JPH0588770B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pressure gauge capable of switching pressure unit display, and more particularly to an analog/digital converter of a one-chip microcomputer (hereinafter referred to as
A variable resistor is connected to the input terminal of the A/D converter, and the voltage input to the A/D converter is adjusted by adjusting the variable resistor. The present invention relates to a pressure gauge that allows switching between a plurality of types of units of the pressure gauge whose unit display is controlled by the pressure gauge.

[Background of the Invention] Pressure fluid, such as pressurized air, is supplied to an actuator, and a pressure gauge is inserted into the pressure fluid line to check whether the actuator is being driven at a normal pressure. It is common practice to mount. In this case, if abnormally low (or abnormally high) pressure fluid is supplied, the actuator itself or various devices driven by this actuator may be damaged, or it may cause a dangerous situation for nearby workers. It is predicted that this will happen. Therefore, various pressure gauges have been developed and used in fluid supply systems.

By the way, Kgf/cm ² is generally used as the unit of pressure displayed on a pressure gauge, but other than Kgf/cm ² other pressure units are PSI,
KPa, MPa, bar, etc. exist, and by country,
Alternatively, they are used selectively depending on the field.
In order to accommodate each of these pressure units, manufacturers have conventionally produced several types of pressure gauges individually according to customer requirements.

However, producing different pressure gauges because of their different units in order to detect the pressure of substantially the same fluid results in a small volume of production, which significantly reduces production efficiency and reduces production efficiency. As a result, this causes an increase in manufacturing costs.

Therefore, in order to solve this problem, a pressure gauge is used in which a switch having, for example, one circuit and five contacts is provided on the panel surface of the pressure system so that the pressure unit can be changed by the user. That is,
As shown in FIG. 1, each contact is connected to a different input port _I0 to I4 of the one-chip microcomputer 2, and each time the five-contact switch ₄ is operated, the input port _I0 to _I4 is used as an address. The unit displayed on the unit display section 8 in the display 6 is Kgf/cm ² ,
This is the method of switching to PSI, KPa, MPa, bar, etc.

However, in this pressure unit switching system, the single-circuit, five-contact switch is large in size, and therefore a pressure gauge (not shown) incorporating the switch has the disadvantage that it occupies an extremely large volume. Moreover, since the absolute quantity of one-circuit five-contact switches on the market is small, the cost is high, and furthermore, the number of input ports of one-chip microcomputer 2 is limited to five.
In order to also use the terminal, microcomputer 2
There is an inconvenience in that the degree of freedom in setting is severely restricted. In addition, six lead wires are required for one circuit, five-contact switch, including the ground wire, which increases the number of wiring steps and significantly limits the freedom of routing the wires defined on the printed circuit board. This has caused a significant increase in manufacturing costs.

[Object of the Invention] The present invention has been made in order to overcome the above-mentioned disadvantages. The sliding terminal is connected, and the fixed terminal of this variable resistor is connected to a DC power source, and the voltage input to the microcomputer is adjusted by adjusting the variable resistor. It is an object of the present invention to provide a pressure gauge which can switch between a plurality of types of unit display of the pressure gauge by an output signal, and which is small in size and inexpensive to manufacture.

[Means for achieving the object] In order to achieve the above object, the present invention includes a semiconductor pressure sensor disposed inside a housing, a passage for introducing pressure fluid to the semiconductor pressure sensor facing, The pressure gauge includes a display section that digitally displays fluid pressure on one surface of the casing, and extracts the fluid pressure detected by the semiconductor pressure sensor as an electrical signal and displays it on the display section, the pressure gauge a first variable resistor which is disposed in a position where the slider position can be adjusted from the outside and which outputs a DC voltage based on the slider position; a first storage unit storing a table with pressure unit information obtained by the first variable resistor; and a search means for searching from the table to determine which voltage range the output DC voltage from the first variable resistor falls within by referring to the table. , display control for reading pressure unit information corresponding to the voltage range searched by the search means and displaying a pressure unit based on the read pressure unit information on the display section at a pressure unit display position of the display section; a second variable resistor disposed on the pressure gauge, the slider position of which can be adjusted from the outside, and which outputs a DC voltage based on the slider position;
reading instruction means for reading the output voltage from the second variable resistor into a second storage section; and reading instruction means for reading the output voltage value from the second variable resistor read into the second storage section and the output voltage value from the semiconductor pressure sensor. The present invention is characterized by comprising a comparison means for comparing the magnitude with a voltage value based on the output, and an indicator that is driven based on the output of the comparison means when the voltage value is large or small, or when either one of the voltage values is large or small.

[Example] Next, preferred embodiments of the pressure gauge according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 2, reference numeral 10 designates a pressure gauge according to the invention. This pressure gauge 10 consists of a rectangular cover member 12 and a base portion 14 that is engaged with the cover member 12 and screwed onto a fluid conduit (not shown). In this case, the base portion 14 is defined with a cylindrical bulge portion 16 for introducing pressure fluid into the main body of the pressure gauge 10 from the fluid conduit. The front surface of the cover member 12 includes a knob 18 for setting the pressure, a digital display, here a liquid crystal display 20, and a button to press when digitally displaying the pressure set based on the setting position of the knob 18. A push-button switch 22, which will be described later, is equipped with a light emitting element 24 that emits light as an alarm when fluid is supplied below a set pressure ^. and
A knob 26 for setting bar to a desired unit is incorporated.

FIG. 3 shows the internal structure of the pressure gauge 10 as an exploded perspective view. That is, the bottom surface of the integrally molded base part 14 is provided with inclined holes 30 and 32 for screwing into the female screw part of the fluid conduit (not shown) and fixing the base part 14, and A passage 3 extends along the axial direction of the bulge 16 into which pressure fluid is introduced.
4 is formed. Note that the base portion 14 is formed with wedge-shaped protrusions 36a to 36d for engaging the cover member 12. Reference numeral 38 is a first printed circuit board disposed parallel to the base portion 14, and the first printed circuit board 3
8 includes a semiconductor pressure sensor 39 and an operational amplifier _A1 for amplifying a pressure detection signal related to the pressure sensor 39.

Here, details of the pressure sensor 39 are shown in longitudinal sectional views in FIGS. 4a and 4b. The pressure sensor 39 has a protrusion 40 defined therein, and the protrusion 40 has a passage 42 communicating with the passage 34 defined in the base part 14.
is defined, and this passage 42 is in communication with a passage 48 defined in a pedestal 46 made of glass.
A sensor chip 50 constituting the pressure sensor 39 is disposed on the upper part of the pedestal 46.
0 is provided with a chamber 52 for surrounding the pressure fluid supplied from the passage 48 (see FIG. 4b). A conducting wire 54 is connected to the sensor chip 50,
This conducting wire 54 is electrically connected to a terminal 56. A cover member 58 made of synthetic resin such as polyester is fixed to the open upper end of the pressure sensor 39 to protect the sensor chip 50. Note that the terminal 56 of the pressure sensor 39 is electrically connected to the first printed circuit board 38 for relaying the electrical signal of the pressure sensor 39, as shown in FIG.

A pattern connector 60 defined by a printed pattern is formed at one end of the surface of the first printed circuit board 38 to which the operational amplifier A ₁ is attached.
The output signal of the printed circuit board 38 is defined on the back surface of the second printed circuit board 66 via the pattern connector 60 and a prismatic first connector 62 whose sides are surrounded on approximately three sides by a flexible printed pattern 61. A second printed circuit board 66 containing a microcomputer 64 is supplied through a pattern connector (not shown). In this case, the second printed circuit board 66 includes a pressure setting variable resistor RV ₁ ,
A variable resistor RV ₂ for setting the pressure unit and a light emitting diode D ₁ as an alarm are provided. Second
Above the printed circuit board 66 is a pattern connector 6.
8 is defined, the pattern connector 68, the second
(not shown) via the prismatic connector 70 of
It is connected to a third printed circuit board 72 on which an LCD driver IC is arranged. A pattern connector 74 is defined above the third printed circuit board 72, and by connecting the pattern connector 74 to a pattern connector (not shown) defined on the back surface of the liquid crystal display 20, the liquid crystal display 20 It communicates with the sensor 39. Note that the second printed circuit board 6
A push button switch 22 for displaying the set pressure is arranged above the pressure setting.

Based on this configuration, the first printed circuit board 3
8, second printed circuit board 66, third printed circuit board 7
2 and the liquid crystal display 20 are surrounded by an inner cover member 78 and are integrated, facing the cover member 12. The hole 1 defined in the cover member 12
8a, 20a, 22a, 24a and 26a are respectively knobs 1 of the pressure unit setting variable resistor RV _2.
8. Liquid crystal display 20, push button switch 2
2. A protruding lens member 80 made of plastic or the like disposed on the inner cover member 78 and the knob 26 of the pressure setting variable resistor RV ₁ are attached. In this case, hook portions 82a to 82d whose tips are bent are formed around the lower end of the cover member 12, and a wedge-shaped protrusion defined on the hook portions 82a to 82d and the base portion 14 is formed. 36a to 36d
are engaged, and the pressure gauge 10 shown in FIG. 2 is assembled.

Next, the first to third printed circuit boards 38, 6
FIG. 5 shows an electric circuit incorporated in 6 and 72, and its configuration will be explained.

First, the output side of the bridge circuit B, which is connected to the constant current circuit I and includes the equivalent resistance R _E of the pressure sensor 39 related to the sensor chip 50, is connected to the operational amplifier _A1 , and the analog output signal of the operational amplifier _A1 is
VS is introduced into the microcomputer 64.
In this case, variable resistor RV ₃ that constitutes the amplifier circuit related to operational amplifier A ₁ is inserted as a feedback resistor of operational amplifier A ₁ . Note that the variable resistor RV ₄ is for adjusting the equilibrium point of the resistances constituting the bridge circuit B.

The microcomputer 64 has RAM 10
0, a variable resistor RV ₁ which includes a register 102 and whose input/output signals, in addition to the analog output signal VS, are externally adjusted by setting a knob 18 to set a desired lower limit fluid pressure;
Setting of pushbutton switch 22 and knob 26 for instructing to store the set pressure value displayed on liquid crystal display 20 in RAM 100 when it reaches a desired value by adjusting RV ₁ . Variable resistor RV ₂ for switching pressure units by
and operational amplifier _A2 , which constitutes _a voltage follower to which the output signal VS of operational amplifier A1 is introduced and taken out to the outside as OUTPUT ₂ .
An open collector transistor TR becomes conductive when the measured pressure is less than the lower limit fluid pressure, OUTPUT ₁ from which the pressure displayed on the liquid crystal display 20 is taken out as a BCD output, and lights up when the measured pressure is less than the lower fluid pressure limit. light emitting diode display
_D1 is connected.

The pressure gauge according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

First, the cylindrical bulge 16 defined on the base portion 14 of the pressure gauge 10 is fitted into a fluid pipe (not shown), and screws are inserted into the inclined holes 30 and 32 to complete the fluid pipe. Only the base part 14 is attached to the female screw part formed in the. Next, the cover member 12, in which the first printed circuit board 38 to the third printed circuit board 72, etc. that constitute the pressure gauge 10 are integrally assembled, is fitted into the base portion 14. As a result, the fluid conduit and the passage 42 of the semiconductor pressure sensor 39 come into communication. In this way, the pressure gauge 10 is secured to the fluid line.

The desired fluid pressure is then set by externally adjusting knob 18, ie, variable resistor RV ₁ , to adjust the pressure switch mechanism.
At the same time, the variable resistor RV ₄ is adjusted to set the output of the bridge circuit B to a zero value in advance.

Next, a method for switching the pressure unit of the pressure gauge according to the main part of the present invention will be explained with reference to FIG.

Figure 6a is a unit switching circuit diagram schematically representing the pressure unit setting variable resistor RV ₂ , in which one end of both fixed terminals of the unit setting variable resistor RV ₂ is connected to the power supply +V, and the other end is connected to the power supply +V. is grounded, and the sliding terminal is connected to an A/D converter input terminal within the microcomputer 64. In this case, the relationship between the set angle θ of the variable resistor RV ₂ and the output voltage V is expressed as shown in FIG. 6b.

That is, the vertical axis represents the output voltage V with respect to the set angle θ on the horizontal axis, and in this case, the set angles θ ₁ to θ ₅ are expressed in pressure units PSI, KPa, Kgf/cm ² , MPa, and
It is made to correspond to bar. In other words, when the set angle θ is within the range of θ ₁ , the output voltage V of the variable resistor RV ₂ is within the voltage range V ₁ , and the pressure unit displayed at this time is PSI. is within the range of θ ₂ , the output voltage V of the variable resistor VR ₂ is within the voltage range V ₂ , and the pressure unit displayed at this time is set to be KPa. The same applies below. When the variable resistor RV ₂ is adjusted, the output voltage V of the variable resistor VR ₂ is introduced to the A/D converter in the microcomputer 64 and the RAM 100
It is configured to be taken inside.

On the other hand, a table of output voltage ranges V ₁ , ..., V ₅ shown in FIG. 6b and pressure unit information corresponding to the output voltage ranges is stored in advance in a ROM (not shown) provided in the microcomputer 64 . Yes, when the output voltage V from the variable resistor VR ₂ is taken into the RAM 100, the table stored in the ROM is referenced to determine which output voltage range the output voltage V from the variable resistor RV ₂ falls within. It is explored whether Pressure unit information corresponding to the output voltage range obtained through this search is read out, and the pressure unit is displayed on the display 2 based on the read pressure unit information.
It is displayed at the unit display position 105 at 0. That is, the pressure unit can be continuously switched by adjusting the slider position of the variable resistor RV ₂ .

Now, a pressure fluid, for example air, is introduced into the fluid conduit. As a result, the balance of bridge circuit B is broken and a differential voltage is generated across its terminals, which is introduced into operational amplifier _A1 . The output signal VS amplified by the operational amplifier A ₁ is introduced into the microcomputer 64 .

Next, the operation of the control circuit made up of the microcomputer 64 will be explained.

Following the initial settings of the microcomputer 64, the output voltage VS of operational amplifier _A1 and the variable resistor are set.
The output voltage V of VR ₂ is taken in at a predetermined period. The output voltage VS taken into the microcomputer 64 is A/D converted, and a digital display based on the A/D converted output is displayed on the display 20. That is, the pressure value is displayed on the display 20.

Further, the A/D-converted output voltage VS is converted into a BCD code and output from OUTPUT ₁ , and the output voltage VS is amplified and impedance-converted by operational amplifier A ₂ and output to OUTPUT ₂ . OUTPUT ₁ is output to display the pressure value on another digital display device,
OUTPUT ₂ is output for display on another analog display.

On the other hand, the output voltage V from the variable resistor RV ₂ taken into the microcomputer 64 is A/D converted, the table in the ROM is referred to, and the voltage V corresponding to the output voltage from the variable resistor VR ₂ is determined. Pressure unit information is searched, and a pressure unit based on the pressure unit information obtained by this search is displayed at the pressure unit display position 105 of the display 20. For example, when the output voltage V from the variable resistor RV ₂ is within the voltage range V ₃ , unit pressure information corresponding to the pressure unit Kgf/cm ² is searched and pressure unit display position 10 of the display 20 is searched.
5, Kgf/cm ² is displayed.

When the push button switch 22 is pressed,
The voltage from the variable resistor RV ₁ is read by an interrupt into the microcomputer 64, A/D converted, and stored in the set pressure storage area of the RAM 100. Therefore, by pressing the pushbutton switch 22 each time the lower limit fluid pressure is changed by changing the slider position of the variable resistor RV ₁ , the lower limit fluid value stored in the set pressure storage area of the RAM 100 can be changed. Pressure value is updated.

The output voltage VS taken in and A/D converted is
It is compared with the lower limit fluid pressure value stored in the set pressure storage area of the RAM 100, and when the measured pressure value is less than the lower limit fluid pressure value, the light emitting diode _D1 is driven.
The light emitting diode _D1 emits light to indicate that the pressure is below the lower limit fluid pressure. At the same time, transistor TR is driven and is controlled to be in an on state. As a result, the transistor
Alarms, etc. are issued depending on the collector load of the TR.

In addition, although the lower limit fluid pressure is set by variable resistor RV ₁ in the above example, it is also possible to set the upper limit fluid pressure by variable resistor RV ₁ and issue an alarm when the output voltage VS exceeds the upper limit fluid pressure. It is possible.

In addition, a variable resistor for setting the upper limit fluid pressure is separately provided, and the upper limit fluid pressure is set by the variable resistor, and the lower limit fluid pressure is set by the variable resistor RV ₁ , so that the fluid pressure is at the lower limit. It is also possible to issue an alarm when the fluid pressure is not reached and when the upper fluid pressure limit is exceeded.

[Effects of the Invention] As explained above, according to the present invention, in order to switch the display of the pressure unit of the pressure gauge, the first variable resistor is provided, and the output voltage from the first variable resistor is adjusted accordingly. The pressure unit information is searched for, and the pressure unit based on the searched pressure unit information is displayed at the pressure unit display position of the display section. Therefore, it becomes possible to switch the display of the pressure unit of the pressure gauge from the outside. Furthermore, the voltage range in which the output voltage from the first variable resistor falls in a table of a plurality of voltage ranges and pressure unit information corresponding to each voltage range is searched. Since the pressure unit based on the pressure unit information corresponding to the voltage range is displayed, the output voltage from the first variable resistor may have a predetermined width and does not need to be particularly accurate. Setting using one variable resistor is easy, and moreover, a large number of pressure units can be displayed. Furthermore, it has a built-in pressure switch function that uses the output voltage from the second variable resistor as the set pressure, allowing for simple configuration and miniaturization, allowing for effective use of space, and making it easy to change the set pressure. It is.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and design changes can be made without departing from the gist of the present invention. Of course.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a pressure unit switching system according to the prior art, FIG. 2 is an explanatory external perspective diagram of a pressure gauge according to the present invention, FIG. 3 is an exploded perspective view of the pressure gauge according to the present invention, and FIG. Figures a and b are longitudinal sectional views of a pressure sensor installed in the pressure gauge shown in Figure 3, Figure 5 is a block diagram of an electric circuit incorporated inside the pressure gauge according to the present invention, and Figure 6a is a In the electric circuit shown in Fig. 5, a schematic explanatory diagram relating to the pressure unit switching circuit, No. 6
FIG. 6b is an explanatory diagram for explaining the operation of the pressure unit switching circuit shown in FIG. 6a. 10...Pressure gauge, 20...Liquid crystal display, 64...Microcomputer, RV ₁ ...Variable resistor for setting lower limit fluid pressure, RV ₂ ...Variable resistor for setting pressure unit, V
...output voltage, θ...setting angle.

Claims (1)

[Claims] 1 A semiconductor pressure sensor is disposed inside a casing, a passage for introducing pressure fluid to the semiconductor pressure sensor is faced, and a display section for digitally displaying fluid pressure is provided on one surface of the casing, A pressure gauge that extracts fluid pressure detected by a semiconductor pressure sensor as an electrical signal and displays it on the display section, the pressure gauge being disposed on the pressure gauge and having a slider position adjustable from the outside. a first variable resistor that outputs a DC voltage based on the rotor position; a first storage unit that stores a table of a plurality of voltage ranges and pressure unit information corresponding to each voltage range; searching means for referring to and searching from the table which voltage range the output DC voltage from the first variable resistor falls within; and reading out pressure unit information corresponding to the voltage range searched by the searching means. a display control means for displaying a pressure unit at a pressure unit display position of the display section based on the pressure unit information read out on the display section; and a display control means disposed on the pressure gauge so that the slider position can be adjusted from the outside. and a second variable resistor that outputs a DC voltage based on the slider position;
reading instruction means for reading into the storage section; and comparison means for comparing the magnitude of the output voltage value from the second variable resistor read into the second storage section and the voltage value based on the output from the semiconductor pressure sensor. and an indicator that is driven based on the output of the comparing means when the pressure is large and/or small.