JP2007139806A - Magnetoresistive-electrode-type size measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a power consumption of an electronic circuit with its power fed from a battery in a portable size measuring device, such as vernier calipers in particular. <P>SOLUTION: The electronic circuit (3) for the size measuring device with a magnetoresistive electrode (100) consists of a power supply circuit for supplying at least one power supply voltage (U<SB>p</SB>, U<SB>n</SB>) for supplying power to a magnetoresistive electrode network (100) and a measurement circuit containing two differential inputs (C, C', S and S') connected with the network. The measurement circuit uses a rough counter and a microinterpolation circuit for determining a sensor position along main scale graduations from two received sine input signals. The power supply circuit periodically reduces the power supply voltage supplied to temporarily reduce energy loss in the magnetoresistive electrode (100). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetoresistive electrode type dimension measuring apparatus and a measuring method using such an apparatus.

  For example, an electronic device for measuring length or angular position in an industrial environment must generally satisfy several conflicting constraints. The device must provide accuracy and sufficient resolution and must be usable in environments exposed to vibrations or contaminants such as dust, oil or moisture. In addition, these sensors are expected to be easily incorporated into small volume instruments, fast measurement speeds, and reduced power consumption without significant adjustments and alignments, for the lowest possible cost.

  In order to meet these diverse requirements, different types of measuring machines based on different physical principles have been developed. In particular, a large number of measurement systems that use capacitance fluctuations caused by sensor displacement relative to the main scale are used in portable devices such as calipers. These devices must be kept fairly clean in order to operate, and are therefore not suitable for operation in wet environments or environments that are prone to, for example, lubricant and cutting oil release. A length measuring device based on the principle of magnetoresistive electrodes is proposed, for example, in German Offenlegungsschrift 4,233,331 (IMO) and provides very good resistance to dirt. The device described in this document includes a sensor with a magnetoresistive electrode network connected to define two Wheatstone bridges. The sensor is attached to a slider and can be displaced facing the main scale which is magnetized with a magnetization period λ. The displacement of the sensor relative to the main scale causes a change in the magnetic field applied to the various magnetoresistive electrodes of the sensor, that is, a change in its resistance. By applying a voltage to the Wheatstone bridge, a periodic function electrical signal at the position of the sensor along the main scale can be taken at their output.

  The two measurement bridges are composed of four magnetoresistive electrodes whose phases are shifted by λ / 2. The electrode corresponding to each bridge occupies a position shifted by λ / 4 phase. The electrodes of the two measuring bridges are mixed. This document further suggests the use of a barber pole structure that can change the direction of the vector of current I. Since the resistance of the magnetoresistive electrode is an angular function between the magnetization vector and the current vector, the barber pole structure allows control of the direction and amplitude of the change in magnetoresistance of the electrode caused by the displacement of the sensor.

  Each arm of the measuring bridge is constituted by a single magnetoresistive electrode and its width must be sufficient to react to a relatively small magnetic field generated by the main scale. Therefore, the resistance of the bridge arm decreases, and a large current flows through the measurement bridge. Therefore, the power consumption of this device increases.

  In the sensor described in US Pat. No. 5,386,642 (Heidenhain), the electrodes are organized in a measuring bridge, each arm of which is in phase and a plurality of magnetoresistors connected in series. It is comprised by the electrode. Therefore, the resistance of the arm of the bridge is much higher, thereby making it possible to greatly reduce the power consumption. However, the power consumption of this type of sensor is too large to be considered for use in electrically self-supporting devices, such as portable precision calipers.

  Japanese Patent Application Laid-Open No. 1-212313 describes an electronic circuit suitable for use in a magnetoresistive electrode type dimension measuring apparatus, in which the magnetoresistive electrode is powered by a DC power source.

  JP 61-173113 describes a novel way of connecting magnetoresistive electrodes in an angular dimension measuring device to reduce power consumption. The reduction in power consumption is due to the unique connection of the electrodes.

  What is described in European Patent Application No. 0924491, the contents of which are incorporated herein by reference, is an electronic circuit for a magnetoresistive dimension measuring device, in which a magnetoresistive electrode is used. In order to limit energy losses, the feeding of the measurement bridge is periodically reduced or interrupted. By feeding the measuring bridge with a 1 / n duty cycle, it is possible to divide the power consumption at the electrode by n.

  The circuit also describes a standby mode circuit that allows to reduce power consumption when the device is not in use. In standby mode, the circuit display and controller are disconnected and therefore no measurement readings are possible. These components then return when sensor displacement is detected by the magnetoresistive electrode, which must remain charged.

Therefore, the standby mode described in EP-A-0 924 491 is not very advantageous, because a device that has entered standby mode cannot be used to display the measured value, but it will power the magnetoresistive electrode. This is because a large current is continued to be used.
US Pat. No. 5,386,642 Japanese Patent Laid-Open No. 1-212313 JP 61-173113 A European Patent Application No. 0924491

  One object of the present invention is to realize a magnetoresistive electrode type measuring device different from the prior art device, the power consumption of which is less than that of the prior art device.

  In particular, one object of the present invention is to realize a portable measuring device such as a vernier caliper powered by a battery.

  According to the invention, these objects are achieved by means of a circuit which exhibits the elements of the characterizing part of the independent claim, and variants thereof are described in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more apparent by reading the following description, given by way of example, with reference to the accompanying drawings, in which:

  FIG. 1 is an exploded view of a portable electronic caliper according to the present invention.

  FIG. 2 is an electrical conceptual diagram showing that the various electrodes of the sensor are connected to form two measurement bridges.

  FIG. 3 shows a time series graph of the power signal of the measuring bridge according to the first variant of the prior art.

  FIG. 4 shows a time series graph of the power signal of the measuring bridge according to the second variant of the prior art.

  FIG. 5 shows a time series graph of the power signal of the measuring bridge according to the first variant of the invention.

  FIG. 6 shows a time series graph of the power signal of the measuring bridge according to the second variant of the invention.

  FIG. 7 shows a time series graph of the power signal of the measuring bridge according to the third variant of the invention.

  FIG. 8 shows a time series graph of the power signal of the measuring bridge according to the fourth variant of the invention.

  FIG. 9 shows a time-series graph of the power signal of the measuring bridge according to the fifth variant of the invention.

  FIG. 10 shows a time series graph of the power signal of the measuring bridge according to the sixth variant of the invention.

  FIG. 11 shows a time series graph of the power signal of the measuring bridge according to the seventh variant of the invention.

  FIG. 12 shows a time series graph of the power signal of the measurement bridge according to the eighth variant of the invention.

  FIG. 1 is an exploded view of a portable electronic caliper according to the present invention. The structure of such vernier calipers is known and is described, for example, in EP-A-719999 in the name of the Applicant, the contents of which are incorporated herein by reference.

  The caliper of the present invention includes a main scale 2 and a slider 1 suitable for displacement in the longitudinal direction along the main scale. The slider has a movable jaw 10, while the main scale has a fixed jaw 20. The permanent scale 21 made of a permanent magnet material is provided with a continuous region fixed to the main scale 2 and magnetized. The main scale 21 is covered with a protective layer made of a nonmagnetic material 22 provided with a print 220.

  The electronic means, generally indicated by reference numeral 11, can display on the liquid crystal electronic display 12 information depending on the distance between the caliper jaws 10 and 20. These electronic means are assembled directly on the printed circuit board 115. The means mainly includes a magnetoresistive sensor 5 assembled under the printed circuit board 115 in front of the main scale 21 of magnetic material. The sensor 5 includes a network formed by a large number of magnetoresistive electrodes organized together, and various resistance values of the network are periodic functions of the position of the slider 1 along the main scale 2. The sensor is, for example, either of the above-mentioned German patent application DE 4233331 or US Pat. No. 5,386,642, or preferably in the name of the applicant, the contents of which are incorporated herein by reference. It can be of the type described in EP 0877228. The electronic means 11 further includes a self-supporting power supply means, in the example shown, a battery 110. The battery 110 is preferably composed of a flat lithium battery and must ensure self-sustained operation in the device for several days, preferably several months.

  The integrated electronic circuit 3 of the ASIC type determines at least one parameter depending on the distance between the jaws 10 and 20 from the resistance value of the magnetoresistive electrode in the sensor 5; the electronic circuit 3 is connected to a standard microcontroller 6 The microcontroller controls the integrated electronic circuit 3 and operates the display device 12 to display the measured distance. The electronic means 11 further preferably comprises a polarizing magnet 114 mounted on the upper surface of the printed circuit 115 facing the sensor 5.

  The electronic means 11 is protected by the case 13 and can be operated by buttons 132 for other functions such as, for example, starting or resetting calipers, adding successive readings or averaging. An optoelectronic serial connector 133 is provided as an interface between the caliper 1 and an external device such as a printer, a personal computer, or an information device.

  The magnetoresistive sensor 5 comprises a number of magnetoresistive electrodes, the dimensions of which are chosen so as to obtain a large resistance and thus reduce the power consumption of the sensor.

  The various magnetoresistive electrodes are arranged on the sensor 5 in the longitudinal direction so as to occupy various positions of the phase with respect to the magnetic field generated by the main scale 2. At a sufficient distance from the main scale 2, the magnetic field is approximately a sine function of the sensor position on the axis x. Thus, the magnetic field generated by the main scale 21 on each magnetoresistive electrode of the sensor is a sine function of the longitudinal position of this electrode; that is, the resistance of each electrode is when the slider 1 is displaced along the main scale. It changes in a sinusoidal manner. The measurement circuits 3 and 6 determine the position of the slider based on various resistance values of the magnetic resistance, and display this information on the display device 12.

  FIG. 2 schematically shows a recommended connection mode of the magnetoresistive electrode. In this example, the magnetoresistive electrodes are connected to define two measurement bridges 100 (Wheatstone bridges). Each arm of the bridge is constituted by a set of a plurality of electrodes connected in series, and the phases of the electrodes in each set are the same or close to each other. In a preferred variant embodiment, each set comprises electrodes, which are not only accompanied by a 180 ° spatial phase difference, but the barber pole structure is oriented oppositely, for example + 45 ° and −45 °. ing. The electrodes to which each measuring bridge corresponds are 90 ° out of phase in this example. Each bridge includes four sets of magnetoresistive electrodes ABCD, each A'B'C'D '. Different connection modes can be used within the scope of the invention, for example with one or three measuring bridges or even with different phase differences between the arms of the bridge.

  The number of magnetoresistive electrodes per set is preferably greater than 4 but limited only by the dimensions of the integrated circuit 5; in one embodiment of the invention, the number of magnetoresistive electrodes per set is 72 equal. In this non-limiting example with two bridges each consisting of four sets of 72 electrodes, the total number of magnetoresistive electrodes 100 in the sensor 5 is then equal to 576.

  In the example shown in FIG. 2, electrode set A, each A ', is 180 ° out of phase with electrode set C, each C'. Similarly, electrode set B, each B ', is 180 ° out of phase with electrode set D, each D'. The sets A, A ', B, B' occupy the same phase position as the respective sets C, C ', D, D'. However, the magnetoresistive electrodes of each pair AB, A'B ', CD, C'D', on the other hand, have a barber pole structure oriented, for example, at + 45 ° and -45 °.

According to the present invention, two measuring bridges 100 via a resistor 101, 103, 105 and 107, are fed between the terminals U _P and U _N; switches 102, 104, 106 and 108, each The resistors can be shorted independently. When all switches are closed, therefore, the two measurement bridges 100 are directly fed with voltages u _P and u _N ; by opening all switches, the applied voltages are u _P sb and u _N respectively. sb, thereby reducing the voltage difference across the bridge terminals and reducing power consumption. In a preferred variant embodiment of the invention, the switches 102, 104, 106 and 108 are all operated simultaneously by the same signal sb; however, within the framework of the invention, these switches are controlled independently. You can also. At the same time, if a plurality of intermediate consumption levels are valid, the measuring bridge can also be fed between a plurality of serially connectable resistors.

  When the slider 1 is shifted with respect to the main scale 21, the measurement bridge has a substantially sinusoidal difference signal c (between terminals C and C ′) and s (between terminals S and S ′) according to the position of the sensor. ), One signal is 90 ° out of phase with the other signal. These signals are transmitted to the electronic circuit 3, which amplifies the signal and determines the position of the sensor from the amplified signal, as will be described later with reference to FIG. The electronic circuit 3 further controls an interface with the keyboard 132 and an optional interface with an external device, such as a serial interface RS232 (133).

  The measuring device according to the invention preferably further comprises for parameters not shown for storing specific parameters, such as selection of measurement units, circuit status, power supply mode of the bridge currently in use, etc. Small random access memory (PRAM or EEPROM). These storage areas can also be incorporated in the circuit 3 or the microcontroller 6.

  A more detailed description of possible variants of the circuit 3 can be found in EP-A-0 924 491, the content of which is incorporated herein by reference.

  Reference will now be made to FIGS. 3 to 12 to discuss various methods of feeding the circuit of the present invention.

In variations of the prior art shown in FIG. 3, while the value U _P max DC voltage u _P (for example, 3 volts) is supplied to the terminal U _P sb, the value of another DC voltage u _N U _N min (e.g. 0 volt) is supplied to a point U _N sb on terminal U _N. Thus, the two measuring bridges are fed in a single mode using the DC voltage _UP max- _UN min, so that the power consumption is constant and high. This variant is therefore not suitable for use on portable devices powered by batteries, where power consumption is an important issue.

A variation of the feeding of the measurement bridge in the pulse feeding mode is shown in FIG. In this variation, the potential applied to the point U _P sb varies between the maximum potential U _P max and the lower potential U _P sb (eg, between Vdd and Vdd / 2). The potential at point U _N sb varies between U _N sb = U _P sb and U _N min (eg, between Vdd / 2 and Vss = 0 volts). The duty cycle is constant and T1 / (T1 + T2).

Neglecting switching losses and sequential logic power consumption, this power supply mode makes it possible to reduce the power consumption in the electrode at a rate equal to the duty cycle. Change in the potential at each cycle, in order to prevent the an amplifier supplies a signal u _P and u _N receiving too large voltage jumps, are distributed between the two terminals U _P and U _N. Therefore, it is possible to use an input amplifier where the common mode rejection ratio (CMRR) is not so important. In addition, the distribution of the voltage fluctuation, power consumption due to charging / discharging of the parasitic capacitance, as well as to reduce the switching time between the feeder section and the feed-reduction intervals, and by a complementary transition U _n of the signal U _P It is possible to compensate for the parasitic coupling induced by the transition.

Signals u _P and u _n from the clock signal of the oscillator (not shown), supplied by sequential logic (not shown). The duty cycle between the feeding section and the feeding reduction section is changed by a suitable command register in the electronic circuit 3. For example, two bits in one of these registers allows selection of four duty cycle operations: 100% (always powered), 50%, 25% (illustrated) and 0% (completely stopped).

  In contrast to the continuous feed shown in FIG. 3, this variant enables a reduction in power consumption at the electrodes. The reduction rate T1 / (T1 + T2) cannot however be chosen freely: during the period T2 during which the power supply is interrupted, no sensor displacement can be detected, so that the value displayed in this period is May be inaccurate. On the other hand, in the common case where the placement and coding of the electrodes cannot make absolute measurements of the position and only the difference can be measured, the absolute position is lost when the sensor is displaced during the interval T2, and subsequent measurements are made. Cause an error. It is therefore necessary to select a sufficiently small value of T2 to detect the minimum displacement of the sensor and to ensure that the position reference is not lost.

Another power supply variant of the measuring bridge according to the invention is shown in FIG. According to this variant, the measuring bridge is connected during the power supply interval at time T1 between the maximum potential U _P max and the potential U _N min and during the power supply reduction interval T2 between U _P sb and U _N sb. Powered, U _P sb is greater than U _N sb. Switching between the feeding section T1 and the feeding reduction section T2 is performed by operating the switches 102, 104, 106, and 108 by the signal sb. Thus, the measuring bridge is fed in a single pulse mode with the terminal voltage always equal to at least U _P sb-U _N sb, these values being chosen to allow a coarse measurement without position interpolation. Is done.

In contrast to the prior art variant shown in FIG. 4, this solution makes it possible to detect the displacement of the sensor and to preserve the absolute position of the sensor even during the power supply reduction interval T2. Thus, a much smaller duty cycle T1 / (T1 + T2) can be selected, thereby limiting the interval T1 during which the maximum voltage is applied. Power is proportional to the square of the voltage difference between the terminals U _P and U _N, whereby, in accordance with the selected values for T1, T2, U _P sb and U _N sb, the variation shown in FIG. 4 On the other hand, power consumption can be further reduced.

  In the variants shown so far, the measuring bridge is powered by a single mode, continuous or pulsed. Therefore, the average power consumption is constant during operation of the caliper regardless of whether or not the caliper is used. However, as revealed in the present invention, the effective use time is generally only part of the time that the caliper was started, but users often leave the caliper energized for several hours. To.

  A magnetoresistive electrode type measuring device having a standby mode circuit has already been described in the above-mentioned European Patent Application No. 0924491. However, in this document, the magnetoresistive electrode remains powered even when the device is in standby mode; therefore, power consumption remains high.

FIG. 6 shows a variant according to the invention that makes it possible to reduce the power consumption taking this observation into account. In this variant, two feeding modes of the measuring bridge are used. In the first mode, the measurement bridge 100 is disconnected, ie, the voltage applied to the upper terminal U _P sb is equal to the voltage applied to the lower terminal U _N sb.

The power supply to the measurement bridge immediately shifts to the second mode when an operation of the apparatus, for example, a sensor displacement or an operation key operation is detected. In this case, a Trig signal is generated, and the voltage applied to the terminals U _P sb and U _N sb is changed via a logic circuit (not shown), and the terminals shift to U _P max and U _N min, respectively. As a result, the measurement bridge is supplied with a voltage sufficient to allow precise measurement of the position by interpolation within the measurement interval. This power supply mode is maintained for a predetermined time ΔT1, and then the power supply to the bridge is cut off.

  The Trig signal is triggered, for example, in response to an event such as: one operation of the caliper key 132, an operation signal to the serial input 133, or the displacement of the sensor 5 relative to the full scale. This displacement is detected, for example, by an additional magnetoresistive electrode, not shown, which remains powered even when the measuring bridge is disconnected and measures its current variation. Thus, a Trig signal is generated.

  The time ΔT1 is preferably long enough, for example 10 minutes, which allows measurement and reading of results in most situations. This time is preferably shorter than the standby period before starting standby or stopping other functions of vernier calipers, eg, stopping display. Thus, readings of the measurements made are still possible within a limited time, even after the electrode supply interruption.

  In the case of a sensor whose position cannot be determined absolutely, this position is preferably stored in a temporary register, for example in a position counter, during the power interruption period.

  Although the solution shown in FIG. 6 is effective, an additional magnetoresistive electrode outside the measuring bridge and a movement detection for detecting the displacement of the sensor when the measuring bridge is disconnected. Requires a circuit. These factors induce cost increases and additional power consumption. On the other hand, the position counting electronics must obey certain constraints to preserve the absolute position when resetting the supply voltage of the measurement bridge.

The power supply variant shown in FIG. 7 makes it possible to solve these problems. According to this variant, the measuring bridge is fed via the resistors 101, 103, 105 and 107 during the feed reduction section. Thus the bridge is powered by a voltage equal to U _P sb-U _N sb, this difference is selected to be sufficient to enable at least motion detection and rough measurement (without position of interpolation) . As soon as displacement is detected by this coarse measurement or other activity is detected, a Trig signal is generated, the activation of the signal sb during the time ΔT1, and the resistors 101, 103, 105 and 107 A short circuit is caused to restore the complete voltage _UP max- _UN min at the bridge terminals.

  For the variant shown in FIG. 6, this solution simplifies the generation of the Trig signal and solves the problem of loss of position reference when the measurement bridge is not powered. It is therefore possible to apply more stringent conditions to the generation of the Trig signal and to enter the full power supply mode of the measuring bridge only when a sufficient amplitude and / or length displacement is detected. However, the direct current continues to flow through the magnetoresistive electrode 100 even when the caliper is in the power supply reduction mode.

FIG. 8 shows a variant similar to that described for FIG. 7, in which the feeding of the measuring bridge is completely cut off after a section ΔT2 longer than ΔT1. This variant therefore uses three different bridge feed modes:
In stop mode (“off”), no power is detected in the bridge when no movement is detected during the interval ΔT2.
In standby mode, the bridge power supply is only reduced when no movement is detected during the interval ΔT1.
In the precise measurement mode, accurate measurement can be performed during the period ΔT1 immediately after detection of motion or operation.

  The caliper shifts from the stop mode to the standby mode or directly to the precision measurement mode after one of the keys of the caliper is operated, for example. In addition, other calipers, such as a display device, can be put into a standby mode or a stop mode after a section ΔT3 exceeding ΔT2, not shown.

  FIG. 9 shows another feed variant similar to that described for FIG. 7, in which the measurement bridge feed provides motion detection and maintains absolute position with minimal power consumption. To enable, it is pulsed with a duty cycle T1 / (T1 + T2) during the power reduction period. The complete and continuous power supply of the bridge is restored for a time ΔT1 'when, for example, a Trig signal is received during the interval T1 indicating detection of displacement.

In FIG. 9, the voltage at the terminal of the measurement bridge oscillates between ( _UP max− _UN min) and 0 when the caliper is in the power supply reduction mode during section T1. In variations not shown, just sufficient for carrying out the rough measurement, a lower voltage _{(U P sb-U N sb} ) be applied for these intervals will obviously possible.

  FIG. 10 shows another variation similar to that described with respect to FIG. 7, where the feeding of the measuring bridge is such that the duty cycle T1 / when the bridge is in precision measurement mode for a time ΔT1. Pulsed at (T1 + ΔT2). This variant can therefore detect displacement, always measure the position with coarse accuracy, and allow a more precise measurement only during the time ΔT1 after the generation of the Trig signal indicating caliper operation. it can.

  In a preferred variant, the interval of time T1 is synchronized with the update display section of the display device 12, so that during or immediately before the update display cycle of the measurement values displayed on the display device, Allows accurate measurement of position.

In variant shown in FIG. 10, the measuring bridge, even when motion is not detected at all, it remains powered by the voltage U _P sb-U _N sb. As is obvious to those skilled in the art, it is possible to enter the stop mode after the period ΔT1 or ΔT2 following the generation of the Trig signal, and to completely stop the power supply.

  FIG. 11 shows another variation of the measurement bridge feed similar to that described for FIG. 10, where the measurement bridge is constantly powered with a pulse voltage. However, the duty cycle increases following detection of the operation indicated by the Trig signal, and transitions from T3 / (T3 + T4) to T1 / (T1 + T2). In a preferred variant, the interval T1 is synchronized with the update display interval of the display device 12, but it allows an accurate measurement of the position during or immediately before the update display period of the displayed measurement value. enable. This variant thus allows frequent updating of the displayed measurement only during the time ΔT1 following the detection of the event indicated by the Trig signal, only when the circuit is in the fine measurement mode.

In FIG. 11, the voltage at the terminal of the bridge always oscillates between ( _UP max− _UN min) and zero. In variations not shown, just sufficient for carrying out the rough measurement, the lower voltage _{(U P sb-U N sb} ), when the measuring bridges is in standby mode, applying during the period T3 is Obviously possible. In addition, as shown in FIG. 12, following the start of the Trig signal, it is also possible not to stop the supply voltage completely during the supply reduction period T2, but this causes a voltage jump and therefore an accurate measurement. Reduce the loss and fluctuation of capacitance during the process.

  As can be understood by those skilled in the art, in the variants of FIGS. 11 and 12, it is possible to completely stop the power supply of the measuring bridge after the interval ΔT1 or ΔT2 following the generation of the Trig signal.

  In one variant, the electronic circuit 3 further comprises a frequency meter, not shown, to determine the frequency of the measurement signal and thus the displacement speed of the sensor. According to an optional feature of the invention, the feeding mode of the measuring bridge depends on the detected frequency, which increases the duty cycle T1 / (T1 + T2) when the sensor is displaced at high speed.

  Furthermore, the duty cycle can also be manipulated by a circuit (not shown) that detects the state of charge of the battery 110 that powers the electronic circuit: to reduce power consumption when the battery supplies a voltage below a predetermined minimum value. , The duty cycle or voltage at the terminal of the bridge decreases.

  On the other hand, it can be understood that the various variants described above can be combined with each other and can also comprise a magnetoresistive electrode feed variant using two or more distinct modes. Each mode is capable of using different voltages and feeds that are continuous or pulsed at various duty cycles. In addition, various conditions can be envisaged for transitioning from one mode to another, for example, detection of displacement or manipulation indicated by one or more Trig signals, frequency of measurement signals. From a change, a change in the state of charge of the battery, various events, for example from a Trig signal, a count of a timer to be started for a variable time ΔT1, or information in at least one suitable command register in the electronic circuit 3. The command register can indicate, for example, the user's desired measurement resolution.

  Thus, it is possible to program the same circuit, for example to operate in different power supply modes, for example to optimize power consumption according to the prescribed use. This programming can be done either by software under the control of the processor 6 or by applying a special voltage to a specific leg of the sensor and / or measuring circuit, to assemble the sensor 5 and / or measuring circuit 3 on the printed circuit board 115. (Bonding).

On the other hand, all illustrated variants show rectangular power supply signals u _P and u _N for simplicity. However, as can be easily understood, the present invention can also be applied to calipers using a power signal of any shape, for example, a sine wave or triangle. Also, without departing from the scope of the present invention, changing the shape of the power signal according to the caliper mode, for example, detecting the displacement in the standby mode using a rectangular impulse train, and A sinusoidal power supply signal can also be used as soon as it is detected.

  Depending on the sensor used, other feeding modes of the magnetoresistive electrode 100 can be considered, for example current feeding, non-differential feeding. On the other hand, in the case of a circuit including a plurality of measurement bridges, these different bridges can be powered in different modes without departing from the scope of the invention.

  As described above, the measurement circuit 3 includes a differential input amplifier (not shown) for amplifying the differential signals s-s 'and c-c' coming from the two measurement bridges 100. In a preferred variant of the invention, these amplifiers can be controlled to operate in two modes, which are distinguished by different noise levels than power consumption. Therefore, the amplifier is preferably controlled to operate in the low noise and high consumption mode only during the interval ΔT1 following the generation of the Trig signal.

  Although the circuit has proved particularly advantageous in portable measuring devices, such as vernier calipers or micrometers, for example, its use is of course fixed or movable for longitudinal or angular dimensional measurements. It is possible in any type of device of the formula.

Exploded view of portable electronic caliper according to the present invention Electrical conceptual diagram showing the various electrodes of the sensor connected to form two measuring bridges Time series graph of the power signal of the measuring bridge according to the first variant of the prior art Time series graph of the power signal of the measuring bridge according to the second variant of the prior art Time series graph of the power signal of the measuring bridge according to the first variant of the invention Time series graph of the power signal of the measuring bridge according to the second variant of the invention Time series graph of the power signal of the measuring bridge according to the third variant of the invention Time series graph of the power signal of the measuring bridge according to the fourth variant of the invention Time series graph of the power signal of the measuring bridge according to the fifth variant of the invention Time series graph of the power signal of the measuring bridge according to the sixth variant of the invention Time series graph of the power signal of the measuring bridge according to the seventh variant of the invention Time series graph of the power signal of the measuring bridge according to the eighth variant of the invention

Explanation of symbols

2 Main scale 3 Electronic circuit 5 Sensor 6 Microcontroller 10 Jaw 11 Electronic means 12 Display device 13 Case 20 Jaw 21 Main scale 22 Nonmagnetic material 100 Magnetoresistive electrode 114 Polarizing magnet 115 Printed circuit 132 Button 133 Optoelectronics Serial connector

Claims (2)

In the dimension measuring device,
A full scale (21) with a series of magnetized regions;
A sensor (5) comprising a network (100) composed of a plurality of magnetoresistive electrodes suitable for displacement parallel to the main scale (21) and connected to form a measurement bridge;
A feeding circuit for providing a bridge signal for measurement,
The power supply circuit is realized so that the measurement bridge can be supplied with power in the first power supply mode or the second power supply mode,
In the first power supply mode, the voltage supplied for the measurement and applied between the terminals of the output bridge is lower than the voltage applied to the terminal of the measurement bridge in the second power supply mode. ,
The second power supply mode enables measurement with higher accuracy than the first power supply mode,
The feature is sufficient that, in the first power supply mode, the voltage applied across the terminals of the measurement bridge allows detection of the displacement of the sensor relative to the main scale,
The dimension measuring device has a trigger signal generation circuit that responds to an operation of the dimension measuring device,
The trigger signal generation circuit shifts from the first power supply mode to the second power supply mode for the generation of the trigger signal,
A supply voltage is supplied between the two terminals (Up, Un) of the measurement bridge,
When the measurement bridge is powered in the second feeding mode, one terminal (Up) is fed with the maximum potential (Up _max ) and the other terminal (Un) is fed with the minimum potential,
When the measurement bridge is supplied with power in the first supply mode, the two terminals are supplied with an intermediate potential between the maximum potential and the minimum potential, respectively. In the dimension measuring apparatus, when the measuring bridge is connected to the external terminal via a resistor (101, 103, 105, 107) and a maximum potential has to be applied to the measuring bridge, a switch ( 102. A dimension measuring device according to claim 1, characterized in that 102, 104, 106, 108) can be able to short-circuit the resistor.

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