JPH04231822A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To realize a mass flowmeter capable of easily performing inspection. CONSTITUTION:A mass flow meter is constituted of the sensor tubes 2, 3 on inflow and outflow sides, the vibrators 23, 24 on the inflow and outflow sides, the pickups 9, 10 on the inflow and outflow sides, a memory 16 storing the time lag between the outputs of the respective pickups on the inflow and outflow sides, a max. value detection means 25 detecting the max. value of the time lag stored in the memory, a min. value detection means 26 detecting the min. value of the time lag, a differential amplifier 27 outputting the difference between the max. and min. values and a display means 14 selectively displaying a flow rate and the difference (irregularity) between the max. and min. values by the operation of a mode change-over switch 28.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flow meter, and more particularly to a mass flow meter that measures the mass flow rate of a fluid using the Coriolis force.

It is desirable that the mass of a fluid be expressed as a mass that is not affected by the type of fluid, physical properties (density, viscosity, etc.), and process conditions (temperature, pressure). Examples of mass flowmeters that measure the mass flow rate of a fluid include a so-called indirect mass flowmeter that measures the volumetric flow rate of a fluid and converts this measured value into a mass flow rate, and an indirect mass flowmeter that directly measures the mass flow rate of a fluid. There was a direct mass flowmeter that could measure with higher accuracy than a flowmeter.

Some direct mass flowmeters directly measure the mass flow rate by flowing fluid through a vibrating sensor tube and utilizing the Coriolis force generated at this time.

0004

[Prior Art] Conventionally, a mass flow meter that measures mass flow rate using the Coriolis force has been designed to flow fluid through a pair of sensor tubes formed in a U-shape. It is known to measure the mass flow rate by vibrating the sensor tube in the direction of separation and detecting the displacement of the sensor tube due to the generation of Coriolis force proportional to the mass flow rate.

[0005] In a mass flowmeter configured to vibrate the sensor tube in this manner, when the flow rate is zero, the displacements of the inflow side and the outflow side of the sensor are the same, so that no time difference occurs. However, in reality, there may be a difference in the resonance frequency between the inflow and outflow sides of the sensor tube due to machining errors in the support part that supports the sensor tube, variations in the dimensions of the sensor tube itself, or vibration noise from the outside. This causes a difference in vibration between the inflow and outflow sides of the sensor tube, which may cause a time difference between the inflow and outflow sides similar to when measuring flow rate using the Coriolis force.

[0006] For this reason, after assembly is completed at a factory, a mass flow meter is installed midway through piping and a flow rate test is conducted by actually flowing fluid to measure the suppression ratio of vibration noise inherent in the mass flow meter. If a large amount of vibration noise occurs and the suppression ratio is small, it is determined to be defective because, for example, there is an abnormality in the machining accuracy of the sensor tube or the welding location.

[0007]

[Problem to be Solved by the Invention] However, in the past, inspectors checked the time difference between the output signal of the inflow side pickup and the output signal of the outflow side pickup, for example, by connecting the output terminal of each pickup to an oscilloscope, etc. ,
The vibration noise suppression ratio was checked by monitoring the time difference waveform displayed on the oscilloscope. Therefore, in the past, when performing a flow rate test on a mass flowmeter, there was a problem in that it was troublesome to connect the mass flowmeter to a measuring instrument such as an oscilloscope, and that much time and effort was required. Furthermore, conventionally, an inspector uses a measuring instrument such as an oscilloscope to inspect the vibration characteristics of the sensor tube, so there is a problem that individual errors by the inspector are included in the detection results, making the inspection unfair.

[0008] Accordingly, an object of the present invention is to provide a mass flow meter that solves the above problems.

[0009]

[Means for Solving the Problems] The present invention includes a sensor tube through which a fluid to be measured flows, an exciter that vibrates the sensor tube at a predetermined frequency, and detects the displacement of the inlet and outlet sides of the sensor tube. a pair of pickups, maximum value detection means for detecting the maximum value of the time difference between the output signal of the inflow side pickup and the output signal of the outflow side pickup, minimum value detection means for detecting the minimum value of the time difference, and the maximum value A display means is provided for displaying the maximum value outputted from the detection means and the minimum value outputted from the minimum value detection means, or a difference thereof, or a determination result based on the difference.

[0010] Also, a sensor tube through which the fluid to be measured flows, an exciter that vibrates the sensor tube at a predetermined frequency, a pair of pickups that detect displacement on the inflow side and outflow side of the sensor tube, and an inflow side pickup. maximum value detection means for detecting the maximum value of the time difference between the output signal of the output signal and the output signal of the outflow side pickup; minimum value detection means for detecting the minimum value of the time difference; and a flow rate value flowing through the sensor tube based on the time difference. a calculation means for calculating, and a maximum value outputted from the maximum value detection means and a minimum value outputted from the minimum value detection means, or a difference thereof, or a judgment result based on the difference, or a flow rate value calculated by the calculation means. a display means for displaying, a switching means for outputting a switching signal for switching the flow rate value displayed on the display means to display the maximum value, the minimum value, the difference thereof, or a judgment result based on the difference; and the time difference is constant. A determination means that determines that the flow rate is zero only when the flow rate is equal to or less than a reference value of display switching means for switching the display to display the flow rate value on the display means when the determination means determines that the flow rate is not zero when the result is displayed;
Equipped with.

Alternatively, a sensor tube through which the fluid to be measured flows, an exciter that vibrates the sensor tube at a predetermined frequency, a pair of pickups that detect displacement on the inflow side and outflow side of the sensor tube, and an inflow side pickup. averaging means for calculating the average value of the time difference between the output signal of the output signal and the output signal of the outflow side pickup; a calculating means for calculating the flow rate value flowing through the sensor tube from the time difference; and an average value output from the averaging means. a display means for displaying a value or a flow rate value calculated by the calculation means; a switching means for outputting a switching signal for switching the flow rate value displayed on the display means to a display of the average value; A determining means determines that the flow rate is zero only when the flow rate is equal to or less than a reference value, and a switching signal is supplied from the switching means, so that when the average value is displayed on the display means, the determining means determines that the flow rate is zero. Display switching means is provided for switching the display so that the flow rate value is displayed on the display means when it is determined that the flow rate value is not zero.

0012

[Function] By displaying the maximum value and minimum value of the time difference between the output signal of the inflow side pickup and the output signal of the outflow side pickup, the difference between them, the judgment result based on the difference, or the average value, the sensor caused by external vibration can be displayed. The presence or absence of abnormal vibration of the tube can be easily confirmed.

[0013] Also, only when the flow rate is determined to be zero, the maximum value and minimum value, the difference between them, the judgment result based on the difference, or the average value is displayed, and when there is a flow rate, the flow rate value is automatically displayed. The display changes to

[0014]

Embodiment FIGS. 1 and 6 show a mass flowmeter 1 according to a first embodiment of the present invention.

In both figures, the mass flowmeter 1 has an inflow side flange 1a with an inflow port 1a1 opening at its center, and an outflow port (1a1).
A manifold 4 to which a pair of sensor tubes 2 and 3 are connected between the outflow side flange 1b and the outflow side flange 1b (not shown) that opens
and a box-shaped cover 1c that houses and protects the sensor tubes 2 and 3.

The pair of centubes 2 and 3 extend horizontally from the manifold 4 and are arranged symmetrically in the horizontal direction with respect to a vertical plane that stands upright in the vertical direction. One sensor tube 2 is connected and fixed to the inflow side connection port of the manifold 4 by brazing or the like, and has a first straight pipe section 2a extending in the piping direction and a base end connected to the manifold 4.
A second straight pipe part 2b is connected and fixed to the outflow side connection port and extends parallel to the first straight pipe part 2a. It consists of curved portions 2c and 2d bent to the side, and a U-shaped connecting portion 2e that connects the curved portions 2c and 2d.

The other sensor tube 3 is formed in the same shape as the sensor tube 2, and is symmetrical to the sensor tube 2 so that the straight pipe parts 3a and 3b are parallel to the outflow pipe 6 and the straight pipe parts 2a and 2b. It is located in Note that the connecting portions 2e and 3e of the sensor tubes 2 and 3 are connected and held together by a holding member 8.

Note that this holding member 8 is not in contact with the outflow pipe 6, so that piping vibrations of the outflow pipe 6 are not directly transmitted to the sensor tubes 2 and 3.

In the pair of sensor tubes 2 and 3, pickups 9 and 10 are disposed between the straight pipe sections 2a and 3a on the inflow side and between the straight pipe sections 2b and 3b on the outflow side. ing.

Note that since the pickups 9 and 10 have the same configuration, only one pickup 9 will be explained.

The pickup 9 consists of a coil portion held on the straight tube portion 2a of the sensor tube 2, and a magnet provided on the straight tube portion 3a of the sensor tube 3 so as to face the coil portion in the left and right directions. .

Therefore, when the sensor tubes 2 and 3 vibrate, the coil portion provided in the straight tube portion 3a is relatively displaced between the magnets in the direction of arrow X. Therefore, an electromotive force is generated in the coil portion according to the relative displacement of the straight tube portions 2a and 3a, and the pickup 9 detects the displacement of the straight tube portion 3a from the voltage of the coil portion.

[0023] 23 and 24 are vibration exciters, which have straight pipe parts 2a and 2b.
and between the tips of the straight pipe portions 3a and 3b.

The vibrator 23 has substantially the same structure as an electromagnetic solenoid, and includes a coil section attached to the straight pipe section 2a on the inflow side, and a magnet fitted into the coil section, which is attached to the straight pipe section 2b on the outflow side. It becomes more than the department. Therefore, the vibrator 23
When the coil part is energized, the straight pipe parts 2a and 2b are shown by the arrow X.
Excite in the direction (up, down).

The vibrator 24 has the same structure as the vibrator 23 described above, so its explanation will be omitted.

Next, the measurement operation of the mass flowmeter 1 having the above configuration will be explained.

[0027] When measuring the flow rate, a pair of sensor tubes 2 and 3
is excited by the operation of the vibrators 23 and 24 with fluid flowing inside. Manifold 4 from inflow pipe 5
The fluid to be measured that has flowed into the sensor tubes 2 and 3 is divided into
It flows into the lower straight pipe parts 2a, 3a, and the curved parts 2c, 3c,
It passes through the connecting parts 2e, 3e and the curved parts 2d, 3d, reaches the upper straight pipe parts 2b, 3b, merges at the outflow path (not shown) of the manifold 4, and flows out from the outflow pipe 6. In addition, since the sensor tubes 2 and 3 are vibrated by the vibrators 23 and 24, they vibrate in the arrow X direction ( vibrates in the vertical direction).

Coriolis force acts in the vibration direction of the sensor tubes 2 and 3, and acts in opposite directions on the inflow and outflow sides, so that the straight pipe portions 2a, 2b, 3a of the sensor tubes 2 and 3
, 3b is twisted, and this twist angle is proportional to the mass flow rate. The pickups 9 and 10 are sensor tubes 2 like this.
, 3 due to the torsion is measured as a time difference in the output signal to measure the mass flow rate.

FIG. 1 shows the flow rate measuring section 11 of the mass flowmeter 1.
FIG. In FIG. 1, 12 is a time difference detection circuit that detects the time difference (phase difference) between the output signal from the pickup 9 on the inflow side and the output signal from the pickup 10 on the outflow side. The signal from the time difference detection circuit 12 is input to a calculation unit 13, which is a calculation means, and the calculation unit 13 calculates the flow rate from the time difference, and displays the flow rate on the display unit 14, which is a display unit.

Reference numeral 15 denotes a zero point correction section, which is composed of a memory 16, an averaging section 17 serving as averaging means, a latch section 18, and a switch circuit 19. The memory 16 stores the time difference determined within a certain period of time (for example, about 10 seconds),
Memories are erased after a certain period of time. The averaging unit 17 calculates the average value of the time differences stored in the memory 16. The switch circuit 19 supplies the average value of the averaging section 17 to the latch section 18 when the zero point correction switch 20 is turned on. The average value output from the averaging section 17 is displayed on the display section 14.
It is also output and displayed.

Furthermore, when the L level is applied to the clock terminal of the latch section 18, the average value from the averaging section 17 is sampled, and the new average value is held even when the level becomes H level, and the new average value is set as the zero point. Remember. Further, a maximum value circuit 25 of maximum value detection means and a minimum value circuit 26 of minimum value detection means are connected to the output terminal of the memory 16. The memory 16 stores the time difference outputted from the time difference detection circuit 12 from the present time to a certain period of time (10 seconds in this embodiment). Therefore, the maximum value circuit 25 detects the maximum value of the time difference between the current time and 10 seconds ago. Also, minimum value circuit 2
6 detects the minimum value of the time difference between the current time and 10 seconds ago.

The output of the maximum value circuit 25 is input to the + terminal of the differential amplifier 27, and the output of the minimum value circuit 26 is input to the - terminal of the differential amplifier 27. Then, the differential amplifier 27 subtracts the minimum value of the - terminal from the maximum value of the + terminal, and the difference (
variation) is displayed on the display unit 14.

28 is a mode changeover switch, and the display section 14
Select the display content from among flow rate, average value, and variation, and switch the display content.

The operation during zero point correction will now be explained. As for the operation during zero point correction, first, a main valve (not shown) provided on the upstream side of the mass flowmeter 1 is closed to make the flow rate zero. When the flow rate is zero, the vibrators 3 and 4 are driven to vibrate the sensor tubes 2 and 3 at a constant frequency, similar to when measuring the flow rate.

Since the flow rate in the sensor tubes 2 and 3 is zero, no Coriolis force is originally generated in the sensor tubes 2 and 3, and the output signals from the pickups 9 and 10 must be output with a time difference of zero. However, if a misalignment occurs between the inlet side of the sensor tubes 2 and 3 due to machining errors in the manifold 4 that supports the sensor tubes 2 and 3, variations in the dimensions of the sensor tubes 2 and 3 themselves, and the effects of temperature, pressure, etc., the flow rate will be reduced. Even though they are zero, a time difference occurs between the output signal of the pickup 9 on the inflow side and the output signal of the pickup 10 on the outflow side.

The time difference when the flow rate is zero is stored in the memory 16.
When the zero point correction switch 20 is turned on, the target range is a certain period of time from the time the switch 20 was turned on, up to 10 seconds in this embodiment,
The time difference within that range is read from the memory 16. The calculated average value is then stored in the latch unit 18 as a new zero point.

When the zero point correction switch 20 is turned on, the output of the switch circuit 19 becomes L level, so the sample signal is given to the clock terminal of the latch section 18, and the new average value from the averaging section 17 is held. be done.

The calculation section 13 calculates the flow rate from the time difference from the time difference detection circuit 12 and the zero point stored in the latch section 18. The zero point stored in the latch unit 18 when the zero point correction switch 20 is turned on as described above is the past average value from the time the switch 20 was operated until 10 seconds ago. Therefore, the zero point can be corrected at the same time as the switch 20 is operated, and there is no need to wait until the new average value is output after the switch 20 is operated. Therefore, the time required to interrupt flow rate measurement for zero point correction is shortened.
The impact on production lines, etc. is minimized.

Here, the external vibration is applied to the sensor tubes 2 and 3.
Consider the case where it is added to Since the pickups 9 and 10 output signals based on the relative displacement of the sensor tubes 2 and 3, external vibrations transmitted to the sensor tubes 2 and 3 are canceled. However, due to variations in the machining accuracy of the sensor tubes 2 and 3, there may be a difference in resonance frequency between the inlet and outlet sides (high-order vibration mode, etc.).
Fluctuations (including bubbles, etc.) in the density of the fluid flowing through the sensor tubes 2 and 3 may occur, which may cause a difference in vibration between the inflow side and the outflow side of the sensor tubes 2 and 3. This deviation between the vibrations of the sensor tubes 2 and 3 appears as a deviation similar to the time difference between the vibrations of the sensor tubes 2 and 3 due to the Coriolis force during flow rate measurement.

The magnitude of the vibration deviation between the sensor tubes 2 and 3 can be confirmed from the output value of the differential amplifier 27. In addition, sensor tube 2 due to external vibration etc.
, 3. If the difference (dispersion) between the maximum and minimum time differences exceeds a certain value, the average value will deviate significantly, and as a result, the zero point mentioned above will also deviate, causing the flow rate measurement accuracy to exceed the allowable range. I end up. In that case, the mass flowmeter becomes a defective product.

[0041] Therefore, the mass flowmeter 1 completed at the factory is attached to a flow rate testing device to perform zero point correction, and
By simply operating the mode selector switch 28, it is possible to easily check the difference (variation) between the maximum value and the minimum value of the time difference. Therefore, the pickup 9,
This eliminates the need for troublesome operations such as connecting the 10 to an oscilloscope, allowing you to check the external vibration suppression ratio in a short time. Furthermore, since variations in the time difference due to external vibration can be confirmed from the numerical values displayed on the display section 14, the vibration characteristics of the sensor tubes 2 and 3 can be accurately known.

Furthermore, when checking the influence of external vibrations at the installation site where the mass flowmeter 1 is actually installed, the variation in the time difference can be displayed on the display section 14 by simply operating the mode changeover switch 28 in the same manner as above. Display.

Further, the above-mentioned variation in time difference can be similarly performed using a microcomputer. Figure 2
indicates processing by a microcomputer.

The configuration of the microcomputer consists of a CPU,
It has the same configuration as a one-chip microcontroller consisting of memory, timer counter, etc. Therefore, the configuration diagram of the microcomputer will be omitted. In FIG. 2, when the power is turned on, the CPU initializes the memory in step S1 (hereinafter the step is omitted) and clears a timer counter for measuring the time difference and time between the outputs of the pickups 9 and 10.

In the next step S2, since the time difference changes every cycle, it is checked whether the vibrations of the sensor tubes 2 and 3 have completed one cycle. And sensor tubes 2 and 3
When the sensor oscillates, the time difference between the inflow and outflow sides of the sensor tubes 2 and 3 caused by the Coriolis force is measured and stored in the memory (S3).

At S4, the mass flow rate is calculated by multiplying the time difference by a certain constant, and the flow rate display is rewritten. Note that the above-mentioned time difference is stored in the memory in chronological order. In the next S5, a certain period of time (
In this embodiment, it is checked whether 10 seconds) have elapsed, and if 10 seconds have not elapsed, the process returns to S2 and repeats the processes of S2 to S5.

In addition, in S5, if 10 seconds have elapsed, the maximum value, minimum value, and average value of the time difference between the output signal from the pickup 9 detected for the past 10 seconds and the output signal from the outflow side pickup 10 are determined. At the same time, the minimum value is subtracted from the maximum value to find the variation in time difference, and these are stored in memory. Subsequently, the display of the variation of the time difference and the average value is rewritten (S7). Then, return to S2, and S2~S
7 is repeated.

Here, when the mode changeover switch 28 is operated, the display content of the display unit 14 is changed from the flow rate display to the display content selected from the above-mentioned time difference variation or average value.
It is changed and displayed based on the value rewritten in step 7.

[0049] Note that the processing in S6 and S7 above is performed in S5, for example.
Instead of determining whether 10 seconds have elapsed in the process, it may be determined whether or not the mode changeover switch 28 has been operated, and the process may be performed only when it is determined that the mode changeover switch 28 has been operated. In this case, in S6, calculation is performed based on the time difference data stored in the memory for 10 seconds before the operation.

In the above embodiment, the difference (variation) between the minimum value and the maximum value input to the differential amplifier 27 is displayed on the display section 14.
However, it is of course not limited to this. For example, in FIG. 1, the signal from the differential amplifier 27 is input to a separately provided comparator circuit, and a reference value (threshold value) at the time of occurrence of an abnormality is set in advance in the comparator circuit. When the maximum value is not exceeded, the display section 14
When the maximum value exceeds the reference value, an abnormality is displayed on the display section 14. In this way, instead of displaying the difference between the maximum value and the minimum value, the display unit 14 may display "abnormal" or "normal" as a judgment result based on the difference.

Alternatively, the differential amplifier 27 may be omitted and the maximum and minimum values may be directly displayed on the display section 14 based on the outputs of the maximum value circuit 25 and minimum value circuit 26.

Furthermore, in the above embodiment, the maximum value of the time difference,
Although the maximum value and the minimum value are detected from among the time differences stored in the memory 16 in order to obtain the minimum value, the present invention is not limited to this. For example, the time difference detected by the time difference detection circuit 12 is detected by the maximum value circuit 25. The maximum value and the minimum value may be detected by inputting the maximum value and minimum value directly to the minimum value circuit 26, and always latching the maximum value and minimum value from among the sequentially input values. In this case, if the latched values are cleared every predetermined time (for example, 5 seconds), the maximum and minimum values can always be updated to the latest values.

FIG. 3 shows a block diagram of a flow rate measuring section 51 of a mass flow meter 50 according to a second embodiment of the present invention.

The mass flowmeter 50 is obtained by replacing the flow rate measurement section 11 of the mass flowmeter 1 of the first embodiment with a flow rate measurement section 51. Therefore, the configuration shown in FIG. 6 is the same configuration as the mass flowmeter 1. Regarding the flow rate measurement section 51, the same components as those of the flow rate measurement section 11 in FIG.

[0055] The flow rate measurement unit 51 has the following functions for the flow rate measurement unit 11:
Roughly, determination means 52, inspection range truncation circuit 33, integration unit 3
4. Display switching means 53a is added, and display section 1 of the display means is added.
4 is changed to the display section 53b, and the mode changeover switch 28
has been changed to a mode changeover switch 28' serving as a changeover means.

The determining means 52 includes an inspection range setting circuit 30 and an output range determining circuit 31.

A certain reference value is set in the inspection range setting circuit 30 for distinguishing between the "inspection range" and the "measurement range".

The output range judgment circuit 31 receives the output signal of the calculation result of the calculation unit 13 which is the calculation means, and the output value exceeds a certain reference value set in the inspection range setting circuit 30. ” or within the “inspection range” within a certain reference value, and if the value is determined to be within the “measurement range”, it outputs an “H” signal and '', an "L" signal is output to the display switching command circuit 32 and inspection range cutoff circuit 33 of the display switching means 53a.

[0059] Here, the term "measurement range" refers to a range in which the value of the calculated output of the mass flow rate, that is, the output value of the calculation unit 13 is a constant reference value, for example, in the case of this embodiment, the full scale of the mass flow meter 50. If it exceeds 1%, it is determined that fluid is flowing through the mass flowmeter 50, that is, the flow rate is not zero, and this range is treated as a valid mass flow rate value.

[0060] Also, the "inspection range" means that if the calculated output value of the mass flow rate is within 1% of the full scale of the mass flowmeter 50, which is the above-mentioned constant reference value, the fluid is flowing through the mass flowmeter 50. In other words, the flow rate is determined to be zero, and the value is not an effective mass flow rate value, but is within the range of being treated as an error value caused by, for example, external vibration or product manufacturing error.

The display switching means 53a includes a display switching command circuit 32 which receives a switching signal from the mode switching circuit 28' of the switching means and a signal from the output range judgment circuit 31 of the discrimination means 52, and display switching devices 35, 37. Therefore, the display section 53b of the display means consists of the displays 36 and 38.

The display switching command circuit 32 constitutes a logical sum (OR) circuit, and the output range judgment circuit 3 of the judgment means 52
1 and a signal from the mode switching circuit 28', if both signals are "L", a "L" signal is sent to the display switch 35; otherwise, a "H" signal is sent to the display switch 35. Output to 37. Here, the mode changeover switch circuit 28' of the changeover means outputs an "L" signal when the mode changeover switch 29 is on, indicating that a switching signal is present, and outputs an "H" signal, indicating that there is no switching signal, when it is off. do.

The display switch 35 outputs the output A of the integrating section 34,
That is, the integrated flow rate value and the output signal B of the averaging section 17, which is the averaging means of the zero point correction section 15, that is, the average value are input,
If the signal from the display switching command circuit 32 is "H", output A is displayed on the display 36, and if it is "L", output B is displayed on the display 36. In addition, the display switch 37 outputs the output signal A of the inspection range cutting circuit 33, that is, the instantaneous flow rate value, and the signal B from the differential amplifier 27.
That is, if the difference (variation) between the maximum value and the minimum value is input, and the signal from the display switching command circuit 32 is "H", the output A
is “L”, output B is displayed on the display 38.

[0064] Here, the output A is the "measurement output" that is displayed in the "measurement mode" in which the mass flow rate is measured when fluid is flowing through the mass flowmeter 50, and in the case of this embodiment, These are the integrated flow rate value and the instantaneous flow rate value.

[0065] Output B is the "inspection output" that is displayed in the "inspection mode" in which error values caused by external vibrations, etc. are measured when no flow is flowing through the mass flowmeter 50. In the case of the example, it is the average value and the difference (variation) between the maximum value and the minimum value.

The inspection range truncation circuit 33 receives the output from the calculation unit 13 in response to the judgment result that the output of the output range judgment circuit 31 of the judgment means 52 is "H", that is, in the "measurement range" and that fluid is flowing. Print the output as is. In addition, determination means 5
In response to the judgment result that the output of No. 2 is “L”, that is, the “inspection range”, and the fluid is not flowing, the output from the calculation unit 13 is set to the value “0”, so that the output A, that is, the “measurement output” The instantaneous flow rate value and the integrated flow rate value are set to "0".

Next, the operation of the flow rate measuring section 51 having the above configuration will be explained. However, the operations of the same components as the flow rate measuring section 11 of the first embodiment are the same as those of the flow rate measuring section 11, and the explanation thereof will be omitted.

First, when fluid is flowing through the mass flowmeter 50, the output of the calculation section 13 is within the "measurement range", that is, the range exceeding 1% of the full scale set as a certain reference value.

Therefore, the output range determining circuit 31 of the determining means 52 outputs an "H" signal.

Display switching means 53a receiving this output signal
Since the display switching command circuit 32 is an OR circuit as described above, it outputs an "H" signal regardless of the presence or absence of a switching signal from the mode switching switch 29 of the switching means.

Further, when the inspection range truncation circuit 33 receives an "H" signal from the output range judgment circuit 31, the calculation section 13
Outputs the output as is.

Furthermore, the display switching devices 35 and 37 which received the "H" signal from the display switching command circuit 32 respectively switch the "A" output "
The measured output, that is, the integrated flow rate value and the instantaneous flow rate value are displayed on the displays 36 and 38, respectively.

Next, when no fluid is flowing through the mass flowmeter 50, the output of the calculation section 13 is set as the "test range" set in the test range setting circuit 30 of the determining means 52, that is, as a constant reference value. Therefore, the output range judgment circuit 31 outputs an "L" signal.

At this time, if the mode changeover switch 29 of the changeover means is on, that is, the "inspection mode" is selected, an "L" signal is output indicating that a changeover signal is present, and this signal and the output range judgment circuit 31 output a "L" signal. The display switching command circuit 32 of the display switching means 53a that receives the "L" signal outputs an "L" signal.

Further, when the inspection range truncation circuit 33 receives the "L" signal from the output range judgment circuit 31, the test range truncation circuit 33 outputs the value "0".
Output. Therefore, the instantaneous flow rate value and the integrated flow rate value which is the output of the integrating unit 34 become "0".

Display switching command circuit 3 of display switching means 53a
The display switchers 35 and 37 which received the "L" signal from 2 display the "test output" of the B output, that is, the average value and the difference (variation) between the maximum value and the minimum value, on the display devices 36 and 38, respectively. do.

If the mode changeover switch 29 is off, that is, the "measurement mode" is selected, a "H" signal is output as there is no switching signal, and this signal and "L" from the output range judgment circuit 31 are output. The display switching means 5 receives the signal of
Since the display switching command circuit 32 of 3a is an OR circuit, "
Outputs a “H” signal.

Accordingly, the display switching devices 35 and 37 that receive this "H" signal select the "measurement output", that is, the integrated flow rate value and the instantaneous flow rate value, respectively. However, the integrated flow rate value and the instantaneous flow rate value are "0" due to the function of the inspection range truncation circuit 33, so the displays 36 and 38 respectively show this "0" value.
” is displayed.

FIG. 4 shows a block diagram of a flow rate measuring circuit 61 of a mass flow meter 60 according to a third embodiment of the present invention. The mass flowmeter 60 is the display switching command circuit 32 of the display switching means 53a of the flow rate measurement circuit 51 of the mass flowmeter 50 of the second embodiment.
becomes the display switching command circuit 40, and the display switching means 63a
It became. Furthermore, the mode changeover switch circuit 2 of the changeover means
An inverter circuit 39 is inserted between the display switching command circuit 8' and the display switching command circuit 40. The configuration other than these differences is the same as that of the mass flowmeter 50, and the same components are denoted by the same reference numerals, and their descriptions and operations will be omitted.

Display switching means 6 of flow rate measuring circuit 61 in FIG.
The display switching command circuit 40 of 3a is constituted by an RS latch circuit, the signal from the mode changeover switch 29 is inverted and inputted to the R terminal via the inverter circuit 39, and the output range judgment circuit 31 of the discriminating means 52 is input to the S terminal. The branch signal of the output circuit is input.

Here, when the "L" signal is input to the S terminal, the display switching command circuit 40 of the RS latch circuit
When the “H” signal is input to the terminal, it outputs the “L” signal,
Even if the "H" signal of the R terminal changes to "L" signal after that,
The output is “L” unless an “H” signal is input to the S terminal.
The signal is preserved. Also, when an “L” signal is input to the R terminal, if an “H” signal is input to the S terminal, the signal goes “H”.
Even if the "H" signal at the S terminal changes to an "L" signal after a signal is output, the "H" signal is maintained at the output unless an "H" signal is input to the R terminal.

[0082] When the mode changeover switch 29 is on, that is, "
“L” with switching signal when “inspection mode” is selected
A signal is output, which is inverted by the inverter circuit 39 to become an "H" signal, which is input to the R terminal of the display switching command circuit 40. At this time, if fluid is not flowing through the mass flowmeter 60 and therefore the output of the output range determination circuit 31 of the determination means 52 is "L", the display switching command circuit 40
The output of becomes “L”, and then the mode changeover switch 29
is turned off and the output of the mode switching circuit 28 becomes "H" without a switching signal, which is inverted by the inverter circuit and input as an "L" signal to the R terminal of the display switching command circuit 40. The output is held at “L” and “
The "inspection output", that is, the average value and the difference (variation) between the maximum value and the minimum value, are kept displayed.

In this state, fluid is flowing through the mass flowmeter 60, the output of the calculation section 13 is in the "measurement range", that is, a range exceeding 1% of the full scale, and the output range judgment circuit 31 of the discrimination means 52 is " It is held until the L" signal is output.

Therefore, when an instantaneous switch, that is, a switch that is turned on only when pressed and turned off when the finger is released, is used as the mode changeover switch 29 of the changeover means, the mode changeover switch is activated when fluid is not flowing through the mass flowmeter 60. By pressing once, the display of "Test output" will be maintained even if you release your finger afterwards. Further, when fluid is flowed through the mass flowmeter 60, the "
The mode switches from "inspection mode" to "measurement mode" and switches to the display of "measurement output."

Furthermore, the automatic switching between the above-mentioned "inspection mode" and "measurement mode" can be similarly performed using a microcomputer.

FIG. 5 shows processing by a microcomputer.

The configuration of the microcomputer is the same as that described in the first embodiment, and may include the functions of the first embodiment.

In FIG. 5, steps S1 to S4 are the same as those described in the flowchart of FIG. 2 of the first embodiment, and will therefore be omitted here.

[0089] In step S15 (the step will be omitted hereinafter), the determining means determines whether the calculation result in S4 is a "measurement range" or an "inspection range".

[0090] Here, if it is determined YES in the determination branch as to whether or not it is within the "inspection range", that is, it is determined that no fluid is flowing into the mass flowmeter, that is, the flow rate is zero, then the process proceeds to step S16.
Then, the mass flow rate value of “measurement output” becomes “0”. Furthermore, S1
In 7, switch input is used as display switching means, or "inspection mode" is selected according to pre-programmed steps.
or "measurement mode". Here, if the determination as to whether or not it is "inspection mode" is YES, that is, "inspection mode" is selected, in S18, an inspection mode flag is set as a display switching means, so that "inspection output" is selected.
is selected, and the average value and variation are displayed on the display unit 53b of the display means in S20.

If the zero point correction switch is pressed in S22, the zero point correction value is rewritten in S23, and the process returns to S2. Further, if the zero point correction switch is not pressed in S22, the process directly returns to S2.

After returning to S2, the above-described operations are repeated.

[0093] In addition, if the determination in S15 is NO whether it is in the "inspection range", that is, the fluid is flowing through the mass flowmeter and the mass flow rate is in the "measurement range", or if the determination in S17 is in the "inspection mode" If the selection is NO, that is, the "measurement mode" is selected, the inspection mode flag is cleared in S19, and the integrated flow rate value and instantaneous flow rate value of the "measurement output" are displayed in S21.

However, at this time, if it is determined in S15 that it is in the "inspection range" and the mass flow rate value is set to the value "0" in S16, the value "0" is displayed for both the integrated flow value and the instantaneous flow rate value. .

[0095]

As described above, according to claim 1, the mass flowmeter according to the present invention displays variations in the time difference between the output signal of the inflow side pickup and the output signal of the outflow side pickup. , the presence or absence of abnormal vibration of the sensor tube due to external vibration or fluid density fluctuation can be easily confirmed. Moreover, since the time difference between the inflow and outflow sides generated in the sensor tube due to external vibration can be quantitatively determined, the influence of external signals (external signal suppression ratio) can be determined by applying the same external noise at the factory. can be accurately inspected. Another advantage is that it is possible to easily check how external vibrations have changed due to piping conditions, etc. at the installation site.

According to claim 2 or 3, only when it is determined that the fluid is not flowing (flow rate is zero), the switching signal is supplied from the switching means, so that the variation or the average value, that is, the "test output" When it is determined that the fluid is flowing, the display automatically switches to displaying the flow rate, that is, the "measurement output", which prevents the error of misreading the "inspection output" as the "measurement output". It has the advantage of being able to prevent

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a flow rate measuring section 11 according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining processing executed by a microcomputer in the first embodiment of the present invention.

FIG. 3 is a block diagram of a flow rate measuring section 51 according to a second embodiment of the present invention.

FIG. 4 is a block diagram of a flow rate measuring section 61 according to a third embodiment of the present invention.

FIG. 5 is a flowchart for explaining processing executed by a microcomputer in second and third embodiments of the present invention.

FIG. 6 is a perspective view of a mass flowmeter 1 according to a first embodiment of the present invention.

[Explanation of symbols]

1, 50, 60 Mass flowmeter 2, 3 Sensor tube 9, 10 Pickup 11, 51, 61 Flow rate measuring section 12 Time difference detection circuit 13 Computing section (computing means) 14, 53b Display section (display means) 15 Zero point correction section 16 Memory 17 Averaging section (averaging means) 18 Latch section 19 Zero point correction switch circuit 20 Zero point correction switch 23, 24 Exciter 25 Maximum value circuit (Maximum value detection means) 26 Minimum value circuit (Minimum value detection means ) 27 Differential amplifier 28, 28' Mode changeover switch circuit (switching means)
29 Mode changeover switch (switching means) 30 Inspection range setting circuit 31 Output range judgment circuit 32 Display switching command circuit (OR) 33 Inspection range cut-off circuit 34 Integration section 35, 37 Display switch 36, 38 Display 39 Inverter circuit 40 Display switching command circuit (RS latch) 52 Discrimination means 53a, 63a Display switching means 53b Display means

Claims (3)

[Claims] 1. A sensor tube through which a fluid to be measured flows, an exciter that vibrates the sensor tube at a predetermined frequency, a pair of pickups that detect displacement on the inflow side and outflow side of the sensor tube, maximum value detection means for detecting the maximum value of the time difference between the output signal of the inflow side pickup and the output signal of the outflow side pickup; minimum value detection means for detecting the minimum value of the time difference; and output from the maximum value detection means. 1. A mass flowmeter comprising display means for displaying the maximum value output from the minimum value and the minimum value outputted from the minimum value detection means, or the difference thereof, or a judgment result based on the difference. 2. A sensor tube through which a fluid to be measured flows, an exciter that vibrates the sensor tube at a predetermined frequency, a pair of pickups that detect displacement on the inflow side and outflow side of the sensor tube, and maximum value detection means for detecting the maximum value of the time difference between the output signal of the inflow side pickup and the output signal of the outflow side pickup; minimum value detection means for detecting the minimum value of the time difference; a calculation means for calculating a flow rate value; and a maximum value output from the maximum value detection means and a minimum value output from the minimum value detection means, or a difference thereof, or a judgment result based on the difference, or a judgment result calculated by the calculation means. a display means for displaying a flow rate value; a switching means for outputting a switching signal for switching the flow rate value displayed on the display means to display the maximum value, the minimum value, the difference thereof, or a judgment result based on the difference; A discriminating means for discriminating that the flow rate is zero only when the time difference is less than a certain reference value, and a switching signal from the switching means are supplied to the display means to display the maximum value and the minimum value or the difference therebetween. and display switching means for switching the display to display the flow rate value on the display means when the determination means determines that the flow rate is not zero when the determination result based on is displayed. mass flow meter. 3. A sensor tube through which a fluid to be measured flows, an exciter that vibrates the sensor tube at a predetermined frequency, a pair of pickups that detect displacement on the inflow side and outflow side of the sensor tube, and averaging means for calculating the average value of the time difference between the output signal of the inflow side pickup and the output signal of the outflow side pickup; a calculation means for calculating a flow rate value flowing through the sensor tube from the time difference; and an output from the averaging means. display means for displaying the average value calculated by the calculation means or the flow rate value calculated by the calculation means, switching means for outputting a switching signal for switching the flow rate value displayed on the display means to display the average value, and the time difference. a determining means that determines that the flow rate is zero only when the flow rate is less than a certain reference value; and a determining means that determines that the flow rate is zero only when the average value is displayed on the display means by supplying a switching signal from the switching means. 1. A mass flowmeter comprising: display switching means for switching a display to display the flow rate value on the display means when the flow rate is determined to be not zero.