SU951696A1 - Signal average value to code conversion method - Google Patents

Description

(5) METHOD FOR CONVERSION OF AVERAGE VALUE OF SIGNAL TO CODE

The invention relates to the technique of converting analog values to digital and is used in high-precision analog-digital converters, digital devices and systems. There is a known method of converting the average value of a signal into a code with an intermediate conversion of a signal into a time interval based on alternate (at different times) comparison of the integrals (areas) of the converted and compensating constant reference signals 1. The disadvantage of this method is that it is not possible to improve the accuracy of the conversion sinfulness from the imperfection of the integrator. There is a known method of converting the average value of a signal into a code in which both converting and compensating linearly varying signals are simultaneously and jointly integrated over a time interval from the onset of the compensating signal until the integrals of the said signals are equal and encode the specified time interval 2j. low conversion accuracy due to significant impact -. nor comparison error due to noise affecting the comparison operation. The purpose of the invention is to reduce the relative error of conversion while increasing sensitivity. This goal is achieved in that according to the method of simulating the average signal value into a code, the KOTODOM simultaneously and jointly integrate the converted signal and the compensating linearly varying signal, the polarity of which is opposite to the polarity of the converted signal, separate the time interval from the beginning of the compensating signal to the moment equality of the signal that is the result of the integration and transform the resulting interval of the yehemus into the code; an auxiliary signal is added to the wired signals, field the polarity of which is chosen as the opposite polarity of the compensating signal, and after converting the time interval to the code, the code proportional to the value of the auxiliary signal is subtracted from the resulting code. FIG. 1 shows a variant of the block diagram of the device that implements the method; in fig. 2 - time diagrams explaining the method. The device contains input 1 of the converted signal, source 2 of the auxiliary signal, integrator 3 generator of a compensating reference linearly varying signal, source 5 of the threshold signal, comparing the device 6, generator 7 pulses of the reference frequency, bus 8 Start, bus 9 Mode, memory register 10, control unit 11, counter 12, outputs 13 of the counter. The average signal transducer. The code (Fig. 1) contains the source of the auxiliary signal 2, the output of which is connected to the first input of the integrator 3. The second input of the integrator 3 is input 1 of the converted signal U-, To the third input of the integrator 3 is connected the generation of a t-compensated reference linearly varying signal, the control input of which is connected to the output of a comparison device 6, whose inputs are connected to the source 5 of the threshold signal and the output of the integrator 3. The output of the comparison device 6 Besides, it is connected to the first input of control unit 11, the second and third inputs of which are the control and start inputs of the control signals, §, and the fourth and fifth inputs of the control unit are connected respectively to the output of the generator 7 pulses of the reference frequency and the counter overflow output 12. The first output of the control unit 1 is connected to the write input (W) of the memory register 10, the information inputs of which i are the device inputs for writing a code proportional to the value of the auxiliary signal and can be connected to the output faces 13 of the counter 12 June 9, which are output devices. Inputs Y4 (preset /, C + (pulse summation), C - (pulse pulsing), (setting 0 to counter 12 are connected to the corresponding outputs of control unit 11. Information inputs d of counter 12 are connected to outputs of memory register 10. Conversion method The mean value of the signal in the code is as follows. The analog part of the device, including source 2, integrator 3, generator A, source 5, and comparing device 6 operates in an asynchronous mode continuously. In the initial state, the output signal of the Oral 3 UH is equal to the threshold signal and (Fig. 2, d and the output signal of the generator U | (Fig. 2, c) is zero. The auxiliary ir is fed to the first and second inputs of the integrator (0ig. 2.6 and convertible .//fig 2, a) signals. The auxiliary signal is selected from the condition that there are no nonlinear distortions at the integrator output when integrating the sum of the maximum input and auxiliary signals. At time x-o it starts to unfold in time 0, and integrator 3 simultaneously integrates the convertible U) (, auxiliary J and compensating th u signals. The output signal of the integrator, changing according to a parabolic law, at a time instant t becomes equal to the threshold signal LVi (Fig. 2e). By the output signal of the comparison device 6, the generator C is reset and restarted. The process is then repeated in the same way. The time interval between the two response times of the comparison device 6 (t, t) is recorded and encoded using the control unit 11, the counter 12 and the generator 7 of the pulses of the reference frequency. The operation of the digital part of the device, including the control unit 11, the estimator 12, the generator 7 and the register 10, depends on the method of obtaining the digital equivalent of the value of the auxiliary signal Up. The same, in particular, determines the internal structure of the control unit 11.

With a known code proportional to the auxiliary signal (Jg, the digital part of the device works as follows.

Code N / J-. is written to memory register 10 from the outside on inputs d and is stored in the register permanently. According to the Start signal sent to the control unit 11 via bus 8, the N code is rewritten into counter 12 by inputs and N4. With the arrival of the first after the start of the pulse from the comparison device 6, the control unit 11 transmits pulses from the generator 7 to the subtractive input C of the counter 12. For positive values of the converted signal Uy, i.e. when the code N is proportional to the sum of Uy and Ug and, consequently, the N Ml overflow pulse from the output P of the counter 12 acts on the control unit 11, which transfers the counter 12 to the summation of pulses from the generator 7. On the next pulse from the comparison device 6, the control unit 11 stops the counter 12 from outputs 13 of which the code AND M | 2 is taken, which is proportional to the value of the converted signal Uy. For negative values of the converted signal, i.e. when N N2 counter 12 is operated only for subtraction, until the control unit 11 cuts off the pulses from generator 7 to the counter by a signal from comparing device 6. The code Ы / 2.1 proportional to the value of the auxiliary signal U can be obtained using the same device. For this, the signal on bus 9 changes the mode of operation of the control unit 11, and input 1 is disconnected from the source of the signal being converted and closed on the common bus of the device, i.e. make Uy 0. By the Start signal, the counter 12 is set to the zero state, and by the first pulse from the output of the comparison device 6, the control unit 11 transmits pulses from the generator 7 to the summing input C + of the counter 12. When the next pulse arrives from the comparison device 6, control 11 disables the counting of pulses, and in the counter 12 a code L-2 is formed. proportional to the auxiliary signal. Next, code N is rewritten into memory register 10.

Mathematically (mathematically, the conversion operation is described by the following equation:

Vt-Un-I% u.-47) "UntUu,

where DV is the threshold signal;

 the time constants of the integration of the convertible (U) and compensating reference linearly varying Sc Kt) signals;

and the actual value of the signal of noise; constant integration time; drove -l / i.

In this case, the relative error

comparison of the proposed method

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1TG to

-.

g.

A -: ..

wed

tv and

In V-PX

Claims (2)

Therefore, this method allows to reduce many times the error in the conversion of small levels of the converted signal Ujt and to increase the sensitivity of the devices that implement the method. The formula linking the N code and the pre-formed Uy and auxiliary UB signals has the form Vl, -fj, (t, 4o), about TTK, where -J.Q is the sample frequency of the trace-. no impulses. Since the Btopoe addend is the code Y, then. ., kth-hili relative to and .jt to 1fV -V-V Consequently, the signal to be converted is ± 1) t (directly proportional to the N code formed at the end of the conversion cycle at the outputs 13 of counter 12. However, if the code N is proportional to the value of the auxiliary signal O g is obtained on the same device, the relative conversion error caused by the slow drift of the zero level of the tegrator transform equation (4v-4; V 4 Kt) at - Un decreases, it follows that the Ni code is proportional to the case of the sum of the auxiliary signal and the zero drift signal integrator, etc. .g +1 DR N -fota -tn t, V Uft-I o St K is the integration integration time Udr. Consequently, the code proportional to the CDR value is fixed, and during the conversion Ux it is subtracted in which the component of the code is also present, is proportional to ii) -vl (.- p Ap-i) a4.-Un mot.,. t о TDRK as a result, the resulting code N5. is absent, proportional to CDR. Thus, the proposed method of converting the average value of a signal into a code allows reducing the relative error of conversion and increasing the sensitivity and, consequently, increasing the accuracy of the conversion. Moreover, the method allows to expand the dynamic range of the converted signal and transform different polarity signals compensating signal. The method of converting the average value of a signal into a code in which the converted signal is summed and integrated and the compensating linearly varying signal, the polarity of which is opposite to the polarity of the converted signal, is separated from the beginning of the compensating signal until the signal is equal to zero, which is result of the integration, and convert the resulting time interval to a code, which is indicated by the fact that, in order to reduce the relative error of conversion and The sensitivities add an auxiliary signal to these signals, the polarity of which is chosen opposite to the polarity of the compensating signal, and after converting the time interval into the code, a code proportional to the value of the auxiliary signal is subtracted from the resulting code. Sources of information taken into account during the examination 1. V. Nishnikov, Integrating digital DC voltmeters, L., Energie, 1976, p. 6-49. 2. USSR author's certificate №, cl. G01 R 19/02, 1972 (prototype).