JPH0221531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an eddy flow rate inspection method that enables constant monitoring of whether the amplitude ratio between the maximum amplitude and the minimum amplitude of the eddy signal obtained from the vortex flowmeter under inspection is within a predetermined range. Regarding equipment.

As a testing device for a vortex flowmeter, for example, a reference device such as a reference wet gas meter is placed in the same flow path as the vortex flowmeter to be tested, and the frequency of the vortex signal obtained from the vortex flowmeter to be tested is measured when fluid flows through the vortex flowmeter. Generally, the instrumental error is determined by measuring the flow rate of the flow rate, etc., and comparing it with the specified flow rate value of the reference path. However, the vortex signal obtained from the vortex flowmeter may have some amplitude fluctuation over time due to various factors. For example, abnormally large amplitude fluctuations may occur due to manufacturing defects or improper installation when mounting on an inspection device. Therefore, when this amplitude fluctuation is large, it means that the inspection condition is not normal or that the vortex flowmeter to be tested is defective. Also, because the amplitude fluctuation is too large, the minimum amplitude is beyond the capability of the measuring instrument. If it falls below the threshold, a miscount will occur during testing, resulting in erroneous test results.

For this reason, conventionally, during inspection, amplitude fluctuations of the vortex signal have been constantly monitored using, for example, an oscilloscope during the inspection period.

However, as vibration fluctuations may suddenly decrease in amplitude for a short period of time, there are limits to human monitoring ability, and it is difficult to completely visually inspect such amplitude fluctuations using an oscilloscope, etc. Not only is it impossible to completely eliminate errors in the test results, but the labor required by the tester is extremely large, and large instruments such as oscilloscopes are indispensable for the test. Therefore, there was a problem that the overall configuration of the inspection device became large.

The present invention has been made to solve the above-mentioned disadvantages, and an object of the present invention is to provide a vortex flowmeter inspection device equipped with an amplitude fluctuation monitoring circuit that does not require a measuring instrument such as an oscilloscope during inspection.

Another object of the present invention is to obtain error-free test results and lighten the burden on the tester by completely monitoring the amplitude fluctuations of the vortex signal during the test time without involving the tester. An object of the present invention is to provide a vortex flow meter inspection device that can improve work efficiency.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of a vortex flowmeter inspection device in which a sonic nozzle is used to obtain a constant flow rate. In the figure, reference numeral 1 denotes a vortex flowmeter to be inspected placed in the flow path, and an air filter 2 is provided on the upstream side of the vortex flowmeter. Reference numeral 3 denotes a reference flow rate section capable of obtaining an accurate constant flow rate, and includes, for example, a plurality of sonic nozzles 4 each having a different flow rate value, which can be selected as required. Reference numeral 5 denotes a vacuum pump, which is disposed on the downstream side of the same flow path as the air filter 2, the vortex flowmeter to be inspected 1, and the reference flow section 3, so that the fluid can flow through the flow path. There is.

Reference numeral 7 indicates a control section, and 8 indicates an inspection section that receives the vortex signal and measures and inspects the flow rate value. Reference numeral 9 denotes an amplitude fluctuation monitoring section, which is a feature of the present invention, and is capable of constantly monitoring whether the amplitude fluctuation of the vortex signal exceeds a desired set value during the inspection period.

An example of a specific configuration of this amplitude fluctuation monitoring section 9 is shown in FIG. In the figure, numeral 10 is a full-wave rectifier circuit that outputs the absolute value of an alternating current vortex signal that changes from positive to negative. 11 and 12 are first and second peak hold circuits, respectively, and have set input terminals 11a, 12a and set input terminals 11b, 12.
It is equipped with b. 13 is a conversion circuit that converts the output signal of the first peak hold circuit 11 into a desired value, and 14 is a set input terminal 11 at a desired setting time.
15 is a timer circuit that outputs a signal to a, and 15 is a reset input terminal 12 when the amplitude of the vortex signal becomes zero.
b is a zero level detection circuit that generates a reset signal; 16 and 17 are first and second comparison circuits (comparators), respectively; 18 is an AND circuit;
9 is a flip-flop circuit.

The operation of the amplitude fluctuation monitoring section 9 will be explained based on the time charts shown in FIGS. 3 and 4.

The input vortex signal A is rectified by the full-wave rectifier circuit 10 and becomes an absolute value signal B. When the test is started, a reset signal C is applied to the reset input terminal 11b, and at the same time, the timer 14 starts operating. At this time, the output signal D of the first peak hold circuit 11 is sequentially updated to the maximum peak value as the peak value of the absolute value signal B changes. Here, a predetermined time t (for example, 2
seconds), the output signal D is maintained at the maximum peak value V _M within the predetermined time t.

E is a comparison signal obtained by passing the output signal D of the first peak hold circuit through the conversion circuit 13,
If the amplitude ratio of the minimum and maximum allowable vortex signals is R _O , that is, Vmin/Vmax = R _O , then V _MO = V _M
×R _O level is set. F is the output signal of the second peak hold circuit, which is set by the output signal G of the first comparison circuit 16, reset by the output signal H of the zero level detection circuit 15, and is reset during other times, that is, the reset is released. During the period from when it is set to when it is set, it follows the absolute value signal B, so it has a waveform as shown in the figure. J is the second comparison circuit 17
, K is the output signal of the AND circuit 18, and L is the output signal of the AND circuit 18.
is the output signal of the flip-flop circuit 19.

Here, V _MO is the minimum allowable peak value with respect to the maximum peak value V _M , so if it is smaller than the peak value V _MO in each period of the absolute value signal B, the vortex signal A
This means that the amplitude fluctuation is abnormal.

In FIG. 4, the output signal G of the first comparison circuit
indicates the period during which the output signal F of the second peak hold circuit holds the peak value of the absolute value signal B, and the output signal J of the second comparison circuit 17 is the output signal F of the second peak hold circuit. Since the level of the signal F is lower than the level V _MO of the comparison signal E, the first
It can be seen that the output signal K of the AND circuit 18 inputting the output signal G of the second comparison circuit and the output signal J of the second comparison circuit indicates that the amplitude fluctuation of the vortex signal A is abnormal. Further, the output signal L of the flip-flop circuit changes its state when an abnormality occurs and also stores and holds this state.

Therefore, the overall operation of the inspection device is to select a desired one of the sonic nozzles 4 of the reference flow section 3 to open the flow path, and to cause the fluid to pass through the flow path at a saturated flow rate using the vacuum pump 5. If so, the flow rate at this time is determined by the sonic nozzle, and since the accurate flow rate can be known, inspection can be performed using this flow rate as a reference. The vortex signal from the vortex flow meter 1 to be tested is compared with the reference value in the inspection section 8. At this time, since the vortex signal A is also added to the amplitude fluctuation monitoring section 9, the amplitude fluctuation of the vortex signal is constantly monitored during the inspection, as described above.

Although the full-wave rectifier circuit 10 is provided in the above embodiment, a configuration may be adopted in which this is not provided. Further, although the output signal of the first peak hold circuit is configured to hold the maximum peak value within a predetermined time, the configuration is such that this can be updated at any time during the inspection without providing the timer circuit 14. You can also use it as Furthermore, although the absolute value signal B is added to the input of the zero level detection circuit 15, the vortex signal A may be directly input.

According to this invention, since the amplitude fluctuation monitoring circuit is provided to automatically monitor the amplitude fluctuation of the eddy signal, an oscilloscope is not required, and the inspection equipment can be made smaller without taking up space. The burden on the examiner is extremely light because such complicated operations and the work of gazing at the cathode ray tube are no longer necessary. In addition, since the amplitude fluctuation of the vortex signal can be electrically monitored reliably, there is no error caused by miscounting, and it is possible to completely prevent erroneous operation due to improper installation of the vortex flowmeter to be inspected during inspection. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the vortex flow meter inspection device according to the present invention, FIG. 2 is a block diagram showing the specific configuration of an amplitude fluctuation monitoring circuit, and FIGS. 3 and 4 are 3 is a time chart for explaining the operation of the amplitude fluctuation monitoring circuit. 1...Vortex flow meter to be inspected, 4...Sonic nozzle, 5
...Vacuum pump, 9...Amplitude fluctuation monitoring section, 11...
...First peak hold circuit, 12... Second peak hold circuit, 13... Conversion circuit, 16...
1st comparison circuit, 17... second comparison circuit.

Claims (1)

[Claims] 1. In a vortex flowmeter that measures the flow rate of gas flowing at a standard flow rate and compares the measured value with the standard flow rate,
full-wave rectifier means for full-wave rectifying the vortex signal transmitted from the vortex flowmeter; a timer circuit that determines a monitoring time for the full-wave rectified signal; and a timer circuit that maintains the maximum value of the full-wave rectified signal within the monitoring time. a first peak hold circuit; a conversion circuit that determines a minimum value limit of the full-wave rectified signal with respect to a stored value of the first peak hold circuit;
a second peak hold circuit that holds a maximum amplitude value for each half-wave signal of the full-wave rectified signal, and the output of the second peak hold circuit and the full-wave rectified signal are compared and the second peak hold circuit is reset. a first comparison circuit that transmits a reset signal; a second comparison circuit that compares the output of the second peak hold circuit with the output of the conversion circuit; and the output of the second comparison circuit and the output of the second peak hold. 1. A vortex flowmeter inspection device comprising a flip-flop circuit that issues an alarm that the vortex signal is abnormal when the vortex signals match.