JP2599503Y2 - Sensor device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor device which amplifies an output signal of a sensor such as a photoelectric sensor and changes the degree of amplification to adjust the sensor sensitivity.

[0002]

2. Description of the Related Art For example, in an amplifier circuit used for an optical sensor, a method for automatically adjusting the sensitivity is as follows.
There are the following: In other words, for example,
Japanese Patent Application Laid-Open No. 123119 discloses a method in which the amplification degree is sequentially changed in each of a state where a detected object is arranged in a detection area and a state where the object is not arranged, and an on-point and an off-point at that time are detected. The sensitivity is set by adding or subtracting a predetermined value to or from the amplification degree to obtain an intermediate value.

[0003]

However, in the above-described conventional configuration, for example, in the case of the former configuration,
The amplification level is set for a fixed slice level.However, the amplification level cannot be set finely, and only the coarse level can be set. In the case of a very small size, there arises a problem that the amplification degree cannot be set to an appropriate level for the slice level.

That is, for example, when the ON point and the OFF point are both equal to or higher than the slice level at a certain amplification degree A, if the amplification degree is lowered by one step and set to the amplification degree B, on the other hand, both the ON point and the OFF point become opposite. In some cases, the level becomes lower than the slice level. In this case, it suffices that an intermediate amplification degree between the amplification degree A and the amplification degree B can be set. However, in practice, it is often impossible to set such a fine amplification degree. When the amplification degree is set by using this method, it is impossible to set the amplification degree to an appropriate level, which causes a problem that stable detection cannot be performed.

In the case of the latter one of the above-mentioned conventional configurations, the amplification degree is determined in advance, so that when the difference between the sensor signals at the on-point and the off-point is very small, the difference is small. In some cases, the amplification degree is set so that a sufficient difference cannot be obtained between the ON point and the OFF point in the amplified signal. In this case, a sufficient difference is not obtained between the ON point and the OFF point of the amplified signal obtained by amplifying the sensor signal having a small difference between the ON point and the OFF point. Is set, the margin between the slice level and the ON point or the OFF point is small. Therefore, if the sensor signal fluctuates due to the variation of the detected object or noise, the amplified signal may fluctuate beyond the slice level. As a result, a stable detection operation may not be performed.

[0006] The present invention has been made in view of the above circumstances, and has as its object the purpose of performing a stable detection operation by setting an appropriate sensitivity even when the level difference of the sensor signal between the ON point and the OFF point is very small. It is an object of the present invention to provide a sensor device capable of performing such operations.

[0007]

The sensor device according to the present invention comprises:
It has an amplifying means for amplifying a sensor signal and outputting an amplified signal, and is intended to determine an object to be detected by comparing an amplified signal output from the amplifying means with a comparison reference value. A setting switch for performing a reading operation of each amplified signal from the amplifying means in a state where the detected object is present in the detection area and in a state where the detected object is not present in the detection area; and a setting switch. Is operated, the amplified signal is read from the amplifying means in a state where the detected object is present in the detection area, and the amplified signal is read from the amplifying means in a state where the detected object is not present in the detection area. The amplification degree is set so that the intermediate value with the amplified signal is substantially at the center of the dynamic range of the amplifying means, and the intermediate value at this time is used as a comparison reference value. Characterized in place of providing a constant sensitivity setting means.

[0008]

According to the sensor device of the present invention, the sensitivity setting means sets both the state in which the detected object is present in the detection area and the amplified signal from the amplification means in the state where the detected object is not present in the detection area. Since the amplification degree is set so that the intermediate value is substantially at the center level of the dynamic range of the amplifying means, and the intermediate value at that time is set as the comparison reference value, the difference in the sensor signal between the on point and the off point is very small. In this case, the slice level must always be set to an intermediate value between the ON point and the OFF point, and the sensitivity must be set so that a sufficient difference between the amplified signal between the ON point and the OFF point can be obtained. Therefore, a stable detection operation can always be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a reflection type photoelectric sensor will be described below with reference to FIGS.

In FIG. 1 schematically showing the entire circuit configuration, a control circuit 1 for controlling light emission, light reception and object detection is shown.
1 is a microcomputer, RAM, ROM and A
/ D conversion circuit, and also has a function as sensitivity setting means, in which an object detection program and a program for sensitivity adjustment are stored in advance and supplied with power from a DC power supply terminal VC. . A / D
The conversion circuit is, for example, of 8 bits, and converts an input analog signal into a digital signal having a value in a range of 0 to 255.

The light receiving circuit 12 as a sensor is configured as described later, and its output terminal is connected between input / output terminals a and b of a light receiving amplifier 13 to be described later and via an amplifier 14 having a predetermined amplification degree. Input terminal A of the control circuit 11
It is connected to the. In this case, the control circuit 11 A / D converts the signal input from the input terminal A and inputs the signal to the microcomputer. Further, the light receiving amplifier 13 is provided with three switching input terminals u, v, w as described later, and each is connected to the output terminals U, V, W of the control circuit 11.

The light projecting circuit 15 is constructed by connecting a series circuit of a light emitting diode 16 and an npn transistor 17 between a DC power supply terminal VC and the ground. The base of the transistor 17 is connected to the output terminal of the control circuit 11. B, and a light emission pulse is supplied from the control circuit 11.

The display circuit 18 is for displaying an output and displaying a stable operation. A series circuit of a light emitting diode 19 for output display and a resistor 20 is connected between the DC power supply terminal VC and the output terminal C of the control circuit 11. And a series circuit of a light emitting diode 21 for stable operation display and a resistor 22 is connected between the DC power supply terminal VC and the output terminal D of the control circuit 11.

In the output circuit 23, the base of the output npn transistor 24 is connected to the output terminal E of the control circuit 11 via a resistor 25, the collector is connected to the output terminal P via a resistor 26, and the emitter is Grounded.

One end of an ON setting switch 27 for setting the sensitivity of object detection is connected to the input terminal F of the control circuit 11, and the other end is grounded via a mode setting switch 28. One end of the off setting switch 29 for setting the sensitivity for non-object detection is connected to the input terminal G of the control circuit 11, and the other end is grounded via the mode setting switch 28.

The input terminal of the power supply circuit 30 is connected to an external power supply terminal + V, and the output terminal is connected to a DC power supply terminal VC. The power supply circuit 30 converts the voltage applied to the external power supply terminal + V into a predetermined DC voltage. The power is supplied to the entire circuit via the DC power supply terminal VC.

Next, with reference to FIG.
The details of the light receiving amplifier 13 will be described. First,
In the light receiving circuit 12, the collector of the npn transistor 31 is connected to the DC power supply terminal VC via the resistor 32, and the emitter is grounded. The base of the transistor 31 is a photodiode 3 as a light receiving element.
3 is connected to the collector via a resistor 34 while being grounded via the polarity shown. The collector of the transistor 31 is connected to the input terminal a of the light receiving amplifier 13 as an output terminal.

After the light received by the photodiode 33 is converted into an electric signal, the light is supplied to the input terminal a of the light-receiving amplifier 13 via the transistor 31 as a light-receiving signal having, for example, a 1.6-fold voltage. Has become.

The light receiving amplifier 13 has a configuration in which first to third three amplifier circuits 37, 38 and 39 are cascaded, and these have exactly the same configuration.
The configuration of the amplifier circuit 37 will be described as a representative, and the amplifier circuit 38
Descriptions of the configurations 39 and 39 are omitted, and are denoted by the same reference numerals in the drawings.

In the first amplifier circuit 37, the collector of an npn transistor 47 as a transistor at the input stage is connected to a DC power supply terminal VC via a load resistor 48, and the emitter is a resistance switching circuit 4 as a variable resistor circuit.
9 is grounded. The base of the transistor 47 is connected via the input resistor 50 and the capacitor 51 to the first
Is connected to the emitter of the transistor 40 of the amplifier circuit 37 of FIG.

The collector of an npn-type transistor 52 as a transistor at the output stage is connected to a DC power supply terminal VC, the emitter is grounded via an output resistor 53, and connected to the base of a transistor 47 via a feedback resistor 54. I have. The base of the transistor 52 is connected to the collector of the transistor 47.

The resistor switching circuit 49 comprises a parallel circuit of a resistor 55 and a switching npn transistor 56. The base of the transistor 56 is grounded via a resistor 57 and an input terminal via a resistor 58. u. Then, the first (second and third) amplifier circuits 3
7 (38, 39) except for the switching circuit 49 is a portion corresponding to the amplifier circuit in the present invention.

The emitter of the transistor 52 of the first amplifier 37 is connected to the second amplifier 38 as an output terminal.
Is connected to the base of the transistor 47 via the capacitor 51 and the input resistor 50, and the emitter of the transistor 52 of the second amplifier circuit 38 is connected to the capacitor 51 and the input resistor 50 of the third amplifier circuit 39 as output terminals. Is connected to the base of the transistor 47 through
The emitter of the transistor 52 of the third amplifier circuit 39 is connected to the output terminal b of the light receiving amplifier 13. The base of the transistor 56 of the second amplifier circuit 38 is connected to the resistor 5
8 to the input terminal v, and the third amplifying circuit 39
The transistor 56 has a base connected to an input terminal w via a resistor 58.

Next, regarding the operation of the present embodiment, first, the first to third amplifying circuits 37 constituting the light receiving amplifier 13 will be described.
The principle of the switching operation of the amplification degree of thirty-nine or thirty nine is explained,
Subsequently, the operation of the sensitivity adjustment will be described with reference to the flowcharts shown in FIGS.

(1) Explanation of Principle of Switching Amplification Degree In the first to third amplification circuits 37 to 39,
Since the same operation is performed, the first amplifier circuit 3
7 will be described as a representative.

First, the amplification of the transistor 47 in the input stage is A, and the amplification of the transistor 52 in the output stage is "1".
Then, the overall amplification factor is A when the feedback resistor 54 is not considered. Further, the closed-loop amplification Avc taking the feedback resistor 54 into consideration is given by the following equation, where the resistance values of the input resistor 50 and the feedback resistor 54 are R50 and R54.

[0027]

(Equation 1)

On the other hand, the amplification degree A of the transistor 47 in the input stage is set to a different value according to the setting state of the resistance switching circuit 49. That is, in the resistance switching circuit 49,
When the level of the control signal supplied from the output terminal V (or W) of the control circuit 11 is at the “L” level, the transistor 56 is off, so that the resistor 55 is interposed at the emitter of the transistor 47 in the input stage. In this state, when the level of the control signal becomes "H" level, the transistor 56 is turned on, and the emitter of the transistor 47 in the input stage is set to a substantially ground level.

Therefore, the amplification factor A of the transistor 47 in the input stage is the amplification factor AON when the transistor 56 is on and the emitter of the transistor 47 is substantially grounded, and the amplification factor AON when the transistor 56 is off.
Amplification AOF with resistor 55 interposed between emitter 7
F can be switched to both. Therefore, the resistance 5
Assuming that the resistance value of R5 is R55, each amplification degree AON and AOFF
Can be expressed as follows:

[0030]

(Equation 2)

In the above equations (3) and (4), rb is the base resistance of the transistor 47 expressed by the T parameter, re is the emitter resistance, and β is the transistor 4
The above equation is derived assuming that the grounded emitter current amplification factor is 7, and the on-resistance and leak current of the transistor 56 are zero.

The overall amplification Avc of the first to third amplifier circuits 37 to 39 shown in the above equation (1) is:
As shown by the above equations (3) and (4), the values differ depending on the values of the amplification factors AON and AOFF of the transistor 47 in the input stage. Therefore, the equations (3) and (4) are respectively replaced by the equations (1) and (4). Then, the amplification factors AvcON and AvcOFF of the whole circuit can be expressed as the following equations.

[0033]

(Equation 3)

Next, using the specific numerical values, the respective amplification factors AvcON and AvcOFF of the first to third amplifier circuits 37 to 39 in this embodiment are obtained. First, the input resistance 50,
The respective resistance values R50, R48, R55 and R54 of the load resistor 48, the resistor 55 and the feedback resistor 54 are calculated as follows.
kΩ, R48 = 20 kΩ, R55 = 13.47 kΩ and R
54 = 53.24 kΩ, and the base resistance rb, the emitter resistance re, and the common emitter current amplification factor β of the transistor 47 in the input stage are rb = 500 Ω, re, respectively.
= 200Ω and β = 100. Then, the amplification factors AON, AOFF and R are approximated by substituting into equations (2), (3) and (4), respectively, and AON = −97.56 (7) AOFF = −1.463 (8) ) R = 0.581 (9)

Therefore, when the values of equations (7), (8) and (9) are substituted into equations (5) and (6), AvcON = −5.00 (10) AvcOFF = −1.00 ( 11) As a result, the degree of amplification of the first to third amplifying circuits 37 to 39 is switched to both 1 times and 5 times according to the level of the control signal from the output terminal V or W of the control circuit 11. You can do it.

Further, the light receiving amplifier 13 is constituted by the three amplifier circuits 37, 38, and 39 as described above, and each of them can be switched to one and five times the amplification degree. Depending on the control signals from the output terminals U, V, W, the minimum is 1 to 5 times, 25 times and the maximum is 12 times.
It is possible to change and set the amplification degree up to 5 times.

When the digital value of the 8-bit A / D converter provided in the control circuit 11 is used from 51 to 255, the amplification degree is increased from 1 to 125 as described above. By switching between the stages, the output signal input to the control circuit 11 can be converted with a resolution of 2%,
In this case, as a result, the light receiving signal from the light receiving circuit 12 can be converted with a dynamic range of 625 times.

Thus, for example, assuming that the optical signal obtained by the photodiode 33 of the light receiving circuit 12 is about 1 mV, the output signal becomes about 1.6 mV, which is from a minimum of 1.6 mV to a maximum of about 1.0 V. A / D in range
It can be obtained as a conversion output.

(2) Explanation of Operation of Detection and Sensitivity Adjustment Next, the operation of sensitivity adjustment of this embodiment will be described. The control circuit 11 performs a detection operation and a sensitivity adjustment operation in accordance with the flowcharts of the programs shown in FIGS. That is, when the power is supplied, the control circuit 11 starts (starts) the program of the flowchart shown in FIG. 3, performs an initialization process in step S1, and subsequently has the amplification degree initialized in step S2. Control signals are output from output terminals U, V, and W as described above.

Thereafter, the control circuit 11 proceeds to step S3 to perform a light emitting operation. In this case, the control circuit 11
A light emitting pulse is output from the output terminal B at a predetermined frequency, the light emitting diode 16 of the light emitting circuit 15 is turned on, and pulse light is output. When this pulsed light is incident on the light receiving circuit 12 by being reflected on an object or the like, the pulse light is transmitted from the light receiving circuit 12 to the control circuit
The amplified light receiving signal is input to the input terminal A.

When the control circuit 11 proceeds to step S4, the control circuit 11 A / D converts the light receiving signal input from the light receiving circuit 12 to the input terminal A, and then performs A / D conversion in step S5.
It is determined whether or not the value of the converted light receiving signal is equal to or greater than a preset comparison reference value. At this time, A / D
When the value of the converted light receiving signal is equal to or greater than the comparison reference value, the control circuit 11 determines “YES” in step S5 and shifts to step S7.
O ”is determined, and the process proceeds to step S8.

Then, in step S7, the control circuit 11 applies a display output from the output terminal C to the light emitting diode 19 for output display of the display circuit 18 to turn on the light, and performs the A / D operation as the output on process. When the value of the converted light receiving signal is equal to or higher than the stable operation level, a display output is also given from the output terminal D to the light emitting diode 21 for stable operation display, and the light emitting diode 21 is turned on. When the number of detections has reached the predetermined number, the control circuit 11 supplies an output signal from the output terminal E to the transistor 24 of the output circuit 23 to output the signal to the output terminal P.
Is inverted to a state indicating the detection state. on the other hand,
In step S8, the control circuit 11 stops the output on process as the output off process.

Subsequently, in steps S9 and S10, the control circuit 11 determines whether the ON setting switch 27 or the OFF setting switch 29 is ON while the mode setting switch 28 is ON. to decide. Then, the control circuit 11 controls the ON setting switch 27
Is turned on, the process proceeds to an on-setting process in step S11, and if the off-setting switch 29 is on, the process proceeds to an off-setting process in step S12. In addition, when the above state is not satisfied, the control circuit 11
Returns to step S3 to repeat the above-described detection operation again.

In this case, the ON setting process in step S11 is that the pulse light from the light projecting circuit 15 is actually reflected by the object to be detected, and the detection state of the object is determined by the light receiving signal output from the light receiving circuit 12 at this time. This processing is performed in a state where the object to be detected is actually arranged in the detection area.

On the other hand, the off setting process in step S12 is a setting process performed when it is not desired to output a detection state by a light reception signal even when reflected light is incident to some extent from the detection area. Is a setting process for surely outputting a detection state only when reflected light from an object to be detected is received, for example, when there is a background that reflects the pulse light output from the light projecting circuit 15 to some extent around the object. .

The control circuit 11 executes the on-setting processing program shown in FIG. 4 in the on-setting processing in step S11. That is, the control circuit 11
First, in step T1, the amplification degree of the light receiving amplifier 13 is set to the maximum value based on the principle described above. In this case, the control circuit 11 outputs “H”, “H”, and “H” level signals from the output terminals U, V, and W, respectively.
The amplification degree of each of the first to third amplifier circuits 37 to 39 is set to a larger one.

Subsequently, the control circuit 11 causes the light emitting circuit 15 to perform a light emitting operation (step T2), samples and holds the received light signal (step T3), and converts the received light signal to an A / A signal.
D conversion is performed (step T4). At this time, an object to be detected is arranged in advance, and the pulse light from the light emitting circuit 15 is reflected and made incident on the light receiving circuit 12 side. Then, the control circuit 11 proceeds to step T5 to determine whether or not the value of the A / D-converted light receiving signal has overflowed. If "YES", the control circuit 11 increases the amplification degree by one step in step T6. After performing the lowering process, the process returns to step T2 and repeats steps T2 to T5 again.

If the value of the A / D-converted light-receiving signal does not overflow and the result of the determination is "NO" in step T5, the control circuit 11 proceeds to step T7. The value of the A / D converted light receiving signal and its amplification degree are stored in the internal memory as ON point data.

Subsequently, the control circuit 11 proceeds to step T8, and performs the following calculation as a new comparison reference value. That is, the value of the currently stored A / D-converted light receiving signal and the amplification degree at that time, and the A / D as the initially set off-point data or the off-point data set and stored as described later. From the value of the converted light receiving signal and the amplification at that time, an intermediate value between them is calculated to obtain a new comparison reference value, which is stored in the memory.

In this case, the control circuit 11 sends the digital value as the A / D conversion value serving as the comparison reference value to the light receiving amplifier 1
3 is selected and set so as to be substantially at the center of the dynamic range (output range when amplifying the input signal), and the amplification degree is set between the ON point and the OFF point. If different, A /
The above setting is performed by converting to a D conversion value.

When the amplification degree and the comparison reference value are calculated and stored in this way, the control circuit 11 determines in step T9 that
A control signal is output from the output terminals U, V, and W to set the amplification degree calculated and stored, and the program returns to the aforementioned detection program.

On the other hand, the control circuit 11 executes the off setting processing program shown in FIG. 5 in the off setting processing in step S12. That is, the control circuit 11 controls the object placed in advance and which is not to be detected.
As in the case of the above-described ON setting processing program, through steps P1 to P6, a light receiving signal of an object not to be detected is input.

Then, in step P7, the control circuit 11 stores the value of the A / D-converted light-receiving signal of the object not to be detected and the amplification at that time in the internal memory as off-point data. Become. Subsequently, the control circuit 11 proceeds to Step P8 and performs the next calculation as a new comparison reference value. That is, the value of the currently stored A / D converted light receiving signal and the amplification degree at that time, the value of the A / D converted light receiving signal as the data of the ON point set as described above, and the value at that time From the amplification degree, an intermediate value between them is calculated to obtain a new comparison reference value, which is stored in the memory.

In this case, the control circuit 11 sends the digital value as the A / D conversion value serving as the comparison reference value to the light receiving amplifier 1
3 is selected and set so as to be substantially at the center of the dynamic range (output range when amplifying the input signal), and the amplification degree is set between the ON point and the OFF point. If different, A /
The above setting is performed by converting to a D conversion value. When the amplification degree and the comparison reference value are calculated and stored in this way, the control circuit 11 outputs and sets a control signal from the output terminals U, V, W so that the calculated and stored amplification degree is obtained in step P9. Then, the process returns to the above-described detection program.

Thus, according to the use conditions of the user,
The comparison reference value of the intermediate point between the object to be detected and the object not to be detected is set at a predetermined amplification degree, and the control circuit 11 in the object detection program in FIG.
Can detect and output only the object to be reliably detected.

According to this embodiment, the control circuit 1
According to 1, when the sensitivity is set, an intermediate value between the ON point and the OFF point is set as a comparison reference value based on the light receiving signal data at the ON point and the OFF point and the amplification at that time. Even if the difference between the received light signals as the sensor signal between the two is very small, the comparison reference value can always be set to an intermediate value between the two, and the difference between the amplified signals between the ON point and the OFF point must be sufficiently obtained. And a stable detection operation can always be performed.

According to the present embodiment, the light receiving amplifier 13
The first to third amplifier circuits 37 to 39 can be configured without using large IC parts such as operational amplifiers and analog switches, so that the entire circuit can be downsized and the manufacturing cost can be reduced. it can.

Further, according to the present embodiment, each of the amplifier circuits 37 to 39 is used by using the first to third amplifier circuits 37 to 39.
By switching the amplification degree from 39 to 39 by outputting a switching signal from the control circuit 11, the overall amplification degree is switched to adjust the sensitivity, so that a wide dynamic range can be secured, and the received light signal can be greatly increased. The detection operation can be performed according to any change.

Further, according to the present embodiment, the first through third
Of the amplifying circuits 37 to 39 are arranged such that a resistance switching circuit 49 is provided on the emitter side of the transistor 47 in the input stage to switch the resistance value by interposing or short-circuiting the resistor 55, and the feedback type by the feedback resistor 54. , The gain can be stabilized and the frequency characteristics can be improved.

In the above embodiment, the resistance switching circuit 49 is used as the variable resistance circuit, and the resistance 55 is switched by the transistor 56. However, the present invention is not limited to this. For example, the resistance may be changed using a variable resistor. The value may be changed.

Further, in the above embodiment, the case where the three amplifier circuits 37 to 39 are connected has been described. However, the present invention is not limited to this, and a configuration in which two amplifier circuits 37 to 39 are connected may be used. A configuration in which the dynamic range is further increased by connecting in multiple stages may be adopted.

[0062]

As described above, according to the sensor device of the present invention, amplification is performed by the sensitivity setting means in a state where the detected object is present in the detection area and in a state where the detected object is not present in the detection area. The amplification degree is set so that the intermediate value between the two amplified signals from the means is substantially at the center level of the dynamic range of the amplification means, and the intermediate value at that time is set as a comparison reference value, so that the ON point and the OFF point Even when the difference between the sensor signals is small, the slice level is always set to an intermediate value between the ON point and the OFF point, and the difference between the amplified signals between the ON point and the OFF point is sufficiently obtained. Since such sensitivity is set, there is an excellent effect that a stable detection operation can always be performed.

[Brief description of the drawings]

FIG. 1 is an overall electrical configuration diagram showing an embodiment of the present invention.

FIG. 2 is an electrical configuration diagram of a light receiving circuit and a light receiving amplifier.

FIG. 3 is a flowchart of a detection and sensitivity setting program (part 1).

FIG. 4 is a flowchart of a detection and sensitivity setting program (part 2).

FIG. 5 is a flowchart of a detection and sensitivity setting program (part 3).

[Explanation of symbols]

11 is a control circuit (sensitivity setting means), 12 is a light receiving circuit, 1
3 is a light receiving amplifier, 14 is an amplifier (amplifying means), 15 is a light emitting circuit, 16 is a light emitting diode, 18 is a display circuit, 23
Is an output circuit, 27 is an on setting switch, 28 is a mode setting switch, 29 is an off setting switch, 30 is a power supply circuit, 33 is a photodiode, 37, 38, and 39 are first, second, and third amplifier circuits, 47 is an input stage transistor, 48 is a load resistance, 49 and 62 are resistance switching circuits, 50
Is an input resistor, 51 is a capacitor, 52 is an output stage transistor, 53 is an output resistor, and 54 is a feedback resistor.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-85404 (JP, A) JP-A-4-144410 (JP, A) JP-A-8-82637 (JP, A) JP-A-59-1984 185415 (JP, A) JP-A-9-105669 (JP, A) JP-A-3-123119 (JP, A) JP-A-2-278906 (JP, A) JP-A-2-147922 (JP, U) 6-34325 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H03G 1/00-3/18 H01L 31/12 H03F 3/00-3/195

Claims (1)

(57) [Scope of request for utility model registration] An amplifying means for amplifying a sensor signal and outputting an amplified signal, wherein an amplified signal output from the amplifying means is compared with a comparison reference value to determine an object to be detected. A setting switch for performing a reading operation of each amplified signal from the amplifying means in a state where the detected object is present in the detection area and in a state where the detected object is not present in the detection area, When this setting switch is operated, the amplified signal read from the amplifying means in a state where the detected object is present in the detection area and the amplified signal in a state where the detected object is not present in the detection area. The amplification degree is set so that an intermediate value between the read amplified signal and the dynamic range of the amplifying means is substantially at the center, and the intermediate value at this time is compared. Sensor apparatus characterized in that a sensitivity setting means for setting a reference value.