RU2565813C1 - Microcontroller-based converter of resistance, capacitance and voltage into binary code - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: microcontroller-based converter of resistance, capacitance and voltage into binary code comprises four resistors, two voltage-controlled generators provided with generation resolution inputs and microcontroller. First outputs of resistors are connected to microcontroller 1sr, 2^nd, 3^rd and 4^th outputs. Second outputs of the 1^st and 2^nd resistors are connected to first generator voltage control input. Second outputs of the 3^rd and 4^th resistors are connected to second generator voltage control input. Outputs of generators are connected to count inputs of the 1^st and 2^nd binary counters built in said microcontroller.

EFFECT: higher accuracy of conversion.

2 cl, 1 dwg

Description

FIELD OF THE INVENTION

The invention relates to measuring equipment, in particular to devices for measuring active resistance, capacitance and voltage, and can be used to measure physical quantities using resistive and capacitive sensors, as well as sensors whose output signal is voltage.

State of the art

A microcontroller device for measuring capacitance and resistance is known, containing a microcontroller (MK), a capacitive sensor, a capacitor of exemplary capacity, resistors of exemplary and measured resistance, first, second and third resistors and a digital indicator, and the resistors of exemplary and measured resistance are connected to the first plates by the first leads respectively a capacitive sensor and a capacitor of exemplary capacity, a digital indicator is connected to the MK, the first conclusions of the first, second and third resistors are connected are connected to the first input of the MK analog comparator, the second terminals of the first and second resistors are connected respectively to the plus and minus terminals of the MK power supply, the second terminal of the third resistor is connected to the first MK output, the first conclusions of the reference and measured resistance resistors are connected to the second input of the MK analog comparator, the second the findings of the resistors of the exemplary and measured resistances are connected respectively to the second and third outputs of the MK, the second plates of the capacitive sensor and the capacitor are exemplary The components are connected respectively to the fourth and fifth outputs of the MC (see US Pat. RF №2392629, class G01R 27/26).

A disadvantage of the known solution is low accuracy due to the influence of changes in capacitance under the influence of temperature on the result of measuring the active resistance.

A device is known - a microcontroller measuring transducer of capacitance and resistance into a binary code containing MK, a capacitive sensor, a capacitor of exemplary capacitance, an exemplary resistor, a resistive voltage divider and a resistor of measured resistance, and the resistors of exemplary and measured resistance are connected to the first plates of the capacitive sensor and capacitor of exemplary capacity, the first conclusions of the resistors of the voltage divider are connected to the first input of the analog compa MK, and the second leads are connected respectively to the MK power leads, the first leads of the reference and measured resistors are connected to the second input of the analog comparator MK, the second leads of the reference and measured resistors are connected to the first and second outputs of the MK, the second plates of the capacitive sensor and the capacitor of the standard capacity connected respectively to the third and fourth outputs of the MK (see US Pat. RF No. 2391677, CL G01R 27/26).

A disadvantage of the known solution is the low sensitivity of the converter, due to the organization of measurement of a relatively small time interval during which only one cycle of the transition process in the RC circuit is carried out.

The closest in technical essence to the claimed technical solution and adopted by the authors for the prototype is a microcontroller measuring resistance converter in binary code with a voltage-controlled generator containing MK, a voltage-controlled generator, first, second, third and fourth resistors, the first conclusions of the first and the second resistors are connected respectively to the first and second outputs of the MK, the voltage-controlled generator, and the first conclusions of the third and fourth resistors are connected respectively, to the third and fourth outputs of the MK, the second conclusions of all resistors are connected to the voltage control input of the generator, the output of which is connected to the counting input built into the binary counter MK, the fifth output of the MK is connected to the generator generation enable input (see Pat. RF No. 2502076 Cl. G01R 27/26).

A disadvantage of the known solution is the low accuracy of the converter, due to the fact that the conversion of the model and measured resistance into binary code is performed at different time intervals during which electromagnetic interference can have different effects on the model and measuring circuit.

Disclosure of invention

The technical result that can be achieved using the present invention is to increase the accuracy of the conversion.

The technical result is achieved by the fact that in a microcontroller measuring resistance, capacitance and voltage to a binary code containing MK, voltage-controlled first generator, first, second, third and fourth resistors, and the first conclusions of all resistors are connected respectively to the first, second, third and the fourth outputs of the MK, the second conclusions of the first and second resistors are connected to the voltage control input of the first generator, the output of which is connected to the counting input built into the MK of the first a secondary counter, the fifth output of the MC is connected to the permission input for generating a voltage-controlled first generator, a voltage-controlled second generator is introduced, and the second outputs of the third and fourth resistors are connected to the voltage control input of the second generator, the output of which is connected to the counting input built into the MC of the second binary counter , the fifth output of the MC is connected to the enable input of the voltage-controlled second generator. The voltage-controlled first and second generators are equipped with timing RC circuits, and a capacitive sensor can be included as a measured capacitance as one of the capacitive elements of the timing RC circuit of one of the generators.

Brief Description of the Drawings

In FIG. The block diagram of a microcontroller measuring converter of resistance, capacitance and voltage to binary code is presented.

The implementation of the invention

The microcontroller measuring converter of resistance, capacitance and voltage to binary code contains (Fig.) A first resistor 1 (R ₁ ), a second resistor 2 (R ₂ ), a third resistor 3 (R ₃ ), a fourth resistor 4 (R ₄ ), voltage-controlled and generators 5 and 6 and MK 7, equipped with generation permission inputs. As generators 5 and 6, RC generators are used, built, for example, on the basis of NE555 microcircuits (domestic analogue of KR1006VI1), NE556 - two NE555 are made on one semiconductor chip.

The first conclusions of resistors 1, 2, 3 and 4 are connected respectively to the first, second, third and fourth outputs of MK 7, the second conclusions of resistors 1 and 2 are connected to the voltage control input of the generator 5, the second conclusions of resistors 3 and 4 are connected to the input of the voltage control of the generator 6, the outputs of the generators 5 and 6 are connected to the counting inputs of the first and second binary counters built into MK 7, respectively (binary counters are not shown in Fig.), The fifth output of the MK 7 is connected to the generation enable inputs of the generators 5 and 6.

The microcontroller measuring converter of resistance, capacitance and voltage to binary code works as follows.

Resistors 1, 2, and 3 are exemplary, with R ₁ = R ₂ , resistor 4 being a sensor, for example, thermal resistance. MK 7 outputs to the fifth output a logic level that prohibits generation, i.e. stops generators 5 and 6 and clears binary counters. MK 7 outputs logical “1” to the first and third outputs, and outputs logical “0” to the second and fourth outputs and starts the generators 5 and 6 by outputting the corresponding logical level to the fifth output. Generators 5 and 6 begin to generate rectangular pulses. Generator 5 generates rectangular pulses with a sample period T _O. The value of T _O depends on the reference voltage U _O at the voltage input of the generator 5. The voltage U _O, in turn, depends on the ratio of the resistances of the reference resistors 1 and 2 and is determined by the expression

$$U_O=U_H\cdot R_2/\left(R_{\mathrm{one}}+R_2\right),\text{(one)}$$

where U _H is the voltage of a high level, slightly less (by 0.02 V) of the voltage of the power supply MK 7. MK 7 measures the model time interval defined by the expression: t _O = N _O · T _O , where N _O is the number of model periods, counted by the first binary counter MK 7. The number N _O is set by software. The time interval t _O (time gate) is filled with counting pulses from the internal clock generator MK 7. MK 7 stores the value of the model time interval t _O in memory.

Generator 6 generates rectangular pulses with a current period of T _X. The value of T _X depends on the voltage U _X at the control voltage of the input of the generator 6. The voltage U _O in turn depends on the ratio of the resistances of the reference resistor 3 and measured 4 and is determined by the expression:

$$U_X=U_H\cdot R_{\mathrm{four}}/(R_3+R_{\mathrm{four}}),\text{(2)}$$

MK 7 measures the current time interval, determined by the expression: t _X = N _O · T _X , and stores the value of the current time interval t _X in memory.

Then MK 6 determines the difference in time intervals in accordance with the expression Δt = t _X -t _O. The value of Δt depends on the value of the voltage difference determined by the expression ΔU = U _X -U _O. Since expression (2) includes the resistance R ₄ , which is the resistance of the sensor and the model resistance R ₃ , and expression (1) includes the model resistances R ₁ and R ₂ , the values of which are known, Δt is a function of the change in R ₄ . MK 7 converts Δt into binary code and stores it in RAM for future use.

When measuring voltage MK 7 works as follows. The measured voltage is fed to the voltage control input of the generator 6. MK 7 puts the third and fourth outputs in a high resistance state. The state of the first and second outputs MK 7 does not change. Then MK 7 repeats the cycle described when measuring the resistance of the resistor 4, and determines the difference between the measured voltage and the reference, as well as the sign of the measured voltage relative to the reference.

If you want to use the external reference voltage, the output of the source of the external reference voltage must be connected to the voltage control input of the generator 5, while MK 7 puts the first and second outputs in a high-resistance state and repeats the previously described cycle of measuring the resistance of the resistor 4.

If it is necessary to measure the capacitance of, for example, a capacitive sensor, then this sensor is included as a capacitive element in the timing RC circuit of one of the voltage-controlled oscillators (FIG. Timing RC circuits are not shown). The second voltage controlled oscillator comprises an exemplary capacitance during the RC master circuit. All resistors should at best be exemplary and equal to each other, i.e. R ₁ = R ₂ = R ₃ = R ₄ . MK 7 performs the conversion cycle according to the previously described algorithm for measuring the resistance of the resistor 4, determines the frequency difference of the generators 5 and 6, and determines the increment of the capacitance, capacitive sensor by known expressions.

The present invention, in comparison with the prototype and other known solutions, has increased accuracy, as a result of using two generators made on the same semiconductor chip, which eliminates the influence of external factors, such as temperature, electromagnetic interference, instability of the supply voltage, aging processes.

Claims (2)

1. A microcontroller measuring resistance, capacitance and voltage to binary code converter comprising a microcontroller, a voltage controlled first generator, first, second, third and fourth resistors, the first terminals of all resistors being connected to the first, second, third and fourth outputs of the microcontroller, second the conclusions of the first and second resistors are connected to the voltage control input of the first generator, the output of which is connected to the counting input of the first a secondary counter, the fifth output of the microcontroller is connected to the enable input of the voltage-controlled first generator, characterized in that a second voltage-controlled generator is introduced into it, the second terminals of the third and fourth resistors connected to the voltage control input of the second generator, the output of which is connected to the counting input of the built-in to the microcontroller of the second binary counter, the fifth output of the microcontroller is connected to the voltage enable output of the second about the generator. 2. The microcontroller measuring transducer of resistance, capacitance, and voltage into a binary code according to claim 1, characterized in that the voltage-controlled first and second generators are equipped with timing RC circuits, and one of the capacitive elements of the timing RC circuit of one of the generators can be a capacitive sensor is included as a measured capacitance.