JP2011169774A - Amplifier for displacement meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an amplifier for a displacement meter usable in common, even when either one of a differential transformer type displacement meter or a strain gauge type displacement meter is used. <P>SOLUTION: The amplifier for the displacement meter is equipped with a non-volatile memory element for storing whether a displacement meter is the differential transformer type displacement meter or the strain gauge type displacement meter; an instrumental amplifier 55 for altering the value of a gain to the output signal received from the displacement meter on the basis of the kind of the displacement meter; a correlation coefficient calculating unit 58 for altering a detection method with respect to the output signal received from the displacement meter, on the basis of the kind of the displacement meter; a waveform memory 53 for altering the waveform of the power supply voltage transmitted to the displacement meter on the basis of the kind of the displacement meter; and a waveform control unit 54. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a displacement meter amplifier device, and more particularly to a displacement meter amplifier device capable of selectively using a differential transformer displacement meter and a strain gauge displacement meter used in a material testing machine.

  In a material testing machine that performs a static test or a fatigue test, a displacement meter is used to measure the displacement of a test piece. As such a displacement meter, for example, a differential transformer displacement meter, which is also called an LVDT (Linear Variable Differential Transformer) type, which measures displacement by detecting a difference in electromotive force generated in a differential coil, There is known a strain gauge type displacement meter called SG (Strain Gauge) type that measures displacement by detecting a resistance change of a gauge. These displacement meters are connected to a material testing machine via a displacement meter amplifier (see Patent Document 1).

  Further, in Patent Document 2, when an LVDT output corresponding to a displacement amount is supplied to an instrumentation amplifier via a cable unit, the gain of the instrumentation amplifier must be adjusted every time the material testing machine is turned on. In order to solve the problem, a material testing machine using a cable unit with a calibration impedance for electrically supplying a virtual displacement output without giving an actual displacement to a differential transformer displacement meter is disclosed. ing.

JP 2005-331256 A JP 2009-250678 A

  There is a difference in electrical characteristics between the differential transformer type displacement meter and the strain gauge type displacement meter. For example, a differential transformer displacement meter is driven only by an alternating current, whereas a strain gauge displacement meter is driven by a direct current. In addition, since the detection sensitivity of the differential transformer displacement meter is relatively high, the gain of the receiving circuit is set low, whereas the detection sensitivity of the strain gauge displacement meter is relatively low, and the gain of the receiving circuit is set high. There are differences such as necessity. For this reason, when both the differential transformer type displacement meter and the strain gauge type displacement meter are used, it is necessary to prepare a plurality of displacement meter amplifiers corresponding to the type of the displacement meter.

  The present invention has been made to solve the above-described problem, and can be used in common regardless of whether a differential transformer displacement gauge or a strain gauge displacement gauge is used. An object of the present invention is to provide an amplifier device.

  The invention according to claim 1 is an amplifier device for a displacement meter capable of selectively using a differential transformer type displacement meter used in a material testing machine and a strain gauge type displacement meter, wherein the connected displacement meter is An identification means for identifying whether it is a differential transformer displacement gauge or a strain gauge displacement gauge, and a gain value for an output signal received from the displacement gauge based on the type of the displacement gauge identified by the identification means A gain changing means for changing the detection method, a detection changing means for changing the detection method for the output signal received from the displacement meter based on the type of the displacement meter identified by the identifying means, and the displacement meter identified by the identifying means And a power supply voltage changing means for changing the waveform of the power supply voltage transmitted to the displacement meter based on the type of the power supply.

  According to a second aspect of the present invention, in the first aspect of the present invention, the type of whether the displacement meter is a differential transformer type displacement meter or a strain gauge type displacement meter, and an electric characteristic specific to the displacement meter. A cable unit having a storage unit storing information for automatic calibration, and the identification unit is a differential transformer type displacement meter or a strain gauge type displacement meter stored in the storage unit By reading this type of information, it is possible to identify whether the connected displacement meter is a differential transformer type displacement meter or a strain gauge type displacement meter.

  According to the first aspect of the present invention, a single displacement meter amplifier can be used regardless of whether a differential transformer displacement meter or a strain gauge displacement meter is used. Therefore, it is economical and the installation space can be reduced. Further, it becomes possible to obtain expandability in selecting the displacement meter.

  According to the second aspect of the present invention, the displacement gauge connected using the displacement gauge type information stored in the storage section of the cable unit is a differential transformer displacement gauge or a strain gauge displacement gauge. Can be identified, and electrical calibration can be performed using information for electrical calibration unique to the displacement meter stored in the storage unit.

1 is a schematic diagram of a material testing machine to which a displacement gauge amplifier device according to the present invention is applied. 3 is a schematic diagram of a cable unit 24. FIG. It is explanatory drawing which shows the function of the cable unit 24 corresponding to the displacement meter 15. FIG. 3 is a block diagram of an amplifier controller 25. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a material testing machine to which a displacement gauge amplifier device according to the present invention is applied.

  This material testing machine is movable along a table 16, a pair of screw rods 11, 12 that are erected on the table 16 so as to be vertically oriented, and these screw rods 11, 12. A crosshead 13 and a load mechanism 30 for moving the crosshead 13 to apply a test force to the test piece 10 are provided.

  The cross head 13 is connected to the pair of screw rods 11 and 12 via nuts (not shown). Worm speed reducers 32 and 33 in the load mechanism 30 are connected to lower ends of the screw rods 11 and 12. The worm speed reducers 32 and 33 are connected to a servo motor 31 that is a drive source of the load mechanism 30, and the rotation of the servo motor 31 is transferred to the pair of screw rods 11 and 12 via the worm speed reducers 32 and 33. It is configured to be transmitted. As the pair of screw rods 11 and 12 rotate in synchronization with the rotation of the servo motor 31, the crosshead 13 moves up and down along these screw rods 11 and 12.

  The crosshead 13 is provided with an upper gripping tool 21 for gripping the upper end portion of the test piece 10. On the other hand, the table 16 is provided with a lower gripping tool 22 for gripping the lower end portion of the test piece 10. When performing a tensile test, the test force (tensile load) is applied to the test piece 10 by raising the cross head 13 in a state where both ends of the test piece 10 are held by the upper gripping tool 21 and the lower gripping tool 22. ).

  At this time, the test force acting on the test piece 10 is detected by the load cell 14 and input to the arithmetic control unit 23. Further, the displacement amount of the distance between the gauge points in the test piece 10 is measured by the displacement meter 15. The displacement measured value by the displacement meter 15 is input to the arithmetic control unit 23 via the cable unit 24 and the amplifier controller 25. The cable unit 24 and the amplifier controller 25 constitute the displacement meter amplifier device according to the present invention.

  The arithmetic control unit 23 is constituted by a computer, a sequencer, and peripheral devices thereof, and takes in test force data and displacement amount data from the load cell 14 and the displacement meter 15 and executes data processing. The servo motor 31 is feedback controlled by the arithmetic control unit 23.

  FIG. 2 is a schematic diagram of the cable unit 24 shown in FIG.

  The cable unit 24 connects between the displacement meter 15 and the amplifier controller 25, and includes a displacement meter-side connector 241, a tester-side connector 242, and a cable body 243 that connects them. A board 244 is disposed inside the tester-side connector 242, and a passive circuit and a nonvolatile memory element described later are mounted on the board 244.

  As will be described later, the displacement meter 15 includes a differential transformer type displacement meter and a strain gauge type displacement meter. Not only their characteristics are different from each other, but even the same type of displacement meter is used. The electrical characteristics are different, and even if the products are exactly the same, there are differences in the characteristics due to variations in manufacturing and assembly. For this reason, the contents stored in the non-volatile storage means mounted on the substrate 244, and the resistance value of the resistor and the capacitance value of the capacitor in the passive circuit are set to contents adapted to the specific characteristics of each displacement meter 15. Is set. That is, the non-volatile storage element stores information for electrical calibration unique to the displacement meter, and the passive circuit is set corresponding to each displacement meter.

  FIG. 3 is an explanatory view showing the function of the cable unit 24 corresponding to the displacement meter 15. Here, FIG. 3 (a) shows a cable unit 24a for the differential transformer type displacement meter 15a, and FIG. 3 (b) shows a cable unit 24b for the strain gauge type displacement meter 15b.

  The cable unit 24a for the differential transformer displacement meter 15a shown in FIG. 3A includes a passive circuit 245a for the working transformer displacement meter and a nonvolatile memory element 246a. The non-volatile storage element 246a stores information for electrical calibration unique to the operating transformer displacement meter 15a, and the passive circuit 245a is set corresponding to the operating transformer displacement meter 15a. On the other hand, the cable unit 24b for the strain gauge displacement meter 15b shown in FIG. 3B includes a passive circuit 245b for the strain gauge displacement meter and a nonvolatile memory element 246b. The non-volatile memory element 246b stores information for electrical calibration unique to the strain gauge displacement meter 15b, and the passive circuit 245b is set corresponding to the strain gauge displacement meter 15b.

  However, the shapes and pin assignments of the displacement gauge side connector 241 and the testing machine side connector 242 for the differential transformer type displacement meter 15a and the strain gauge type displacement meter 15b are exactly the same. For this reason, it becomes possible to use these selectively.

  FIG. 4 is a block diagram of the amplifier controller 25 shown in FIG.

  The amplifier controller 25 includes an amplifier unit 50 and a control circuit 60. The amplifier unit 50 transmits an analog signal as a primary drive signal of the displacement meter 15 to the passive circuit 245 in the cable unit 24, and an analog signal as a secondary reception signal of the displacement meter 15 from the passive circuit 245. Receive. In addition, the control circuit 60 accesses the nonvolatile memory element 246 in the cable unit 24, so that the displacement meter 15 connected from the nonvolatile memory element 246 via the cable unit 24 is connected to the differential transformer type displacement meter 15a. Or the strain gauge type displacement meter 15b and the electrical calibration information specific to the displacement meter 15 are read. The control circuit 60 is connected to the arithmetic control unit 23 in the material testing machine body.

  In the amplifier controller 25, as described above, when the control circuit 60 accesses the non-volatile storage element 246 in the cable unit 24, the displacement meter 15 connected via the cable unit 24 becomes the differential transformer type displacement meter. 15a or strain gauge displacement meter 15b is identified. Then, the following operation is executed based on information on whether the identified connected displacement meter 15 is the differential transformer displacement meter 15a or the strain gauge displacement meter 15b. The control circuit 60 and the non-volatile memory element 246 function as identification means for identifying whether the connected displacement meter 15 is the differential transformer displacement meter 15a or the strain gauge displacement meter 15b.

  The drive side circuit in the amplifier controller 25 generates a primary side drive signal to be output to the displacement meter 15 based on the information of the displacement meter 15 identified by the control circuit 60. That is, under the control of the control circuit 60, the waveform memory 53 outputs the power supply voltage waveform data corresponding to the displacement meter 15. More specifically, a sine wave is output as a power supply voltage to the differential transformer displacement meter 15a, and DC data is output as a power supply voltage to the strain gauge displacement meter 15b. At this time, the waveform controller 54 recommends the address of the waveform memory 53 for the differential transformer displacement meter 15a, and fixes the address of the waveform memory 53 for the strain gauge displacement meter 15b. The waveform controller 54 selects a frequency corresponding to each differential transformer displacement meter 15a. The output from the waveform memory 53 is D / A converted by the D / A converter and then output to the displacement meter 15 via the power amplifier 51.

  On the other hand, in the circuit on the receiving side in the amplifier controller 25, the secondary side received signal received from the displacement meter 15 is processed based on the information of the displacement meter 15 identified by the control circuit 60. That is, first, the instrumentation amplifier 55 changes the amplification factor for the received signal between the differential transformer displacement meter 15a and the strain gauge displacement meter 15b. At this time, the amplification factor is adjusted based on electrical calibration information unique to the displacement meter 15. This signal is transmitted to the correlation coefficient calculation unit 58 via the low-pass filter 56 and the A / D converter 57 while leaving the carrier signal.

The correlation coefficient calculation unit 58 performs carrier signal detection, that is, demodulation. The correlation coefficient calculation unit 58 functions as a detection change unit that changes the detection method for the output signal received from the displacement meter 15 according to the type of the displacement meter 15 identified by the control circuit 60. The detection method is changed based on information on whether 15 is the differential transformer type displacement meter 15a or the strain gauge type displacement meter 15b. More specifically, the differential transformer displacement meter 15a performs detection by correlating with e ^jωt, and the strain gauge displacement meter 15b performs detection by correlating with a constant value. Such a detection method is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-76300.

  The received signal after detection is averaged by the digital filter 59 for the measurement results for each period of the carrier signal and input to the control circuit 60. And the control circuit 60 transmits the secondary side received signal processed in the amplifier unit 50 to the calculation control part 23 shown in FIG.

  As described above, in the displacement meter amplifier device according to the present invention, as the displacement meter 15, the differential transformer displacement meter 15a and the strain gauge displacement meter 15b can be selectively used.

DESCRIPTION OF SYMBOLS 10 Test piece 11 Screw rod 12 Screw rod 13 Crosshead 14 Load cell 15 Displacement meter 16 Table 17 Illumination device 21 Upper grip 22 Lower grip 23 Operation control part 24 Cable unit 25 Amplifier controller 30 Load mechanism 31 Servo motor 50 Amplifier unit 51 Power amplifier 52 D / A converter 53 Waveform memory 54 Waveform control unit 55 Instrumentation amplifier 56 Low pass filter 57 A / D converter 58 Correlation coefficient calculation unit 59 Digital filter 60 Control circuit 241 Displacement meter side connector 242 Test machine side connector 243 Cable body 244 Substrate 245 Passive circuit 246 Non-volatile element

Claims (2)

An amplifier device for a displacement meter capable of selectively using a differential transformer displacement meter used in a material testing machine and a strain gauge displacement meter,
Identifying means for identifying whether the connected displacement meter is a differential transformer displacement meter or a strain gauge displacement meter;
Based on the type of displacement meter identified by the identifying means, gain changing means for changing a gain value for the output signal received from the displacement meter;
Based on the type of displacement meter identified by the identifying means, detection changing means for changing the detection method for the output signal received from the displacement meter;
Based on the type of displacement meter identified by the identification means, power supply voltage changing means for changing the waveform of the power supply voltage transmitted to the displacement meter;
An amplifier device for a displacement meter, comprising: In the displacement meter amplifier device according to claim 1,
A type of whether the displacement meter is a differential transformer displacement meter or a strain gauge displacement meter, and a cable unit including a storage unit that stores information for electrical calibration unique to the displacement meter;
The identification unit reads information on a type of whether the displacement gauge stored in the storage unit is a differential transformer displacement gauge or a strain gauge displacement gauge, so that the connected displacement gauge is differentially An amplifier device for a displacement meter, which identifies whether it is a transformer displacement meter or a strain gauge displacement meter.

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