SU493915A1 - Frequency converter correction device - Google Patents

Description

one

The invention relates to the field of measurement technology, automation and computer technology.

A device for correcting frequency converters is known, which contains a frequency converter connected through a coincidence circuit, the control input of which is connected to the control device, and a counter to the input of time interval selectors, another input of which is connected to the control device and the reference frequency generator via a frequency divider.

The purpose of the invention is to improve accuracy and simplification.

For this, the output of the time slot selector is connected to the inputs of two additional matching circuits, the other inputs of which are connected respectively to the output of the control unit and the outputs of the frequency divider, with the output of the first additional matching circuit through the serially connected first additional counter and code-to-frequency converter connected to the control input analog key correction slope of the frequency converter included in the supply circuit to the input integrator input signal, and the output of the additional matching circuit through a second additional counter connected in series and a code to time converter

the interval is connected to the control input of the analog key for correcting the initial frequency of the frequency converter included in the supply circuit to the input of the integrator of the reference signal.

The functional diagram of the correction device is shown in FIG. 1 and contains schemes 1, 2, 3 matches, main counter 4, time selector 5, control device 6, frequency divider 7, reference frequency generator 8, additional counters 9, 10, code-frequency converter, converter 12, code-time interval, analog key 13 for correcting the slope of the frequency converter, analog key 14 for correcting the initial frequency of the frequency converter, and integrator 15 of the reference signal, outputs 16, 17 and 18 of the divider 7.

To simplify the following reasoning, we consider a correction using the example of adjusting the multiplicative and additive errors of a scanning transform unbalance converter of a resistive bridge to a proportional change in the pulse frequency, the block diagram of which is shown in FIG. 2 - and includes a resistive bridge 19, a differential amplifier 20, an integrator 21, a comparison device 22, feedback resistors 23, 24, 25, 26. If the resistances of the resistors of the opposite shoulders of the bridge change in antiphase when the input changes, the transformation function of the converter in question has the following form: d, LCH, K + KI, 4. (1-K,) where b is the relative change in the resistance of the bridge arm, - constant of the integrator time, K - amplifier gain factor 20. Кзз / + KS In FIG. Figure 3 shows the timing diagrams of the integrator output voltages —V "and the comparison device -VQ. The initial frequency of the converter / o is determined from the expression (1) at 6 0 and is 4g (,) In the device, the initial frequency is adjusted by delaying the start time of integrating the VoKi signal by time ti into each half-period of converter operation, as shown in FIG. 4. Here Vi is the voltage at the non-inverting input of the integrator. In this case, the expression (2) takes the form: tf iSZ) 4- (I - K,) - t-2K ,, The integration delay is performed using an analog switch 14, which is included in the open circuit at point A (Fig. 2) . The correction of the slope of the conversion function 5 is performed at the adjusted initial frequency / o by periodically turning off the signal time to proportional to the value of the parameter being converted to the inverting input of the integrator 21. The switching of the specified signal is performed with a certain frequency slope / k correction. The timing diagram of the change in the power supply voltage l / i of the bridge is placed in FIG. 5. The law of voltage variation at the inverting input of the integrator is similar, with the difference that its amplitude is equal. Here (Fig. 5) there is a diagram showing the variation of the output voltage Vii of the integrator corresponding to the work of the integrator with the adjusted initial frequency and the adjusted slope of the conversion function 5. If you close the key set to point A (in Fig. 2), every time correction frequency / k, the conversion function (expression 1) can be represented as: / g -, (l- / A) + K, .. 4t (1-K,) + 2Ki (i From the last expression it follows that the slope 5 of the conversion function depends on the frequency of the correction pulses / k (with / o const). Trim the operation of the correction circuit in the event of a correction of the initial frequency / o value (see Fig. 1). With a zero input signal, the time specifying elements of the converter should have such values that, if there is no correction, the output frequency of the converter / o would be greater than the required nominal fon value and the conversion slope would also be larger than the required nominal value of the slope. When the correction command is given, the control device 6 starts the frequency divider 7 and supplies the enable potentials to the circuit inputs 1 and 3 coincidences. As a result, the main counter 4, whose capacity is equal to N, through the coincidence circuit 1, counts the pulses of the output frequency of the integrator 15. After a period of time (L / o) the counter is filled, the overflow pulse from it goes to the selector of 5 time intervals. As noted above, simultaneously with the start of counting pulses fo, counter 4 triggers frequency 7 to start. The division factor of divider 7 at output 16 is such that after time t N / foa from its output 16, a pulse arrives at the selector 5. If (t. 6.), then at the output of the selector 5, according to a Wits, a pulse of duration D - T - A / o -: {V / he / o. A pulse with a duration from the output of the selector 5 will act as a control for the coincidence circuit 3. Now, through the scheme 3, coincidence to the counter 10 during the time A / o receive pulses from the output 18 of frequency divider 7, the frequency of which is foii foa / 2N, after which the counter 10 will contain the recorded number or taking into account the expression (5) N. (foilfo NI is a time code / 1 for which it is necessary to delay the beginning of the integration of the reference signal arriving at the non-inverting input of the integrator 21 (see Fig. 2) in each half-period of the transformation so that the value of the real initial frequency / o is equal to its nominal value fon.C By recording the number of the inverter's initial frequency into the counter 10, the end of the fo correction, the slope correction process of the conversion function, or the input action of the code-time converter 12 "interval-time interval, synchronized by the output voltage of the converter 15, at the beginning of each half-period of the conversion Gives a pulse of duration i to the control input of the key 14, as a result of which a delay in the start of the integration of the reference signal occurs T in each half-period of the output frequency of the converter.

At the second stage of correction, the slope S of the conversion function is corrected. As mentioned earlier, to change the slope it is necessary to change the frequency of the correction pulses applied to the control input of the key 13. To obtain the initial information, the source of the oscillation effect is connected to the input of the converter.

The control device 6, in the same way as when adjusting the initial frequency, triggers the frequency divider 7, and enables the potential potential to circuits 1 and 2. As a result, the main counter 4 (with the capacity L) through the coincidence circuit 1 performs the pulse counting of the output frequency of the integrator 15. After a period of time is Л // OX the counter is filled, the overflow pulse from it goes to the selector 5 time intervals. Simultaneously with the start of the counting of the pulses f out by the counter 4, the frequency divider 7 is started up. The division factor of divider 7 output 16 in the case of adjusting the slope of the converter

is such that after time ts, ixm (/ vyht is the nominal value of the output with corrected slope of the conversion) from its output 16 a pulse will go to the selector 5. If

s tf, (i.e.), THEN At the output of the selector 5, the Wits pulse duration

eleven

-) L (7)

four

four

In this expression

P 5; KKP1- / A) H-KI

  4t (1 - KI) -f 2K ,,

corresponds to expression (3) with dR 8JRm, and РБЫХ obtained from (3) with regard to, i.e.

 CKa + K,

out -

(1 -K,) + 2K ,,

An impulse of duration L4 from the output of the selector 5 will act as a control for the coincidence circuit 2. Now, through scheme 2, coincidence at counter 9 for the time & .. ts will receive pulses from output 17 of frequency divider 7, whose frequency is foH, then counter 9 will contain the recorded number N2 f tsfoff NZ, which is the correction frequency code /to. With the entry in the counter 9 of the number N, the process of correcting the slope of the conversion function of the converter 15 is terminated. After the adjustment is completed, during the conversion of the input action, the code-frequency converter 11 continuously pulses the duration tn with the frequency / k of the slope correction S to the control input of the key 13, as a result of which periodic integration of the SPD proportional to the input action occurs, i.e., an adjustment is made to the slope S of the conversion function.

To determine the value of the correction frequency, we assume that the L pulses of the frequency emitter counter 3 will count over a certain time l -. i.e.

L7. R. () + K,

4t (1-K,) + 2K ,,

1 - m - IV

Then the same number of pulses N. but already the converter frequencies with uncorrected torque, counter 3 counts the time from where

N. (t - AQ zyh (ff - TO X

 + Ki

(9)

X

.. (. to,) + 2Kii

-to,)

In the right-hand side of (8) and (9), and solving the equation for fi ;, we get:

f -. l / software

"Th /," KKLg dg

If you encode a certain number of NZ pulses of the frequency foH, i.e.

one

-L

(eleven)

BUT,

/P

and rewrite (10) in view of (11), we get:,,. 4- K.L.,

., + k,

(12)

I J ..

.ov

in this expression

oh „KK, -K,

 - rnnst 5R; "KK, foV -

Therefore, if you select the division factor of the divider 7 at the output 17 such that the pulse frequency modulus at this output 40 is equal to

/ + K, ° a-

then we get

(13)

. about

When the correction circuit is operating in the measurement mode of the input parameter of circuit 2 and 3

matches are closed. The transducer 15 converts the input parameter to the pulse frequency. Due to the fact that the meters L and L / 2 are stored in the meters 10 and 9, respectively, in each half-conversion, a delay of integrating the VoKi reference signal over the integrator's non-inverting input is delayed by time t and off for the voltage that carries information about the input parameter, from the inverting input of the integrator with a frequency fr ;. In this case, the voltages at the inputs of the integrator will be changed according to the V diagrams (see Fig. 5) (at the non-inverting input) and Vz (see Fig. 5) (at

inverting input). The process of converting the value of the input parameter to the frequency proceeds as follows. Voltage Vo from the output of converter 15 (see Fig. 5) is applied to coincidence circuit 1. The control unit 6 opens the coincidence circuit 1 for measuring Gizm-Counter 4 counts the output frequency pulses of the converter 15, then the received code value is decrypted and fed to the digital reading device in units of the input parameter (the decoder and the digital reading device are not shown in the diagram). The subject of the invention A frequency converter correction device comprising a frequency converter connected via a matching circuit, a control input of which is connected to a control device and a counter to the input of time interval selectors, another input which is connected to a control device and frequency reference generator through the frequency divider that, in order to increase accuracy and simplify, in it, the output of the time selector is connected to the inputs of additional coincidence circuits, other inputs which are connected respectively to the output of the control unit and the outputs of the frequency divider, where the output of the first additional matching circuit through the first additional counter connected in series and the code-to-frequency converter is connected to the control input of the analog key for correcting the slope of the frequency converter connected to the input circuit of the integrator of the input signal and the output of the second additional coincidence circuit is connected through the second additional counter in series and transform spruce code during the time interval is connected to the control input of analog switch correction start frequency of the frequency converter included in the circuit for supplying the reference signal input of the integrator.

g ;.

H

0-,

-foK

Current -

ti

R

i

with, ",

i

, one : /

/ //