SU1651232A1 - Device for converting resistance to frequency - Google Patents

Description

The invention relates to a measurement technique and can be used in devices for tele-measurement of temperature using thermistors.

The purpose of the invention is to improve the accuracy of the conversion by reducing the ripple of the output signal.

Figure 1 shows the block diagram of the device; Fig. 2 is a circuit diagram of a logic unit; FIG. 3 shows time diagrams of voltages illustrating the operation of the device.

The device contains a sinusoidal voltage generator 1, a resistor-sensor-2, a rectifier 3, an adder 4, a variable component extraction unit 5, a comparator 6, a logic unit 7, an integrator 8, a voltage-frequency converter 9.

{frequency converter - voltage 10, where the logic unit and integrator contain an inverter 11, RS trigger 12, RS trigger 13 with read resolution key, pulse shaper 14, integrating chains 15 and 16, voltage follower 17,

A sinusoidal voltage generator 1 is connected to a variable resistor-sensor 2 (for example, a resistance thermometer), the potential output of which is connected to the input of rectifier 3, the output of rectifier 3 is connected to the first input of adder 4, the second input of which is connected to the output of block 5 variable component. The output of the adder, 4 is connected to the first input of the comparator 6, to which logic block 7, integrator 8, voltage frequency converter 9 are serially connected, frequency converter - voltage 10, the output of which is connected to another input of comparator bis by input of variable selection block 5 . The output of the device is the output of the voltage converter 9, which is also connected to the second (control) input of the logic unit 7,

The input of the logic block (FIG. 2) is connected to the input of the RS flip-flop 12 and to the input of the inverter 11, the output of which is connected to the input of the RS flip-flop 12, the direct and inverse outputs of which are connected, respectively, to the S input and the R input of the trigger 13. Second (pack

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Equal to the input of the logic unit through the pulse shaper 14 is connected to the E input (read enable key) of the trigger 13, the direct output of the trigger 13 is connected to the resistor 15, the second output of which is connected to the output of the capacitor 16 and the input of the voltage follower 17, and the second the output of the capacitor 16 is grounded. The output of the voltage follower 17 is the output of the integrator 8.

The resistance-to-frequency conversion device operates as follows.

The voltage drop on the variable resistor-sensor 2 is rectified by rectifier 3 and in the form of a direct-current voltage is fed to the first input of the adder 4, in which it is added to the voltage supplied from the block 5 by the selection of the variable component. The total voltage is fed to the first input of the comparator 6, where it is compared with the voltage coming from the output of the frequency converter - voltage 10, having a similar ripple component. The selected difference of the compared voltages is fed to the input of the logic unit, and in each trans. The oscillation period of the output signal of the device in logic block 7 analyzes the sign of the difference between the 6 voltages compared in the comparator. Thus, for example, if the voltage at the output of the adder 4 exceeds the voltage at the output of the frequency-voltage converter, then a logical unit pulse is generated in the logic block 7 . If this condition is not observed, the pulse in the logical block does not form a logical zero. The pulses from the output of the logic unit 7 are fed to the input of the integrator 8, in which a voltage is generated that controls the operation of the voltage-frequency converter 9.

A negative feedback loop containing a frequency converter - voltage 10 and a variable component extraction unit 5, covers the adder 4, comparator 6, logic block 7, integrator 8 and voltage converter - frequency 9 and ensures the stability of the device operation. Additional feedback from the output of the frequency converter - voltage 10 to the input of the adder 4 transmitted through the variable component extracting unit 5, corrects for the fluctuation of the useful signal, since the syncation and synchronism of the pulsating component voltages at both inputs of the comparator is achieved, resulting in the elimination of these components is provided (fig. 3). The output signal from converter 10 has a constant and a variable component (Fig. 3, Uw) and is fed to the 31st input of the comparator 6. At the same time, it enters block 5, where a variable component is extracted (Fig. 3, U-.) which is fed to the second input of the adder 4 ". To the first lead of the adder 4, a well-smoothed straightened voltage proportional to the measured resistance (Fig. 3, U-) is applied. In the adder 4 both signals are added and to the first input of the comparator 6 is fed exact value of the voltage copy and {0 (| u3. U.). Thus, the in-phase and synchronous pulsating components of the voltages 11f and U at the inputs of the comparator 6 significantly reduce the fluctuations of the output signal (eb | x)

The technical and economic effect of the expression is expressed in increasing the accuracy of the conversion of resistance

ten

6512326

Claims (1)

into the frequency due to the correction of fluctuations of the useful signal. Invention Formula A device for converting impedance into a frequency, containing a generator, resistor - sensor, logic unit, integrator, test voltage and frequency - frequency and frequency - voltage, a comparator, the output of which is connected to the output of the logic unit, its output - to the input integrator, its output is connected to the input of the converter voltage - frequency, the output of which is the output of the device and connected to the third input of the logic unit, and the output of the frequency converter - voltage is connected to the input of the comparator, In order to increase the accuracy of the conversion, an allocation unit with a variable component, an adder, a rectifier, whose input is connected to the generator output and a sensor-resistor output, the second output of which is connected to the common bus of the device, output the rectifier is connected to the input of adders; the output of the adder is connected to the second input of the comparator, and the input of the variable selection block — to the output of the frequency converter — is voltage, and its output is connected to the second input of the adder 15 20 figure 1 el. I   Nj.  J-bf -j tf " s i, s i x1 . I Y. ult . -j aJ I Fig.Z