SU756424A1 - Logaritmic analogue-digital converter - Google Patents

Description

The invention relates to functional transducers of electrical signals and can be used in computers. d

A device for logarithmic analog-digital conversion of signals is known, which contains an exponential voltage generator, a comparator, a trigger, a digital conversion circuit £ £].

This device is characterized by low speed.

The closest to the proposed is a logarithmic analogue {5 digitizer containing a series-connected amplifying unit and a comparator, to the second input of which a reference voltage source is connected, an integrating capacitor and a series resistor connected in series to the inverting input and output of the amplifier unit element, the input of the amplifying unit through -25 rez large-scale resistor is connected to the input of a logarithmic analog-digital converter, non-inverter tamping input of the amplifier block, connect to the bus of zero potential, 30

but

2

the digital readout output unit, to the first input of which the first output of the reference frequency generator is connected, the second output of which is connected via a modulator to the auxiliary input of the amplifying unit [7].

This device has a complex functional diagram.

The purpose of the invention is to simplify the functional diagram of the Converter while maintaining the specified speed.

This goal is achieved by the fact that it introduces a one-shot, the input of which is connected to the output of the comparator and the control inputs of the key element and the modulator, the output of the one-shot is connected to the second input of the output digital display unit.

The drawing shows a functional diagram of the proposed logarithmic analog-to-digital Converter.

The device contains a scale resistor 1, a discharge resistor 2, an integrating capacitor 3, an amplifying unit 4, a key element 5, a modulator 6, a comparator 7, a single vibrator 8, a generator frequency 9, a digital display output 10,

3

756424

four

reference voltage source 11, zero potential bus 12 and input 13

converter.

The converter works as follows. '

The input signal through the scale resistor 1 is fed to the input of the amplifying block TG'y integrated on the integrating capacitor 3. The integrating capacitor 3 is charged to the voltage of the reference potential directly proportional to the input signal of the device and inversely proportional to the time constant of the integrating circuit formed by the scale resistor 1 and the integrating capacitor 3. In this case, the key element 5 is open.

At the moment when the voltage on the integrating capacitor 3 (respectively, at the output of the amplifier unit 4) exceeds the potential value of the reference voltage source 11, the comparator 7 simultaneously closes the key element 5 with its output signal, allows the signal from the reference frequency generator 9 to pass through the modulator 6 and sets one-shot 8 in the state of the beginning of the conversion.

Since the key element 5 is closed, then at the output of the amplifier unit 4 a decreasing voltage of the exponential form is formed, which is determined by the discharge of the integrating capacitor 3 through the discharge resistor '2 and the key element 5.

At the moment when the decreasing voltage at the output of the amplifying unit 4 is equal to or less than the potential value of the source of the reference voltage 11, the comparator 7 simultaneously opens the key element 5 with its output signal and prohibits the signal from passing through the modulator 6.

Since the key element 5 is open, the integrating capacitor 3 is charged again and all the processes are repeated. Therefore, the output of the comparator 7 will be a frequency sequence of pulses, and their frequency is proportional to the logarithm of the signal being converted and inversely proportional to the discharge constant circuit formed by the integrating capacitor 3 and the discharge resistor 2. The one-oscillator 8 will return to its original state, marking the end of the conversion, at each moment

re-closure of the key element 5. The time from the beginning to the end of the conversion is filled with the frequency from the reference frequency generator 9. The digital display output unit 10 records the conversion result,

Using the proposed logarithmic analog-to-digital converter, we obtain the logarithm of the input signal converted to the pulse frequency, and the speed of the device has not changed, and the functional diagram is simpler than the functional scheme of the known device.

Claims (1)

Claim A log-analog-to-digital converter containing a series-connected amplifying unit and a comparator, to the second input of which a voltage source is connected, an integrating capacitor connected between the inverting input and the output of the amplifier unit, and a discharge resistor and a key element connected in series, the input of the amplifier unit through a scale resistor connected to input of a logarithmic analog-to-digital converter, the non-inverting input of the amplifying unit is connected to the zero potential bus, the digital display output unit, to the first input of which the first output of the reference frequency generator is connected, the second output of which is connected via a modulator to the auxiliary input of the amplifying unit, characterized in that, for the sake of simplicity while maintaining the specified speed, a one-shot is inserted into it whose input is connected to the comparator output and the control inputs of the key element and the modulator, the one-shot output is connected to the second input of the digital display output unit.