Sensor provided with adjusting function

Abstract

An object of the present invention is to provide an automatic compensation sensor that can eliminate an exclusive input terminal for the compensation mode signal. To achieve this object, the present invention comprises a sensor body (1), a signal output terminal (5) for outputting signals from the sensor body (1), and a controller for compensating the output signal from this signal output terminal (5).

Description

Here, N is the number of pieces of data used for taking the average, which must be sufficiently numerous.

The initial value of the mean value X (T) at the time the automatic compensation sensor is incorporated into the system is set as the sensor reference value.

Next the operation for updating the compensation value, when the microcomputer 40 evaluates secular changes in the offset drift, is explained with reference to the flow chart shown in FIG. 12.

Updating the compensation value needs to take sufficiently longer time than updating a mean value. Although the update interval may vary depending on the size of the sensor offset drift and the displacement detection frequency of the system, a one-week cycle is generally considered appropriate. In the following explanation, the interval is set to one week.

The microcomputer 40 calculates a mean value of all temperatures with regard to a mean value X (T) of error from a sensor reference value at each temperature T. More specifically, it can be shown using the following formula:
X=ΣX (T)/M

Whereas M is the number of compensation value setting temperatures T.

Then, in step S34, the above error mean value X (T) is added to a compensation value F (T) at each temperature for all temperatures to create a new compensation value.
F (T)←F (T)+X

In the remaining processes, this new value is used as the output of the compensation value.

The above configuration enables temperature and secular offset drift of the sensor to be reduced. With respect to secular offset drift, the configuration of this exemplary embodiment is particularly effective when the characteristics unique to the sensor tend to shift with voltage changes.

Eighth Exemplary Embodiment

FIG. 13 shows an automatic compensation sensor in an eighth exemplary embodiment of the present invention. In FIG. 13, the configuration of the automatic compensation sensor is identical to that of the sixth exemplary embodiment shown in FIG. 9. Only the control procedures of the microcomputer 40 are different. Explanation of other configurations is thus omitted here.

The operation of this automatic compensation sensor is explained next. As described in the sixth exemplary embodiment) the automatic compensation sensor operates in the compensation value setting mode and normal operation mode. In the compensation value setting mode, the offset drift of the sensor by temperature is compensated by employing the same operation as described in the compensation value setting mode of the sixth exemplary embodiment. Explanation is thus omitted here. Next, operation in the normal operation mode is explained with reference to a flow chart shown in FIG. 14.

In the normal operation mode, the automatic compensation sensor is considered to be built into some kind of system for operation. The microcomputer 40 operates according to the flow chart shown in FIG. 8, which is the same as in the sixth exemplary embodiment. In addition, the microcomputer 40 operates according to the flow chart shown in FIG. 11, which is the same as in the seventh exemplary embodiment.

Next, the operation of the microcomputer 40 for updating a compensation value taking into account secular changes of the offset drift is explained with reference to a flow chart shown in FIG. 14.

Updating the compensation value needs to take sufficiently longer time than updating a mean value. It is further necessary to be set longer than that in the sixth exemplary embodiment. Although the update interval may vary depending on the size of the sensor offset drift and displacement detection frequency of the system, one-month interval is generally appropriate. In the following explanation, the interval is set to one month.

The microcomputer 40, in step S35, is provided with several temperature zones between the minimum operating temperature and maximum operating temperature, and each temperature zone is called Ri. For all temperatures T included in each temperature zone Ri, zone displacement (Ri) is calculated based on a mean X (T) of error against the reference value of the sensor output at each temperature. More specifically:
X (Ri)=ΣX (T)
Whereas, T is included in Ri.

The above calculation is implemented for all zones Ri. Then, in step S36, each compensation value is updated. Here, zone displacement is smoothed while each compensation value is updated. Zone smoothing is applied to eliminate a gap in compensation amount between a zone Ri and a zone Ri+1. For example, next method can be applied.

First the lowest temperature zone R0 and the next zone R1 are compared. If they are different zone displacement X (R0) in the zone R0 and a value in the zone X (R1) are used for the M0 number of compensation value included in the zone R0. In the zone R0, a value consistent with the zone displacement X (R0) for the lowest temperature, and the zone displacement X (R1) for the highest temperature are added to update a compensation value F (T) at each temperature T included in the zone R0. More specifically:
F (T)←F (T)+X (R0)+(X (R0)−X(R1))[T−TR0]/M

Whereas TR0 is a starting temperature in the zone R0. In the same way, the same calculation as the above is executed sequentially for all zones Ri.

With the above configuration, temperature and secular offset drift of the sensor can be reduced. With respect to secular offset drift, the configuration of this exemplary embodiment is particularly effective when there is no constant trend in characteristics unique to the sensor, which may be difficult to improve accuracy of the offset compensation using the configuration of the sixth exemplary embodiment. However, compared to the configuration of the sixth exemplary embodiment, compensation value update cycle may need to be set sufficiently longer. Thus compensation accuracy may degrade in temperature zones which are not frequently used.

Ninth Exemplary Embodiment

FIG. 15 shows an automatic compensation sensor in a ninth exemplary embodiment. In FIG. 15, the basic configuration of this exemplary embodiment is the same as that in the fifth exemplary embodiment shown in FIG. 7. The same reference numerals are given to same components, and thus omitting the need for a detailed explanation.

In FIG. 15, reference numeral 90 is an abnormal value detection output terminal, which is connected to the microcomputer 40. The output of the D/A converter 42 connected to the adder 33 is also connected to the A/D converter 41.

The operation of the above automatic compensation sensor is explained next. This is basically the same as that in the sixth exemplary embodiment. Only the parts which are different are explained in details.

The sensor body 30 only executes its intrinsic operations. The microcomputer 40 has the compensation value setting mode and normal operation mode. These modes operate in the same way as in the sixth exemplary embodiment. However, at executing the following operation, abnormality is judged as shown in a flow chart in FIG. 16.

More specifically, as shown in FIG. 16A, the output of the temperature sensor 50 is converted from analog to digital in step S41. At reading the output of the temperature sensor 50, in steps S42 and S43, whether the output is the maximum temperature value or the minimum temperature value is checked. If the A/D converter 41 detects voltage generated from other than the temperature sensor 50, it is considered abnormal. In this case, in step S44, the abnormal detection output terminal 90 is activated.

In step S45 shown in FIG. 16B, D/A conversion is executed, and the output of the D/A converter 42 is read by the A/D converter 41. In step S46, A/D conversion is executed. In step S47, matching of DA value and AD value is checked. If the value is out of the allowable error range, it is judged abnormal, making the abnormal value detection output terminal 90 activated in step S48.

Next, as shown in FIG. 16C, the output of the error amplifier 70 is converted from analog to digital in step S49. At reading the sensor output in steps S50 and S51, whether the output is above the maximum error value or below a minimum error value is checked. If a value out of the sensor output range is detected, it is considered abnormal. In step S52, the abnormal value detection output terminal 90 is activated.

With the above configuration, abnormality occurred in the automatic compensation sensor can be informed to the outside, thus improving the reliability.

As explained in the fifth to ninth exemplary embodiments, the microcomputer used as a controller has a function to compensate for the sensor output. This enables the reduction of offset drift against temperature and secular changes even for a sensor which intrinsically has large offset drift and shows complicated temperature and secular changes.

INDUSTRIAL APPLICABILITY

As described above, the present invention has a control means for compensating the output signal from the signal output terminal. This enables the elimination of the exclusive input terminal normally required for the compensation mode signal.

Claims

1. An automatic compensation sensor comprising:

a at least one signal output terminal for outputting a compensated sensor signal in a normal mode and for receiving inputting an external compensation signal in a compensation mode;

a sensing unit for outputting a sensor signal responsive to a condition which is sensed by said sensing unit;

compensation value means processor coupled to the signal terminal for determining selecting and outputting based on a further condition, one of a plurality of compensation value values in the normal mode and for setting storing the plurality of compensation value values in the compensation mode based on when the external compensation signal is input to the signal terminal and received by the compensation value processor; and

an adder for summing the sensor signal and the selected one of the plurality of compensation value values and for producing the compensated sensor signal.

2. The automatic compensation sensor of claim 1, wherein the compensation value means processor receives the compensated sensor signal in the compensation mode and sets the one of a plurality of compensation value values based on the compensated sensor signal and the external compensation signal.

3. The automatic compensation sensor of claim 1, further comprising:

a diagnosis circuit responsive to the sensing unit and to the compensation value means processor for outputting a diagnosis signal, wherein the compensation value means processor receives the compensation signal diagnosis signal.

4. An The automatic compensation sensor according to claim 1, further comprising:

a sensing unit for outputting a sensor signal;

an Alternating Current (AC) component separator for outputting said external compensation signal which is an AC component signal;

compensation value means for determining and outputting a compensation value in a normal mode and for setting the compensation value in a compensation mode based on the AC component signal; and

an adder for summing the sensor signal and the compensation value and for producing the compensated sensor signal .

5. An The automatic compensation sensor according to claim 1, further comprising:

a sensor body having an analog input for receiving an analog signal, the sensor body including:

a sensing unit for producing a first sensor signal,

an adder for summing the analog signal with the first sensor signal and for producing a compensated sensor signal, and

a signal output stage for adjusting and outputting the compensated sensor signal;

a sensor for producing a second sensor signal;

an error amplifier for generating an error signal based on the compensated sensor signal and a predetermined reference value; and , wherein the

compensation value means, having a memory for storing a plurality of compensation values, for generating processor generates the analog external compensation signal based on at least one of the plurality of compensation values, the second sensor signal, and the error signal.

6. The automatic compensation sensor of claim 5, wherein the sensor is a temperature sensor.

7. The automatic compensation sensor of claim 6, wherein the compensation value means processor calculates a mean value of a plurality of error signal measurements for each of a plurality of temperatures, and wherein the compensation value means processor updates each of the plurality of compensation values based on the mean value.

8. The automatic compensation sensor of claim 6, wherein the compensation value means processor calculates a plurality of mean values each associated with a plurality of error signal measurements taken in one of a plurality of temperature zones, and wherein the compensation value means processor updates each of the plurality of compensation values based on the mean value.

9. The automatic compensation sensor of claim 5, wherein the compensation value means processor further includes an abnormal value detection output which is activated by the detection of an abnormality.

10. The automatic compensation sensor of claim 1, wherein each of said plurality of compensation values corresponds to a respective temperature.

11. The automatic compensation sensor according to claim 1, wherein said further condition includes temperature information.