JPH0326920A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To automatically adjust a zero point by automatically adding a compensating input to obtain an output value which is to be obtained when the flow rate is zero. CONSTITUTION:When a switch 13 is turned ON with the flow rate set zero, an FF12 is set, and counters 10, 11 count the number of pulses from an oscillator 9 by a Q output of the FF12. The outputs from the counters 10, 11 are input to a T3 terminal of a variable resistor 7 equipped with a memory. On the other hand, the Q output from the FF12 is input to a T2 terminal of the variable resistor 7 thereby to release the lock of the variable resistor. Therefore, the variable resistor 7 is increased or decreased in accordance with an input from the T3 terminal. The increasing/decreasing direction is determined by an input to a T1 terminal. An output from the variable resistor 7 is added to a signal of a detector by an operational amplifier 4 and output therefrom. Whether the output from the variable resistor 7 is positive or negative is detected by a comparator 2. Depending on the result of the comparison, a command is generated to the T1 terminal of the variable resistor 7 to change the output so that the output from the operational amplifier 4 becomes zero. After a predetermined time later, the counter 11 overflows and the FF12 is reset thereby locking the variable resistor 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a VT flow meter, and more particularly to a quality flow meter that utilizes the Coriolis force.

Conventional technology Since the volume of liquid depends on the conditions of use, it is not easily affected by the conditions of use such as temperature. . A fluid is passed through the vibrating sensor tube in the overflow ink 1, and the displacement of the sensor tube caused by the Coriolis force acting on the fluid is detected to estimate the flow rate of the fluid.

Conventionally, in the purchase flow rate meter that utilizes Coriolis force, when the flow rate is low, the 1io point setting U is used, while looking at the flow rate display device, so that the displayed value This was done by operating variable means such as variable resistors.

Problems to be Solved by the Invention However, when the fluid is not flowing in the vibrating sensor tube that responds to the conventional mass flow rate using the Coriolis force, that is, 8! When the loss is zero, the user adjusts the zero point while looking at the display and operating variable means such as a variable resistor, which takes time and makes it difficult to set the zero point accurately. rlaffl cannot be performed, etc.
There was a point.

The present invention has been made in view of the above points, and an object of the present invention is to provide a quality flow meter that can easily and accurately perform zero point A adjustment.

Means for Solving the Problems The present invention deforms the conduit by the Coriolis force generated by flowing fluid through the vibrating W conduit, and deforms the inflow side and the outflow side of the conduit depending on the quality of the fluid. In a flow meter that detects the flow rate of the fluid by detecting a phase difference between vibrations occurring between the two sides as a detection signal whose level changes depending on the phase difference, the fluid flows through the pipe line. a comparison circuit that compares the detection signal level detected when the mass flow rate is not detected with a reference level that is a level that should be detected when the mass flow rate is zero, and the level changes according to the comparison result of the comparison circuit. I) Film signal generation circuit that generates the tll signal and the output 1j of the till signal @ushisei circuit
and a level variable circuit that varies the detection signal level according to the I9 signal level so that the difference between the detection signal level and the reference level becomes zero.

The action comparison circuit compares the detection signal level detected when the fluid is not flowing in the pipe with a reference level that is the level that should be detected when the 'Rffi flow rate is zero, and generates a warning signal. The circuit generates a v4wJ signal whose level changes in a direction according to the comparison result of the comparison circuit.

The level variable circuit varies the detection signal level by this restriction signal 9. When the detection signal level is higher than the reference level, reduce the detection signal level! , 13111 signal 8 level, and conversely, when the detection signal level is smaller than the reference level, the detection signal is increased.
The JgA signal level is changed so that the difference between the detected signal level and the reference level becomes zero. Therefore, the detection signal level can be made equal to the reference level, that is, the zero point can be adjusted.

Embodiment FIG. 1 shows a block diagram of a flowmeter using the Coriolis force, which is a practical example of the present invention. In the figure, 1 is a level variable circuit, 2 is a comparison circuit, and 3 is a control signal generation circuit.

The level variable circuit 1 includes an operational amplifier 4, a resistor R+. R2.
It is constituted by an addition amplifier circuit made up of R3. The comparison circuit 2 is composed of a comparator 5 and a resistor R4,
If the signal input to the comparator circuit 2 is positive, a low level signal <<Ov>> is output, and if it is negative, a high level signal (+15V>) is output.

The control signal generation circuit 3 includes a variable resistor 7 with memory, a transistor Q1 for output inversion, and a resistor Rs. Rs. An operational amplifier 8 for amplifying the output control signal to an appropriate value, an oscillation circuit 9 for generating clock signals, counters 10, 11. It consists of a flip-flop 12 and a switch circuit 13.

The zero point adjuster shown in FIG. 1 is used to adjust the zero point of a mass flow meter using the Coriolis force as shown in FIG. 3.

FIG. 3 shows a perspective view of 51 measuring sections of an embodiment of the present invention.

The II current meter is constructed by assembling a pair of sensors 1-114 and 15 into a hold 16. The manifold 16 is provided 1 m between the inflow pipe 17 and the outflow pipe 18, and the sensor search 1
The inlet pipe 17 and the outlet pipe 18 are connected via -714.15.

The sensor tube 14 is connected to a straight pipe i14a extending in the piping direction connected to the inflow pipe 17 and to the outflow pipe 18,
A straight pipe part 14b extending parallel to the straight pipe part 14a, and a straight pipe part 14a. A curved portion 14c that is bent back at the tip of 14b. 14d, and a U-shaped connecting portion 14e that connects the curved portions 14c and 146.

The sensor tube 15 is formed in the same shape as the sensor tube 14, and the sensor tube 15 is arranged so that the straight pipe section 158.15b is parallel to the outflow pipe 17 and the straight pipe sections 14a and 14b.
It is arranged symmetrically with respect to the block 14. Note that the connection portion 14e. of the sensor tube 14.15. 15e! ．． tOutflow pipe 1
A ring 19 having a gap around the outflow pipe 17 and the outflow pipe 17.
It is fixed to a T-shaped holding member 19b fixed to a.

Straight pipe portions 14a, 14b of sensor search 1-b 14.15. 1
5a and 15b pass through the support plate 20 and are fixed to the support plate 20 by welding, and their ends are connected and fixed to the manifold 16.

Moreover, this mass flow! In the first lesson, Senrichi l-114.1
5 is provided so as to extend in the piping direction of the inflow pipe 16 and the outflow pipe 17, the configuration is less susceptible to the effects of pipe vibration, and the flow back can be measured with higher accuracy.

A big up 21.2 is provided between the straight pipe parts ff4a and 15a on the inflow side and between the straight pipe parts 14b and 15b on the outflow side.
2 are arranged and the straight pipe portions 14a, 15a and 14b.
15b is detected.

23.24 is an exciter, and the circumference of the tip of the straight pipe portions 14a and 14b, the straight pipe I! It is provided between the tips of l5a and 15b.

When measuring the flow rate, the pair of sensor probes 14 and 15 are vibrated with fluid flowing inside them. The fluid flowing into the manifold 16 from the FI & man pipe 17 is divided and flows into the straight pipe section 14a of the sensor probe 14.15. 15a,
Curved portion 14c. 15c, connection 114e, 15e, song Pif
It passes through ll4d and 15d, reaches the straight pipe parts 14b and 15b, joins at the manifold, and flows out from the outflow pipe 18.

The sensor tube 14.15 is also excited by a vibrator 23.24 at a natural frequency determined by the spring constant of the sensor tip 14.15 and the mass of the fluid inside the sensor tube 14.15! B moves.

Therefore, when the fluid passes through the vibrating sensor tip 14.15, the Coriolis force is generated and the straight tube section 14a. 14
b, 15a, iSbk: Displacement occurs due to Ko'J force. The sensor probes 14 and 15 are each excited with a phase difference of 18 G''. For example, when the straight pipes W14a and 14blil of the sensor probe 14 move #I1, the straight pipe m15a of the sensor probe 1-115 is excited. 15b is proximity slot 1
, that is, when the sensor unit 14 is displaced as shown in FIGS. 4(A) and 4(B), the sensor unit 1115 is displaced as shown in FIG. 4(C). (D). Therefore, the straight pipe portion 14a of the sensor tube 14. In 14b, Fig. 5 (A)
．． As shown in (B), Coriolis occurs and the sensor is
- Straight pipe portion 15a of tube 15. 15b, Fig. 5(C), (
Coriolis as shown in D) grows.

The big ups 21, 22 detect the relative displacement of the sensor 14, 15 which vibrates as described above. Then, the quality of the fluid flowing in the sensor search 1-114.15 is determined based on the phase difference between the signals of the big ups 21 and 22. Straight pipe parts 14a, 15a, and 14b due to Cory A Rica produced in Sensachi 1-714.15 in the quality cutting process.
．． The relative displacement of 15b is doubled and can be detected, making RWI accurate! I can take one measurement. In addition, when detecting the phase difference of the sensor tubes 14 and 15 due to the occurrence of Coriolis,
Even if external vibration (vibration noise) is input, it is canceled out and the flow can be measured stably without being affected by external vibration.

Sensu search 1-bu 1 generated in big 7p 21.22
The input detection signal @ in which the detection signal corresponding to the phase difference of the displacement of sensor search 1-114.15 generated based on the signal corresponding to the displacement of 4.15 is inputted to the input terminal 'IN in Fig. 1 is The output terminal F is set to an appropriate value by Obeamp 4. , 1. Further, the signal set to an appropriate value by the operational amplifier 4 is not only outputted from the output signal 8 OUT but also supplied to the comparator circuit 2, where it is compared with a reference level. In this case, when the fluid is not flowing, the sensor tube 14,
15 are vibrated by the vibrators 23 and 24, the output signals match and no phase difference occurs, so no detection signal is input. This state is the zero time and zero point of the flow. Therefore, the reference level is used as the ground level for comparison.

Comparison circuit 2&j When the input {g level is higher than the reference level, it outputs a low level signal, and when it is lower, it outputs a high level signal.

The output signal of the comparator circuit 2 is supplied to the control signal generating circuit 3 through a resistor KRs of an npn transistor Q+. The collector of transistor Q1 is connected to 5 through resistor R5.
A variable resistor 7 with memory is connected to the power supply line of v.
The emitter of the transistor Q1 is connected to the positive and negative control terminals T1 of the transistor Q1, and the emitter of the transistor Q1 is grounded. Therefore, transistor Q1 is turned on and off in response to a high level or low level signal from comparison circuit 2.

The variable resistor 7 with memory is a variable resistor whose resistance value is varied by a human input signal to the terminal J"T'+-Ta.

11 Supine end F'r I is the iiiIII terminal for determining the variable direction of the resistance according to the level of the human power trust 3,
The control terminal T2 controls the start and stop of the variable operation of the resistor.
Control wJ terminal as chip select for IW,
l1m@child r3 is a terminal for varying the resistance according to the input pulse signal. In addition, the power supply terminals "FVH" and "VL" of this variable resistor 7 with memory are a +10V power supply and a -10V power supply terminal.
power is connected.

Inside the variable resistor 7 with memory is a power supply terminal VH and an output terminal V.
A variable resistor Rx is connected between the terminal VL and the output terminal VW, and a variable resistor RY is connected between the terminal VL and the output terminal Vw.

In the variable resistor 7 with memory, the ratio of the resistance values of the variable resistor Rx and the variable resistor RY changes according to the input t@ to the t4til terminal r3, and therefore the voltage at the output terminal Vw changes. Become.

A resistor R6 is connected to the outside of the variable resistor 7 with memory between the electric terminal IIA terminal VH to which a voltage of +IOV is applied and the output terminal Vw.
is connected, and a resistor R7 is connected between the output terminal Vw and the power supply terminal VL to which an N voltage of -10V is applied. Resistance Re, R7 is variable resistance R× in variable resistor 7 with memory
The voltage at the output terminal Vw for the resistance value υ} of the resistance values of and RY is zero when the variable resistance R× and RY are approximately equal, and the output terminal where the variable resistance R× or Ry becomes zero. This is to non-linearly change the voltage at the output terminal Vw depending on when the voltage at Vw is maximum or minimum, so that zero point adjustment can be performed smoothly.
Resistance Rs. Zero point adjustment can be performed without Ry <.

When adjusting the zero point, the sensor tube 14.15 should be adjusted with fluid flowing into the sensor tube 14.15.
is vibrated, and a switch provided in the switch circuit 13 is turned on. By turning on the switch circuit 13, the switch circuit 13 supplies a signal 8 as shown in FIG. 2(D) to the flip-flop 12. This trigger {ffl signal causes the output of the flip-flop 12 to go high as shown in FIG. 2(G).

The output high level signal of the control circuit 12 is supplied to the terminal 2 of the variable resistor 7 with memory to start the operation of the variable resistor 7 with memory, and is also supplied to the counter 10.11. Start the operation.

The counter 10 receives a constant frequency pulse t@ from the oscillation circuit 9, and in response thereto outputs a pulse signal 8 as shown in FIG. 2(E). Does the output pulse signal of the counter 10 enter the control Il terminal T3? and the memory {
=j variable resistor 7 pulse signal g from SEL counter 10
The resistance value is varied according to the The detection signal generated at this time is input to the terminal 'IN. The detected signal u at this time is normally at zero level, but due to the installation condition of the meter m, for example, a deviation Vd from the reference level (zero level) as shown in Fig. 2 (A) may occur. ing.

A signal corresponding to this deviation V (1m) is generated at the output terminal T.U■, and this signal is compared with the reference level by the comparator circuit 2.The comparator circuit 2 outputs a low level signal if it is higher than the reference level. Therefore, in this case, a 0-level confidence horse as shown in Fig. 2 (B) is output.
A high level signal is supplied to the I terminal T3 as shown in FIG. 2(C).

As a result, the variable resistor with memory Vi 7 and the paper resistor Rs. R7
1 ft. The generated υ1w signal has a waveform that gradually rises as shown in FIG. 2 (H). Since the control signal 8 and the input detection signal g are added, the waveform of the output detection signal gradually falls as shown in FIG. 2(A). Here, when the output signal 8 is almost zero, the output of the comparator circuit 2 alternately outputs a high level and a 0-level. As a result, the input to the input terminal T'+, which determines the direction in which the variable resistance changes, is also controlled so that the output signal @8 becomes zero instead of the alternating current.

In other words, when the output of the comparator circuit 2 is at a high level, the output signal 3A changes in the H- direction, where the output signal 8 becomes high, and when the output signal 3A changes in the direction of the H- direction, where the output signal 3A becomes low when the output signal is at a 0-level. do.

On the other hand, the output pulse signal of the counter 10 (FIG. 2(E)) is also supplied to the counter 11. The counter 11 counts the pulse signals of the counter 10, and when it counts a certain number of pulses, it generates a pulse as shown in Fig. 2 (〉. Output pulse signal of the counter 11〈Fig. 2《F)〉)
is input to the reset @f of the flip knob O-tub 12, and sets the output of the flip-knob O-tub 12 to a low level. For this reason, variable resistor with memory 7. The operations of the counters 10 and 11 are stopped, and the resistance value of the memory variable resistor 7 is maintained at a constant value.

Therefore, the output detection signal is set to the m-sub level, and the zero point adjustment is completed.

In this way, in this embodiment, the zero point can be automatically adjusted by 15 times simply by pressing the switch.

Effects of the Invention As described above, according to the present invention, the detection signal level can be improved even when no fluid is flowing through the pipe. A flill goshin bow is constructed by comparing it with the standard level that should be detected when the first-ryu suspension is zero, and the level changes depending on the comparison result.
Since the zero point adjustment is performed by approximating the detection signal level to the reference level by changing the level of the detection signal according to the signal 8, all you need to do is stop the fluid flowing in the pipe and operate the circuit. Zero points automatically! ! ! has become popular, and operations for JV by humans have become almost non-existent.
It has features such as easy and accurate adjustment.
j dimension,,

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a waveform diagram for explaining the operation of an example of an algae of the present invention, and Figs.
FIG. 5 shows jt! which generates a detection signal according to an embodiment of the present invention.
It is a diagram for explaining the s part. 1...Level variable circuit, 2...Comparison@path, 3...
Control signal 3 generation circuit.

Claims (1)

[Claims] Vibrations generated on the inflow side and outflow side of the conduit depending on the mass flow rate of the fluid when the conduit is deformed by the Coriolis force generated by flowing a fluid through the vibrating conduit. In a mass flowmeter that detects the mass flow rate of the fluid using a phase difference as a detection signal whose level changes according to the phase difference, the detection signal level detected when the fluid is not flowing in the pipe line and the a comparison circuit that compares a reference level that is a level that should be detected when the mass flow rate is zero; a control signal generation circuit that generates a control signal whose level changes according to the comparison result of the comparison circuit; A mass flowmeter comprising: a level variable circuit that varies the detection signal level according to the output control signal level of a signal generation circuit so that the difference between the detection signal level and the reference level becomes zero. .