Automatic variable resistor adjustment system, and hydraulic system

Abstract

To provide an automatic variable resistor adjustment system for efficiently enabling highly accurate measurement by a sensor by adjusting a variable resistor, and a hydraulic system using the automatic variable resistor adjustment system.SOLUTION: A controller 7 can control a variable resistor 5. The controller 7 includes an input part 11 capable of inputting information, a calculation part 13 capable of calculating an adjustment value (a wipe amount) of the variable resistor 5, and a variable resistor adjustment part 15 for adjusting the variable resistor 5. The input part 11 can input information such as use condition information and measurement scale condition information to the controller 7. The controller 7 can automatically adjust the wipe amount of the variable resistor 5 by the variable resistor adjustment part 15 on the basis of a condition calculated by the calculation part 13 or on the basis of information stored in a storage part storing the information calculated in advance by the calculation part 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an automatic adjustment system for a variable resistor for adjusting the output voltage of a sensor before inputting it to an A / D converter, and to a hydraulic system using the same. [Background technology]

[0002] For example, to control a hydraulic system, there is a controller that A / D converts and inputs analog voltage signals from pressure sensors and the like installed in hydraulic circuits. Pressure sensors with an output voltage of, for example, 1 to 5 V are used. If the measurable range of the pressure sensor is, for example, 0 MPa to 60 Ma (for simplicity, the lower limit is set to 0), a voltage of 1 to 5 V is output in accordance with a pressure of 0 to 60 Ma.

[0003] FIG. 7(a) is a conceptual diagram showing the relationship between the pressure measured by a pressure sensor and the sensor output voltage. As shown in the figure, for example, a voltage of 1 V is output at 0 MPa, and a voltage of 5 V is output at 60 MPa. On the other hand, if the detection value range input to the A / D converter is 0 to 4000, and this voltage is directly A / D converted, the output voltage range of 0 to 1 V, which does not actually need to be detected, will also be converted, resulting in waste. On the other hand, if the sensor output voltage range is 1 to 5 V, and a voltage of 0 to 4 V is made to correspond to the detection value range of 0 to 4000 input to the A / D converter, there will be a range that cannot be detected.

[0004] For this reason, in order to eliminate such problems of waste and inability to measure and to make subsequent processing easier, it is common to use a variable resistor or the like to adjust the voltage before inputting it into the A / D converter.However, in many cases, this adjustment is done by an operator actually turning an adjuster such as a trimmer, which takes a lot of man-hours and requires skill to achieve sufficient accuracy.

[0005] Therefore, for example, Patent Document 1 proposes a method of setting a correction value using a microcomputer based on the detection result of A / D conversion. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-221127 Summary of the Invention [Problem to be solved by the invention]

[0007] By appropriately setting the gain adjustment variable resistor and the operating point adjustment variable, it is possible to set 0 MPa as the lower detection limit of the A / D converter and detect the 4 V range of 1 to 5 V at full scale, as shown in Figure 7(b), for example. In this way, it is possible to trim the 0 to 1 V range that is not output from pressure sensors that are not actually used, thereby eliminating waste.

[0008] In conventional technology, such adjustment requires the actual application of an input voltage, which is time-consuming. Also, for example, in Patent Document 1, it is possible to match the detection range of the A / D converter with the output voltage range of the pressure sensor (B in Figure 7(a)), but this does not take into account the actual operating pressure range.

[0009] For example, if the pressure fluctuation range of the actual pressure circuit in which the pressure sensor is used is 15 to 25 MPa, the output voltage from the pressure sensor in the operating range will be in the range of 2 to 3 V, but the detection range of the A / D converter (for example, 0 to 4000) corresponds to the output voltage range of 1 to 5 V, so the range of detection values actually input as detection values is only a portion of the total range. This results in wasted detection range in the A / D converter.

[0010] The present invention has been made in consideration of such problems, and aims to provide an automatic variable resistor adjustment system that enables efficient and accurate measurement by a sensor by adjusting a variable resistor, and a hydraulic system using the same. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, a first invention is an automatic adjustment system for a variable resistor used in a sensor, comprising: a sensor; a variable resistor to which a sensor output voltage from the sensor is input; an A / D converter that performs analog / digital conversion of the adjusted detection value adjusted and output by the variable resistor; and a controller that controls the variable resistor, wherein usage condition information and measurement scale condition information for the sensor can be input to the controller, and the controller is capable of adjusting the variable resistor so that a detection range input to the A / D converter that corresponds to the maximum measurable range of the sensor includes the usage condition information and corresponds to a scale based on the measurement scale condition information.

[0012] The sensor may be a pressure sensor, and the use condition information may be a use pressure condition under which the pressure sensor is used.

[0013] The measurement scale condition information may be a ratio of a detection value set in the use condition information to a maximum detection value input to the A / D converter.

[0014] The measurement scale condition information may be a usable setting range of the sensor, and the controller may adjust the variable resistor so as to assign a sensor output voltage corresponding to the usable setting range of the sensor to a maximum detection range input to the A / D converter.

[0015] According to the first aspect of the present invention, the controller adjusts the variable resistor so that the maximum detection range input to the A / D converter, which corresponds to the maximum measurable range of the sensor, corresponds to a scale based on measurement scale condition information including usage condition information, thereby making it possible to accurately measure the usage condition range of the sensor.

[0016] In particular, such a sensor is suitable as a pressure sensor used in a hydraulic system.

[0017] For example, previously, the 1 to 5 V output from a pressure sensor corresponding to a range of 0 to 60 MPa was made to correspond to the detection value range input to the A / D converter (e.g., 0 to 4000). In contrast, if the operating pressure range is, for example, 15 to 25 MPa, by inputting this condition, the variable resistor can be automatically adjusted so that the output voltage from the pressure sensor, 2 to 3 V, corresponds to the detection range (0 to 4000) of the A / D converter, enabling more accurate measurements.

[0018] Furthermore, the measurement scale condition information can be the ratio (scaling adjustment value) of the detection value set in the usage condition information to the maximum detection value input to the A / D converter. This makes it easy to set the usage conditions and the upper limit of the measurement range.

[0019] Furthermore, by using the sensor's usable setting range as the measurement scale condition information, the variable resistor can be adjusted so that the sensor output voltage corresponding to the sensor's usable setting range is assigned to the maximum detection range input to the A / D converter. In this case, the measurement scale can be kept constant.

[0020] A second invention is a hydraulic system using the variable resistor automatic adjustment system according to the first invention, comprising a hydraulic circuit and a control unit that controls the hydraulic circuit, wherein the sensor is a pressure sensor, the pressure sensor is installed in the hydraulic circuit, the control unit includes the controller, and the control unit controls the operation of hydraulic equipment in the hydraulic circuit and is capable of controlling the variable resistor according to the operation based on the preset usage condition information and measurement scale condition information, thereby adjusting the measurement scale of the pressure sensor that is input to the A / D converter.

[0021] According to the second aspect of the present invention, the control unit that controls the hydraulic system grasps the state of the hydraulic system and automatically adjusts the variable resistor to provide an appropriate pressure measurement range depending on the state, so that measurements can be performed under appropriate conditions for each state, thereby enabling the hydraulic system to be controlled with high precision.

[0022] A third invention is a hydraulic system using the variable resistor automatic adjustment system according to the first invention, comprising a hydraulic circuit and a control unit that controls the hydraulic circuit, wherein the sensor is a pressure sensor, the pressure sensor is installed in the hydraulic circuit, the control unit includes the controller, and has a first state in which measurements are performed over the entire measurement range of the sensor, and a second state in which measurements are performed only over the measurement range set by the preset usage condition information and measurement scale condition information for the sensor, wherein in the first state, the control unit allows the entire sensor output voltage range of the sensor to be input to the A / D converter, and when a measurement value of the sensor remains within a predetermined range for a predetermined time, the control unit transitions to the second state and controls the variable resistor based on the usage condition information and the measurement scale condition information corresponding to the measurement value, to adjust the measurement scale of the pressure sensor that is input to the A / D converter, and in the second state, when the measurement value falls outside the set predetermined pressure range, the control unit transitions to the first state.

[0023] According to the third aspect of the present invention, under normal circumstances, measurements are made over the entire pressure range, making it possible to grasp pressure fluctuations over the entire pressure range, and when the pressure remains within a predetermined pressure range for a predetermined time, the variable resistor is adjusted to improve measurement accuracy over that pressure range, thereby enabling accurate control of the hydraulic system. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide an automatic variable resistor adjustment system that enables efficient and highly accurate measurement by a sensor by adjusting a variable resistor, and a hydraulic system using the same. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a block diagram showing the configuration of a variable resistor automatic adjustment system 1. [Figure 2] 1 is a diagram showing how to use the variable resistor automatic adjustment system 1. FIG. [Figure 3] 1 is a conceptual diagram showing the correspondence between the output voltage of the sensor and the detected value of the A / D converter when the variable resistor is adjusted using the variable resistor automatic adjustment system 1. FIG. [Figure 4] FIG. 2 is a diagram showing the configuration of a hydraulic system 20. [Figure 5] 3 is a diagram showing a control method of the automatic variable resistor adjusting system 1 in the hydraulic system 20. FIG. [Figure 6] 10 is a diagram showing another control method of the variable resistor automatic adjustment system 1 in the hydraulic system 20. FIG. [Figure 7] A conceptual diagram showing the relationship between the sensor output voltage and the A / D converter detection value when adjusting a variable resistor using a conventional method. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following describes a variable resistor automatic adjustment system 1 according to an embodiment of the present invention. Fig. 1 is a block diagram showing the configuration of the variable resistor automatic adjustment system 1. The variable resistor automatic adjustment system 1 is mainly composed of a pressure sensor 3, a variable resistor 5, a controller 7, an A / D converter 9, etc.

[0027] The pressure sensor 3 outputs a predetermined sensor output voltage (analog voltage) for the operating pressure range. For example, as shown in Fig. 7, when the pressure measurement range is 0 to 60 MPa, the sensor output voltage is 1 to 5 V. Note that although this embodiment shows an example in which the sensor is a pressure sensor, it is also applicable to other sensors such as a position sensor or an illuminance sensor.

[0028] The variable resistor 5 is a digital variable resistor to which the sensor output voltage from the pressure sensor 3 is input. In this embodiment, the variable resistor 5 includes both the variable resistor for gain adjustment and the variable resistor for operating point adjustment. For example, the variable resistor for gain adjustment can change the wipe amount in approximately 1000 steps, and by changing the wipe amount of the variable resistor 5, it is possible to change the scale of the detection value input to the A / D converter 9. The wipe amount is a value used when adjusting the variable resistor, and the larger the wipe amount, the greater the resistance value. As described above, the variable resistor for operating point adjustment can change the operating point of the detection value input to the A / D converter 9 (the sensor output voltage corresponding to a detection value of 0).

[0029] The A / D converter 9 converts the adjusted detection value (analog) adjusted and output by the variable resistor 5 into digital data. The digitally converted data is processed, for example, in the controller 7 to obtain pressure data, which is then processed as necessary.

[0030] The controller 7 has an input unit 11 that can input information, a calculation unit 13 that can calculate the adjustment value (wipe amount) of the variable resistor 5, and a variable resistor adjustment unit 15 that adjusts the variable resistor 5. In other words, the controller 7 is capable of controlling the variable resistor 5. The controller 7 is, for example, a computer, and may have a storage unit that stores various information, a display unit that displays information, etc. as needed.

[0031] Information such as use condition information and measurement scale condition information, which will be described later, can be input to the controller 7 via an input unit 11. The input unit 11 may be a user interface such as a keyboard or a touch panel, or may be a communication unit that can input information to the controller 7 from other devices.

[0032] Furthermore, the controller 7 can adjust the wipe amount of the variable resistor 5 using the variable resistor adjustment unit 15 based on the conditions calculated by the calculation unit 13 or based on information stored in a storage unit that stores information calculated in advance by the calculation unit 13. Note that the configuration of the controller 7 is not particularly limited as long as it can perform the above functions.

[0033] Next, a method of using the variable resistor automatic adjustment system 1 will be described with reference to Fig. 2. First, the initial characteristics (characteristics at the time of shipment) of the variable resistor 5 are measured (step S101). Note that since there are individual differences in variable resistors 5 at the time of shipment, measurement is required for each product, but if the accuracy is known to a certain extent, that information may be used.

[0034] Next, for example, at the site of use, the specifications of the pressure sensor 3 to be used (maximum measurable pressure, maximum and minimum sensor output voltage), usage condition information of the pressure sensor 3, and measurement scale condition information are input to the input unit 11 (step S102). The usage condition information of the pressure sensor 3 is, for example, the usage pressure condition (maximum pressure). Also, the measurement scale condition information is, for example, a scaling adjustment value that indicates the upper limit of the usage pressure to be measured.

[0035] The scaling adjustment value is the ratio of the detection value set in the usage condition information to the maximum detection value input to the A / D converter 9, and is a value that adjusts what percentage of the maximum value the operating pressure is detected as. For example, if the A / D converter 9 can detect in 1000 steps, and the operating pressure is set to 15 MPa and the scaling adjustment value is set to 60%, the detection value at 15 MPa will be 600 (60% of 1000). In this case, the maximum pressure that the A / D converter 9 can detect will be 25 MPa (15 MPa / 0.6).

[0036] Next, the calculation unit 13 calculates the wipe amount of the variable resistor 5 so that the maximum value of the sensor output voltage range of the pressure sensor 3 becomes the maximum value of the detection value of the A / D converter 9, and the variable resistor adjustment unit 15 sets the wipe amount of the variable resistor 5 (step S103). In this way, an appropriate wipe amount can be calculated from the characteristics of the variable resistor 5 measured and saved at the time of shipment in accordance with the parameters input on-site, and the variable resistor 5 can be automatically set.

[0037] As described above, the controller 7 can adjust the variable resistor so that the detection range (e.g., 0 to 4000) input to the A / D converter, which corresponds to the maximum measurable range (e.g., 0 to 60 MPa) of the pressure sensor 3, corresponds to a scale (e.g., a measurement range of 0 to 25 MPa) based on the measurement scale condition information including the use condition information. Details of the adjustments made by the controller 7 will be described later.

[0038] An actual calculation example is shown below. Note that not all of the following calculations are necessarily required. It is sufficient to calculate the wipe amount of the variable resistor 5 by determining in advance the amount of change (amplification) after A / D conversion when the wipe amount of the variable resistor 5 is changed by 1, and the conversion result after A / D conversion when the reference voltage input and reference wipe amount are set, and then setting the operating pressure and measurement scale. Furthermore, the controller 7 may further perform corrections to the conversion result after A / D conversion that are less than the resolution of the wipe amount.

[0039] First, the maximum voltage V when the A / D converter detects the maximum value (4000) dmax is calculated using formula 1. However, P use is the operating pressure of pressure sensor 3, P smax is the maximum measurable pressure of pressure sensor 3, V smax is the maximum output voltage of the pressure sensor 3, and ρ is the scaling adjustment value. The minimum sensor output voltage is assumed to be fixed (1 V). Formula 1 is set so that a voltage greater than the sensor maximum voltage is not detected.

[0040]

number

[0041] Next, the reference voltage V ini (3.4V) input target detection value D ini is calculated using formula 2. Also, from the reference voltage 3.4V, the required amplification amount δ calc is calculated using formula 3. However, D 3.4V represents the parameter setting value for the reference detection value of 3.4V.

[0042]

number

number

[0043] Wipe amount required for amplification W calc is expressed by Equation 4 using the set value δ of the amplification convolution parameter. However, 1 in Equation 4 is the reference detection value D 3.4V Indicates the wipe value at the time of measurement.

[0044]

number

[0045] Here, the wipe value can only be set to an integer value between 0 and 1023. set and amplification error δ remain is W calc The integer part of W ini Then, it can be expressed by equations 5 and 6.

[0046]

number

number

[0047] Also, the detection value D when 0 MPa (1 V) is input offset is the parameter setting value D for the reference detection value 1V 1VUsing the above, it is expressed by Equation 7. Also, the error W remain and offset D offset is the corrected value of the detected value, D adjsut , the detected value (raw value) is D raw Then, it is expressed by equation 8.

[0048]

number

number

[0049] The pressure P read from the above is obtained by equation 9.

[0050]

number

[0051] 3 is a conceptual diagram showing the adjustment of a variable resistor by the automatic variable resistor adjustment system 1. As described above, under normal circumstances, the pressure sensor 3 and A / D converter 9 have a correspondence relationship as shown in FIG. 7. That is, the sensor output voltage range (1 to 5 V) of the pressure sensor 3 is made to correspond to the detection range (0 to 4000) of the A / D converter 9. By doing so, the unused range of 0 to 1 V is not detected by the A / D converter 9, thereby reducing waste.

[0052] In contrast, the variable resistor automatic adjustment system 1 further inputs use condition information and measurement scale condition information. For example, as described above, if the use condition information specifies a maximum use pressure of 15 MPa and the measurement scale condition information specifies a scaling adjustment value of 60%, the maximum measurement pressure will be 25 MPa. In this case, the sensor output voltage output from the pressure sensor 3 will be approximately 1 V to approximately 2.7 V (range A in the figure).

[0053] The controller 7 (calculation unit 13) sets the wipe amount based on the pre-calculated post-A / D conversion amplification amount per wipe amount 1 and the converted value after A / D conversion at a reference voltage, etc., so that the voltage range output from the pressure sensor 3 falls within the detection value range of the A / D converter 9. The controller 7 (variable resistor adjustment unit 15) also adjusts the variable resistor 5 (for gain adjustment). By doing so, it is possible to input a range of 0 to 25 MPa to the A / D converter as a detection value in the range of 0 to 4000, whereas before adjustment a range of 0 to 60 MPa was input to the A / D converter as a detection value in the range of 0 to 4000. In other words, measurements can be performed with more than twice the accuracy compared to conventional methods.

[0054] It is also possible to set a reference operating pressure as the operating condition information and a pressure range as the measurement scale condition information. For example, by inputting 15 MPa, which is the reference operating pressure (average pressure during use or set pressure), as the operating condition information, and inputting a pressure range of 10 MPa or upper and lower limits of ±5 MPa as the measurement scale condition information, it is possible to set the device to measure 10 to 20 MPa. In other words, the measurement scale condition information can be the usable setting range of the pressure sensor 3.

[0055] In this case as well, the controller 7 (calculation unit 13) sets the wipe amount based on the pre-calculated amplification amount after A / D conversion per wipe amount 1 and the converted value after A / D conversion at a reference voltage, etc., so that the voltage range output from the pressure sensor 3 falls within the detection value range of the A / D converter 9. In addition, the controller 7 (variable resistor adjustment unit 15) adjusts the variable resistor 5 (for adjusting the gain and operating point).

[0056] In this way, it is possible to input to the A / D converter a detected value corresponding to the pressure obtained by measurement within the usable setting range of the pressure sensor 3. For example, if a range of 0 to 60 MPa was input to the A / D converter before adjustment, the variable resistor 5 can be adjusted so that a setting range of 10 to 20 MPa is assigned to the A / D converter 9 as a detected value range of 0 to 4000.

[0057] In this way, the method of specifying the use condition information and measurement scale condition information is not particularly limited as long as it is possible to set the pressure to be measured and its range. For example, the upper and lower limits of the measurement range (e.g., lower limit = 15 MPa, upper limit = 30 MPa) may be set. Even in this case, the lower limit value can be considered to be the use condition information, and the upper limit value can be considered to be the measurement scale condition information.

[0058] Next, a hydraulic system using the variable resistor automatic adjustment system 1 will be described in detail. Fig. 4 is a diagram showing the configuration of a hydraulic system 20. In addition to the variable resistor automatic adjustment system 1, the hydraulic system 20 has a hydraulic circuit 21, a control unit 23, a storage unit 27, etc. In the hydraulic system 20, the controller 7 of the variable resistor automatic adjustment system 1 is included in the control unit 23.

[0059] The configuration of the hydraulic circuit 21 is not particularly limited, but a pressure sensor 3 is installed in a part of the circuit. In other words, the pressure sensor 3 is capable of measuring the pressure at a predetermined location in the hydraulic circuit 21. The control unit 23 has the function of a controller 7 that can control the variable resistor automatic adjustment system 1, and a hydraulic circuit control unit 25. The hydraulic circuit control unit 25 is capable of controlling the operation of each part in the hydraulic circuit 21.

[0060] A memory unit 27 is connected to the control unit 23. Various setting conditions are stored in the memory unit 27. For example, the memory unit 27 stores operation information of the hydraulic circuit 21, the reference pressure (use condition information) at the installation location of the pressure sensor 3 in each operation state, and the measurement range at that time (measurement scale condition information).

[0061] Next, a control method for the hydraulic system 20 will be described. Fig. 5 is a diagram showing an example of the control method for the hydraulic system 20. First, the control unit 23 controls the operation of the hydraulic circuit 21 (step S201). For example, the control unit 23 operates the solenoid valves of each unit to operate the hydraulic circuit 21.

[0062] Next, the control unit 23 reads out predetermined use condition information and measurement scale condition information from the storage unit 27 in a predetermined operation (state) set in advance (step S202). For example, at the location where the pressure sensor 3 is installed, the control unit 23 reads out the maximum use pressure and scaling adjustment value of the pressure sensor 3 in that state and inputs them to the controller 7.

[0063] The controller 7 (control unit 23) calculates and sets an appropriate wipe amount for the variable resistor 5 according to the operating conditions of the hydraulic circuit 21, and adjusts the variable resistor 5. For example, if the operating pressure of the measurement unit of the hydraulic circuit 21 is 15 MPa and the scaling adjustment value is 60% in that state, the controller 7 adjusts the variable resistor 5 to adjust the sensor output voltage corresponding to 0 to 25 MPa to within the detection range of 0 to 4000 in the A / D converter 9. This enables highly accurate measurements. The controller 23 also controls the hydraulic circuit 21 as needed based on the measured pressure. For example, if the pressure measured by the pressure sensor 3 is lower than specified, the controller 7 adjusts the pressure to increase it.

[0064] As described above, the control unit 23 controls the hydraulic circuit 21. At this time, the control unit 23 determines whether or not the state of the hydraulic circuit 21 has changed (step S204). That is, the control unit 23 determines whether or not the pressure at the location where the pressure sensor 3 is installed has changed due to the change in the state of the hydraulic circuit 21. If there is no change in pressure and the state continues, the control unit 23 continues to measure the pressure under the same conditions (step S205).

[0065] On the other hand, for example, if the maximum operating pressure of the pressure sensor 3 in the state of the location where the pressure sensor 3 is installed changes, the operating condition information and scaling adjustment value corresponding to the state are read out and input to the controller 7 (step S202). For example, if in the state the operating pressure of the measurement part of the hydraulic circuit 21 is 30 MPa and the scaling adjustment value is 60%, the variable resistor 5 is adjusted so that the sensor output voltage corresponding to a pressure of 0 to 50 MPa falls within the detection range of 0 to 4000 in the A / D converter 9.

[0066] In this way, when the pressure change in the measurement section is known in advance according to the operating state of the hydraulic circuit 21 (for example, 15 MPa → 30 MPa → 5 MPa → 15 MPa →...), the control section 23 adjusts the variable resistor 5 under preset conditions according to the state each time. That is, the control section 23 can control the operation of the hydraulic devices in the hydraulic circuit 21 as well as the variable resistor 5. Therefore, the measurement scale of the pressure sensor 3 input to the A / D converter 9 can be automatically adjusted based on preset use condition information and measurement scale condition information according to the operating state of each section in the hydraulic circuit 21.

[0067] As described above, according to this embodiment, by automatically adjusting the variable resistor 5 to the pressure measurement range of the pressure sensor 3, it is possible to efficiently use the detection range of the A / D converter 9 and measure pressure with high accuracy without having to manually set it according to the usage conditions.

[0068] Furthermore, in the hydraulic system 20, the variable resistor 5 is automatically adjusted in accordance with the operating state of the hydraulic circuit 21, thereby making it possible to measure pressure under optimal conditions in each state.

[0069] The control method for the hydraulic system 20 is not limited to the above-described example. Fig. 6 is a diagram showing another example of a control method for the hydraulic system 20. In the above-described embodiment, the control unit 23 controls the variable resistor 5 based on the use condition information and measurement scale condition information preset for the control state while controlling the hydraulic circuit 21. In contrast, in this embodiment, the control unit 23 controls the variable resistor 5 in accordance with the actual measurement value obtained by the pressure sensor 3.

[0070] First, the control unit 23 adjusts the variable resistor 5 so that the entire measurement range of the pressure sensor 3 (e.g., 0 to 60 MPa) becomes the detection range of the A / D converter 9 (e.g., 0 to 4000) (step S301). In this state, the pressure of the target part is measured over the entire measurement range of the pressure sensor (step S302). That is, the measurement in this state is the state shown in FIG. 7. This measurement state is referred to as the first state.

[0071] Next, the control unit 23 determines whether a certain pressure state is maintained (whether there is no pressure fluctuation of a predetermined amount or more within a certain period of time) (step S303), and if there is a pressure fluctuation of a predetermined amount or more within the predetermined period of time, the control unit 23 continues the first state. On the other hand, if there is no pressure fluctuation and the pressure is below the predetermined level, the control unit 23 sets the use condition information and measurement scale condition information of the pressure sensor 3 for the corresponding state of the part where the pressure sensor 3 is installed (step 304).

[0072] As for the use condition information and measurement scale condition information, for example, a plurality of use condition information and measurement scale condition information may be linked in correspondence with the measured pressure and stored in the storage unit 27. In this case, the relevant use condition information and measurement scale condition information may be read from the storage unit 27 in accordance with the measured pressure and input to the controller 7. Alternatively, a measurement range may be set in advance as the measurement scale condition information, and the actually measured pressure may be used as the use (set) pressure as the use condition information.

[0073] Next, the control unit 23 calculates and sets an appropriate wipe amount for the variable resistor 5 according to the use conditions, etc., adjusts the variable resistor 5 (step S305), and measures pressure within the set pressure range (step S306). Therefore, the actual measurement pressure can be measured more accurately than in the measurement state over the entire range (first state). This measurement state is referred to as the second state.

[0074] In the second state, the control unit 23 determines whether the measured pressure exceeds a predetermined pressure range within the set measured pressure range (step S307). If the control unit 23 determines that the measured pressure is within the predetermined pressure range, it maintains the second state, but if the measured pressure exceeds the predetermined pressure range, it returns to step S301 and transitions to the first state.

[0075] As described above, this embodiment has a first state in which measurements are performed over the entire measurement range of the pressure sensor 3, and a second state in which measurements are performed only over the measurement range set by the preset use condition information and measurement scale condition information for the pressure sensor 3. In the first state, the control unit 23 inputs the entire sensor output voltage range of the pressure sensor 3 to the A / D converter 9. On the other hand, when the measurement value of the pressure sensor 3 remains within a predetermined range for a predetermined time, the control unit 23 transitions to the second state.

[0076] In the second state, if the measured value falls outside the set predetermined pressure range, the control unit 23 transitions back to the first state. In this way, it is possible to automatically adjust between full-range measurement and detailed measurement depending on the measured pressure state. That is, it is possible to set usage condition information and measurement scale condition information depending on the measured value, control the variable resistor 5, and adjust the measurement scale of the pressure sensor 3 that is input to the A / D converter 9.

[0077] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical scope of the present invention is not limited to the above-described embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the technical ideas described in the claims, and it is understood that these modifications and alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0078] 1. Variable resistor automatic adjustment system 3...Pressure sensor 5...Variable resistor 7...Controller 9...A / D converter 11....Input section 13...Calculation section 15...Variable resistor adjustment section 20...Hydraulic system 21...Hydraulic circuit 23...Control unit 25...Hydraulic circuit control unit 27……Storage section

Claims

1. 1. An automatic adjustment system for a variable resistor used in a sensor, comprising: A sensor, a variable resistor to which a sensor output voltage from the sensor is input; an A / D converter that performs analog-to-digital conversion of the adjusted detection value adjusted by the variable resistor and output; a controller for controlling the variable resistor; Equipped with The controller is capable of inputting usage condition information of the sensor and measurement scale condition information, The controller is capable of adjusting the variable resistor so that the detection range input to the A / D converter, which corresponds to the maximum measurable range of the sensor, corresponds to a scale based on the measurement scale condition information, including the usage condition information.

2. 2. The automatic variable resistor adjustment system according to claim 1, wherein the sensor is a pressure sensor, and the use condition information is the use pressure condition under which the pressure sensor is used.

3. 2. The variable resistor automatic adjustment system according to claim 1, wherein the measurement scale condition information is a ratio of a detection value set in the use condition information to a maximum detection value input to the A / D converter.

4. the measurement scale condition information is a usable setting range of the sensor, 2. The variable resistor automatic adjustment system according to claim 1, wherein the controller adjusts the variable resistor so as to assign a sensor output voltage corresponding to a usable setting range of the sensor to a maximum detection range input to the A / D converter.

5. A hydraulic system using the automatic variable resistor adjustment system according to any one of claims 1 to 4, A hydraulic circuit; a control unit that controls the hydraulic circuit; Equipped with the sensor is a pressure sensor, and the pressure sensor is installed in the hydraulic circuit; a control unit including the controller, the control unit controlling the operation of hydraulic equipment in the hydraulic circuit, and capable of adjusting the measurement scale of the pressure sensor input to the A / D converter by controlling the variable resistor based on the preset use condition information and measurement scale condition information in accordance with the operation.

6. A hydraulic system using the automatic variable resistor adjustment system according to any one of claims 1 to 4, A hydraulic circuit; a control unit that controls the hydraulic circuit; Equipped with the sensor is a pressure sensor, and the pressure sensor is installed in the hydraulic circuit; the control unit includes the controller, a first state in which measurements are performed over the entire measurement range of the sensor; a second state in which the sensor measures only a measurement range set by the preset use condition information and the preset measurement scale condition information; the control unit, in the first state, allows an entire sensor output voltage range of the sensor to be input to the A / D converter; When the measurement value of the sensor remains within a predetermined range for a predetermined time, the control unit transitions to the second state, and controls the variable resistor based on the use condition information and the measurement scale condition information corresponding to the measurement value, to adjust the measurement scale of the pressure sensor input to the A / D converter, A hydraulic system characterized in that, in the second state, when the measured value changes to fall outside a set predetermined pressure range, the control unit transitions to the first state.

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