GB2195776A - Determining average sensor output ratios over both short and long periods - Google Patents

Abstract

After integration at 14, the signals 12 from two sensors 13 for different variables are periodically added to the contents of respective stores 21, and integrators 14 are reset. The outputs 27 of the stores are divided at 25 to provide directly a quotient 26 of the integrated outputs of the sensors at least over the short term. For longer periods, every time either signal 27 reaches a threshold 28 at which errors occur, e.g. commencement of non-linear storage (or overflow of a digital store, Fig. 2), circuit elements 29, 30, 34, 38, 43 are operated to divide both stored signals by the same factor and element 35 reduces the inputs to stores 21 correspondingly. Any part of signal 19 not transferred via circuit 35 to store 21 is returned to the reset integrator 14 for the next cycle. Cycle times of integrators 14 may be fixed or (as shown) be terminated whenever a signal 19 reaches a threshold value 23. Applications given are average speed from distance and time, and average fuel consumption over the whole useful life of a motor vehicle. <IMAGE>

Description

SPECIFICATION An arrangement for, and method of, determining an average value This invention relates to an arrangement for, and method of, determining an average value of a dependentlyvariable measurand over an independently-variable measurand.

Such arrangements are always needed in measuring techniques when the mean value as a quotient derived from a dependent and an independent variable is of interest; such as, for example, the consumption of working materials (Betriebsmittel) as a function of the output of a production plant or an average speed as a quotient derived from distance traversed and time elapsed. If, in such instances, from two measurands (measured variables or quantities measured or metered) a third, related variable or quantity is to be ascertained by forming a quotient, a measuring sensivity which is seemingly as high as possible is to be striven after, so that with small values of the independent variable sufficient accuracies (and thus useful average-value results) can be obtained.On the other hand, with a larger independent variable the dependent variable accumulates to such a large measured value that analog processing circuits can be modulated or controlled out of the non-linear characteristic region into saturation, whilst digital information processing leads to such large numerical values that these are often no longer rationally manipulable with simple technical circuit means, because, for example, the digital arithmetical computing operations require too much time. This is, for example, the case when over the entire useful life of a machine (for instance of a motor vehicle) the average consumption of working materials (Betriebsmittel) e.g. fuel is to be observed or recorded.

In recognition of these factors, an object of the present invention is to attempt to provide an arrangement, which after very brief time periods of the independent variable supplies an average-value result of good accuracy and, despite the great measuring resolution necessary for this, also after long time periods of the independent variable possibly results in no loss of information through saturation phenomena or numerical rounding errors; thus over extremely long time periods of the independent variable a change of one variable also possibly allows small influences on the quotient to become perceptible in the average value.

According to the present invention there is provided an arrangement for, or method of, determining the average value of a dependently-variable measurand over an independently-variable measurand, which measurands are in each case picked up or received by means of an integrating measuring instrument (e.g. 14.1 or 14.2) and placed into relationship with one another in a divider, characterised in that connected subsequent to each measuring instrument is a balancing store for periodic acceptance of the measured value along with resetting of the measuring instrument into an initial or starting position, and in that associated with each of the balancing stores is a reducing stage which reduces the balanced measurement result upon overflow of one of the stores by a factor, with writing back or feedback of the reduced measuring indicator (e.g. 31.1 or 31.2) into the associated balancing store instead of the previous measurement result which has led to the overflow; with each store overflow the reduction factor in the reducing stages is increased.

The solution thus represents, to a certain extent, a sensitivity in forming the quotient which is reduced quasi-continuously with the incremental growth of the independent variable. The average value present as a quotient is, however, thereby not impaired in its accuracy if, upon the growth of one of the variables beyond a limiting value afforded or set by circuitry technique respects, both the accumulated dividend and the accumulated divisor for the quotient are reduced by a common factor which is then applied in future also as a divisor to the measured-value attainment.The division of the actual measured value by this factor is also non-critical in digital circuit realisation, because merely the integral portion of the measured-value quotient has to be taken into account and rounding error can be avoided in that the fraction remaining from the division is written (fed) back again into the counting measuring instrument, and thus is not lost upon the measured-value attainment.

With a digital circuit, the division of the actual measured values may be effected by a dividing device to which the divisor is fed from a counter, so that no rounding errors can adulterate the actual measured value. On the other hand, the binary-coded accumulated variables may be advantageously divided down simply by shifting the content of shift registers, since the divisor for the reduction of the actual and of the accumulated measured values is freely selectable.

If the exact average-value determination is of less interest than the influence of the latest or most recent measured-value past compared with the older antecedents, then merely the divisor for the actual measured value needs to be increased less severely than that for the accumulated variables. If the divisor for the actual measured value is no longer carried at all, the arrangement in accordance with the present invention is usable practically over an unlimited time span of the independent variable, because no register overflow can occur if the division of the accumulated variables is effected by register-location shift of the binary-coded information.

Additional alternatives and further develop ments as well as further features and advantages of the invention will be apparent from the claims and, two preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying much simplified schematic circuit drawings, in which: FIGURE 1 shows an arrangement for average-value determination in analog signal-processing circuit technique; and FIGURE 2 shows a corresponding arrangement in digital signal-processing circuit technique.

The block circuit diagram representation of FIGURE 1 shows signal processing channels 11.1 and 11.2, for a dependent and for an independent measurand 12.1, 12.2 respectively, utilisable for the aforementioned exemplary variables which are picked up by means of sensors 13.1, 13.2. The integrating measuring instrument 14.1 or 14.2 which is in each case connected subsequent to the sensor 13 is, in each case, shown as an operational amplifier 15 with inverse capacitive feedback 16 behind the input resistor 17. In the interests of clarity, sample-and-hold members for the input-side or output-side decoupling information acceptance or transfer are not shown in the drawing.

Initialised by way of a control circuit 18, after a specific measuring timespan the actual measured value 19.1 or 19.2 at the output of the measuring instrument 14.t or 14.2 is interrogated, by being transferred by way of a switch 20.1 or 20.2 to a balancing store 21.1 or 21.2 respectively, which in principle may have the same construction as the measuring instruments 14. Thus, now the measured values 19 can be cleared, by the measuring instruments 14 being reset again into their starting measuring position; something which is shown in the drawing symbolically by a discharge switch 22 for the negative capacitive feedback 16 of the amplifier 15.If this restoration of the measuring instrument 14 into the initial operating position after transfer of the actual measured value 19 occurs sufficiently-often, it is ensured that the amplifier 15 is not modulated as far as into saturation, thus the measuring instrument 14 cannot be overloaded with the measurand 12. With severely fluctuating or unknown behaviour of the measurand 12, provision can be made (as taken into account in a broken line in FIGURE 1) for connecting subsequent to the respective output of the measuring instruments 14.1 and 14.2 a limiting-value device 23.1 or 23.2, which by way of an OR-member 24 activates the control circuit for the measured-value acceptance and return of the measuring instruments 14 into the initial functional position, if in one of the channels 11 the measured value 19 threatens to reach the overmodulation overload limit.

Connected subsequent to the balancing stores 21.1 and 21.2 is a divider 25 which issues, in the form of a quotient, the actual average value 26 of the balanced measurement result 27.1 for the dependent variable over the balanced measurement result 27.2 of the independent variable. This issuance is quasi-continuous only insofar as the measurement results 27 actually switched onto (fed into) the divider 25 represent only the balance after the latest or most recent measured-value acceptance, thus still do not take into account the measured value 19 which has newly accumulated additionally at the measuring instrument 14. The degree of this discontinuity can be adjusted by way of the control circuit 18, thus by way of the recurrence frequency of the acceptance of actual measured values 19 into the balancing stores 21.

Also the capacity of the balancing stores 21 isnot unlimited. In accordance with the measuring instruments 14, therefore, these too are set back into their initial position if limitingvalue devices 28.1 or 28.2 respond after the actual balanced measurement result 27.1 or 27.2 has been transferred by way of switches 29.1 or 29.2 into the associated reducing stage 30.1 or 30.2. In these, the respective measurement result 27 is reduced to a fraction of the actual value, and the respective store 21 is set to this reduced measured value 31.1 or 31.2 respectively as the measurement result 27.1/27.2 that is to be processed in future by means of the divider 25.

This reduction procedure is illustrated in the basic block diagram of FIGURE 1 for the reducing stage 30 by an operational amplifier 15 having ohmic (proportional) circuitry 32, which is reduced by a further step every time one of the measurement-result limiting-value devices 28 has by way of an OR-input 33 controlled the control circuit 34 for the measurementresult reduction.

So that, despite this reduction of the balanced measurement result 27, the relation with respect to the input variable of the store 21 (thus with respect to the measured value 19) is again correct, an appropriate reduction stage 35.1 or 35.2 is connected subsequent to each measuring instrument 14.1, 14.2.

Since, in each of the two channels 11.1 and 11.2, the same measured-value reduction is undertaken, this has no effect on the average value 26 ascertained by the divider 25.

Basically, it is possible to transfer only part of the respective measured value 19 by way of the reducing stage 35 to the associated balancing store 21, as indicated in FIGURE 1, by the dotted-line divider stages 36.1, 36.2.

The overshoot or excess measured-value remainder 37.1 or 37.2 is returned to- the associated measuring instrument 14.1 or 14.2 and is taken into account in the next cycle of the measured-value transfer, and thus is not lost for the ascertainment of the average value 26.

This has, for example, the advantage of not having to operate the measuring instruments 14 as from the zero value and thereby of being able to avoid non-linear regions of the measuring characteristic.

As can be seen from FIGURE 2, the circuittechnique with regard to the solution in accordance with the invention is simplified if it is effected in digital circuit form. Since the circuits in accordance with FIGURE 1 and FIGURE 2 correspond to one another with respect to the average-value ascertainment, as far as possible the same reference numbers are chosen, so that explanation of similar individual parts in FIGURES 1 and 2 is not required.

The sensors 13 supply as measurands 12 impulses which are added up (counted) in the measuring instruments 14, constructed as multi-digit binary counters.

The reducing stages 30 are shift registers, thus stores for binary numbers, which, simply by shifting the store content towards the highest-value or towards the lowest-value location (thus in the conventional switching representation "to the left" or respectively "to the right") can be multipled or divided by the value "2".

In order to define initial states at the start of operations, the control circuit 19 sets the measuring instruments 14, by way of their reset inputs 38, to the initial counting position ZERO and the shift register of a divider transmitter 45 for the reducing stage 35 to the value ONE; whilst the control circuit 18 sets the shifting registers of the reducing stages 30 by way of the set inputs 39 (in the case of the dividend reducing stage 30.1 to the initial value ZERO and in the case of the divisor reducing stage 30.2 to the initial value ONE) and thus brings about at the output of the divider 25 a value of ZERO for the initial average value 26.

Upon the transfer of the measured values 19 to the balancing stores 21 there is effected in the reducing stages 35 a digital division by the number supplied by the data output of the shift-register transmitter 45 used as the divider. A modulo stage 41 (Modulo-stufe) (which corresponds to that extent functionally to the divider stages 36 in accordance with FIGURE 1) supplies not the complete division result, but only the integral part of the quotient to the balancing store 21 (shown in the drawing as a digital adding device); whilst the division remainder is returned as measuredvalue excess 37 to the data input of the counting measuring instrument 14 as an initial current counting position (so that no rounding error arising from the digital division enters into the balance of the respective store 21, because indeed the division remainder is taken into account again upon the next measuredvalue transfer).

If at one of the digital balancing stores 21 (adding devices) at the carry output 42 an overflow item of information occurs, the control circuit 34 is controlled by way of its ORinput 33, in order to issue the reducing information 43 for the further processing of supplied measured values 19. With the shift-register realisation of the reducing stages 30, this means the control of the shifting inputs 4 thereof, so that the shift-register contents are shifted by one location (a drop of the lowestvalue location place), which corresponds to halving of the register content.At the same time, the register content of the divisor transmitter 45 for the reducing stages 35 is shifted by one location in the sense that the low-value contents pass into the positions of the neighbouring higher-value places; which corresponds to a multiplication with the same constant as in the case of the other shift register, thus to a doubling of the divisor for the reducing stages 35. So that the overflow at the balancing stores 21 is cancelled, there is thus effected an overwriting of the content of the balancing store 21 with the reduced value 31 every time when an overflow takes place; and in future the measured values are taken into account only in reduced manner.

When the capacity of the divisor transmitter 45 with shift-register overflow is exhausted, the regular operating limit is reached. Beyond this limit, however, work can be further carried out in the approximation procedure for the average-value determination, in that (controlled by means of a carry output 46 at the divisor transmitter 45 and of a logic gate member 47) henceforth the largest shift-register content is retained, although the shift registers of the reducing stages 30 are stepped up (WEITERGETAKTET) upon each carry command from one of the balancing stores 21.Since now no corresponding reduction of the measured values 19 is any longer effected (these are added-in uncurtailed in future despite reduction of the balancing result in the store 21) the resulting quotient of the average value 26 is henceforth only an approximation result, into which the more recent part or past of the measured-value development 19 enters more strongly than the earlier one and gains increasingly in weight. This applies naturally accordingly for the same measures in analog circuit technique in accordance with FIGURE 1.

Merely in the interests of clarity, in FIGURE 2 three individual dividing devices are shown as the reducing stages 35 and the output divider 25. Since measured values 19 are transferred only at discrete points in time, controlled from the circuits 18 or 34 respectively, also only a single dividing device can be provided, which in multiplex operation and in cyclically successive manner is connected subsequent to the two counting measuring instruments 14.1 and 14.2 and then to the just newly-fed balancing stores 21.1 and 21.2 for the discontinuous issuance of average values 26.Furthermore, the digital circuit version in accordance with FIGURE 2 can within the scope of the present invention equally be realised by discrete wiring of individual modules of the digital circuit as also within the framework of measured value processing control in store-programmed manner or by means of a microprocessor.

Further according to the present invention there is provided a method of determining a quotient which is the average value of a measured dependent variable divided by a measured independent variable, in which method an upper limiting value is set for each variable beyond which a reduction factor is applied (usually to each measured variable) for determining the quotient. Preferably, in said method any fraction of the variable remaining after application of the reducing factor is fed back to an instrument measuring the variable to adjust the initial measuring value or position of the instrument, in order that said fraction is not lost from the overall measurement.

Still further according to the present invention there is provided apparatus for determining the average value of a measured dependent-variable divided by a measured independent variable comprising measurement means for measuring said variables, balancing stores for the periodic acceptance of said measured variables, divider means for dividing the dependent variable by the independent variable, reducing means associated with the balancing stores for reducing the measured value result upon overflow of one of the stores, and for applying a reduction factor to the associated balancing store. The apparatus, preferably, has facility for the introduction df progressively larger reduction factors to be applied to the store should subsequent overflows of the store occur.

The scope of the present invention should not be unduly limited by the use of particular terminology and the scope of individual terms may extend to any convenient equivalent or generic term where sensible. Individual features of the arrangement, combinations thereof or function or method relating thereto may be individually patentably inventive and in this respect the arrangement or method might be used to determine the average value of any required relationship between two measured variables which is not a quotient, and said variables need not necessarily be dependent and independent.

To summarise, an arrangement for determining the average value of a dependently-variable measurand over an independently-variable measurand, which measurands are in each case picked up by means of an integrating measuring instrument and are placed into relationship with one another in a divider, is designed, on the one hand, for supplying after very short time periods of the independentlyvariable measurand a useable average value and, on the other hand, for supplying after long time periods of the independently-variable measurand, without loss of information, an average value in which input quantity changes are as rapidly as possible of discernible influence.For this, the measured values supplied from the measuring instruments are periodically transferred into balancing stores which are connected prior to an output divider and the store contents of which upon overflow of one of the stores are reduced by identica I-and with each store overflow increased divisors. If, in this respect, the antecedents of the measured values in the result average value are to be given the same weighting as measured values occurring in future after respective resetting of the measuring instruments into their initial measuring position, then from now on also these future measured values are divided by the same factor as the accumulated content of the balancing stores.

Rounding errors do not in this respect occur, if indeed only the integral portion of the division result is transferred into the associated balancing store, but the measured-value remainder from the division is written back as initial measuring position into the associated measuring instrument.

Claims (8)

1. An arrangement for, or method of, determining the average value of a dependentlyvariable measurand over an independently-variable measurand, which measurands are in each case picked up or received by means of an integrating measuring instrument (e.g. 14.1 or 14.2) and placed into relationship with one another in a divider, characterised in that connected subsequent to each measuring instrument is a balancing store for periodic acceptance of the measured value along with resetting of the measuring instrument into an initial or starting position, and in that associated with each of the balancing stores is a reducing stage which reduces the balanced measurement result upon overflow of one of the stores by a factor, with writing back or feedback of the reduced measuring indicator (e.g.

31.1 or 31.2) into the associated balancing store instead of the previous measurement result which has led to the overflow; with each store overflow the reduction factor in the reducing stages is increased.

2. An arrangement or method according to Claim 1, in which for the measured values (e.g. 19.1 and 19.2) in each case a reducing stage (e.g. 35.1 or 35.2) is provided in front of the respective balancing store.

3. An arrangement or method according to Claim 2, in which the reducing stages for the measured values work with the same divisor, increased in each case upon store overflow, as the reducing stages for the balanced measurement results.

4 An arrangement or method according to any one of the preceding claims, in which with each resetting of the measuring instrument only a part of the measured value is transferred to the balancing store and the measured-value remainder is written or fed back as an initial starting value into the associated measuring instrument.

5. An arrangement or method according to any one of the preceding claims, having settable incremental counters as the measuring instruments, digital adding devices as the balancing stores for the measured values and stepwise displaceable shift registers as the reducing stages, connected subsequent to the balancing stores, for balanced binary-coded measurement results with shift control from the carry output of one of the stores.

6. An arrangement or method according to Claim 5 when dependent from Claim 2 or Claim 3 having a digital dividing device as the respective reducing stage (e.g. 35.1 or 35.2) for the measured values and in which a shift register, which can be stepped up or influenced to carry output of the balancing stores as divisor transmitter and with in each case a modulo stage (e.g. 41.1 or 41.2) for transfer of the integral division result to the following balancing store and of the division measuredvalue remainder as new initial counting position to the associated measuring instrument.

7. An arrangement or method according to Claim 6, in which only one dividing device is provided as the reducing stage for the measured values and as divider for the balanced measurement results which is acted upon in multiplex operation successively with the measured values as well as their common divisor and with the balanced measurement results.

8. An arrangement, or method, as claimed in Claim 1 and substantially as herein described with reference to FIGURE 1 or FIGURE 2 of the accompanying drawings.