JPH06331416A - Device for detecting quantity of state of liquid - Google Patents

Abstract

PURPOSE:To obtain the complicated conversion calculation output of quantity of state of liquid in high accuracy in a liquid state quantity detecting device and simplify the instrumentation. CONSTITUTION:The title device is provided with a plurality of pressure sensors 1, 2 and 3 which are independently fitted to a tank 4, a converter 5 which is connected with the sensors 1, 2 and 3 through a multi-drop communication means 6 and converts the pressure signals detected by the sensors 1, 2 and 3 in order to calculate respective quantities of state of liquid within the rank 4, and a man-machine interface 7 which is provided onto the converter 5 and is composed of a display 9 for indicating the operation state of the converter 5 and a switch 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid state quantity detecting device for detecting various state quantities such as level, density, capacity, differential pressure or static pressure of a liquid in a tank.

[0002]

2. Description of the Related Art FIG. 13 is a block diagram showing a first example of a conventional liquid state quantity detecting device. FIG. 14 is a block diagram showing a second example of a conventional liquid state quantity detection device.
FIG. 15 is a block diagram showing a third example of a conventional liquid state quantity detecting device. FIG. 16 is a block diagram showing a fourth example of a conventional liquid state quantity detection device. FIG. 17 is a block diagram showing a fifth example of a conventional liquid state quantity detection device. In FIG. 13, 4 is a sealed tank, 1 is a static pressure sensor provided on the peripheral wall of a portion located approximately in the middle of the tank 4, and 2 is a differential pressure type pressure provided with detection ends at the upper and lower parts of the tank 4, respectively. A sensor (differential pressure sensor) 29 is a sensor power source connected to the static pressure sensor 1 and the differential pressure sensor 2. Reference numeral 18 denotes an input control device connected to the output ends of the static pressure sensor 1 and the differential pressure sensor 2, and is composed of, for example, a programmable logic controller. Reference numeral 22 is a host processor connected to the output terminal of the analog input controller 18, which is, for example, a personal computer.

In FIG. 13, when measuring the liquid level in the tank 4, the differential pressure in the tank 4 is measured by the differential pressure sensor 2, and the static pressure in the tank 4 is measured by the static pressure sensor 1. The current or voltage signals from these sensors 1 and 2 are input to an analog module or the like of the input control device 18,
The data analog-digitally converted by this module is sent to the host processor 22, and the host processor 22 converts the data into a necessary state quantity such as capacity.

In FIG. 14, 5a is a first converter, 5a
b is a second converter. And these converters 5a,
5b converts the analog signals from the sensors 1 and 2 into digital signals.

In FIG. 14, when measuring the liquid level in the tank 4, the differential pressure in the tank 4 is measured by the differential pressure type pressure sensor 2
And the static pressure inside the tank 4 is measured by the static pressure sensor 1, and the static pressure and current or voltage signals from the differential pressure sensors 1 and 2 are input to the signal converters 5a and 5b. After the signal converters 5a and 5b convert the necessary state quantities, the signal is input to the input control device 18, that is, the programmable logic controller. This input control device 18
In (1), analog-to-digital conversion is performed, and the converted data is sent to the host processor 22.

In FIG. 15, first, second and third gauge pressure sensors 1, 2 and 3 are attached to the peripheral wall of a portion of the tank 4 located approximately in the middle thereof and to the upper and lower portions of the tank 4. . The first gauge pressure sensor 1 is the first signal converter 5
Input terminal of a and upper input control device (upper controller)
18, the second gauge pressure sensor 2 is connected to the input terminal of the first signal converter 5a, and the third gauge pressure sensor 3 is connected to the first signal converter 5a and the second signal converter 5a. It is connected to the input end of the device 5b. The output terminal of the first signal converter 5a is connected to the input control device 18 and the input terminals of the third signal converter 5c. The output terminal of the second signal converter 5b is connected to the input terminal of the third signal converter 5c. The output terminal of the third signal converter 5c is connected to the input terminal of the fourth signal converter 5d, and the fourth signal converter 5d is connected to the input control device 18.

In FIG. 15, the first gauge pressure sensor 1
The static pressure of the liquid in the tank 4 is output to the input control device 18, and the density of the liquid in the tank 4 is output to the input control device 18 by the first signal converter 5a. Also the first
The third signal converter 5c outputs the liquid level to the input control device 18 based on the density of the liquid from the signal converter 5a and the differential pressure from the second signal converter 5b. Further, the capacity of the tank 4 is output by the fourth signal converter 5d. In this example, it is possible to measure the density of the liquid as compared with the configurations shown in FIGS.

In these conventional examples 1, 2, and 3, (a) a large number of devices are required for instrumentation, and a large space is required.
The cost is high. (B) The number of wires is large and the work cost is high. (C) The signal paths are all analog, and the accuracy capability of the sensor is not exhausted. (D) There are many adjustment points and the instrumentation cost is high.

Next, as shown in FIG. 16, the output ends of the gauge pressure sensors 1, 2 and 3 are connected to an interface unit 30 having a scanning function via a first communication means 6a, and the first communication means 6a. The upper controller 1
8 via the second communication means 6b.

FIG. 17 has the same structure as that shown in FIG. 16, except that the signals of the gauge pressure sensors 1, 2, 3 are sent to the interface unit 30 by the first communication means 6a. Is sent to the host controller 18 by the second communication means 6b, and all adjustments, conversions and calculations are performed by the host controller 18.

As shown in FIGS. 16 and 17, (a) the function of the host controller 18 is increased and the cost becomes high. (B) If the communication physical layer and application layer are not disclosed, the sensor or controller of the same manufacturer must be used for refurbishment. (C) On the contrary, when the physical layer and the application layer are open to the public, it is necessary for the user or the maker to create software for adjustment and exchange calculation in accordance with the controller. (H) Since the communication means is interposed twice, the real-time property of the conversion state quantity is reduced accordingly.

[0012]

Since the conventional liquid state quantity detecting device is constructed as described above, a large number of instruments are required for instrumentation, a large space is required, a large number of wirings are required, and working cost is high. Is high. Moreover, the signal paths are all analog, and the accuracy capability of the sensor is not exhausted. Furthermore, there are problems that there are many adjustment points and the cost of instrumentation is high. In addition, the function performed by the communication means increases the function of the host controller and becomes expensive, and when the physical layer and application layer of the communication means are not disclosed, the sensor or controller of the same manufacturer must be used for refurbishment. On the contrary, when the physical layer and the application layer are open to the public, the user or the maker has to create the software for the adjustment and exchange operation in accordance with the controller. Further, since the communication means is used twice, there is a problem that the real-time property of the conversion state quantity is deteriorated by that amount.

The present invention is intended to solve the above-mentioned problems of the prior art, obtains a complicated conversion operation output of the state quantity with high accuracy, and simplifies the instrumentation of the liquid state quantity detecting device. That is the purpose.

[0014]

A liquid state quantity detecting device according to the present invention is provided with a plurality of independent pressure sensors mounted on a tank, and these pressure sensors are connected by a communication means and detected by the pressure sensors. A converter that converts and calculates from the pressure signal to each state quantity of the liquid in the tank,
And a man-machine interface provided with a switch and a switch, which is provided in the converter and displays an operating state of the converter.

[0015]

In the liquid state quantity detecting device according to the present invention, the detection signals from a plurality of independent pressure detectors are sent to the converter by the communication means which communicates with these pressure detectors independently or by multi-drop. . The pressure signal input to this converter is calculated by that converter, and further digitally converted into each state quantity of liquid level, density, differential pressure and static pressure in the tank with high precision, and obtained by this conversion processing. The state quantity is converted into an analog quantity and output.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a liquid state quantity detecting device 1 according to the present invention.
It is a block diagram showing an example of composition. In the figure, 1, 2,
Reference numeral 3 denotes a pressure sensor, which is an independent three gauge pressure type pressure sensor, like the pressure sensors shown in FIGS. 4 is a tank having a closed structure. The pressure sensors 1, 2, and 3 are IDFs whose liquid contact shape is sanitary standardized.
It is attached to the tank 4 with a ferrule, flange, or non-standard, but tank spud attachment structure.
This mounting structure is particularly advantageous when used for food applications. The converter 5 is connected to the pressure sensors 1, 2, 3 by means of a communication means 6 comprising multi-drop communication. In the converter 5, 7 is a man-machine interface having a key switch 8 and a display 9. 10
Is a CPU connected to the man-machine interface 7,
Reference numeral 11 is a communication interface connected to the CPU 10, similarly 12 is a memory connected to the CPU 10, and 13 is a digital-analog converter connected to the CPU 10.

Next, the operation of the above configuration will be described. In the man-machine interface 7, the control parameter is input in advance by the key switch 8 and stored in the memory 12 via the CPU 10. On the other hand, the tank 4 detected by the pressure sensors 1, 2, and 3
The pressures P1, P2, P3 of the liquid therein are supplied to the converter 5 by means of the communication means 6, i.e. multidrop communication. The supplied pressure signal is received by the communication interface 11 in the converter 5 and supplied to the CPU 10. In the CPU 10, the calculation parameters stored in the memory 12 and the pressure signals obtained from the sensors 1, 2 and 3 are calculated by the communication means 6, and further the liquid level, density, volume and static pressure state quantities are obtained. The converted signal is converted into a current by the digital-analog converter 13 and output to the outside of the converter 5.

FIG. 2 is a block diagram showing a part of the converter 5 of the liquid state quantity detecting device according to the present invention. In the figure, 14 is a differential amplifier, to which the output signals from the pressure sensors 1, 2, 3 are supplied. The output terminal of the differential amplifier 14 is connected to the CPU 10 via the analog-digital converter 15. A first changeover switch 16 is provided between the output terminal and the input terminal of the differential amplifier 14 via resistors r1, r2, and r3, and the differential amplifier 14 is also provided.
A second changeover switch 17 is provided between one of the input terminals and the ground via resistors r4, r5, and r6. These changeover switches 16 and 17 are connected to the CPU 10.

Generally, in the level measurement of the tank 4, there are many applications for measuring that all the liquid in the tank 4 has flowed out. For example, when trying to determine the zero level at a 10 mm liquid level in an open tank with a 3 m liquid level, a sensor having an accuracy of 1/3000 (0.03% FS) is required, but it is not realistic. Therefore, as shown in FIG. 2, a function for changing the amplification factor of the differential amplifier 14 is added inside the detector. Figure 2
In the configuration, when the outputs of the pressure sensors 1, 2, 3 become small, the outputs are input to the differential amplifier 14, converted into a digital amount by the analog-digital converter 15, and supplied to the CPU 10. Pressure sensor 1, 2,
When the output from 3 decreases, a gain switching signal is output from the CPU 10 to the selector switches 16 and 17. As a result, the resistors r1, r2, r3, r
4, r5, r6 are switched, and the amplification factor of the differential amplifier 14 increases. That is, the pressure sensors 1, 2, 3 themselves switch the amplification factor of the differential amplifier 14 to increase the amplification factor, thereby equivalently increasing the detection accuracy in the vicinity of the minute pressure. As a result, the zero level determination is performed with high accuracy.
There are various methods for changing the amplification factor, and the method is not limited to this embodiment. Further, in the present embodiment, the determination of gain switching is automatically made on the detector side, but it can be made by an instruction by communication from the converter 5 side.

FIG. 3 is a characteristic diagram showing a temporal change in the tank capacity calculated by the CPU 10. The amount of liquid flowing in or out of the tank 4 shown in FIG. 1, that is, the flow rate, changes with time as shown by the characteristic curve in FIG.
This change is transmitted to the converter 5 by the pressure sensors 1, 2, and 3. In the converter 5, the CPU 10 uses the calculating means to calculate the change amount ΔV of the capacity value of the tank 4 per unit time.
1, ΔV2, ΔV3 are calculated. The calculation result is output from the converter 5.

FIG. 4 is a flow chart of zero adjustment of the pressure sensor. The pressure sensors 1, 2, and 3 shown in FIG. 1 are ordinary pressure sensors. In this type of pressure sensor, the pressure sensor element is generally separated by a stainless diaphragm to expand the object to be used, and oil is sealed as a pressure transmission medium inside the diaphragm. If a pressure sensor of this type has a different attitude during the adjustment work during production and the attitude during installation at the site, offset pressure will be generated due to the self-weight of the oil enclosed inside it, so it will be installed at the site. At that time, it is necessary to correct the offset pressure. In addition, after installation on site, in regular maintenance,
The pressure sensor is being adjusted to zero. Therefore, when there is an external input to the pressure sensors 1, 2, and 3, that is, when the pressure sensors 1, 2, and 3 enter the operating state, and the pressure is not yet detected, that is, the device to be detected. The pressure PO in the state where is not operating is detected (step 1) and stored in the memory 12. When the apparatus is operating, the pressure P0 in the non-operating state is subtracted from the pressures P1, P2, P3 detected by the pressure sensors 1, 2, 3 (step 2), and this value is used as the true value P (step 3). In FIG. 4, the pressure sensor 1,
Of the pressures P1, P2, P3 detected by a few, only P1 is shown as a representative.

FIG. 5 is an explanatory diagram showing the liquid level in the tank 4. FIG. 6 is a characteristic diagram showing the tank capacity with respect to the liquid level in FIG. In FIG. 5, the tank 4 has a conical shape from the level 0% to the point of L3, and L3 to L4 (10
Up to 0%) is cylindrical. Therefore, the function of the tank capacity with respect to the level is a curve from 0 to L3 and a straight line from L3 to L4. Generally, a line approximation is used for the capacity conversion of the tank 4. The polygonal line approximation is the polygonal line points (L1, V1) of the polygonal line in FIG.
(L2, V2) (L3, V3) (L4, V4) is obtained by manual calculation, or a coefficient pair (ak, bk) between arbitrary levels Lm and Ln of the polygonal line function V = akL + bk is obtained by manual calculation. However, in this embodiment, after the pressure sensors 1, 2, 3 are attached to the tank 4 in the field, a known volume amount (V1, V2, V3, V4) is put into the tank 4 and the volume amount at that time is added. By inputting V1, V2, V3 and V4 to the CPU 10 of the converter 5, the converter 5 side is made to calculate the polygonal line approximated polygonal line points L1, L2, L3, L4 and the coefficient pair (ak, bk) of the polygonal line function. , In the memory 12. This function eliminates the need for the site adjustment operator to perform manual calculation work for capacity conversion, and eliminates the error between the actual tank shape and its drawing. By using a spline function as the above approximation function, it is possible to eliminate the discontinuity that has conventionally occurred at the break point portions (L1, V1) (L2, V2) (L3, V3) and obtain a discontinuous output. You can

FIG. 7 is a flow chart for converting the pressure signal into a level signal. The density value is required when converting a pressure signal into a level signal for calculation or when converting from a volumetric capacity to a mass capacity. Now, a case of converting a pressure signal into a level signal will be described with reference to FIG. In the converter 5, the CPU 10 calculates the density ρ based on the pressure signals P from the pressure sensors 1, 2, and 3 (step 1). Next, by the density ρ, the pressure signal P
The liquid level in the tank 4 is calculated by dividing.

FIG. 8 is an explanatory diagram showing the relationship between the density selection input signal to the converter and the density. FIG. 9 is a flowchart in FIG. The memory 12 in the converter 5 has four densities ρ 0, ρ corresponding to the type of liquid in the tank 4.
1, ρ2, ρ3 are stored in advance. Further, the converter 5 is provided with two density selection input signals a0 and a1 from the outside by remote control or the like. That is, the input of the converter 5 is adjusted according to the type of liquid in the tank 4, and the CPU 10 determines the four densities ρ0 and ρ based on the adjusted values.
Levels L1, L2, L3, L4 for 1, ρ2, ρ3
Is calculated. In this embodiment, the operation is a selective operation from the outside, but the invention is not limited to this, and continuous operation by analog input such as linear input is also possible. In FIG. 9, the pressure P in the tank 4 is measured, and the CPU 10 switches the switches 16 and 17 based on this pressure P to select the density value (step 1). The previous pressure is then divided by the selected density value (step 2). As a result, the level L at that time is calculated (step 3).

FIG. 10 is a characteristic diagram showing the log output of the 4-20 mA output of the converter 5 with respect to the level of the tank 4. As the tank level, it is sometimes necessary to have an accurate resolution in the small signal area. In particular, when the zero level determination is performed with high accuracy without changing the resolution of the analog-digital conversion of the device connected to the subsequent stage of the converter 5, as shown in FIG.
Transform the mA output as a log function.

FIG. 11 is a block diagram of a state quantity detecting device in which various devices are connected to the rear stage of the converter 5. In FIG. 11, various devices such as the first, second and third devices are provided after the converter 5.
Further, the fourth controller 18, 19, 20, 21 and the host processor 22 for monitoring are connected. RS232C host communication means 23 is added to the host processor 22. By this upper communication means 23, this upper processing device 2
2 is placed in, for example, a central monitoring room, the controllers 18, 19 and 2 other than the upper monitoring computer 22.
Each state quantity can be monitored and parameters can be changed independently of 0 and 21.

FIG. 12 is a block diagram showing another embodiment of the liquid state quantity detecting device according to the present invention. In the figure, 23 is a pipe for flowing a liquid, 24 is an orifice provided in the middle of this pipe 23, 25 is a high pressure side pressure sensor attached to the high pressure side of the pipe 23, and 26 is a low pressure side pressure attached to the low pressure side of the pipe 23. A sensor, 27 is a temperature sensor attached to the low pressure side of the pipe 23, and 28 is an atmospheric pressure sensor. These sensors 25, 26, 27, 28 are connected to the input ends of the converter 5. The converter 5 has the same structure as that shown in FIG. In FIG. 12, a high pressure side pressure sensor 25, a low pressure side pressure sensor 26, a temperature sensor 27, and an atmospheric pressure sensor 28.
The output from the sensor 5 is input to the converter 5, and the output from the sensors 25, 26, 27, 28 is high pressure, low pressure, atmospheric pressure, temperature, differential pressure, standard large pressure. Externally output as a volumetric flow rate at atmospheric pressure or reference temperature.

It should be noted that the converter 5 judges that normal operation cannot be expected as a liquid state quantity detection device, and this is displayed.
It has a judging means for displaying and outputting by such as.

The present invention is appropriately implemented by the following embodiments. (1) The liquid state quantity detection device according to claim 1, wherein the liquid contact portion of the detector has a sanitary structure. (2) The liquid state quantity detecting device according to claim 1, further comprising a gain switching means for switching an internal gain on the detector side in order to improve detection accuracy in the vicinity of zero pressure. (3) The liquid state quantity detection device according to claim 1, further comprising means for calculating and outputting a change quantity of the capacity per fixed time. (4) The liquid state quantity detecting device according to claim 1, further comprising adjusting means for adjusting the zero pressure of the detector by remote input from the outside. (5) The parameters required to convert the pressure signal to each state quantity of level, density, and capacity are placed in a known state of level, density, and capacity, and the device to be controlled is placed in that state. 2. The liquid state quantity detection device according to claim 1, further comprising arithmetic means for calculating an appropriate state quantity by inputting the above into the equipment. (6) The liquid state quantity detection device according to claim 1, further comprising switching means for changing the density value used for the conversion calculation by remote input from the outside. (7) The liquid state quantity detection device according to claim 1, further comprising a calculation means using a spline function for the capacity conversion calculation. (8) The liquid state quantity detection device according to claim 1, further comprising a conversion unit configured to log-convert and output current and voltage outputs. (9) The liquid state quantity detection device according to claim 1, further comprising a standardized upper communication means such as RS232C, RS485, GPIB. (10) The liquid state quantity detection device according to claim 1, further comprising event output and window-comparator output means. (11) The liquid state quantity detection device according to claim 1, further comprising a determination unit that determines and outputs as a level sensor that normal operation cannot be expected. (12) The liquid state quantity detection device according to claim 1, comprising the above (1) to (11).

[0030]

As described above, according to the liquid state quantity detecting device of the present invention, a plurality of independent pressure sensors attached to the tank are connected to these pressure sensors by the multi-drop communication means, and the pressure is detected. A converter for converting and calculating each state quantity of the liquid in the tank from the pressure signal of the sensor, and a man-machine interface consisting of a switch and a display provided in the conversion calculating means for displaying the operation state of the calculator. Since it is provided, wiring and instrumentation become very simple, and in the converter, signal deterioration hardly occurs until the CPU calculates each state quantity. Further, since it has an analog output for each state quantity, it is possible to connect a generally inexpensive loop controller in the subsequent stage. Furthermore, by having a man-machine interface,
Adjustments and parameter changes can be made on site easily and without affecting other control loops or sensors. Moreover, there is an effect that the user can freely select the calculation of the pressure, the volume, the flow rate, the density and the like in the field instrument by the configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a liquid state quantity detecting device according to the present invention.

FIG. 2 is a block diagram showing a part of a converter of the liquid state quantity detecting device according to the present invention.

FIG. 3 is a characteristic diagram showing temporal changes in tank capacity.

FIG. 4 is a flowchart of zero adjustment of the pressure sensor.

5 is an explanatory diagram showing the level of liquid in the tank 4. FIG.

FIG. 6 is a characteristic diagram showing the tank capacity with respect to the liquid level in FIG.

FIG. 7 is a flowchart for converting a pressure signal into a level signal for calculation.

FIG. 8 is an explanatory diagram showing the relationship between the density selection input signal to the converter and the density.

FIG. 9 is a flowchart in FIG.

FIG. 10: 4-2 converter 5 to tank 4 level
It is a characteristic view which shows the log output of 0 mA output.

FIG. 11 is a configuration diagram of a level detection device in which various devices are connected to a stage subsequent to the converter 5.

FIG. 12 is a block diagram showing an application example of the liquid state quantity detecting device according to the present invention.

FIG. 13 is a block diagram showing a first example of a conventional liquid state quantity detection device.

FIG. 14 is a block diagram showing a second example of a conventional liquid state quantity detection device.

FIG. 15 is a block diagram showing a third example of a conventional liquid state quantity detection device.

FIG. 16 is a block diagram showing a fourth example of a conventional liquid state quantity detection device.

FIG. 17 is a block diagram showing a fifth example of a conventional liquid state quantity detection device.

[Explanation of symbols]

 1, 2, 3 Pressure sensor 4 Tank 5 Converter 6 Communication means 7 Man-machine interface 8 Switch 9 Display

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuhide Yoshikawa 1-12-2 Kawana, Fujisawa-shi, Kanagawa Yamatake Honeywell Co., Ltd. Fujisawa factory (72) Yoshinori Ito 1-2-2 Kawana, Fujisawa, Kanagawa Yamatake Honeywell Co., Ltd. Fujisawa Factory

Claims (1)

[Claims] 1. A plurality of independent pressure sensors attached to a tank 4 are connected to these pressure sensors by a multi-drop communication means 6, and each state of the liquid in the tank 4 is determined from the pressure signal of the pressure sensor. A liquid state quantity detection device including a converter 5 for converting and calculating an amount, and a display 9 provided on the converter for displaying an operating state of the converter and a man-machine interface 7 including a key switch 8. .