RU2028002C1 - Device to measure ratio of analog signals - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: device to measure ratio of analog signals has integrator 1 which output is connected to first input of comparator 2, operational amplifier 3 which noninverting input is linked to output of integrator 1 (its setting input is connected to output of amplifier 3 via analog key 5), control unit 4 which input is coupled to output of comparator 2, first output is connected to control input of key 5 and second output is coupled to output of device. Inputs of integrator 1 are linked to input terminals 6 and 7. Second inputs of amplifier 3 and comparator 2 are linked to input terminals 8 and 9 and form two differential inputs of device. EFFECT: simplified design, enhanced authenticity of measurements. 3 cl, 3 dwg

Description

 The invention relates to electrical engineering and can be used to measure the ratio of two analog signals.

 A known voltage ratio meter (ed. St. USSR No 1265633, class G 01 R 19/10) containing an operational amplifier, attenuator, ADC, multiplier, threshold device and module isolation device.

 This device provides the conversion of the ratio of input voltages into a digital code, however, it has low measurement accuracy due to the use of an analog multiplier of two signals, and low reliability due to the considerable complexity of the device.

 The closest in technical essence to the proposed is a device for measuring the ratio of analog signals (ed. St. N 1051445, class G 01 R 19/10, G 06 G 7/16), containing an integrator, two comparators, a controlled exponential voltage generator and two keys. The first input of the integrator is the first input of the device, the second input is connected to the second input of the device through the first key, and the output is to the first input of the comparator, the second input of which is connected to the output of another comparator, and the output is the output of the device and connected to the control inputs of two keys. A controlled generator is connected between the input of another comparator and the first output of the second key, the second output of which is connected to a common bus.

The disadvantage of this device is the narrow dynamic range due to the fact that the formation of the output signal requires the formation of two time intervals t _n and t _in , and complexity.

 In addition, the inability to work with input differential voltages significantly reduces the functionality of the device and its scope.

 The purpose of the invention is the expansion of functionality and dynamic range and increase the reliability of the device due to its simplification.

 This goal is achieved by the fact that in the device for measuring the ratio of analog signals containing an integrator, the first input of which is the first input of the device, and the output is connected to the first input of the comparator, the output of which is connected to the control input of the key, a former is inserted, connected between the output of the comparator and the input key control, the first output of which is connected to the input of the integrator installation, the second input of which is the second input of the device, the amplifier, the inverting input of which is the third input th device, its non-inverting input connected to the output of the integrator and an amplifier output coupled to a second terminal of the key, the second input of the comparator is a fourth input device.

Thus, distinctive features from the prototype are: the introduction of an amplifier, which allows the device to work with differential input signals;
the introduction of the shaper and the inclusion of the key between the output of the amplifier and the input of the integrator installation allows you to convert the ratio of the two voltages during only one time interval, which increases speed and extends the dynamic range of the device;
the connection of the corresponding inputs of the amplifier, comparator and integrator with the inputs of the device increases its input impedance and provides work with differential input signals.

 In addition, the reliability of the device is significantly increased due to its simplification by eliminating the key, the exponential voltage generator and the comparator.

 Figure 1 presents the functional diagram of the proposed device; figure 2 and 3 are possible options for implementation.

 A device for measuring the ratio of analog signals contains an integrator 1, a comparator 2, an operational amplifier 3, a driver 4, which controls the operation of the key 5 and the inputs from the first to the fourth 6-9.

 The first input of the integrator 1 is the input 6 of the device, and the output of the integrator 1 is connected to the first input of the comparator 2, the output of which is connected through the driver 4 to the control input of the key 5. The first output of the key 5 is connected to the installation input of the integrator 1, the second input of which is the second input 7 devices. The second output of the key 5 is connected to the output of the amplifier 3, the inverting input of which is the third input 8 of the device, and the non-inverting input is connected to the output of the integrator 1. The second input of the comparator 2 is the fourth input 9 of the device.

 The device operates as follows.

 In the initial state, key 5 is closed.

The operational amplifier of the integrator 1 forms a negative feedback, covering the amplifier 3. To the inputs 6-9 applied voltage U ₁ , U ₂ , U ₃ , U ₄ . In this case, the output of the integrator 1 sets the voltage U ₃ . At the signal of the shaper 4, the key 5 is opened.

(U₁-U₂)dt, (1) где τ - постоянная времени интегратора 1,
t_x - время разряда конденсатора интегратора 1, или при стабильных в течение цикла измерения значениях U₁ и U₂.At the output of the integrator 1, the voltage U * changes in accordance with the expression
U ^* = U ₃ -

(U ₁ -U ₂ ) dt, (1) where τ is the time constant of integrator 1,
t _x is the discharge time of the capacitor of the integrator 1, or when values U ₁ and U _{2 are} stable during the measurement cycle.

(U₁-U₂). (2)
При U = U₄ происходит срабатывание компаратора 2. Выражение (2) принимает вид:
U₄= U₃-

(U₁-U₂). (3)
При этом в течение времени t_x (от размыкания ключа 5 до срабатывания компаратора 2) напряжение на выходе интегратора 1 изменяется от U₃ до U₄ со скоростью, определяемой разностью напряжений U₁ - U₂. Выразив t_x из (3), получим, что
t_x= τ

. (4)
Таким образом, фиксируемый интервал времени t_x есть функция отношения разности приложенных напряжений к входам устройства.U ^* = U ₃ -

(U ₁ -U ₂ ). (2)
When U = U ₄ , the comparator 2 is triggered. Expression (2) takes the form:
U ₄ = U ₃ -

(U ₁ -U ₂ ). (3)
Moreover, during the time t _x (from opening the switch 5 to the operation of the comparator 2), the voltage at the output of the integrator 1 changes from U ₃ to U ₄ at a speed determined by the voltage difference U ₁ - U ₂ . Expressing t _x from (3), we obtain
t _x = τ

. (4)
Thus, the fixed time interval t _x is a function of the ratio of the difference of the applied voltages to the inputs of the device.

When the comparator 2 is activated, at its output, for example, a unit level is established at which the installation pulse is generated at the output of the former 4, by which the key 5 is closed and the circuit is brought back to its initial state. At the output of the integrator 1, the voltage U _{3 is} again set, at the output of the comparator 2 is a logical zero. At the end of the installation pulse, when the key 5 is opened, the measurement process is repeated. The off time of key 5 determines the desired time t _x .

, (U₂ и U₄ заданы равными нулю). (5)
При С = 0,1 мкФ; R = 10 кОм; U₃ = 0,2 В; U₁ = 10В; интервал t_x = 20 мс.On the schematic diagram of the device (see figure 2), the shaper 4 is made on a single vibrator using a D-trigger and two elements OR-NOT. As key 5, the 590KN2 chip is used (the open state of the key corresponds to a logic zero signal at its control input). Parallel RC circuit 10 is used as a correction element when setting the integrator to its original state. The formed time interval t _{x is} defined by the expression
t _x = RC

, (U ₂ and U _{4 are} set equal to zero). (5)
At C = 0.1 μF; R = 10 kΩ; U ₃ = 0.2 V; U ₁ = 10V; interval t _x = 20 ms.

At C = 0.1 μF; R = 10 kOhm; U ₃ = 10V; U ₁ = 0.2V; interval t _x = 50 ms.

 Thus, the device according to one of its differential inputs has a high initial resistance, high measurement accuracy, since the conversion coefficient is determined by the values of the parameters of only two elements (integrator resistor and capacitor), increased speed due to the determination of the output parameter from only one generated time interval, and as a result This has enhanced functionality and scope. The reliability of the device is significantly improved due to its simplification.

 It is advisable to use the device when measuring the ratio of the resistances of the resistors at a single current flowing through them, in particular in temperature meters using resistance thermometers.

 It should be noted that the input impedance is constant across another differential input throughout the entire measurement cycle.

; генератора тактовых импульсов ГТИ.In FIG. 3 shows an embodiment of the shaper 4, in which the independence of the period T _{and the} sequence of output pulses t _x from their duration is ensured. The installation pulse t _y for closing the key 5 is formed independently of the output pulse t _{x of the} device using a single vibrator on the D-flip-flop T, periodically triggered with a frequency f _o =

; GTI clock generator.

Claims (3)

 1. A DEVICE FOR MEASURING THE RELATIONSHIP OF ANALOGUE SIGNALS, comprising an amplifier, an inverting input of which is connected to one of the device inputs, an integrator, a comparator, and a control unit connected in series, the first output of which is connected to a control input of the key, characterized in that, in order to expand the scope while simplifying, the non-inverting input of the amplifier is connected to the output of the integrator, the first input of which is connected to the first input of the device, the second input to the second input of the device, the input is set ki is connected to the first output of the key, the second output of which is connected to the output of the amplifier, the second input of the comparator is connected to the fourth input of the device, the second output of the control unit is connected to the output of the device.  2. The device according to p. 1, characterized in that the control unit contains a single vibrator on the D-trigger and two elements OR - NOT, the C-input of the D-trigger is connected to the input of the unit and the first input of the second element OR is NOT, the output of which is connected to the first output of the block, the second input is connected to the second output of the block and the output of the first element OR is NOT, the inputs of which are combined and connected to the output of the D-trigger.  3. The device according to p. 1, characterized in that the control unit contains a single vibrator on the D-trigger, two elements OR - NOT and a clock pulse generator, the output of which is connected to the C-input of the D-trigger, the D-input of which is connected to the input of the unit and the first input of the second element OR is NOT, the output of which is connected to the second output of the block, the second input is connected to the output of the first element OR is NOT, the inputs of which are combined and connected to the output of the D-trigger and the first output of the block.

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