspondingly,

  the S2 form of the signal at the output of the sample circuit-

  and hold 17 or at point 2 is a

  gular; this signal is a measure of amplitude

  previously saved. At exit A (point 2) of the

  cooked sampling and holding, positive amplitude

  of the input signal SE is always available for the

  so much negative tripping of the comparator.

  At time b, the maximum rectifier is reset. The residual time is represented in the exemplary embodiment by a monostable flip-flop. This time can

  extend from instant to the positive threshold of comparison

  tor; this has the advantage that the output value is

  cease at the instant of the positive rise of the signal. To measure the maximum to maximum value of

  alternating voltage signal, the circuit must be

  on the one hand a positive maximum rectifier and a

  maximum negative trainer. The difference of the two signals

  output of the sampling and holding circuit cor-

  respondent then represents the value of maximum to maximum

  desired for the input signal.

  The circuit as described makes it possible to determine the

  the quality of the input signal over a wide range of

  quences and tensions, by a plausibility check. In particular, when the speed sensor signals are used in the case of ABS / ASR systems, this allows the entire range of the wanted signal to be monitored.

  1> The plausibility check is carried out in

  the voltage values of the signal S2 to values of

plausible tension.

R E V E ND I C A T IONS

  1) Amplitude measurement circuit, especially for

  measure the amplitude of the output signal of an inductive sensor.

  tif in which the AC voltage signal is applied

  to a maximum value rectifier, characterized in that

  that the voltage available at the output of the voltage rectifier

  their maximum is applied by switching means (16) to a sampling and holding circuit (17) and

  the switching means (16) as well as the voltage rectifier

  their maximum (12) are switched or erased by

  especially monostable flip-flops, flip-flops

  (20, 21) switching from sensor signals to

  ploiter. 2) Circuit according to claim 1, characterized in that at the input, there is an amplifier (11), in particular

  a logarithmic amplifier that amplifies the signal to be ex-

  before applying it to the maximum value rectifier

male (12).

  3) Circuit according to any one of the claims

  1 or 2, characterized in that the output of the rectifier

  maximum value (12) is connected to the mass via

  mediates the collector-emitter path of a transistor (14) and the base of the transistor (14) is controlled by the flip-flop

monostable (21).

  4) Circuit according to any one of the claims

  previous arrangements, characterized in that the switch

  (16) is controlled by the monostable flip-flop (20).

   Circuit according to Claim 4, characterized in that the switch (16) is a transistor whose

  base is controlled by the mono-flop (20).

  6) Circuit according to any one of the claims

  previous arrangements, characterized in that the signal to be

  ploiter is applied to a comparator (19)

  output a rectangular signal supplied to the monosta-

  ble (20), whose output is connected to the entrance to the

monostable agent (21).

  7) Circuit according to any one of the claims

  tions, characterized in that for applications

  ABS / ASR, it is used to control the

  plausibility of signals to exploit.