SU1377745A1 - Device for measuring liquid flow rate and temperature - Google Patents

Abstract

This invention relates to a measurement technique. The purpose of the invention is to reduce the measurement error. For this, the heater 3 is embodied in the form of a ring with a thermometer 4 in the center. In any direction of motion in the flow permeability, the heat label travels the same distance from the heater to the thermometer 4. The error associated with a change in the amplitude of the heat label decreases, which is achieved by normalizing the input signal by compensating for the constant component and additional amplification. The reduction in the measurement error associated with the small steepness of the fronts and the finite maximum duration of the thermal tag is achieved by measuring half the time interval at the top of the signal. Expansion of functionality is achieved by outputting the code of counter 10 with the help of register 12, which carries information about the temperature of the fluid flow at the moment when the input signal is normalized. 1 hp f-ly, 4 ill. (L

Description

with "

4 ate

The device relates to a measurement technique and can be used to measure the speed and temperature of water streams in laboratory hydraulic models.

The aim of the invention is to reduce the measurement error.

Figure 1 shows the block diagram of the proposed device; Fig. 2 are diagrams showing its operation: n Fig. 3 is a block diagram of the control; Fig. 4 is a diagram of the voltages of the control unit.

The device contains sequentially connected control unit 1, generator 2 of heating pulses and heater 3, thermometer 4 connected in series, receiving

The device 5, the first amplifier 6, the first comparator 7, the first trigger 8, the circuit 9 coincidence, the first with the sensor 10 and the digital-to-analog converter (D / A) P, and the digital gyroscope module 11 is connected to the first amplifier 6 as controlled negative feedback Z, S-input of the first trigger 8 and input Reset of the first counter IO are connected to the first output of the control unit 5, and the reference input of the second comparator 7 is connected to the bias voltage bus Uj ,, the second register 12, the information inputs of which are connected to the outputs of the first counter 10 and the control input is from the output ode first trigger 8, the second amplifier 13, the input of which is connected to the output of the first amplifier 6 and the input bias to the bus Uo, the generator 14 clock pulses, the output of which is connected to the second input of the second circuit 9 coincidence, sequentially connected to the third reversible counter 15, second DAC 56 and second. voltage comparator 1 7, the second input of the voltage comparator 17 connected to the output of the second amplifier 13, the reference input NAL 16 - with the U bus and the counting input of the third counter 15 - with the generator 14 clock pulses, the second trigger 1B, the D input i is connected to the output of the first voltage comparator 17, the C input to the 4 clock pulse generator, and the direct output to the control input of the reverse of the third counter 15, the third 19 and the fourth 20 coincidence circuits, the first inputs of which are connected to the delayed output of the generator 14 clock pulses, and the second inputs - respectively with inverse and direct outputs of the second trigger 18, fourth 21 and. 22 second counters, the counting inputs of which are connected respectively to the outputs of the third 19 and fourth 20 coincidence circuits, Reset inputs - with the direct and inverse outputs of the second trigger 18, respectively, the third trigger 23, the S and R inputs of which are connected to the outputs of the fourth 21 and the fifth 22, respectively, of the register 24, the information inputs of which are connected to the outputs of the third counter 15, a. input Reset - with the second output of the control unit 1 and the input of the heating pulse generator 2, the code comparison circuit 25, the inputs of which are connected to the codes of the third counter 15 and the register 24, the fifth 26, the sixth 27 and the seventh 28 coincidence circuits, the first inputs of which are connected to the output of the circuit 25 comparison codes, the second inputs of the sixth

27 and seventh 28 coincidence circuits are connected to the outputs of the fourth 21 and fifth 22 counters, respectively, the second input of the fifth coincidence circuit 26 is connected to the right of the second trigger 18, and the third input is connected to the output of the third trigger 23, the second counter 29, the INPUT which is reset with control input of register 24 and output of the seventh circuit

28 matches, the sixth counter 30, the counting input and the input, the Reset of which is connected respectively to the outputs of the fifth 26 and sixth 27 coincidence circuits, the first matching circuit 31 of the input of which is connected to the output of the clock generator 14 and the third output of the control unit 1,

and the output with the counting input of the second counter 29, the arithmetic unit 32, whose information inputs are connected to the outputs of the second register 12, the second 29 and the sixth 30 meters, and the control input to the fourth output of the control unit 1, as well as indicator 33, connected to the output of the arithmetic unit 32.

The control unit (Fig. 3) contains a synchronizer 34 and serially connected shapers 35 of heating pulses, a driver 36

measurement time, the trigger pulse driver 37.

The device works as follows.

The signal (Fig. 2a) resets the first output of the control block I - the first trigger 8 is ejected from the first counter 10 to allow the passage of clock pulses from the generator 14 through the second coincidence circuit 9 to the input of the first counter 10, which changes the state of the digital signature module 11 increases the gain of the first amplifier 6. The increase of the gain occurs until the signal from the output of the receiving device 5, proportional to the temperature of the liquid (Fig. 26), reaches the U value at the output of the first amplifier 6, (Fig. 2c), this with It is activated a second voltage comparator 7 and sbra- sshaet first flip-flop 8 which, in turn, perepisshaet with the first counter 10 outputs the code K 1 to the second register 12 and permits. the formation by the control unit 1 of the control heating pulse (Fig. 2d). From the second output of the control unit 1 / control, the control heating pulse resets the second register 24 and starts the generator 2 heating pulses, which with the help of the annular heater 3 forms an annular heat label in the fluid flow. The heat label, moving in the fluid flow, passes through the thermometer 4, while the conditions of the heat mark propagation in the fluid flow relative to the thermometer 4 are the same in all directions of the flow in the flow plane. Since the gain of the first amplifier 6 is determined by the level of the signal from the output of the receiving device 5, which is proportional to the temperature of the fluid flow, there is a need for additional amplification of the heat tag signal. For this purpose, a second amplifier 13 is introduced, in which a constant compensation of the input input signal U and an amplification of the heat label signal to the required value is made up (fig. 2e). The comparator 17, the second trigger 18, the counter counter 15 and the D / A converter 16 form an analog-to-digital converter (ADC) of the following type.

0

five

0

five

0

five

0

five

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five

When the signal from the output of the second amplifier arrives at the ADC input at the output of the I7 comparator and the forward and inverse outputs of the second trigger 18 form, respectively, pulse sequences W, 3, I, and at the outputs of the third 19 and fourth 20 coincidence circuits - pulses K and L, moreover, the appearance of pulses L corresponds to the use of a stepped signal at the output of the digital cylinder 16 (Fig. 2d), and the pulses K to its rise. The pulses K and L are fed to the counting inputs of the fourth 21 and fifth 22 counters, to the Reset inputs of which, respectively, pulses 3 and I come from the outputs of the second trigger 18, Counters 21 and 22 are software counters; the outputs of which, after a reset, appear pulses after the second and every (M-1) successive (until reset) counting pulses. In this case, counters with M 3 are considered. Sequence of pulses. H at the output of the counter 21 corresponds to the increase of the signal D, and the pulses M at the output of the counter 22 to a decrease. The third trigger 23 forms the time intervals (Fig. 2o) from the beginning of the increase in signal D to the beginning of its decline. Since at the beginning of the measurement, the register 24 is reset to the zero state, the output of the code comparison circuit 25 is a signal P, indicating that the code of the third counter 15, proportional to the current value, of the signal D, is greater than the register code 24, and permits the passage of signals through the fifth 26, sixth 27 and seventh 28 coincidence schemes. The sixth counter 30 is reset by each pulse H transmitted through the matching circuit 27 and reads the pulses passed through the matching circuit 26, resulting in a short code in the counter 30 whose numerical value is equal to the integer part of the expression (t, –t) fo / 2, where fjj is the oscillator frequency of 14 clock pulses. The counting lasts until time t, when, after the first two drops of the next step signal D, the third flip-flop 23 is reset and the counting pulses are prevented from passing through the fifth coincidence circuit 26. At the same time, the second counter 29 is reset and the counting begins.

pulses fg from the output of the first matching circuit 31. At the same time, the signal P from the output of the seventh coincidence circuit 28 to the register 24 rewrites from counter 15 a code corresponding to the maximum signal level D, after which the output of the code comparison circuit 25 disappears the signal U and the operation of the fifth 26, sixth 27 and seventh 28 coincidence circuits is prohibited. The second counter runs until the end of the measurement time T and records the code K 2 in it, the numerical value of which is (T-tj + t,) fg.

If there are peaks in the signal preceding the maximum of the thermal tag (FIG. 2 d, 1), the operation of the device is similar to that indicated above, with the only difference that with the arrival of the maximum of the thermal tag (FIG. 2d, 11) the amplitude of the previous peak that is higher the outputs of the third counter 15 will become greater than the code recorded in register 24, and the code comparison circuit 25 will give permission to re-measure, and the previous maximum in the second 29 and sixth 30 counters will be reset. The peaks following the maximum thermal marks (FIG. 2d, III) do not affect the further operation of the device, since the code at the outputs of the third counter 15 does not exceed the code recorded at time tj in register 24, and the code comparison circuit 25 will not allow reset information in the second 29 and sixth 30 counters. If there is interference in the signal, which are smaller in amplitude of the maximum of the thermal tag, the operation of the device is similar to the above.

Codes K 1 from the output of the second register 12, K 2 from the output of the second counter 29 and K 3 from the output of the sixth counter 30 arrive at the arithmetic unit, which, using the signal from control unit 1, at the end of the measurement time T, calculates the temperature and the flow rate of the liquid. The calculation of the temperature of the fluid flow is made according to the formula that takes into account the temperature characteristics of the thermometer 4, as well as the parameters of the receiving device 5 and the negative feedback circuit of the first amplifier 6. Thus, for a semiconductor thermistor, the temperature characteristic is

0

) VT t „/

(one)

where R is the current value of the resistance of the thermistor; T - the current value of temperature, K; B - temperature deficit

specifications;

R is the resistance of the thermistor at temperature T. The voltage and X at the output of the resistance to voltage converter is determined by the formula U A R, where A is the conversion factor.

The gain of the first amplifier is determined by the ratio

20

TO

WooCop

and R

Since the code K1 corresponds to the number of pulses recorded in the first counter 10, the resistance of the DAC II is determined by the ratio AR K, where & R is the quantization step of the DAC 1I divider. Then from (2) we find

RT

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to,

From the formula (1) we go

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(3) in view of (3) on T - ..

. Jo r in

 A ZR - K R :) tG

(four)

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The flow rate is determined by the formula

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T 1

-J (5)

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where 1 is the base distance between

heater 3 and thermometer 4.

The calculation results arrive at indicator 33, from where information is read.

The start of one measurement time is set by the synchronizer, with the pulse from the output of which the first trigger B is raised and the counter 10 is reset. After the first trigger is reset, the pulse pulse heating starts up

The strength of which is given by the electrical elements of this circuit. Next, the heating pulse is sweet, the measurement time generator T starts up, after which the starting pulse generator AU generates a control pulse allowing the start of the mathematical processing of the measurement results.

The error in measuring the flow rate of a fluid will not increase with the annular shape of the heater with a thermometer in the center, since with any direction of movement in the flow plane, the heat mark travels the same distance from the heater to the thermometer. The uncertainty associated with a change in the amplitude of the thermal tag decreases, which is achieved by normalizing the input signal by compensating for the constant component and additional gain. A reduction in the measurement error associated with the small steepness of the fronts and the finite maximum duration of the thermal mark is achieved by measuring half the time interval (t, - t) at the top of the signal. Expansion of the functional capabilities of the device is achieved by outputting the code of the first counter 10 with the help of the second register 12, which carries information about the temperature of the fluid flow at the time when the input signal is completed.

Claims (2)

1. An apparatus for measuring the velocity and temperature of a fluid flow comprising a control unit connected in series, a heating pulse generator and a heater, a thermometer connected in series. the receiver and the first amplifier, the first digital-to-analog converter included in the feedback circuit of the first amplifier, the first counter, the input of which is connected to the first output of the control unit, and the outputs to the control inputs of the digital-to-analog converter, serially connected clock generator, first a coincidence circuit and a second counter, the second input of the first coincidence circuit being connected to the third output of the control unit, j 0 5 o five 0 0 a third reversible counter, a second digital-to-analog converter and a comparator voltage are connected in series, the counter input of the third counter is connected to a clock generator, and the reference input of the second digital-analog converter with a bias voltage voltage of 5 serially connected arithmetic unit and indicator, the second information input of the arithmetic unit is connected to the output of the second counter, and the control input to the fourth output of the control unit, which distinguishes In order to reduce the measurement error, the heater is designed as a ring located in the flow plane, the thermometer is placed in the center of this ring, and a second voltage comparator, three triggers, six coincidence circuits, three counters, the second the amplifier, the first register and the code comparison circuit, while the second voltage comparator, the first trigger and the second matching circuit 5 are serially connected to the output of the first amplifier, the reference input of the second voltage comparator being connected an offset voltage bus, the setup input of the first trigger — with the first output of the control unit, and the output — with the input of the control unit, the second input of the second coincidence circuit is connected to the clock generator, and the output is with the counting input of the first counter, the input of the second amplifier is connected to the output the first amplifier, the ACV bias - with the bias voltage race, and the output - with the second - input of the first voltage comparator, the D-input of the second trigger is connected to the output of the first comparator, and the C-input - with the output of the clock pulse generator, P The third inputs of the third and fourth coincidence circuits are connected to the delayed output of the clock-output pulse generator, and the second to the inverse and direct outputs of the second trigger, respectively; the counting inputs of the fourth and fifth counters are respectively connected to the outputs of the third and fourth coincidence inputs - Reset - corresponding to direct and inverse outputs of the second the trigger, the S and R inputs of the third trigger are connected to the outputs of the even and fifth counters, the information inputs of the register and the first information inputs of the code comparison circuit are connected to the outputs of the third counter, the second inputs of the code comparison circuit are with the outputs of the register, and the input Register reset - with the second output of the control unit and the input of the heating pulse generator, the first inputs of the fifth, sixth and seventh matching circuits are connected to the output of the code comparison circuit, the second inputs of the sixth and seventh matching circuits are connected to the outputs of the fourth and fifth counters, the second input of the coincidence circuit — with the direct output of the second trigger, and the third input — with the output of the third the trigger, the output of the seventh coincidence circuit is connected to the Reset input of the second counter and the control input of the register, the counting input of the sixth counter and its input Reset are connected respectively to the outputs of the fifth and sixth coincidence circuits, and the output -. with the third input of the arithmetic unit. 2. The device according to claim 1 is characterized by the fact that, in order to expand its functionality, the Hiero additionally introduces a second register, the information inputs of which are connected to the output of the first counter, the control input to the first trigger input, and the output to the first input of the arithmetic devices. fa.e -171 1 2S a 5 linnnilllinnHHIIlHliH (llllllil {lttl} | JllH ini pppsh ldpp 1ppt pppt pp Pppp n ppp and type 1 type p I1P 11 Ml run spike them I} IL 1 GP Well  t ldpp -if ppp - t I} IL 1 GP Well Fie.2