Cosine converter

 

(57) Abstract:

The invention relates to measuring technique and can be used in trigonometric converters. The purpose of the invention is to improve the accuracy of conversion. The Converter comprises an amplifier with an adjustable gain, the block extracting the square root of the difference between known and unknown square values and the block extracting the square root of the sum of known and unknown square values. 1 Il.

The invention relates to measuring technique and can be used as a trigonometric Converter when you want to determine the value of cosX high speed, low accuracy and ease of implementation in the interval of values of the argument from to 4.

Known sine-cosine converters time-pulse type, which, although having a low error in conversion of about 0.1% in the interval from 0 to /4, but have low performance.

For example, the well-known cosine frequency Converter comprising a shaper rectangular pulses, the differentiation block, the delay unit, managed key block of memory.

The device has a small led is practical functions, with two out phase-sensitive rectifier and connected in series time-pulse Converter, the pulse shaper, the integrating amplifier and the amplifier-limiter as well as a generator of sinusoidal oscillations.

Such a device for measuring values of cos X is the error due to drift of the integrator, and most importantly has a low performance.

Known cosine Converter comprising multipliers, adders, reference voltage that determines the scale of the transformation. To ensure a small error conversion using a complex function approximation, which can be represented as follows:

cos( /2)X (1-0,21361 X-0,99914 X2--0,21265 X3)/(1-0,2097 X + 0,2097 X2).

The device can have a high performance, low methodological error, however, it will be very difficult to implement, limited dynamic range due to the presence of the second and third degrees in the argument, and will have quite a lot of instrumental error, define the total error of several nonlinear blocks.

The closest technical solution is the trigonometric cosine is nanomo, using piecewise linear approximation. The desired non-linear function corresponding cosX get when using multiple breakpoints, applying the reference voltage and the diodes in the feedback circuit of the amplifier.

Such a device, though rather simple, but limited by the accuracy of the conversion, as it requires a large number of breakpoints in the piecewise-linear approximation.

The aim of the invention is to reduce the conversion error.

The essence of the invention lies in the fact that with limited argument value, for example H /4, the approximation can be performed with high precision, specifying the following approximate equation:

cosX / 0 for X 0,7854

(1) where X is the value of the argument;

A, A, c coefficients are chosen from the condition of minimization of the approximation error.

The goal in the cosine Converter comprising an amplifier with an adjustable gain, the output of which is the output of the Converter is achieved in that the Converter further comprises a unit for extracting the square root of the difference between known and unknown square units, and the unit root extraction kvadratov the input of the Converter, output unit for extracting the square root of the difference between known and unknown square units connected to the input of the amplifier with adjustable gain control input of which is connected to the output unit for extracting the square root of the sum of known and unknown square values.

The drawing shows a structural diagram of the cosine of the Converter.

It includes: amplifier 1 with an adjustable gain; block 2 to extract the square root of the difference between known and unknown square values; unit 3 for extracting the square root of the sum of known and unknown square values.

Blocks in cosine Converter is connected as follows. The input of the Converter is connected to the input unit 2 to extract the square root of the difference between known and unknown square values and the input unit 3 for extracting the square root of the sum of known and unknown square values. The output of block 2 to extract the square root of the difference between known and unknown square units connected to the input of the amplifier 1 with an adjustable gain control input of which is connected to the output unit 3 DL which has been created by the transfer coefficient is connected with the inverter output.

Cosine Converter operates as follows.

Input voltage Uxcorresponding to the value of the argument X, is fed to the input of block 2 to extract the square root of the difference between known and unknown square values, and the input unit 3 for extracting the square root of the sum of known and unknown square values. Each of these blocks 2 and 3 includes a reference voltage sources Uopthat are connected to the respective reference inputs of these blocks 2 and 3. The output of block 2 to extract the square root of the difference between known and unknown square units receive the voltage U2that depends on the voltage Uxand equals U2= . This voltage U2to the input of the amplifier 1 with an adjustable gain, the value of which is determined by the voltage U3coming to its control input from the output unit 3 for extracting the square root of the sum of known and unknown square values. This voltage U3well U3=

The voltage source of the reference voltage Uopchoose such that when the value of the input voltage Ux=0 at the output of block 2 to retrieve the/SUB> equal to the value cosXcos0=1. The voltage U2from the output of block 2 to extract the square root of the difference between known and unknown square value is fed to the input of the amplifier 1 with an adjustable gain, the value of which TO1in this case, when Ux0 must be equal TO1=1.

The voltage U3the output unit 3 for extracting the square root of the sum of known and unknown square values equal to U3= when a value is selected, for which cUx< Uop. For the input voltage Ux0 get U3Uopso the value of Uopchoose this value so that the voltage at the control input of the amplifier 1 his transfer coefficient K1would be equal TO1=1.

Consequently, the amplifier 1 with adjustable gain is chosen so that when the control voltage U3Uopthe transfer ratio TO1amplifier 1 would be equal TO11 and linearly decreased with the increase of the control voltage U3.

Thus, at the output of the amplifier 1 with a variable gear ratio gain output voltage UoU1that is:

U1= / the particular implementation of the equality (1).

Selecting a 0,788; C0,6156; the output of the amplifier 1 with adjustable gain gain voltage U1corresponding function cosX and defined by the expression:

cosX U1= Uo= /

(3) for 0 Ux0-7854 Uop; 1,0 cosX 0,7071; UopU10,7071 Uop< / BR>
Consequently, the received expression in accordance with the expression (1).

The approximation error of q can be obtained from the following expression:

q-cosX/cosX 0 for X 0,7854

For example, if the selected values of A= 1,0; a 0,788; 0,6156 errors have value not exceeding q 0.16% of all errors have the same signs, so after the introduction of cosine Converter corrective constant multiplier, it is possible to reduce the error in q 0,16% in 2 times.

Hence, the truncation error of the proposed cosine Converter for 0 X 0,7854 will have a value of not more than 0.08% of the Proposed Converter provides a small amount of instrumental error, which will not exceed the truncation error. This is achieved by the fact that when the input voltage 0Ux0,7854 Uoperror q0,08% can be achieved, as used in units 2 and 3 for the extraction of a square to the known and unknown square values 0,788.0,7854 Uop0.6 Uopand unit 3 for extracting the square root of the sum of known and unknown square values 0,6156.0,7854 Uop0.5 Uop. For this reason, error blocks 2 and 3 provide little value for the specified limits of the unknown quantities.

A small error in conversion amplifier 1 with an adjustable ratio transmission is also possible to provide, because it works in a small range of values of this ratio, i.e. the ratio TO1changes from K11,0 just 15%, no more.

Cosine Converter is implemented using a conventional well-known links.

Cosine Converter comprising an amplifier with an adjustable gain, the output of which is the output of the Converter, characterized in that it introduced the block extracting the square root of the difference between known and unknown square values and the block extracting the square root of the sum of known and unknown square values, the inputs of which are connected to the input of the inverter, and outputs connected respectively to the information and the control inputs of the amplifier with adjustable factor per

 

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