SU781836A1 - Difference-logarithmic converter - Google Patents

Description

The invention relates to a measurement technique and can be used, in particular, in hydro-optical meters.

A logarithmic device is known that uses the current-voltage characteristic of nonlinear elements, piecewise linear approximation, and time pulse method of comparing a constant input measured voltage of 10 with a reference exponential voltage. In particular, a device for measuring the logarithm of two ratios provides a neutral obtaining the logarithm of the ratio of 5 amplitudes of two paralleJU voltages to the same diode I1,

However, the diode voltage-current characteristic does not turn off; logarithmic, individual scatter of diode parshes, as well as temperature instability of the characteristics; the reduced error of this device is 5–7%.

The closest to the proposed invention is a device for determining the ratio of voltages with a logarithmic signal, consisting of two comparison circuits, an exponential voltage generator, a multivibrator, a logic circuit, a source of clock pulses and a comparison circuit, and the multivibrator output is connected to the input of an exponential voltage generator, the output of which is connected to the inputs of two comparison circuits. The outputs of the comparison circuits are connected to the inputs of the logic circuit and the comparison circuit of the characters. The voltage of the input signal and the adjustable voltage of the reference signal are compared on the comparator with the exponential signal. The logic circuit forms an output pulse whose duration is proportional to the decimal or natural logarithm of the ratio of the input signal to the reference signal G2,

The disadvantage of this device is the various temperature and time factors, as well as the instability of the sources of the reference and input signals, leading to increased measurement error and a decrease in speed and stability.

The purpose of the invention is to increase the speed, and reduce the error.

The goal is achieved due to the fact that the device has a separate, log-logarithmic converter consisting of an exponent generator, the output of which is connected to the first inputs of the first and second comparators, whose outputs are connected to sorting inputs, a subtractor whose output is output converter, introduced analog switch, coupling capacitor and amplifier limiting device, npiraeM first output of analog switch through coupling capacitor connected to amplifier-limiting elem, the second output of the analog switch connected to the input exponent generator, the third analog switch output is connected to a second input of the first switch, the output of amplifier -ogranychytel connected to the second input of the second comparator,

Fig, 1 shows the functional diagram of the differential-logarithmic converter; FIG. 2, are a diagram of the voltages at the output of the blocks.

The device contains an analog switch 1, a coupling capacitor 2, an inverting amplifier, a limiter 3, the first and second comparators. 4 and 5, generator 6 exponential, you are a emitter 7,

The input two-level signal by the analog switch I is divided into two antiphase signals, one of which is in phase with the reference signal of the generator G exponents is supplied to the comparator 3, and the second signal is antiphase to the first through the separation capacitor 2, which eliminates the fixed component, is fed to the inverting amplifier limiter 3, the output of which is supplied to the comparator 5; To the second inputs of the comparators 4. And 5c. generator, 6 exponents are suppressed reference voltage, ensuring the long-term logging. The exponent generator 6 is synchronized with the frequency of the input signal. The value of the capacitor 2 is selected from the condition of the required speed,

An inverting limiting amplifier generates a signal of equal amplitude and anti-phase signal. input of the coupling capacitor,. Fig. 2 shows voltage plots, where Iru is a two-level input signal; And gj is the output signal from the primary output of the voltage switch 1; .iS is the output signal from the second output of voltage switch 1; And, the output signal after the coupling capacitor 2f Ivyk output signal inverting amplifier limiter 3; And av (.b output 0 signal generator b exponent;

6к4. the output signal of the comparator Ivykh - the output signal of the comparator 5; HgjyxY converter output signal,

The proposed scheme provides a fast logarithmic device with a time constant of 2-10 s, accuracy and stability 0 logarithm of a two-level input signal i 1%,

Claims (1)

Invention Formula A differential logarithmic converter comprising an exponential generator, the output of which is connected to the first inputs of the first and second comparators / outputs of which are connected to the corresponding inputs of a subtractor whose output is the output of the converter, characterized in that in order to increase speed 5 and reduce the error in it An analog switch, a usi, a tamper-limiting device and a coupling capacitor are introduced, the first output of the analog switch being connected through a separate capacitor to the limiting amplifier; the second output of the analog switch is connected to the input of the exponent generator; the third output of the analog switch is connected to the second input of the first 5 cokaratora, the output of the amplifier-limiter connected to the second input of the second comparator. Sources of information taken into account in the examination 0 1, Patent cm 3482115, CL, G 06 G 7/20, published, 1969, 2, Patent SUL 3691473, .kl, G 06 G 7/24, published, 1972 (prototype), U8x Tfm