JP3032634B2 - Switching device of bridge excitation voltage supply system in strain gauge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching device for a bridge excitation voltage supply system in a strain measuring device, and more specifically, to use a BV of an external signal source or a BV of an internal signal source in the strain measuring device. And a device for automatically determining and setting the switching.

[0002]

2. Description of the Related Art There are a DC voltage system and an AC voltage system depending on the type of voltage supplied to a strain gauge bridge in a strain measuring instrument. S / S responds to a phenomenon frequency of about 10 kHz or less. An AC voltage type strain meter which is excellent in N ratio and drift characteristics and can perform stable measurement is used. The AC voltage type strain measuring instrument has a built-in BV oscillator and a synchronizing signal input / output terminal (hereinafter referred to as an “OSC terminal”) in consideration of a case where an external BV is used.

When a phenomenon is measured by using a plurality of measuring instruments, it is necessary to synchronize the BV supplied to the gauge bridge corresponding to each measuring instrument. Connect the external BV with the manual BV switch provided on the back panel of each measuring instrument.
Or the internal BV is selectively switched and set.

The above switching circuit has a specific configuration as shown in FIG. First, when using an external BV, the BV switch 51 is set to the EXT side and the B
The V oscillator 52 is turned off, and the BV oscillator 5 is turned on at S2.
2 from the signal path, and B input from the OSC terminal.
V is output to a BV power amplifier via an automatic gain control circuit (AGC). Conversely, when using the internal BV, the BV switch 51 is set to the INT side, and the BV switch is set at S1.
The oscillator 52 is turned on, the BV oscillator 52 is connected to the signal path in S2, and the BV of the oscillator 52 is output to the BV power amplifier via the AGC. In the latter case, a circuit for outputting the signal without passing through the AGC may be employed.

[0005]

By the way, in the case where a plurality of strain measuring instruments are used as described above, when only one is used, the BV switch of the measuring instrument is set to the INT side. When using multiple instruments, set the BV switch of one measuring instrument to the INT side, and set the BV switches of other measuring instruments to the EXT side. Set the BV switch of the non-powered-on measuring instrument to the EXT side. For example, an extremely complicated switch setting operation is required according to use conditions. The BV switch is
It is often provided on the back panel to avoid crosstalk between BVs and because of the space on the front panel of the measuring instrument, making the setting operation and checking of the setting state very inconvenient. .

[0006] As a result, erroneous operation of the BV switch often causes re-measurement without obtaining accurate measurement data. In addition, poor operability causes a decrease in measurement work efficiency. Therefore, according to the present invention, the presence or absence of an external BV is determined after power-on, and the external BV is automatically determined.
It has been created for the purpose of providing a switching device of a BV supply system for selectively setting an internal BV or an internal BV, thereby resolving the disadvantages described above.

[0007]

The basic structure of the present invention is shown in FIG. 1. In a strain measuring device, an external BV supply circuit 2 and an internal BV supply circuit 3 are connected in parallel to a BV input / output terminal 1. A BV supply circuit 8 having two switches (4, 5) (6, 7) interposed in each supply circuit 2, 3;
Both switches 4 and 5 interposed in the external BV supply circuit 2
An external BV detector 9 for detecting the presence or absence of an external BV from between
Both switches 6, 7 interposed in the internal BV supply circuit 3
A BV generator 10 for outputting a BV between the external B
Internal BV control unit 1 that activates / stops BV generation unit 10 in accordance with the detection / non-detection state of a signal in V detection unit 9
1 and both switches 4 and 5 of the external BV supply circuit 2 are turned ON within a certain time after the power is turned on, and the internal BV supply circuit 3 is turned on.
The two switches 6 and 7 on the side are set to OFF, and when the external BV detector 9 detects the BV within that time, the initial state is maintained. External B
Turn off both switches 4 and 5 on the V supply circuit 2 side,
The present invention relates to a switching device for a bridge excitation voltage supply system in a strain measurement device, comprising a switch control unit 12 for switching both switches 6 and 7 on the V supply circuit 3 side to ON.

In consideration of a case where an abnormal BV input is made, the external BV detecting section is provided with a function of detecting a BV frequency, and when the detecting section detects a BV,
When it is detected and confirmed that the frequency of the BV is different from the frequency of the BV generator of the own device, it is desirable to invalidate the detection of the BV.

Further, in the above invention, when the external BV detecting section 9 does not detect the BV or stops detecting the BV on the way after a predetermined time has elapsed after the power is turned on, the switch control section 12 has a predetermined delay. It is desirable to execute the switch control with a certain time.

A display control section for displaying the external supply state / internal supply state of the BV on the display section 13 provided on the outer panel of the strain gauge in accordance with the detection / non-detection state of the external BV detection section 9. 14 can also be provided.

[0011]

During a fixed time after the power supply (not shown) of the strain measuring device is turned on, the switches 4 and 5 of the external BV supply circuit 2 are always turned on by the switch control unit 12,
Switches 6 and 7 of internal BV supply circuit 3 are set to OFF. Therefore, during that time, the external BV detector 9
Can check whether BV is input from the switch 4 side.

If a BV has been input from the beginning or if a BV has been input within the above-mentioned predetermined time, the external BV detecting section 9 detects it and switches based on the detection. The control unit 12 maintains the state of each of the switches 4, 5, 6, and 7 in the initial state described above, so that the strain meter receives the supply of BV through the external BV supply circuit 2. On the other hand, when the BV is not input from the beginning or when the BV is input but the BV is no longer input after the lapse of the predetermined time, the signal of the external BV detection unit 9 after the lapse of the predetermined time has not been input. The internal BV control unit 11 activates the BV generation unit 10 based on the detection state, and the switch control unit 12 further switches the switches 4, 5, 6,
7 is inverted from the initial state, so that the strain meter itself is connected to the BV supply circuit 3 through the switch 7 of the internal BV supply circuit 3.
Supply V and switch 6 to BV input / output terminal 1
BV is supplied to an external strain measuring instrument through.

Therefore, when a plurality of strain measuring instruments having the configuration of the present invention are turned on while the BV input / output terminal 1 is connected, the measuring instrument which is turned on first has a BV input. It becomes a supply source, and another measuring instrument is in a state of receiving the supply of BV from outside. Here, the certain time after the power is turned on corresponds to a period in which each strain measuring device monitors the startup state of another measuring device. In FIG. 1, the AGC 15 is interposed between the switches 4 and 5 of the external BV supply circuit 2. However, when an external BV is supplied, the level may become unstable. And
It is not required when a stable BV can be obtained.

If a BV different from the frequency of the own device is input from the BV input / output terminal 1, an incorrectly combined strain measuring device is connected or another strain measuring device is connected. The device outputs abnormal BV. In response to this, the external BV detection unit 9 is provided with a function of detecting the BV frequency,
This can be dealt with by invalidating the detection when the frequency is different from the V frequency. That is, an abnormal BV supply is rejected, and an effective abnormality notification means can be configured in combination with a display function when the self becomes a BV supply source.

If the switch control section 12 is provided with a fixed delay time when shifting to the internal BV supply state, the BV generation section 10 can output the BV to the inside and outside of the measuring instrument in a stable state. it can. The display unit 13 and the display control unit 14 use the monitoring signal of the external BV detection unit 9 to easily confirm the BV supply state of the measuring device.

[0016]

Embodiments of the present invention will be described below in detail with reference to FIG. The figure shows an electric circuit diagram of a switching device of a BV supply system in a strain measuring instrument, 21 is an OSC terminal provided on a rear panel of the measuring instrument, and 22 is an OC terminal when power is turned on.
N, a relay switch, 23, 24, 25, and 26 are turned on by a “H” control voltage, and are turned off by a “L” control voltage; and 27 is connected between the analog switches 23 and 24. AG
C and 28 are BV oscillators branched and connected between the analog switches 25 and 26. These components are connected as shown in the figure, and the analog switch 23 → AGC2
7 → the external BV path of the analog switch 24 and the internal BV path of the analog switch 25 → the analog switch 26 constitute a parallel circuit.

On the other hand, 30 is a timer for switching the output from "L" to "H" at a predetermined time T (about 2 seconds) after the power is turned on, and 31 is a band branched and connected between the analog switch 23 and the AGC 27. Pass filter (BP
F) and 32 are detection circuits, 33 is a constant voltage source, 34 is a comparator for comparing the output voltage of the constant voltage source and the detection circuit, and 35 is an AND for ANDing the output of the comparator 34 and the output of the timer 30.
Circuit, 36 is a reset diode, 37 is a pull-up resistor, 38 is a delay circuit having a time constant t, 39 is an AND circuit for ANDing the reset diode 36 and the output of the delay circuit 38, and 40 is an AND circuit 39. INV circuit for inverting the output; 41, an INV circuit for inverting the output of the INV circuit 40; 42, a display control unit for displaying the output state of the AND circuit 35 on the display unit 43; 43, a display unit for displaying the BV supply state These elements are connected as shown in the figure, the output side of the AND circuit 35 is connected to the BV oscillator 28, the output side of the INV circuit 40 is connected to the analog switches 23 and 24, and the output side of the INV circuit 41 is connected. The side is connected to the analog switches 25 and 26, and constitutes a control circuit of the analog switches 23, 24, 25 and 26 as a whole. . Note that the BPF 31 is the B
It has a filtering band characteristic of passing only a BV having the same frequency as the V frequency (for example, 5, 12, 28 kHz).

Next, the operation of the BV supply system switching device in each state will be described. First, when the power switch 44 is turned on, the relay switch 22 is turned on, the timer 30 is reset, and the output is set to “L”. In the initial state for the first T seconds after the power is turned on, since the output of the AND circuit 35 is “L”, the output of the AND circuit 39 also becomes “L”, and the INV circuit 4
The output of 0 is set to “H”, and the output of the INV circuit 41 is set to “L”. Therefore, the analog switches 23 and 24 are turned ON.
Then, the analog switches 25 and 26 are set to OFF, and in this state, the OSC terminal 21 is supplied from an external signal source.
Is input to the BV power amplifier through the analog switch 23 → AGC27 → analog switch 24 which is an external BV path. In this state, the internal BV path is naturally cut off by the analog switches 25 and 26, and the output of the AND circuit 35 is "L", so that the BV oscillator 28 is also in the OFF state.

In the initial state, the OS
When BV is input from the C terminal 21, the signal is input to the BPF 31 from the output side of the analog switch 23, and the detection circuit 32 detects and outputs the output of the BPF 31 that passes the frequency band. The input voltage to the comparator 34 is increased to a value equal to or higher than the comparison value on the constant voltage source 33 side.
Accordingly, since the output of the comparator 34 is inverted from “H” in the initial state to “L” and one of the inputs of the AND circuit 35 is inverted, the timer 30 changes its output from “L” after T time has elapsed. Even when inverted to "H", the output of the AND circuit 35 maintains the state of "L" as it is, and the state of each analog switch 23, 24, 25, 26 is maintained in the initial state, and the output from the external signal source is maintained. The BV supply state is maintained.

On the other hand, if the signal from the OSC terminal 21 is interrupted in the switch setting state after the initial state, B
The input to the PF 31 disappears, and the output of the comparator 34 is inverted from “L” to “H”. As a result, timer 3
Since the output of 0 is already at "H", the output of the AND circuit 35 is inverted from "L" to "H", and the BV oscillator 28 is turned on to start. Further, the output of the AND circuit 35 is also output to the delay circuit 38, and the output of the same circuit 38 is inverted to “H” after the elapse of a predetermined time t.
The output of the D circuit 39 is inverted from “L” to “H” by “H” on the pull-up resistor 37 side and output “H” of the delay circuit 39. Note that the delay time t of the delay circuit 38 is set as a time until the BV oscillator 28 is stabilized after starting. As a result, after a lapse of time t after the signal from the OSC terminal 21 stops, the output of the INV circuit 40 is inverted from “H” to “L”, and the output of the INV circuit 41 is inverted from “L” to “H”. And the analog switches 23 and 24 are ON
From OFF to ON, and the analog switches 25 and 26 are switched from OFF to ON.

Therefore, after the start of the BV oscillator 28, the time t
, The stable BV is output to the BV power amplifier through the analog switch 26, and the OSC is output from the analog switch 25 and the relay switch 22.
O of an external strain gauge (not shown) through terminal 21
It will be supplied to the SC terminal. That is, the strain measuring device according to the present embodiment is in a state of being a supply source of BV.
In this state, the analog switches 23 and 24 are off, and the external BV path is shut off.

In the circuit of this embodiment, the AND circuit 3
5 is output to the display control unit 42. Based on the output of the AND circuit 35 becoming “H”, the display control unit 42 Using the source (BV for other measuring instruments)
In the state of being a supply source). There are various types of display modes. For example, when data is displayed on a liquid crystal segment or the like, a display method using a part of the data or an LED indicating a BV supply state is provided on the front panel. In addition, a method of blinking the LED may be considered.

In a rare case, the output of the AND circuit 35 is changed from "L" to "H" as the timing of the BV input from the external BV source after the initial state.
After the inversion, the BV may be input to the OSC terminal 21 with a delay before the output of the delay circuit 38 is inverted. In this case, in this circuit, the reset diode 36 inverts the input on one side of the AND circuit 39 to “L”. As a result, the output of the AND circuit 39 remains “L”, the analog switches 23 and 24 are kept ON, the analog switches 25 and 26 are kept OFF, and the output of the AND circuit 35 is changed from “H” to “L”. And the BV oscillator 28 is turned off.

On the other hand, in the initial state after the power switch 44 is turned on, when the BV is not input from the OSC terminal 21, the following operation is performed.
In this case, there is no input to the BPF 31 even though the BV is supplied from the external signal source, and the output of the comparator 34 remains “L”. And timer 3
When the output inversion time T of 0 elapses, the output becomes “H”.
, The output of the AND circuit 35 becomes “H”, the BV oscillator 28 is activated, and AND
When the output of the circuit 35 is inverted to “H”, the display control unit 42 causes the display unit 43 to display that the internal BV source is in use. After the delay time t of the delay circuit 38 has elapsed, the output of the AND circuit 39 is inverted from “L” to “H”, and as a result, the output of the INV circuit 40 is changed from “H” to “L”, The output of 41 is inverted from “L” to “H”, and the analog switches 23 and 24 are turned off from ON.
And the analog switches 25 and 26 are switched from OFF to ON. That is, when BV is not input from the OSC terminal 21 from the beginning, the output inversion time T
When the time elapses, the BV oscillator 28 is activated and the use state of the internal BV source is displayed, and the external BV path is switched to the internal BV path with a certain delay time.

Furthermore, although this is a rare case, the OSC
Even if a BV is input from the terminal 21, the frequency of the BV may be different from the BV frequency of the own device. The cause is, for example, when the other strain measuring instrument to which the OSC terminal 21 is connected in parallel cannot be combined with this measuring instrument, or when there is an abnormality in the strain measuring instrument serving as the BV signal source. Is assumed. In this embodiment, the BPF 31 effectively functions in such a case, and the detection circuit 32
In order not to output the BV, the state becomes the same as the non-input state of the BV. Moreover, in this case, the strain measuring device is B
The indication is displayed on the display unit 43 as the V supply source, and the other strain measurement devices as the BV supply sources also perform the display in the same manner. Therefore, the supply source is displayed by a plurality of strain measurement devices. Therefore, the occurrence of an abnormality based on the cause can be easily confirmed, and a countermeasure can be taken immediately.

As described above, in this embodiment, the analog switches 23, 24, 25 and 26 provided in the parallel circuit composed of the external BV path and the internal BV path are switched by the control circuit. The action is running. However, this control operation does not necessarily have to be executed by a hardware circuit as shown in FIG. 2, and the control circuit can be replaced by a microcomputer circuit and executed by software.

[0027]

According to the present invention having the above configuration, the following effects can be obtained. According to the first aspect of the present invention, when performing measurement using a plurality of strain measuring devices,
BV from the BV input terminal after starting the strain gauge
Since the input state is monitored and the external BV or the internal BV is automatically selected and set according to the input state, the complexity of the operation of the BV switch in the prior art is eliminated. In addition, the operation time of the operator is shortened, and the operation error is eliminated, thereby realizing the efficiency of the measurement operation. According to the second aspect of the present invention, when the externally supplied BV is different from the own BV frequency, the detection of the external BV is invalidated, so that the abnormal external BV supply can be rejected. Combined with the display function of claim 4, an effective abnormality notification means is provided. According to a third aspect of the present invention, the switch control unit executes the switch control with a delay time when shifting to the internal BV supply state, so that the BV is supplied after the BV generation unit enters the stable output state. It becomes possible to do. The invention according to claim 4 displays whether the supply source of the BV is internal or external, and makes it easy for the operator to confirm the supply state of the BV. Therefore, it is possible to quickly investigate the cause and take measures when an abnormality occurs in the measured value. According to the invention of claim 5, when a BV is supplied from the outside, the signal may be unstable.
It is stabilized and supplied to the strain bridge that is being managed by itself.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is an electric circuit diagram of a switching device of a BV supply system in the strain meter according to the embodiment.

FIG. 3 shows an external BV / internal B in a conventional strain gauge.
FIG. 4 is an electric circuit diagram showing a V switching unit.

[Explanation of symbols]

 1 BV input / output terminal 2 External BV supply circuit 3 Internal BV supply circuit 4, 5, 6, 7 Switch 8 BV supply circuit 9 External BV detection unit 10 BV generation unit 11 Internal BV control unit 12 Switch control unit 13 Display unit 14 Display Control unit 15 AGC

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takao Asai 3-5-1 Chofugaoka, Chofu-shi, Tokyo Inside Kyowa Dengyo Co., Ltd. (56) References JP-A-56-70463 (JP, A) 50-110670 (JP, A) JP-A-5-93733 (JP, A) JP-A-51-117655 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) G01L 1 / 22 G01B 7/16 G01L 9/04

Claims (5)

(57) [Claims] In a strain measuring instrument, an external BV supply circuit and an internal BV supply circuit are connected in parallel to an input / output terminal of a bridge excitation voltage signal (hereinafter referred to as “BV”), and two supply circuits are connected to each supply circuit. A BV supply circuit having a switch interposed therebetween, an external BV detecting section for detecting the presence or absence of an external BV from between the two switches interposed in the external BV supply circuit, and a BV between the two switches interposed in the internal BV supply circuit. A BV generating section for outputting a signal, an internal BV control section for operating / stopping the BV generating section in accordance with the detection / non-detection state of the signal in the external BV detecting section, and an external BV controlling section for a predetermined time after the power is turned on. Both switches on the side of the BV supply circuit are set to ON, and both switches on the side of the internal BV supply circuit are set to OFF. If the external BV detector detects BV within that time, the initial state is maintained. When the BV is not detected after the elapse of the predetermined time or when the BV is not detected on the way, both switches on the external BV supply circuit side are turned off, and the internal BV
A switching device for a bridge excitation voltage supply system in a strain measuring device, comprising a switch control unit for switching both switches on a supply circuit side to ON. 2. An external BV detector has a function of detecting a BV frequency, and when a BV is detected, detects and confirms that the frequency of the BV is different from the frequency of the BV generator of the own device. 2. A switching device for a bridge excitation voltage supply system in a strain measuring device according to claim 1, wherein the detection of the BV is invalidated when the BV is detected. 3. After a certain period of time has passed since the power was turned on, the external B
3. The strain measurement according to claim 1, wherein the switch control unit executes the switch control after a certain delay time has elapsed when the V detection unit does not detect the BV or stops detecting the BV halfway. Switching device for the bridge excitation voltage supply system in the heater. 4. A display control unit for displaying an external supply state / internal supply state of a BV on a display unit provided on an outer panel of a strain meter in accordance with a signal detection / non-detection state by an external BV detection unit. A switching device for a bridge excitation voltage supply system in the strain measuring device according to claim 1, 2 or 3, further comprising: 5. The switching device for a bridge excitation voltage supply system in a strain measuring instrument according to claim 1, wherein an automatic gain control section is interposed between both switches of the external BV supply circuit in the BV supply circuit.