JP2001183106A - Gap detecting device with temperature compensation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measurement precision of a gap sensor which is different in tendency and degree of influence on a high temperature and a low temperature. SOLUTION: This gap detecting device is provided with a coil 11 for a sensor, an oscillation circuit 5 having a capacitor 4, a detection rectification circuit 6, and a linealizer 37 linealizing a detected gap signal G. When temperatures of a coil temperature detecting circuit 12 and the coil 11 are low, the rate of change of a temperature signal T is changed with a first voltage adjusting circuit 32. A low temperature region correcting circuit 20 adds the signal T to a gap signal G on a precedent stage of the linealizer 37. When a temperature of the coil 11 is high, the rate of change of the temperature signal T is changed with another voltage adjusting circuit 41. A high temperature range correcting circuit 21 adds the signal T to the gap signal G on the subsequent stage of the linearlizer 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current loss type non-contact type gap detecting device capable of performing temperature compensation.

[0002]

2. Description of the Related Art Eddy current loss type non-contact type gap detector
Gap sensors (hereinafter abbreviated as gap sensors) are often used to measure the number of revolutions of a high-speed rotating body, the levitation gap of a magnetic levitation traveling vehicle, and the like in a non-contact manner.

An eddy current type gap sensor uses a coil as a detection sensor, and resonates a capacitor built in an oscillation circuit and the coil of the detection sensor to oscillate a fundamental frequency. When an electric material, for example, a metal having low electric resistance, enters the magnetic field of the coil in the oscillation state, the coil generates an eddy current loss in the electric material to be detected and changes to a resonance voltage of the oscillation circuit. And the distance between the electric material and the coil, that is, the gap can be detected based on the change in the resonance voltage.

[0004]

The gap sensor is used by pulling a detection coil as a probe to the outside of the measuring instrument main body through a connection cable. In addition, the probe portion is pulled out from the substrate on which the control electronic circuit is mounted, and is used as a probe-installed gap sensor.

A probe-separated measuring instrument as described above is
In many cases, the temperature atmospheres of the probe portion and the circuit board portion on which the control circuit is mounted are significantly different, and it is difficult to measure the temperature on the board side of the electronic circuit and perform temperature compensation.

In particular, in a gap sensor, a coil used for a probe is wound around a synthetic resin or ceramic winding frame. Since this winding frame expands with an increase in temperature, it is wound. The size of the coil wound around the frame increases, the inductance of the coil increases, and the oscillation voltage increases.

The resistance of the coil changes depending on the temperature atmosphere around the probe. However, the Q (quality factor) indicating the property of the coil changes due to the temperature change of the resistance of the coil, and the transmission voltage fluctuates. I do. Since the coil is made of a metal wire, the resistance value varies with a positive temperature coefficient, and the resistance value increases as the temperature increases.

The effect of the resistance and Q of the coil on the resonance voltage is such that when the temperature is gradually increased from a temperature lower than room temperature, the effect of increasing the inductance at the first low temperature is greater, and the resonance voltage is increased. As the temperature rises, the effect of the decrease in Q of the coil becomes greater, and after the temperature where the mutual effects cancel each other, the effect of the decrease in Q prevails and the resonance voltage decreases.

FIG. 5 specifically shows the above-mentioned relationship, in which the distance between the object to be detected and the probe (hereinafter referred to as a gap) is shown.
9 is a graph showing the relationship between temperature (T) and resonance voltage (V) when (G) is constant. The gap (G) is 0 to 3
The distance between mm is changed at intervals of 0.2 mm.

As can be seen from the temperature characteristic curve of the resonance voltage (V), the resonance voltage (V) of the coil is not uniquely determined only by the gap (G), but depends on the low, middle and high temperatures. And the positive and negative polarities are different, it is difficult to easily obtain an appropriate correction value from the temperature value simply by measuring the temperature of the probe.

Further, as the gap (G) increases, the central portion of the temperature characteristic curve tends to be upwardly convex, and the resonance voltage (V) for one value of the gap (G).
However, since there are two corresponding points in the low and high ranges of the temperature (T), and it is difficult to linearize with the conventional analog calculation broken-line approximation linearization means, this linearization and temperature compensation are performed. It was difficult to consider at the same time.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to obtain a gap output signal in which a temperature is compensated for a wide range of temperatures by a simple means in a gap sensor.

[0013]

According to the present invention, the above-mentioned problem is solved as follows. (1) A sensor coil provided close to an electric material to be detected, an oscillation circuit including a capacitor that resonates with the coil, a detection rectifier circuit that detects an oscillation voltage of the oscillation circuit, and an output voltage of the detection rectifier circuit. And a linearization circuit for linearly associating the relationship between the detected electrical material and the distance of the coil with respect to the temperature of the coil, wherein the coil temperature detection measures the electrical resistance of the coil and converts the ambient temperature of the coil into an electrical value. The output voltage of the circuit and the coil temperature detection circuit
Oscillation circuit output voltage vs. coil temperature when the distance between the detected electrical material and the coil is constant. When the temperature is lower than the extreme point of the temperature characteristic curve of the coil temperature, the temperature vs. output in the temperature vs. output voltage characteristics obtained from the coil temperature detection circuit. The temperature-corresponding signal whose signal change rate is almost constant is converted to a low temperature range correction signal that corresponds to the temperature almost linearly with another change rate by a voltage adjustment circuit that can change the change rate of the temperature versus output signal. ,
There is provided a low temperature range correction circuit which adjusts the low temperature range correction signal to a gap signal obtained from the output voltage of the detection and rectification circuit at a stage preceding the linearization circuit.

(2) An oscillating circuit including a sensor coil provided close to the electric material to be detected, a capacitor for resonating with the coil, a detection rectification circuit for detecting an oscillation voltage of the oscillation circuit, and a detection rectification circuit And a linearizing circuit for linearly associating the relationship between the detected electric material and the distance of the coil with respect to the output voltage of the coil, and converting the ambient temperature of the coil into an electric value by measuring the electric resistance of the coil. When the output voltage of the coil temperature detection circuit and the temperature signal output by the coil temperature detection circuit indicate a temperature higher than the extreme point of the temperature characteristic curve of the oscillation circuit output voltage versus the coil temperature when the gap is constant, the output of the coil temperature detection circuit A temperature-corresponding signal in which the rate of change of the output signal with respect to the temperature obtained from the voltage is substantially constant is converted into another signal by the voltage adjusting circuit capable of changing the rate of change of the output signal with respect to the temperature. Is converted into a high-temperature range correction signal that substantially linearly corresponds to the temperature with the conversion ratio, and the high-temperature range correction signal is converted into a gap signal obtained from the output voltage of the detection and rectification circuit at a subsequent stage of the linearization circuit. And a high temperature range correction circuit configured to adjust the gap signal.

(3) An oscillating circuit including a sensor coil provided close to the electric material to be detected, a capacitor for resonating with the coil, a detection rectifier circuit for detecting an oscillation voltage of the oscillation circuit, and a detection rectifier circuit And a linearizing circuit for linearly associating the relationship between the detected electric material and the distance of the coil with respect to the output voltage of the coil, and converting the ambient temperature of the coil into an electric value by measuring the electric resistance of the coil. When the coil temperature detection circuit and the output voltage of the coil temperature detection circuit indicate a temperature lower than the extreme point of the temperature characteristic curve of the oscillation circuit output voltage versus the coil temperature when the distance between the detected electric material and the coil is fixed, A temperature-corresponding signal in which the rate of change of the temperature-to-output signal in the temperature-output voltage characteristic obtained from the temperature detection circuit is substantially constant, and the rate of change of the temperature-to-output signal is changed. A voltage adjustment circuit converts the low temperature range correction signal to a low temperature range correction signal substantially linearly corresponding to the temperature with another change rate, and outputs the low temperature range correction signal to the output voltage of the detection and rectification circuit at a stage preceding the linearization circuit. And the output voltage of the temperature signal output by the coil temperature detection circuit is calculated from the extreme point of the temperature characteristic curve of the oscillation circuit output voltage versus the coil temperature when the gap is constant. When a high temperature is indicated, a temperature-corresponding signal in which the rate of change of the output signal with respect to the temperature obtained from the output voltage of the coil temperature detection circuit is substantially constant is converted into another signal by the voltage adjusting circuit capable of changing the rate of change of the temperature-output signal. The change rate is converted into a high temperature range correction signal that substantially linearly corresponds to the temperature, and the high temperature range correction signal is output to the output voltage of the detection rectifier circuit at a stage subsequent to the linearization circuit. The gap signal obtained al a linearized gap signal, provided the high temperature region correction circuit so as to moderate.

[0016]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention. The gap detection circuit (1) includes a sensor coil (3) located close to the electrical material to be detected (2).
A capacitor (4) that resonates with the coil (3), an oscillation circuit (5) that resonates the coil (3) and the capacitor (4),
Detection and rectification circuit for detecting the oscillation voltage (e) of the oscillation circuit (5)
(6).

The coil (3) is connected to connection terminals (7) and (8) via a probe leading cable (9) to the outside of a circuit board (10) forming a gap detection circuit (1). , And is derived as a gap detection probe (11).

The detection and rectification circuit (6) detects and rectifies the AC oscillation voltage (e) excited by the coil (3) and the capacitor (4) by the oscillation circuit (5) and performs DC gap detection signal detection.
(V).

The gap detection signal (V) is used for detecting the electric material to be detected.
This corresponds to the distance between (2) and the coil (3), that is, the gap (G).

The coil (3) is DC-connected to the bridge circuit (13) of the temperature detection circuit (12).

The temperature detecting circuit (12) constitutes a bridge circuit (13) by further connecting the resistor (R1) and the coil (3) and the resistors (R2) and (R3) connected in series to each other in parallel.
The resistor (R1) and the coil (3) in this bridge circuit (13)
Series connection point (14) and the series connection point of resistors (R2) and (R3)
(15) and (15) are connected to input terminals (17) and (18) of a balanced voltage detection circuit (16) forming a differential amplifier circuit, respectively.

Each amplifying circuit in FIG. 1 is constituted by an analog operational amplifier, and the-and + symbols shown at the input terminals of each amplifying circuit indicate an inverting input terminal and a non-inverting input terminal, respectively. In the description above, the inverting input terminal of a minus sign is called a negative input terminal, and the non-inverting input terminal of a plus sign is called a positive input terminal.

The input terminals (17) (1) of the balanced voltage detection circuit (16) to which the connection points (14) and (15) of the bridge circuit (13) are connected.
8) has input resistances (R5) (R
4) and a feedback resistor (R
7) (R6) is connected.

The output of the temperature detecting circuit (12), that is, the output of the balanced voltage detecting circuit (16) is provided with a temperature signal (T) whose output voltage changes almost linearly with temperature as shown in FIG. ) Is obtained. This temperature signal (T) is obtained according to the DC resistance value of the coil (3), and depends on the temperature of the coil (3) itself, that is, the temperature of the probe (11) including the winding frame of the coil (3). Yes, it is.

The coil in the bridge circuit (13)
The resistance component of (3) includes the resistance of the cable (9),
Since the coil (3) has a small wire diameter and a sufficiently high resistance value as compared with the resistance of the cable (9), the temperature change relating to the resistance of the cable (9) can be ignored. .

The temperature signal (T) is supplied to a compensation temperature range determination circuit.
(19), low temperature range compensation circuit (20), high temperature range compensation circuit (21)
, Respectively.

The compensation temperature range determination circuit (19) includes a low temperature range determination circuit (22) and a high temperature range determination circuit (23).
2) (23) is composed of a window comparator. In the low temperature range determination circuit (22), a reference voltage (E1) corresponding to a temperature (T1) for distinguishing between a low temperature range and a middle temperature range is set to a positive input terminal (24).

A reference voltage (E2) corresponding to a temperature (T2) for distinguishing between a middle temperature range and a high temperature range is set at the negative input terminal (25) of the high temperature range determination circuit (23). . Both reference voltages
(E1) and (E2) are connected to a stabilized reference voltage source (26), and are provided from variable resistors (R8) and (R9) connected in series to each other.

The reference voltage (E1) of the low temperature range determination circuit (22)
From the sliding terminal (27) of the variable resistor (R8) on the low voltage side,
Further, the reference voltage (E2) of the high temperature range discriminating circuit (23) is taken out from the sliding terminal (28) of the variable resistor (R9) on the high voltage side.

The negative input terminal (29) of the low temperature range determination circuit (22),
The temperature signal (T) of the temperature detection circuit (12) is input to a positive input terminal (30) of the high temperature range determination circuit (23).

The low temperature range detection signal (L) of the low temperature range determination circuit (22) obtained by comparing the magnitude of the reference voltage (E1) with the temperature signal (T) is supplied to the low temperature range compensation circuit (20). The high temperature range detection signal (H) of the high temperature range discrimination circuit (25) obtained by comparing the reference voltage (E2) and the magnitude of the temperature signal (T) is input to the high temperature compensation circuit (21). You are typing. In addition, resistance (R10) (R11)
Is an output resistance for stabilizing the output impedance of both discriminating circuits (22) and (23).

The low temperature range compensation circuit (20) receives an addition / subtraction amplification circuit (31) having a required gain and a temperature signal (T),
The rate of change of the output voltage with respect to the temperature of the temperature signal (T) (δV / δ
T) and a first voltage regulator (32) for adjusting T).
An analog switch (34) for turning on / off the output signal (T1) of (2) with respect to the positive input terminal (33) of the addition / subtraction amplification circuit (31).

The voltage regulator (32) is called a span adjustment circuit or a full-scale adjustment circuit in a general measurement circuit or the like, and is constituted by a variable gain amplifier circuit having a fixed zero point. , That is, a circuit capable of adjusting the gradient, that is, the rate of change.

The addition / subtraction amplification circuit (31) has a negative input terminal (35).
The gap detection signal from the gap detection circuit (1)
(V) is input via an input resistor (R12), and the addition / subtraction amplifier circuit (31) changes the feedback resistor (R13) to
The gain can be adjusted.

A grounding resistor (R14) for stabilizing the input impedance is connected to the positive input terminal (33) of the addition / subtraction amplification circuit (31). The output of the addition / subtraction amplification circuit (31) is connected to a linearization circuit (36). Is being entered.

The linearizing circuit (36) is a linearizer approximating linearizer (3) using operational amplifiers having different addition bias points in multiple stages.
7) (Circuit diagram omitted), and when the analog switch (34) is off, the positive input terminal (3
When the low temperature range temperature compensation signal (TL) is not input to 3), the non-compensation linearization signal (V1) shown in FIGS. 3 and 4 is output.

FIGS. 3 and 4 show temperature characteristic curves corresponding to a plurality of fixed gaps (G) shown in FIG.
This is converted into a characteristic curve of the gap (G) versus the output voltage (V). The output voltage (V1) shown is an output voltage when the addition / subtraction amplifier circuit (31) does not input the low temperature range temperature compensation signal (TL).

The output voltage (V1) shown in FIG. 3 is a characteristic diagram in a low temperature range. In FIG. 5, the characteristic curve appears remarkably at a large gap (G) (upper curve). The gap (G) vs. the oscillation voltage (V1) at each temperature of −20 ° C., 0 ° C., 20 ° C., 40 ° C., and 80 ° C. in the temperature range lower than the temperature of 80 ° C. which is close to the maximum value which becomes the maximum convex. And characteristic curves measured at constant temperature.

The output voltage (V1) shown in FIG. 4 is a characteristic diagram in a high temperature region. In FIG. 5, the characteristic curve which is remarkably shown when the gap (G) is large (upper curve) is higher. FIG. 6 is a characteristic curve obtained by measuring the gap (G) versus the oscillation voltage (V1) at a constant temperature at each of 100 ° C., 140 ° C., and 180 ° C. in a higher temperature range than the temperature of 80 ° C. which is close to the maximum value protruding from .

The temperature characteristics of 40 ° C. and 100 ° C. with a large gap (G) show output voltages that are close to each other in FIG. 5, and almost overlap in FIGS. This 40 ℃ and 1
The portion where the gap (G) at 00 ° C. is small is slightly lower at 100 ° C., but is very close.

In FIGS. 3 and 4, reference numeral 80 indicates a dotted line.
In FIG. 5, the constant temperature characteristic curve of ° C. corresponds to the boundary between the low temperature region and the high temperature region, that is, the constant temperature characteristic curve of the maximum value portion in each gap (G).

As can be seen from the characteristic curve diagrams of FIGS.
The regions of 40 ° C., 80 ° C., and 100 ° C. are very close to each other in FIGS. 3 and 4 and exhibit small temperature characteristics with a small gap between the characteristic curves. It is a medium temperature range.

The linearizer (37) performs calibration adjustment for linearization by selecting, from among a number of characteristic curves in which the temperatures of the low temperature range and the high temperature range are fixed, those whose characteristics are similar to each other. To do.

That is, the linearizer (37) according to the present invention.
Uses a broken-line function converter composed of one circuit (one type) in which the breakpoints are not discontinuous in both the low temperature range compensation and the high temperature range compensation.

More specifically, the linearizer (37) composed of one circuit has a low temperature range of -20 to 80.degree.
Is linearized only for the characteristic curve at any one of the temperatures in the high temperature range.

For this purpose, among the characteristic curves in the low temperature range and the high temperature range, those having a high degree of commonality to both, that is, the constant temperature characteristic curves such as the above-mentioned 40 ° C. and 100 ° C. which overlap each other. Preferably, the characteristic curve of the gap versus the output voltage for those temperatures is similar to the characteristic curve in the low temperature range and the high temperature range, and the calibration of the linearization is performed based on the actually measured value in the low temperature range. (Calibration).

The specific temperature (Tx) at the time of calibration of the linearizer (37) is defined as a temperature (T1) for distinguishing the low temperature range from the medium temperature range, and the constant temperature characteristic of the specific temperature (Tx) is determined. (Tz) of the constant temperature characteristic approximating on the high temperature range side
Is the temperature (T2) for distinguishing between the medium temperature range and the high temperature range.

Specific temperature (Tx = T1) and corresponding temperature
The intermediate temperature range is defined as (Tz = T2). Since the relative temperature dependency of the intermediate temperature range is extremely small as described above, no compensation is made for the temperature compensation.

Specific temperature at the time of calibration of the linearizer (37)
When the positive input terminal (33) of the addition / subtraction amplifier circuit (31) has a zero input, the gap signal (V) at (Tx = T1) is represented by the straight lines (A) and (B) in FIGS. Output characteristics are shown. The output signal (V2 ') of the above linearizer (37)
Are input to the high temperature compensation circuit (21).

The high temperature compensation circuit (21) is provided with an addition / subtraction amplification circuit (3
8) and a voltage regulator (39) similar to the above, and the addition / subtraction amplification circuit (38) has two addition inputs as an addition circuit, and one of the addition inputs has an input resistor (R15). , The output signal (V2) of the linearizer (37) is input.

The other addition input terminal is connected to the input resistance
(R15) is provided between the negative input terminal (40) of the addition / subtraction amplifier (38) via an input resistor (R16) having the same value as that of (R15),
The second input terminal is connected to the second input terminal via an analog switch (41).
The output signal of the voltage regulator (39) is input.

The second voltage regulator (41), like the first voltage regulator (32), adjusts the rate of change of the temperature signal (T) versus the output voltage (δV / δT). is there. However, the second voltage regulator (41) can set a rate of change (δV / δT) suitable for temperature correction in a high temperature range, separately from the first voltage regulator (32). The output signal is a high temperature range temperature compensation signal (TH) input to the addition / subtraction amplifier (38) via the analog switch (41).

The addition / subtraction amplifier (38) has a feedback resistance (R17) connected to the negative input terminal (39) and a ground resistance (R18) connected to the positive input terminal (42). The output signal is substantially linearly proportional to the gap (G), and becomes a gap signal (V3) whose temperature is compensated from a low temperature range to a high temperature range.

In the low temperature range compensation circuit (20), the reference voltage (E1) of the low temperature discrimination circuit (22) corresponds to the linearization calibration temperature (Tx = T1) of the linearizer (37). By setting the voltage to the same value as the voltage of the temperature signal (T), the low temperature discriminating circuit (22) can detect the temperature signal (T) from the calibration temperature (Tx).
Is low, the low temperature range detection signal (L) becomes high level, the analog switch (34) is turned on, and the low temperature range temperature compensation signal (TL) of the first voltage regulator (32) is turned on. , And input to the adjustable amplifier circuit (31).

In the high temperature range compensation circuit (21), the reference voltage (E2) of the high temperature discrimination circuit (23) is converted to the linearizer
By setting the same value as the voltage of the temperature (Tz) corresponding to the characteristic curve of the high temperature range approximated to the characteristic curve of the calibration temperature (Tx) of the linearization of (37), the high temperature discrimination circuit (22 ), When the temperature signal (T) is higher than the temperature (Tz = T2), the high temperature range detection signal (H) becomes high level, the analog switch (41) is turned on, and the second voltage The high temperature range temperature compensation signal (TH) of the regulator (39) is input to the adjustable amplifier circuit (38).

In the intermediate temperature range where the temperature is between 40 ° C. and 100 ° C., the low temperature discriminating circuit (22) and the high temperature discriminating circuit (23)
In both cases, set the output to low level and set the analog switch (34) (4
1) are both in the off state.

Thus, in the intermediate temperature range, the low temperature range compensation circuit (20) and the high temperature range compensation circuit (21) provide the low temperature range temperature compensation signal (TL) and the high temperature range temperature compensation signal (TH).
Is passed without compensation to the original gap signals (V1) and (V2 ') without addition or subtraction.

When the temperature signal (T) is in a low temperature range of 40 ° C. or less, the temperature signal (T) is adjusted by the voltage regulator (32) at a rate of change of temperature versus output voltage. The low temperature range temperature compensation signal (TL) is input to the positive input terminal (33) of the addition / subtraction amplification circuit (31) via the analog switch (34) that is turned on.

At this time, the positive input terminal of the addition / subtraction amplification circuit (31)
As shown in FIG. 3, a low temperature range temperature compensation signal (TL) adjusted so as to become zero level at the calibration temperature (Tx = 40 ° C.) is input to (32). In the addition / subtraction amplifier circuit (31), the gap signal (V) output from the detection rectifier circuit (6)
Is added to

In FIG. 3, the uncompensated gap signal
(V1) and the low temperature range temperature compensation signal (TL) are added and input to the linearizer (37).

(TL ') in FIG. 3 is a low temperature range temperature compensation signal.
(TL) is a characteristic curve when only the linearizer (37) is passed, and the gap signal after compensation is obtained at −20 ° C.
The output voltage of the voltage adjusting circuit (32) is adjusted so that (V2) overlaps the calibration characteristic line (A) at 40 ° C. However, the zero point at 40 ° C. is maintained.

As described above, in the low temperature range, from the temperature of the upper limit of compensation, that is, the calibration temperature for linearization (Tx = 40 ° C.),
In the range of the lower limit temperature of −20 ° C., at both the upper limit temperature and the lower limit temperature, the output voltage reference point (zero point) of the voltage adjustment circuit (32) and the rate of change of the output voltage with respect to temperature (δV / δT)
Thus, the degree of compensation can be appropriately adjusted, and the degree of matching in the middle is compensated with sufficiently higher accuracy than that without compensation, even if it includes a slight error.

Adjustment of these compensations is performed by appropriately changing the target points and values to be adjusted in consideration of the error rate of the entire low temperature range, the error rate of the temperature range having the highest utilization rate, and the like. Preferably, a calibration is performed.

In this low temperature range, the linearizer
The compensated gap signal (V2 = A) output by (37) is
The signal passes through the high temperature range compensation circuit (21) without compensation, and outputs a compensated gap signal (V3) from the output of the addition / subtraction amplification circuit (38).

Similarly, in the high temperature range, the temperature signal
When (T) becomes 100 ° C. or higher, the temperature signal (T) becomes
In the other voltage regulator (41), the rate of change of the temperature with respect to the output voltage is adjusted, and the analog switch (41) which is turned on at that time passes through the negative input terminal (38) of the addition / subtraction amplifier circuit (38). 40) is input as a high temperature range temperature compensation signal (TH).

As shown in FIG. 4, the high temperature range temperature compensation signal (TH) is adjusted so that the addition / subtraction amplification circuit (38) becomes zero level at 100 ° C.

As shown in FIG. 4, in the high temperature range, the uncompensated and linearized gap signal (V2 '= B) is
When the temperature rises in response to a temperature change, a gap signal (V
It shows the characteristic of moving parallel to the straight line (B) so that 2 ′) decreases. In the high temperature range temperature compensation signal (TH), the rate of change of temperature versus output voltage (δV / δT) is adjusted so as to overlap the characteristic curve of 100 ° C at the upper limit temperature of 180 ° C in the high temperature range.

Thus, in the high temperature range of 100 to 180, the high temperature range temperature compensation signal (TH) which increases in proportion to the temperature is added in the addition / subtraction amplification circuit (38), and this addition / subtraction amplification circuit (38) From (38), a compensated gap signal (V3) that has been subjected to high-precision temperature compensation is output. In the middle temperature range of 40 ° C. to 100 ° C., the gap signal (V 2 = A) linearized without compensation passes through the addition amplifier circuit (38) without compensation, and the final gap signal
(V3) is output.

Since the gap detecting device according to the present invention requires a wide temperature compensation range as a portable general-purpose measuring instrument, the low temperature compensation circuit (20) and the high temperature compensation circuit (23) Although a device having both of these is preferable, a gap detection device having a detection coil permanently installed as a probe, for example,
Low temperature compensation circuits are used for indoor magnetic levitation traveling devices such as gap detection devices that are transferred in indoor normal temperature environments.
It has only (20), only for the low temperature range, or for the low temperature range and the middle temperature range, and can sufficiently achieve the temperature compensation function.

As for the gap detecting device used from the middle temperature to the high temperature, a gap detecting device having only the high temperature compensating circuit (21) for the medium temperature region and the high temperature region or dedicated to the high temperature region is sufficient. The function of temperature compensation can be achieved.

In the above description, each electronic circuit used in the embodiment of the present invention is described as being constituted by an analog operational amplifier or the like, but the low temperature compensation circuit (20) and the high temperature compensation circuit
It goes without saying that the present invention can be applied to digitalized parts of (21) and the linearizing circuit (36).

[0072]

According to the present invention, the following effects can be obtained. (a) The temperature of the coil of the detection probe is directly detected as a temperature signal, and the effect on the oscillation characteristics related to various temperature parameters of the coil is similar in the temperature characteristic curve of the gap versus the oscillation voltage. The detected temperature signal is divided into temperature ranges, and the temperature signal is added to the gap signal according to the tendency and degree of influence in the divided temperature range, so that the circuit configuration of the compensation circuit is linear. The circuit is only simple.

(B) For the part where the influence of the divided temperature range appears non-linearly, the non-linear conversion part of the inherent linearizer is used. Therefore, a separate non-linear circuit is not required as a compensation circuit. The configuration is simple and inexpensive.

(C) Aside from the calibration work of the linearizer originally provided as the gap sensor, the calibration work related to the temperature compensation of the present invention is performed by adjusting the lower and upper eyes for each temperature range. And adjustment of compensation is simple.

(D) The temperature signal obtained by measuring the temperature of the coil of the detection probe can be used as a temperature signal representing the ambient temperature of the gap detection environment, and is important for the automatic monitoring system in the automatic control device using the gap sensor. Can be used as a monitoring parameter.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a specific example of a gap detection device with temperature compensation according to the present invention.

FIG. 2 is a temperature characteristic diagram of a temperature detection circuit when the detection coil in FIG. 1 is a temperature sensor.

FIG. 3 is a graph showing a temperature characteristic of a gap-output voltage in a low temperature region in the gap detection circuit of FIG. 1;

FIG. 4 is a graph showing a temperature characteristic of a gap-output voltage in a high temperature region in the gap detection circuit of FIG. 1;

FIG. 5 is a temperature characteristic diagram of a plurality of gaps obtained by sequentially changing the size of the gap and measuring the temperature characteristic of the gap-to-resonance voltage when the gap is constant in a specific detection coil.

[Explanation of symbols]

 (1) Gap detection circuit (2) Electrical material to be detected (3) Coil (4) Capacitor (5) Oscillation circuit (6) Detection and rectification circuit (7) (8) Connection terminal (9) Cable (10) Circuit board ( 11) Gap detection probe (12) Temperature detection circuit (13) Bridge circuit (14) Series connection point (15) Series connection point (16) Balanced voltage detection circuit (17) (18) Input terminal (19) Compensation temperature range discrimination Circuit (20) Low temperature range compensation circuit (21) High temperature range compensation circuit (22) Low temperature range discrimination circuit (23) High temperature range discrimination circuit (24) Positive input terminal (25) Negative input terminal (26) Reference voltage (27) Sliding terminal (28) Sliding terminal (29) Negative input terminal (30) Positive input terminal (31) Addition / subtraction amplifier circuit (32) Voltage regulator (33) Positive input terminal (34) Analog switch (35 ) Negative input terminal (36) Linearizer (37) Linearizer (38) Adjustable amplifier (39) Voltage regulator (40) Negative input terminal (41) Analog switch (42) Positive input terminal (e) Oscillation voltage ( G) Gap (T) Temperature signal (T1) (T2) (Tz) temperature (Tx) Specific temperature (TH) High temperature range temperature compensation signal (TL) Low temperature range temperature compensation signal (V) Gap detection signal (V1) (V2) (V2 ') (V3) Gap signal (E1) (E2) Reference voltage (R1)-(R18) Resistance (R8) (R9) Variable resistor

Continued on the front page F-term (reference) 2F063 AA23 AA50 BD11 CA10 CB01 DA01 DA04 DB03 DC08 DD02 GA08 LA05 LA11 LA23 LA27 2F077 AA13 FF31 TT11 TT35 UU07 5J081 AA02 BB04 CC17 EE02 EE03 FF07 FF08 KK11 H03 MM03

Claims (3)

[Claims] An oscillation circuit including a sensor coil provided close to an electric material to be detected, a capacitor for resonating the coil, a detection rectification circuit for detecting an oscillation voltage of the oscillation circuit, and a detection rectification circuit. A gap detection device comprising: a linearization circuit for linearly associating the relationship between an electric voltage to be detected and the distance of the coil with respect to the output voltage. A coil for measuring the electric resistance of the coil and converting the ambient temperature of the coil into an electric value. When the output voltage of the temperature detection circuit and the coil temperature detection circuit indicates a temperature lower than the extreme point of the temperature characteristic curve of the oscillation circuit output voltage versus the coil temperature when the distance between the detected electric material and the coil is constant,
The temperature-corresponding signal in which the rate of change of the temperature-to-output signal in the temperature-output voltage characteristic obtained from the coil temperature detection circuit is almost constant is changed by a voltage adjusting circuit capable of changing the rate of change of the temperature-to-output signal with a different rate of change. It is converted to a low temperature range correction signal corresponding almost linearly to the temperature, and the low temperature range correction signal is added to or subtracted from the gap signal obtained from the output voltage of the detection and rectification circuit at a stage prior to the linearization circuit. A gap detection device with temperature compensation, comprising a low temperature range correction circuit. 2. An oscillating circuit including a sensor coil provided close to an electric material to be detected, a capacitor that resonates with the coil, a detection rectifier circuit that detects an oscillation voltage of the oscillation circuit, and a detection rectifier circuit. A gap detection device comprising: a linearization circuit for linearly associating the relationship between an electric voltage to be detected and the distance of the coil with respect to the output voltage. A coil for measuring the electric resistance of the coil and converting the ambient temperature of the coil into an electric value. The output voltage of the temperature signal output from the temperature detection circuit and the coil temperature detection circuit is
When the temperature is higher than the extreme point of the temperature characteristic curve of the oscillation circuit output voltage vs. coil temperature when the gap is constant, the temperature-corresponding signal in which the rate of change of the temperature-to-output signal obtained from the output voltage of the coil temperature detection circuit is substantially constant is By a voltage adjusting circuit capable of changing the rate of change of the output signal with respect to temperature, the signal is converted into a high temperature range correction signal substantially linearly corresponding to the temperature with another change rate, and the high temperature range correction signal is converted into the linearization circuit. And a high temperature range correction circuit configured to add or subtract a gap signal obtained from an output voltage of the detection rectifier circuit to a linearized gap signal in a subsequent stage. 3. A sensor coil provided close to an electric material to be detected, an oscillation circuit including a capacitor for resonating with the coil, a detection rectifier circuit detecting an oscillation voltage of the oscillation circuit, and a detection rectifier circuit. A gap detection device comprising: a linearization circuit for linearly associating the relationship between an electric voltage to be detected and the distance of the coil with respect to the output voltage. A coil for measuring the electric resistance of the coil and converting the ambient temperature of the coil into an electric value. When the output voltage of the temperature detection circuit and the coil temperature detection circuit indicates a temperature lower than the extreme point of the temperature characteristic curve of the oscillation circuit output voltage versus the coil temperature when the distance between the detected electric material and the coil is constant,
The temperature-corresponding signal in which the rate of change of the temperature-to-output signal in the temperature-output voltage characteristic obtained from the coil temperature detection circuit is almost constant is changed with a different rate of change by the voltage adjustment circuit that can change the rate of change of the temperature-to-output signal. It is converted to a low temperature range correction signal corresponding almost linearly to the temperature, and the low temperature range correction signal is added to or subtracted from the gap signal obtained from the output voltage of the detection and rectification circuit at a stage prior to the linearization circuit. The output voltage of the temperature signal output by the low temperature range correction circuit and the coil temperature detection circuit is
When the temperature is higher than the extreme point of the temperature characteristic curve of the oscillation circuit output voltage vs. coil temperature when the gap is constant, the temperature-corresponding signal in which the rate of change of the temperature-to-output signal obtained from the output voltage of the coil temperature detection circuit is substantially constant is By a voltage adjusting circuit capable of changing the rate of change of the output signal with respect to temperature, the signal is converted into a high temperature range correction signal substantially linearly corresponding to the temperature with another change rate, and the high temperature range correction signal is converted into the linearization circuit. A gap detection device with temperature compensation, comprising, in a subsequent stage, a high-temperature region correction circuit configured to add or subtract a gap signal obtained by linearizing a gap signal obtained from an output voltage of a detection and rectification circuit.