JP4783142B2 - Sensor body and strain measuring device using the sensor body - Google Patents

Description

  The present invention provides a sensor main body in which a strain sensor formed of a Wheatstone bridge circuit formed of a strain gauge and an information storage medium capable of reading and writing information on the strain sensor are disposed integrally or in the vicinity of each other, The present invention relates to a strain measuring device using a sensor body.

When measuring the physical quantity or mechanical quantity of the measurement target using a strain gauge or strain gauge transducer in strain measurement, the manufacturer name, sensor type, model, serial number of the strain gauge or strain gauge transducer A calibration value or the like is attached to the converter or the like.
On the other hand, in strain measurement, it is often necessary to connect a measuring instrument to a strain gauge or transducer installed at a location away from the measuring instrument via a connection cable and measure strain at a remote location. In particular, a large number of various sensors, including strain gauges and strain gauge transducers, are installed in a large number of locations such as dams and large buildings and facilities, or construction sites, and each channel consists of multiple terminals. In a multi-channel measurement system that connects to each connection terminal via a cable and selectively scans and connects these multi-channel connection terminals to a measuring instrument, the channel ID, installation location, connection on the user side Mode, etc. must be recorded.
Conventionally, information such as data related to such an enormous amount of measurement and measurement conditions has been recorded by writing down a memo or recording it to a personal computer as necessary. For this reason, there are problems that a long time is required for the recording work and a human error occurs.

In consideration of such a problem, an electronic data sheet called TEDS (Transducer Electronic Date Sheet), that is, a readable / writable information storage medium is commercially available.
This TEDS can store sensor-specific information in a nonvolatile memory inside the sensor. For example, it is possible to store information such as manufacturer name, sensor type, model, serial number, and calibration value. The above problems are being solved.
FIG. 4 shows a circuit configuration when this TEDS is used together with a strain sensor.
The sensor body 1 shown in FIG. 4 has a strain sensor 2 composed of a Wheatstone bridge circuit (hereinafter referred to as “bridge circuit”) formed of four strain gauges SG1 to SG4, and a TEDS3. Among these, the input terminal 2a of the bridge circuit of the strain sensor 2 is connected to the positive input terminal A, the input terminal 2c is connected to the negative input terminal C, and the output terminal 2d of the bridge circuit is connected to the positive side. The output terminal D is connected, and the negative output terminal B is connected to the output terminal 2b.

Both ends of the TEDS 3 are connected to the attached terminals F and G.
All the shield wires 4 of the cable are connected to the ground terminal E in common.
In the conventional sensor main body as illustrated in FIG. 4, the functions realized by the TEDS 3 include, for example, a function for specifying the location (position) where the sensor main body is installed, and a measuring instrument based on information read from the TEDS. Functions that automatically adjust, functions that greatly reduce the measurement preparation time by automating maintenance management of the measurement condition table (serial number, calibration value, measurement point), etc. are assumed.
Thus, since TEDS can exhibit many effective functions, it has recently begun to be used for strain measurement.

FIG. 5 is a circuit diagram showing another configuration of a conventional sensor body.
Unlike the sensor body shown in FIG. 4, the sensor body shown in FIG. 4 does not include TEDS.
In this conventional example, the attached terminals F and G are connected to the input terminals 2a and 2c of the bridge circuit, and the wiring from the attached terminals F and G to the measuring instrument is used for the purpose of remote sensing the strain sensor. . This remote sensing is performed for the purpose of compensating for a change due to temperature of the resistance value in the cable from the strain sensor to the strain measuring device (device).
In the case of the configuration shown in FIG. 5, since the attached terminals F and G are used for the sensing purpose, there is a problem that the above-described TEDS cannot be used.

However, in the conventional strain sensor described in the background art above, since the number of cables and connection terminals to the strain measuring device are substantially restricted, TEDS is used in the case of a configuration for performing remote sensing. There was a problem that it was impossible to do.
Hereinafter, this problem will be described in detail.
For example, the above-described TEDS 3 is connected to the attached terminals F and G in the same manner as shown in FIG. 4, and a new terminal is provided in addition to the terminals F and G, and two additional terminals are provided via the new terminal. Although it is possible in principle to connect the lead wire to the strain sensor 2 and connect the new terminal to the measuring instrument with a cable to perform the above remote sensing, the measurement is performed from the new terminal. 8 wires are required to reach the instrument (measuring instrument for measuring strain). However, the number of core wires of the cable is limited to six. (It is equal to the number of terminals excluding the terminal E in FIG. 4).

The reason why the number of wires is limited will be explained. These wires are covered and bundled into one cable and connected to an external measuring instrument. Since it is arranged at multiple points in the area (may exceed 100 points), the number of cables increases and it is physically very bulky, so it is physically difficult to centrally wire external measuring instruments. In addition to this, the cost will increase significantly. Therefore, here, there is a situation where the increase in the diameter of the cable should be extremely suppressed, and as a result, the number of wires (= number of terminals) for connecting the measuring instrument to the strain sensor must be extremely cut off.
The present invention has been made in view of the above-described problems, and measures a physical quantity or a mechanical quantity such as strain, displacement, acceleration, torque, etc. of an object to be measured, and stores it in an information storage medium such as TEDS. A sensor main body capable of reducing the cost as much as possible while maintaining the number of wires necessary for connection with a measuring instrument at the same prescribed number as well as making it possible to read out information. An object of the present invention is to provide a strain measuring apparatus using a sensor body.

In order to achieve the above-described object, a sensor main body according to claim 1 is a strain sensor comprising a Wheatstone bridge circuit formed of a strain gauge, and an information storage medium on which information relating to the strain sensor can be read and written. Is a sensor body arranged integrally or in the vicinity thereof,
An analog signal according to the physical quantity to be measured output from the strain sensor and a digital signal output according to the information stored in the information storage medium are selectively output to two common output terminals. A mode switching circuit for causing
Two input terminals for supplying bridge power to the Wheatstone bridge circuit;
The output terminal of the Wheatstone bridge circuit and the output terminal of the information storage medium are provided with the two output terminals connected in common.

In addition, the mode switching circuit of the sensor body according to the present invention described in claim 2 includes two switching elements interposed between a pair of output terminals of the Wheatstone bridge circuit and the pair of output terminals,
One end is composed of a diode interposed between the other end of the information storage medium connected to the negative output terminal and the positive output terminal,
In a state in which bridge power is supplied to the two input terminals, an analog signal corresponding to a physical quantity to be measured is output from the output terminal from the output terminal, and in a state in which supply of the bridge power is cut off, the positive side When a negative potential is supplied to the output terminal, information stored in the information storage medium can be read from the output terminal.

According to a third aspect of the present invention, there is provided the sensor body according to the present invention, wherein the mode switching circuit is a P-channel junction connected in series between one output end of the Wheatstone bridge circuit and the output terminal on the positive side. A first switching element comprising a type FET;
A second switching element comprising an N-channel junction FET connected between the other output terminal of the bridge circuit and the negative output terminal;
A first resistor connected between the gate of the first switching element and the negative output terminal;
A second resistor connected between the gate of the second switching element and the positive output terminal;
A diode having an anode connected to the other end of the information storage medium and a cathode connected to the positive output terminal;
It is characterized by comprising.

Furthermore, the information storage medium of the sensor main body according to the present invention described in claim 4 is made of TEDS, and at the time of shipment, information on any one of a manufacturer name, a sensor type, a model, a serial number, and a calibration value is stored. The channel ID, installation location, tag number, etc. can be stored as desired by the user after shipment.
According to a fifth aspect of the present invention, there is provided a sensor main body in which a circuit portion including the first switching element, the second switching element, the first resistor, the second resistor, and the diode is formed as an IC chip. It is characterized by.

A strain measuring apparatus according to the present invention described in claim 6 is a strain measuring apparatus using the sensor main body according to any one of claims 1 to 5, wherein the bridge supplies a bridge voltage to the input terminal. Power supply,
An input switch interposed between the input terminal and the bridge power supply;
A pair of differential amplifiers for detecting a difference in output of the bridge circuit;
An output switch interposed between the differential amplifier and the output terminal;
A negative potential supply switch that selectively supplies a negative potential lower than the ground potential to the positive output terminal;
Reading means for reading information stored in the TEDS;
A reading switch interposed between the reading means and the positive side of the output terminal;
A grounding switch for selectively grounding the negative side of the output terminal;
It is characterized by having.

  In the strain measuring device according to the present invention described in claim 7, the input switch and the output switch are turned on, and the negative potential supply switch, the reading switch, and the ground switch are turned off, respectively. The strain sensor output is supplied to the differential amplifier and stored in the TEDS by turning off the input switch and the output switch and turning on the negative potential supply switch, the reading switch, and the ground switch, respectively. It is characterized in that the read information is read by the reading means.

According to the present invention, there is provided a sensor body in which a strain sensor formed of a Wheatstone bridge circuit formed of a strain gauge and an information storage medium capable of reading and writing information on the strain sensor are integrally or in the vicinity. ,
An analog signal according to the physical quantity to be measured output from the strain sensor and a digital signal output according to the information stored in the information storage medium are selectively output to two common output terminals. A mode switching circuit for causing
Two input terminals for supplying bridge power to the Wheatstone bridge circuit;
Since the two output terminals are connected in common to the output end of the Wheatstone bridge circuit and the output end of the information storage medium, the number of wires required for connection between the sensor body and the strain measuring device ( It is possible to measure a physical quantity to be measured and a machine quantity without increasing the number of cores) and to read information stored in an information storage medium such as TEDS. In particular, a prescribed number of wires (usually 6 It is possible to read and write information stored in an information storage medium such as TEDS while using a strain sensor having a remote sensing function as it is, and to obtain highly reliable measurement data. It is possible to provide a sensor body that can be significantly reduced in cost.

According to the invention described in claim 2,
The mode switching circuit includes two switching elements interposed between a pair of output terminals of the Wheatstone bridge circuit and the pair of output terminals,
One end is composed of a diode interposed between the other end of the information storage medium connected to the negative output terminal and the positive output terminal,
In a state in which bridge power is supplied to the two input terminals, an analog signal corresponding to a physical quantity to be measured is output from the output terminal from the output terminal, and in a state in which supply of the bridge power is cut off, the positive side In a state in which a negative potential is supplied to the output terminal, the information stored in the information storage medium can be read from the output terminal. It is possible to provide a sensor main body capable of exhibiting the specific effects of the present invention.

According to the invention of claim 3,
The mode switching circuit includes a first switching element including a P-channel junction FET connected in series between one output terminal of the Wheatstone bridge circuit and the positive output terminal;
A second switching element comprising an N-channel junction FET connected between the other output terminal of the bridge circuit and the negative output terminal;
A first resistor connected between the gate of the first switching element and the negative output terminal;
A second resistor connected between the gate of the second switching element and the positive output terminal;
A diode having an anode connected to the other end of the information storage medium and a cathode connected to the positive output terminal;
Therefore, it is possible to provide a sensor body with a simple configuration and high reliability.

According to the invention described in claim 4,
The information storage medium is composed of TEDS (abbreviation of Transducer Electronic Date Sheet), which is an electronic data sheet incorporated in the sensor, and is shipped from the manufacturer name, sensor type, model, serial number, or calibration value. Information, and after shipment, channel ID, installation location, tag number, etc. can be stored as desired by the user, so that it is possible to use commercially available TEDS, which is a component of TEDS by mass production. It is possible to provide a sensor body that can reduce the cost.
According to the invention described in claim 5,
Since the circuit part consisting of the first switching element, the second switching element, the first resistor, the second resistor, and the diode is formed as an IC chip, the above-mentioned components are reduced in size and weight, It is possible to read information from the TEDS without affecting the characteristics of the strain sensor at all, and to provide a sensor body that can be incorporated together with the strain sensor.

According to the invention described in claim 6,
In the sensor main body according to any one of claims 1 to 5,
A bridge power supply for supplying a bridge voltage to the input terminal;
An input switch interposed between the input terminal and the bridge power supply;
A pair of differential amplifiers for detecting a difference in output of the bridge circuit;
An output switch interposed between the differential amplifier and the output terminal;
A negative potential supply switch that selectively supplies a negative potential lower than the ground potential to the positive output terminal;
Reading means for reading information stored in the TEDS;
A reading switch interposed between the reading means and the positive side of the output terminal;
A grounding switch for selectively grounding the negative side of the output terminal;
Since it is attached, the measurement of the physical quantity and mechanical quantity of the measurement target and the reading of information stored in an information storage medium such as TEDS can be made compatible with the strain measuring device. To provide a strain measuring device that can maintain the number of wires necessary for the connection of the conventional method to the specified number as before, and can reduce the number of wires as compared with the conventional case, and can realize cost reduction. it can.

According to the invention described in claim 7,
The input switch and the output switch are turned on, and the negative potential supply switch, the reading switch, and the ground switch are turned off to supply the output of the strain sensor to the differential amplifier. Since each of the output switches is turned off and the negative potential supply switch, the reading switch, and the ground switch are turned on, the information stored in the TEDS is read by the reading means. By simply controlling the switch on / off, it is possible to easily and reliably switch between the strain measurement mode and the strain sensor information reading mode. Therefore, by automating the operation of the switch, speeding up the measurement work, A strain measurement device that can eliminate human error It can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of a sensor main body and a strain measuring apparatus using the sensor main body of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a circuit diagram showing the configuration of the main part of the sensor main body according to the first embodiment of the present invention and the relationship between terminals.
The sensor main body 11 according to the first embodiment shown in FIG. 1 is roughly composed of a strain sensor 12, a TEDS 13 as an information storage medium, and a mode switching circuit 15.
First, in the strain sensor 12, a Wheatstone bridge circuit (hereinafter referred to as a “bridge circuit”) is formed by four strain gauges SG1 to SG4. More specifically, one end of the first strain gauge SG1 One end of the strain gauge SG2 is connected, and the connection point is defined as a negative output end 12b. The other end of the second strain gauge SG2 and one end of the third strain gauge SG3 are connected, and the connection point is defined as a negative input end 12c. The other end of the third strain gauge SG3 and one end of the fourth strain gauge SG4 are connected, and the connection point is defined as a positive output end 12d.

The other end of the fourth strain gauge SG4 and the other end of the first strain gauge SG1 are connected, and the connection point is a positive input end 12a.
The positive input terminal 12a is directly connected to the positive input terminal A via a cable (or a lead wire; the same applies hereinafter), and the negative output terminal 12b is connected to the negative side via the negative mode switching circuit 15. The negative input terminal 12c is directly connected to the negative input terminal C, and the positive output terminal 12d is connected to the positive output terminal D via the positive mode switching circuit 15. It is connected. The cable shield 14 is connected to the spare terminal E.
That is, the mode switching circuit 15 is inserted in series between the positive output terminal 12d and the positive output terminal of the bridge circuit forming the strain sensor and between the negative output terminal 12b and the negative output terminal B. Will be.
In this embodiment, TEDS 13 is used as an example of the information storage medium.

TEDS is an abbreviation for Transducer Electronic Data Sheet, which refers to an electronic data sheet built into the sensor, has a readable / writable memory inside, and can store the sensor itself and necessary information related to its use. . In the so-called smart transducer or smart sensor, a part of the memory is used for storing the sensor specification defined by the manufacturer, and the other part can be defined by the user.
For example, at the time of shipment from a manufacturer, the manufacturer name, sensor type, model, serial number, calibration value, sensitivity, etc. should be entered as basic information, and the user can enter sensor information, measurement channel ID, point, direction, etc. Further, information such as a tag number, a measurement mode, and a measurement date / time can be added and stored.
The TEDS 13 can read and write each information stored therein by grounding one end and supplying a negative potential lower than the ground potential to the other end.

As will be described later in detail, the mode switching circuit 15 is an analog corresponding to the physical quantity or mechanical quantity to be measured output from the strain sensor 12, such as strain, stress, displacement, operating force, load, pressure, acceleration, torque, etc. A signal and a digital signal corresponding to stored information output from the TEDS 13 are selectively output to two common output terminals B and D.
The operation in the embodiment shown in FIG. 1 will be described.
For example, assuming that the strain sensor 12 is attached to a load transducer, the sensor body 11 is a load transducer.
For example, two strain gauges SG1 and SG3 are attached by adhesion or the like along the load application direction of the strain generating portion of the load transducer, and the other two strain gauges SG2 and SG4 are attached along the direction orthogonal thereto. Assuming that the load transducer is loaded in the compression direction, the two strain gauges SG1 and SG3 are compressed and the resistance value is decreased, and the other two strain gauges SG2 and SG4 are expanded. Increases the resistance value.

Therefore, when a bridge voltage is applied between the positive input terminal A and the negative input terminal C from a bridge power supply (see reference numeral 17 in FIG. 3), based on the change in the resistance values of the strain gauges SG1 to SG4, In other words, since a voltage corresponding to the applied load is output between the positive output terminal D and the negative output terminal B, the output is expanded by a differential amplifier or a differential amplifier, which will be described later. Convert to value. This is the analog mode. In the analog mode, the relationship with the TEDS 13 is electrically disconnected by the operation of the mode switching circuit 15.
Next, the supply of the bridge voltage supplied between the positive input terminal A and the negative input terminal C is cut off, the negative output terminal B is grounded, and the positive output terminal D is grounded. By supplying a lower negative potential, the output of the strain sensor 12 is cut off by the action of the mode switching circuit 15, and the information stored in the TEDS 13 can be read digitally from the output terminal D on the positive side. it can. This is the digital mode.
According to the configuration of FIG. 1, the number of terminals of the sensor main body 11 is only four while the TEDS 15 is connected, and the number of cores of the cable connecting the sensor main body 11 and the measuring device is four, which reduces the cost. Since the thickness of the cable can be reduced and the cable can be thinned, the cable is not bulky, and the cable wiring process is facilitated.

FIG. 2 is a circuit diagram schematically showing the second embodiment of the present invention.
The embodiment of FIG. 2 is different from the embodiment of FIG. 1 in that a sensing function is added.
That is, the configuration and operation of the sensor main body 11 are the same as those in the first embodiment, and thus repeated description thereof is omitted.
In FIG. 2, a sensing lead wire 16b connects between the positive input end 12a of the bridge circuit forming the strain sensor 12 and the attached terminal F, and a sensing lead wire 12a connects between the negative input end 12c and the attached terminal G. It is tied with.
Therefore, the other ends of the pair of cables whose one ends are connected to a bridge power source on the strain measuring instrument side (not shown) are connected to the positive input terminal A and the negative input terminal C, respectively, and one end is connected to the positive side of the strain measuring instrument. The other end of the connected cable is connected to the positive output terminal D, and the other end connected to the negative side of the strain measuring instrument is connected to the negative output terminal B. The other ends of the pair of cables whose one ends are connected to the circuit are connected to the attached terminals F and G, respectively.

By disposing the remote sensing cable as described above, the change in the internal resistance caused by the change in the temperature of the cable from the strain sensor 12 to the measuring instrument side or the change in the cable length gives an error to the measurement value of the strain measurement. Measurement can be realized with high accuracy and high reliability.
That is, the TEDS data reading function and remote sensing function, which could not be realized by the conventional measurement values shown in FIGS. 4 and 5, can be realized by using only six cables (terminals).
FIG. 3 is a circuit diagram specifically showing the third embodiment of the present invention.
In FIG. 3, the circuit portion of the strain sensor 12 is the same as the corresponding circuit portion shown in FIGS. 1 and 2, and therefore the configuration and operation thereof are the same as described above, and detailed description thereof is omitted.

In the figure, a mode switching circuit 15 includes a P-channel junction FET 15a as a first switching element, an N-channel junction FET 15b as a second switching element, a diode D1, a first resistor, and a second resistor. It consists of.
A P-channel junction FET (hereinafter simply referred to as “P-type FET”) 15a is connected in series between the positive output terminal 12d of the bridge circuit and the positive output terminal D, and its gate is connected to the first output terminal 15d. The resistor R1 is connected to the negative output terminal B. An N-channel junction FET (hereinafter simply referred to as “N-type FET”) 15b is connected in series between the negative output terminal 12b and the negative output terminal B of the bridge circuit, and the gate thereof is connected to the second output terminal 12b. The resistor is connected to the positive output terminal D through the resistor R2.
The TEDS 13 has one end connected to the negative output terminal B, the other end connected to the anode of the diode D1, and the cathode of the diode D1 connected to the positive output terminal D.
The positive electrode of the bridge power supply 17 is connected to the positive input terminal A via the input switch S1, and the negative electrode is connected to the negative input terminal C via the input switch S2.

In addition to the bridge power supply 17 and the switches S1 and S2, the strain measuring instrument 24 includes differential amplifiers 18 and 19, a differential amplifier 20, a negative potential supply power source 21, a negative potential supply switch S6, a level shift control unit 22, and a CPU 23. Read switch S5, output switches S3 and S4, and ground switch S7.
The differential amplifier 18 has an input terminal connected to the positive output terminal D via the output switch S4 and a cable, and an output terminal connected to one input terminal of the differential amplifier 20 via a resistor.
The differential amplifier 19 is connected to the negative output terminal B through an output switch S3 and a cable, and the output terminal is connected to the other input terminal of the differential amplifier 20 through a resistor.
The ground switch S7 is interposed between the negative output terminal B and the ground.
A negative potential supply switch S6 is interposed between the negative electrode side of the negative potential supply power source 21 and the positive output terminal D.
A reading switch S5 is interposed between the level shift control unit 22 and the positive output terminal D.

The operation of the strain measuring apparatus having such a configuration will be described in detail with reference to FIG.
First, the digital mode (TEDS information access mode) is set first, and the information stored in the TEDS 13 is read.
Switching between the digital mode and the analog mode is performed by the on / off control of the switches S1 to S7. Specifically, the switching is performed as indicated by the truth values in Table 1.

That is, as shown in Table 1, in the mode for reading TEDS information (digital mode), the reading switch S5, the negative potential supply switch S6, and the ground switch S7 are turned on, and the input switches S1, S2, the output switch S3, Each S4 is turned off.
As described above, by turning off the input switches S1 and S2, both the P-type FET 15a and the N-type FET 15b are turned off, so that the gap between the strain sensor 12 and the positive output terminal D and the negative output terminal is not. Blocked.
On the other hand, by turning on the negative potential supply switch S6, a negative potential is supplied from the negative potential supply power source 21 to one end of the TEDS 13 via the negative potential supply switch S6 → the positive output terminal D → the diode D1. Since the other end is grounded via the ground switch S7, information on the strain sensor 12 stored in the TEDS 13, such as the installation location, direction, sensitivity, calibration value, etc., is level-shifted via the read switch S5. It can be read by the unit 22 and the CPU 23.

Next, in the analog mode, that is, in strain measurement, the input switches S1 and S2 are turned on, a bridge voltage is applied from the bridge power sources 17 and 17 between the input terminals A and C, the output switches S3 and S4 are turned on, and the negative side Output terminal B is connected to the difference amplifier 19, and the positive output terminal is connected to the difference amplifier 18. On the other hand, the reading switch S5 is turned off to disconnect the level shift control unit 22, and the negative potential supply switch S6 is turned off. The power supply 21 for supply is disconnected, and the ground switch S7 is turned off to disconnect from the ground.
When a bridge voltage is applied from the bridge power supply 17 to the bridge circuit via the input switches S1 and S2, both the P-type FET 15a and the N-type FET 15b are turned on, and the analog signal from the strain sensor 12 is output from the output terminals D and B. S4 and S3 are input to the differential amplifiers 18 and 19, and further amplified by the differential amplifier 20 to obtain a measurement output corresponding to the physical quantity to be measured and the mechanical quantity.
In the analog mode of strain measurement, the reading switch S5, the negative potential supply switch S6, and the ground switch S7 are turned off, and the differential amplifiers 18 and 19 are used with high input impedance. The analog measurement signal is only a potential, and the current hardly flows, and the influence on the strain measurement value can be prevented.

Since the P-type FET 15a, the N-type FET 15b, the diode D1, and the resistors R1 and R2 constituting the mode switching circuit 15 are made into an IC chip, this portion can be reduced in size and weight, so that a strain gauge converter It can also be housed inside or integrated.
In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary, it can implement in various deformation | transformation.
That is, in the above-described embodiment, the sensor body has been described with respect to the load transducer, but other strain gauge transducers such as a displacement transducer, a pressure transducer, an acceleration transducer, a torque transducer, an inclinometer, a soil pressure gauge, etc. The present invention can also be applied to a case where a strain gauge is directly bonded to a portion to be measured and the strain at that portion is detected.
Moreover, although the example using TEDS was shown as an information storage medium, it has a readable / writable memory inside, can store necessary information related to the sensor itself and its use, and supply a negative potential. Any device that can read information can be used regardless of its name.

It is a circuit diagram which shows the structure of the sensor main body which concerns on the 1st Embodiment of this invention. It is a circuit diagram at the time of adding the remote sensing function to the sensor main body which concerns on the 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the distortion | strain measuring apparatus which concerns on the 3rd Embodiment of this invention. It is a circuit diagram which shows the state which added and wired TEDS to the conventional strain sensor. It is a circuit diagram at the time of adding a remote sensing function to the conventional strain sensor.

Explanation of symbols

11 Sensor body 12 Strain sensor 12a, 12c Input end 12b, 12d Output end 13 TEDS (Transducer Electronic Date Sheet)
14 Shielded wire 15 Mode switching circuit 15a P-channel junction FET
15b N-channel junction FET
16a, 16b Sensing lead wire 17 Bridge power supply 18, 19 Differential amplifier 20 Differential amplifier 21 Power supply for negative potential supply 22 Level shift control unit 23 CPU
24 Strain measuring instrument S1, S2 Input switch S3, S4 Output switch S5 Reading switch S6 Negative potential supply switch S7 Ground switch SG1-SG4 Strain gauge R1, R2 Resistance D1 Diode

Claims (7)

A sensor body in which a strain sensor formed of a Wheatstone bridge circuit formed of a strain gauge and an information storage medium capable of reading and writing information on the strain sensor are disposed integrally or in the vicinity thereof,
An analog signal according to the physical quantity to be measured output from the strain sensor and a digital signal output according to the information stored in the information storage medium are selectively output to two common output terminals. A mode switching circuit for causing
Two input terminals for supplying bridge power to the Wheatstone bridge circuit;
A sensor body comprising the two output terminals to which an output end of the Wheatstone bridge circuit and an output end of the information storage medium are connected in common. The mode switching circuit includes two switching elements interposed between a pair of output terminals of the Wheatstone bridge circuit and the pair of output terminals,
One end is composed of a diode interposed between the other end of the information storage medium connected to the negative output terminal and the positive output terminal,
In a state in which bridge power is supplied to the two input terminals, an analog signal corresponding to a physical quantity to be measured is output from the output terminal from the output terminal, and in a state in which supply of the bridge power is cut off, the positive side 2. The sensor body according to claim 1, wherein information stored in the information storage medium can be read from the output terminal when a negative potential is supplied to the output terminal. The mode switching circuit includes a first switching element including a P-channel junction FET connected in series between one output terminal of the Wheatstone bridge circuit and the positive output terminal;
A second switching element comprising an N-channel junction FET connected between the other output terminal of the bridge circuit and the negative output terminal;
A first resistor connected between the gate of the first switching element and the negative output terminal;
A second resistor connected between the gate of the second switching element and the positive output terminal;
A diode having an anode connected to the other end of the information storage medium and a cathode connected to the positive output terminal;
The sensor main body according to claim 2, comprising: The information storage medium is made of TEDS, and stores any information of manufacturer name, sensor type, model, serial number, calibration value at the time of shipment, and channel ID, installation location, tag number, etc. after shipment. The sensor body according to any one of claims 1 to 3, wherein the sensor body can be stored according to a user's request. 5. The circuit portion including the first switching element, the second switching element, the first resistor, the second resistor, and the diode is formed as an IC chip. 5. The sensor main body according to claim 1. A strain measuring device using the sensor main body according to any one of claims 1 to 5, wherein a bridge power supply supplies a bridge voltage to the input terminal,
An input switch interposed between the input terminal and the bridge power supply;
A pair of differential amplifiers for detecting a difference in output of the bridge circuit;
An output switch interposed between the differential amplifier and the output terminal;
A negative potential supply switch that selectively supplies a negative potential lower than the ground potential to the positive output terminal;
Reading means for reading information stored in the TEDS;
A reading switch interposed between the reading means and the positive side of the output terminal;
A grounding switch for selectively grounding the negative side of the output terminal;
A strain measuring device characterized by comprising: The input switch and the output switch are turned on, and the negative potential supply switch, the reading switch, and the ground switch are turned off to supply the output of the strain sensor to the differential amplifier. The information stored in the TEDS is read by reading means by turning off the output switches and turning on the negative potential supply switch, the reading switch, and the grounding switch, respectively. The strain measuring apparatus according to claim 6.

Images