CN101598580A - A kind of method that improves precision of transit-time ultrasonic flow meter - Google Patents

Abstract

The invention discloses a kind of method that improves precision of transit-time ultrasonic flow meter, may further comprise the steps, under hydrostatic condition, when upstream transducer emission ultrasound wave, the timer of flowmeter main frame begins counting, stop counting when this transmits when the downstream transducer receives, obtain counting forward N1; When the transducers transmit ultrasonic waves of downstream, the timer of flowmeter main frame begins counting, stops counting when this transmits when upstream transducer receives, and obtains counting in reverse N2; Thoroughly do away with counting forward N1 and counting in reverse N2 and calculate the sound travel flow velocity, and improve precision of transit-time ultrasonic flow meter with this.Beneficial effect of the present invention is for low discharge error effect under the elimination hydrostatic condition obvious.

Description

A kind of method that improves precision of transit-time ultrasonic flow meter

Technical field

The present invention relates to the technology that improves the transit-time ultrasonic flow meter measuring accuracy, particularly utilized the balance method of the just reverse travel-time distribution of transit-time ultrasonic flow meter, by the zeroing of the sound travel flow velocity under hydrostatic condition, realize improving the purpose of transit-time ultrasonic flow meter measuring accuracy.

Background technology

For being installed on user pipe or bigbore transit-time ultrasonic flow meter, the precision of flow measurement is inseparable with the installation accuracy of transducer, particularly the transducer of each sound travel will be aimed at as much as possible, principle of work according to transit-time ultrasonic flow meter, under hydrostatic condition, the just reverse travel-time of ultrasound wave should equate on the same sound travel, positive reversion time difference is zero, the sound travel flow velocity also is zero, the flow that record this moment also is zero, if the transducer on the same sound travel is not aimed at, under hydrostatic condition, the mistiming of the just reverse propagation of ultrasound wave is non-vanishing on the same sound travel, sound travel also has a little flow speed value, this moment, not due low discharge just appearred in flowmeter, and this low discharge that must superpose of the flow value during therefore normal flow measurement influences the flow measurement precision.Limit at present usually the method for minimum flow, this low discharge of shielding under hydrostatic condition, but under moving water condition, low discharge still are added on the normal discharge, form measuring error.To the calibrating in the transit-time ultrasonic flow meter use, can adopt velocity of sound checking method, if owing to the mistiming of the just reverse propagation of ultrasound wave on the same sound travel under the hydrostatic condition is non-vanishing, the velocity of sound of measurement also error must occur, causes the decline of the calibration accuracy of equipment.So, should adopt necessary method and technological means according to the principle of work of transit-time ultrasonic flow meter, eliminate the non-vanishing influence of mistiming of the just reverse propagation of ultrasound wave on the same sound travel under the hydrostatic condition to precision, improve measuring accuracy.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, propose a kind of purpose and provide a kind of method that realizes the transit-time ultrasonic flow meter zeroing by the just reverse travel-time of balance, realize improving the purpose of transit-time ultrasonic flow meter measuring accuracy, have principle clear and rational, convenient feasible, the measuring accuracy effect that improves transit-time ultrasonic flow meter is obvious.

A kind of method of utilizing the zeroing of the just reverse travel-time realization of balance transit-time ultrasonic flow meter, realize improving the transit-time ultrasonic flow meter measuring accuracy, its characteristics are to utilize the ultrasound wave balance in just reverse travel-time, and total travel-time is constant substantially, there are not other negative effects, principle is clear, convenience is feasible, according to Fig. 1, specify.

Idiographic flow and step as shown in Figure 1, details are as follows:

A. under hydrostatic condition, when upstream transducer P1 emission ultrasound wave, the timer of flowmeter main frame begins counting, stops counting when this transmits when downstream transducer P2 receives, and obtains counting forward N1;

B. when the transducers transmit ultrasonic waves of downstream, the timer of flowmeter main frame begins counting, stops counting when this transmits when upstream transducer receives, and obtains counting in reverse N2;

C. under hydrostatic condition, sound travel flow velocity v=0 in theory, this moment, positive reversion time should equate, i.e. N1=N2, because the alignment error of transducer, form the just reverse mistiming, if N1 ≠ N2 in fact is N1＞N2, then get Δ N=N1-N2, when Δ N is even number, gets forward correction counting and be-Δ N/2 counting forward N1 '=N1-Δ N/2, reverse correction counting is+Δ N/2, counting in reverse N2 '=N2+ Δ N/2 when Δ N is odd number, makes Δ N '=Δ N ± 1, getting forward correction counting is-Δ N '/2, counting forward N1 '=N1-Δ N '/2 gets reverse correction counting and is+Δ N '/2 counting in reverse N2 '=N2+ Δ N '/2; In like manner, if N1＜N2 then gets Δ N=N2-N1, when Δ N is even number, gets forward correction counting and be+Δ N/2 counting forward N1 '=N1+ Δ N/2, getting reverse correction counting is-Δ N/2, counting in reverse N2 '=N2-Δ N/2 when Δ N is odd number, makes Δ N '=Δ N ± 1, getting forward correction counting is+Δ N '/2, counting forward N1 '=N1+ Δ N '/2 gets reverse correction counting and is-Δ N '/2 counting in reverse N2 '=N2-Δ N '/2; Like this, make N1 '=N2 ', and the tale of just reverse propagation is constant substantially, and sound travel flow velocity v=0 has realized the flow zeroing under the hydrostatic condition.

When D. carrying out flow rate calculation:

Forward-propagating time T 1=(N1+ forward correction counting) * Δ t,

Wherein: N1---the forward-propagating counting,

T---gate time at interval;

Reverse travel-time T2=(the reverse correction counting of N2+) * Δ t,

Wherein: N2---reverse propagation counting,

T---gate time at interval;

Sound travel flow velocity then

$v=\frac{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A2009101816300009H1.png"\; state="\{\{state\}\}">L</figure-callout>}}{2\mathrm{COS\&theta;}}(\frac{1}{T_1}-\frac{1}{T_2})=\frac{L\&times;(T_2-T_1)}{2\&times;T_1\&times;{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="A2009101816300009H1.png"\; state="\{\{state\}\}">T</figure-callout>}}_2}$

Wherein: the L=sound travel is long

The angle of the θ=sound wave path and the flow direction

The sound travel flow velocity that calculates has been eliminated the error that minimum velocity forms under the hydrostatic condition.

Beneficial effect of the present invention is for low discharge error effect under the elimination hydrostatic condition obvious.

Description of drawings

Fig. 1 is a process flow diagram of the present invention

Embodiment

The invention will be further described below in conjunction with example.

V is that 0.9 meter square sectional Fang Han has installed a transit-time ultrasonic flow meter in the length of side, sound travel length is 1.23 meters, the sound travel angle is 45 °, host count device resolution is 1 counting 6.25ns, under hydrostatic condition, and ultrasonic emitting and receiver operate as normal, owing to there is the alignment error of transducer, show sound travel forward-propagating counting N1=135680, reverse propagation counting N2=135682, then

T1＝135680×6.25×10E-9s＝8.48×10E-4s，

T2＝135682×6.25×10E-9s＝8.480125×10E-4s，

Have according to the flow velocity computing formula:

$v=\frac{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A2009101816300009H1.png"\; state="\{\{state\}\}">L</figure-callout>}}{2\mathrm{COS\&theta;}}(\frac{1}{T_1}-\frac{1}{T_2})=0.01479$ (m/s)

Always there is the hydrostatic flow velocity error of 0.01479m/s, causes about 0.012m ³The flow error of/s.

During normal flow measurement, show sound travel forward-propagating counting N1=135703, reverse propagation counting is N2=135659, shows that as calculated the sound travel flow velocity is 0.3326m/s, has wherein comprised hydrostatic flow velocity error.

In order to eliminate hydrostatic flow velocity error, revise according to method of the present invention, N1＜N2, get Δ N=N2-N1=2, make N1 '=N1+ Δ N/2=135680+1=135681, forward correction counting is for+1, make N2 '=N2-Δ N/2=135682-1=135681, reverse correction counting is-1, N1 '=N2 ' like this, and the sound travel flow velocity is 0 under hydrostatic condition.

During normal flow measurement, N1=135659, N2=135703,

Then count the balance correction

T1＝(N1+1)×6.25×10E-9＝8.47875×10E-4s，

T2＝(N2-1)×6.25×10E-9＝8.48137×10E-4s，

Have according to the flow velocity computing formula:

$v=\frac{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A2009101816300009H1.png"\; state="\{\{state\}\}">L</figure-callout>}}{2\mathrm{COS\&theta;}}(\frac{1}{T_1}-\frac{1}{T_2})=0.3175$ (m/s)

Eliminated the hydrostatic flow velocity error of bringing because of installation after revising, made the measuring accuracy of flow velocity improve 4.7%, corresponding flow accuracy also is improved significantly.

Claims (1)

1, a kind of method that improves precision of transit-time ultrasonic flow meter is characterized in that, may further comprise the steps:

1) under hydrostatic condition, when upstream transducer emission ultrasound wave, the timer of flowmeter main frame begins counting, stops counting when this transmits when the downstream transducer receives, and obtains counting forward N1;

2) when the transducers transmit ultrasonic waves of downstream, the timer of flowmeter main frame begins counting, stops counting when this transmits when upstream transducer receives, and obtains counting in reverse N2;

3) under hydrostatic condition, sound travel flow velocity v=0 in theory, this moment, positive reversion time should equate, i.e. N1=N2, because the alignment error of transducer, form the just reverse mistiming, if N1 ≠ N2 in fact is N1＞N2, then get Δ N=N1-N2, when Δ N is even number, gets forward correction counting and be-Δ N/2 counting forward N1 '=N1-Δ N/2, reverse correction counting is+Δ N/2, counting in reverse N2 '=N2+ Δ N/2 when Δ N is odd number, makes Δ N '=Δ N ± 1, getting forward correction counting is-Δ N '/2, counting forward N1 '=N1-Δ N '/2 gets reverse correction counting and is+Δ N '/2 counting in reverse N2 '=N2+ Δ N '/2; In like manner, if N1＜N2 then gets Δ N=N2-N1, when Δ N is even number, gets forward correction counting and be+Δ N/2 counting forward N1 '=N1+ Δ N/2, getting reverse correction counting is-Δ N/2, counting in reverse N2 '=N2-Δ N/2 when Δ N is odd number, makes Δ N '=Δ N ± 1, getting forward correction counting is+Δ N '/2, counting forward N1 '=N1+ Δ N '/2 gets reverse correction counting and is-Δ N '/2 counting in reverse N2 '=N2-Δ N '/2; Like this, make N1 '=N2 ', and the tale of just reverse propagation is constant, and sound travel flow velocity v=0 has realized the flow zeroing under the hydrostatic condition;

When 4) carrying out flow rate calculation:

Forward-propagating time T 1=(N1+ forward correction counting) * Δ t,

Wherein: N1---the forward-propagating counting,

T---gate time at interval;

Reverse travel-time T2=(the reverse correction counting of N2+) * Δ t,

Wherein: N2---reverse propagation counting,

T---gate time at interval;

Sound travel flow velocity then

$v=\frac{L}{2\mathrm{COS\&theta;}}(\frac{1}{T_1}-\frac{1}{T_2})=\frac{L\&times;(T_2-T_1)}{2\&times;T_1\&times;T_2}$

Wherein: the L=sound travel is long

The angle of the θ=sound wave path and the flow direction.

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