CN114199353A - Strain bridge input sampling circuit and weighing system - Google Patents
Strain bridge input sampling circuit and weighing system Download PDFInfo
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- CN114199353A CN114199353A CN202111500642.4A CN202111500642A CN114199353A CN 114199353 A CN114199353 A CN 114199353A CN 202111500642 A CN202111500642 A CN 202111500642A CN 114199353 A CN114199353 A CN 114199353A
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- 238000005070 sampling Methods 0.000 title claims abstract description 50
- 238000005303 weighing Methods 0.000 title claims abstract description 11
- 238000001914 filtration Methods 0.000 claims abstract description 79
- 230000005284 excitation Effects 0.000 claims description 23
- 238000005259 measurement Methods 0.000 abstract description 14
- 238000010586 diagram Methods 0.000 description 6
- 239000003990 capacitor Substances 0.000 description 3
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- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
- G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
- G01G3/14—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing measuring variations of electrical resistance
- G01G3/142—Circuits specially adapted therefor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
- G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
- G01G3/14—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing measuring variations of electrical resistance
- G01G3/1402—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
- G01G3/1404—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports combined with means to connect the strain gauges on electrical bridges
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- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
The invention discloses a strain bridge input sampling circuit and a weighing system. The strain bridge input sampling circuit includes: the pair of power signal output ends are electrically connected with the power signal input ends of the strain bridge; at least one pair of feedback signal input ends which are correspondingly and electrically connected with a pair of differential signal output ends of the strain bridge; at least one switch module and at least one differential filter module corresponding to at least one pair of feedback signal input ends; the switch module is used for short-circuiting a pair of filtering input ends of the differential filtering module according to the first control signal and connecting the corresponding pair of filtering input ends of the differential filtering module with a pair of power signal output ends according to the second control signal; the input end of the analog-to-digital converter is electrically connected with the filtering output end of the differential filtering module; and the controller is electrically connected with the output end of the analog-to-digital converter and is used for generating a first control signal and a second control signal so as to calibrate the weight formula of the strain bridge. The invention can improve the accuracy of strain bridge weight measurement.
Description
Technical Field
The embodiment of the invention relates to a sampling technology, in particular to a strain bridge input sampling circuit and a weighing system.
Background
The strain bridge is a weighing sensor, is mainly used for weight measurement, and has wide application in the industries of mechanical equipment manufacturing, road traffic, metallurgy, petrochemical industry and the like.
One key index of strain bridge measurement is measurement accuracy, and the main factors influencing measurement accuracy include the technological level of a sensor, the resolution, stability and anti-interference level of a measurement circuit, the field environmental influence (such as temperature) and the like. In order to improve stability and anti-interference level, a differential filter circuit is added to an existing measuring circuit, but the introduction of the differential filter circuit may cause a voltage value of a strain bridge acquired by a controller to be different from an actual voltage value of the strain bridge, so that measurement accuracy is low.
Disclosure of Invention
The invention provides a strain bridge input sampling circuit and a weighing system, which are used for improving the accuracy of measurement.
In a first aspect, an embodiment of the present invention provides a strain bridge input sampling circuit, where the strain bridge input sampling circuit includes:
the pair of power supply signal output ends are used for being electrically connected with the power supply signal input end of the strain bridge;
at least one pair of feedback signal input ends which are correspondingly and electrically connected with a pair of differential signal output ends of the strain bridge;
at least one switch module and at least one differential filter module corresponding to the at least one pair of feedback signal input terminals; the switch module is used for short-circuiting a pair of filtering input ends of the differential filtering module according to a first control signal and connecting a pair of corresponding filtering input ends of the differential filtering module with a pair of power signal output ends according to a second control signal;
the input end of the analog-to-digital converter is electrically connected with the filtering output end of the differential filtering module;
and the controller is electrically connected with the output end of the analog-to-digital converter and is used for generating the first control signal and the second control signal so as to calibrate the weight formula of the strain bridge.
Optionally, the weight formula of the strain bridge is W ═ K ═ U (U)SEX+/SEX-÷USIG+/SIG-) + B, where W is the weight, K and B are fixed values, USEX+/SEX-And USIG+/SIG-The voltage values corresponding to the two pairs of differential signal output ends of the strain bridge are obtained; the controller is configured to calibrate voltage values corresponding to at least one pair of differential signal output ends of the strain bridge, and the calibrating step comprises the following steps:
generating a first control signal, and collecting a zero code value corresponding to the input end of the feedback signal;
generating a second control signal, and collecting a full-scale code value corresponding to the input end of the feedback signal;
substituting the zero code value, a first preset voltage value corresponding to the zero code value, a full-scale code value and a second preset voltage value corresponding to the full-scale code value into a preset formula to obtain a constant of the preset formula, wherein the preset formula is U-k ADC + b, and the constants in the preset formula are k and b; u is the voltage value that difference signal output terminal of straining bridge corresponds, and the ADC is the code value that feedback signal input terminal that the controller gathered obtained corresponds.
Optionally, the strain bridge input sampling circuit includes a pair of excitation voltage feedback signal input ends and a pair of strain voltage feedback signal input ends, and the two pairs of feedback signal input ends are electrically connected to an excitation voltage differential signal output end of the strain bridge, and the strain voltage feedback signal input end is electrically connected to a strain voltage differential signal output end of the strain bridge;
the at least one switch module comprises a first switch module and a second switch module; the at least one differential filtering module comprises a first differential filtering module and a second differential filtering module;
the first switch module is used for short-circuiting a pair of filtering input ends of the first differential filtering module according to a first control signal and connecting the pair of filtering input ends of the first differential filtering module with the pair of power signal output ends according to a second control signal;
the second switch module is used for short-circuiting the pair of filtering input ends of the second differential filtering module according to a first control signal and connecting the pair of filtering input ends of the second differential filtering module with the pair of power signal output ends according to a second control signal.
Optionally, the first switch module includes a first analog switch, a second analog switch, and a third analog switch;
a normally open end of the first analog switch is electrically connected to one of the pair of power signal input terminals, a normally closed end of the first analog switch is electrically connected to one of the pair of excitation voltage feedback signal input terminals, and a common end of the first analog switch is electrically connected to a normally closed end of the third analog switch;
a normally open end of the second analog switch is electrically connected to a ground terminal of the pair of power signal input terminals, a normally closed end of the second analog switch is electrically connected to the other of the pair of driving voltage feedback signal input terminals, and a common terminal of the second analog switch is electrically connected to a normally open end of the third analog switch;
the common end of the third analog switch is electrically connected with one of the pair of filter input ends of the first differential filter module, and the normally open end of the third analog switch is also electrically connected with the other of the pair of filter input ends of the first differential filter module.
Optionally, the first switch module is configured to conduct the common terminal of the third analog switch with the normally-open terminal of the third analog switch according to a first control signal; the first switch module is further configured to conduct a normally-open end of the first analog switch with a common terminal of the first analog switch, conduct a normally-open end of the second analog switch with a common terminal of the second analog switch, and conduct a normally-closed end of the third analog switch with a common terminal of the third analog switch according to the second control signal.
Optionally, the controller is configured to output a third control signal to a first switch module after calibrating the weight formula of the strain bridge if the strain bridge is a six-wire strain bridge, the first switch module being configured to conduct the pair of excitation voltage feedback signal input terminals and the pair of filter input terminals of the first differential filter module according to the third control signal; and if the strain bridge is a four-wire strain bridge, the second control signal is output to the first switch module after the weight formula of the strain bridge is calibrated.
Optionally, the second switch module includes a fourth analog switch, a fifth analog switch, and a sixth analog switch;
a normally open end of the fourth analog switch is electrically connected to one of the pair of power signal input terminals, a normally closed end of the fourth analog switch is electrically connected to one of the pair of strain voltage feedback signal input terminals, and a common end of the fourth analog switch is electrically connected to a normally closed end of the sixth analog switch;
a normally open end of the fifth analog switch is electrically connected to a ground terminal of the pair of power signal input terminals, a normally closed end of the fifth analog switch is electrically connected to the other of the pair of strain voltage feedback signal input terminals, and a common terminal of the fifth analog switch is electrically connected to a normally open end of the sixth analog switch;
and the common end of the sixth analog switch is electrically connected with one of the pair of filter input ends of the second differential filter module, and the normally open end of the sixth analog switch is also electrically connected with the other of the pair of filter input ends of the second differential filter module.
Optionally, the second switch module is configured to conduct the common terminal of the sixth analog switch with the normally-open terminal of the sixth analog switch according to a first control signal; the second switch module is further configured to conduct a normally-open end of the fourth analog switch with the common terminal of the fourth analog switch, conduct a normally-open end of the fifth analog switch with the common terminal of the fifth analog switch, and conduct a normally-closed end of the fifth analog switch with the common terminal of the fifth analog switch according to the second control signal; the controller is configured to output a third control signal to a second switch module after calibrating the weight formula of the strain bridge, the second switch module being configured to turn on the pair of strain voltage feedback signal inputs and a pair of filter inputs of the second differential filter module according to the third control signal.
Optionally, the strain bridge input sampling circuit further includes an input driving module, an output end of the input driving module is electrically connected to the pair of power signal output ends, and an input end of the input driving module is electrically connected to the analog power source end.
In a second aspect, an embodiment of the present invention further provides a weighing system, where the weighing system includes a strain bridge and the strain bridge input sampling circuit of the first aspect.
According to the technical scheme of the embodiment of the invention, the adopted strain bridge input sampling circuit comprises: the pair of power supply signal output ends are used for being electrically connected with the power supply signal input end of the strain bridge; at least one pair of feedback signal input ends which are correspondingly and electrically connected with a pair of differential signal output ends of the strain bridge; at least one switch module and at least one differential filter module corresponding to at least one pair of feedback signal input ends; the switch module is used for short-circuiting a pair of filtering input ends of the differential filtering module according to the first control signal and connecting the corresponding pair of filtering input ends of the differential filtering module with a pair of power signal output ends according to the second control signal; the input end of the analog-to-digital converter is electrically connected with the filtering output end of the differential filtering module; and the controller is electrically connected with the output end of the analog-to-digital converter and is used for generating a first control signal and a second control signal so as to calibrate the weight formula of the strain bridge. The controller outputs the first control signal and the second control signal, so that zero point calibration and full-scale calibration can be performed on the weight formula of the strain bridge, the weight formula of the strain bridge after calibration is obtained, and the accuracy of weight measurement is greatly improved.
Drawings
Fig. 1 is a schematic circuit diagram of a strain bridge according to an embodiment of the present invention;
fig. 2 is a schematic circuit structure diagram of a strain bridge input sampling circuit according to an embodiment of the present invention;
fig. 3 is a schematic circuit structure diagram of another strain bridge input sampling circuit according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Fig. 1 is a schematic circuit structure diagram of a strain bridge according to an embodiment of the present invention, and fig. 2 is a schematic circuit structure diagram of a strain bridge input sampling circuit according to an embodiment of the present invention, and with reference to fig. 1 and fig. 2, the strain bridge input sampling circuit includes: a pair of power signal output terminals, in this embodiment, a first power signal output terminal IEX + and a second power signal output terminal IEX-; at least one pair of feedback signal input ends which are correspondingly and electrically connected with a pair of differential signal output ends of the strain bridge; at least one switching module 11 and at least one differential filtering module 12 corresponding to at least one pair of feedback signal input terminals; the switch module 11 is configured to short-circuit a pair of filtering input ends of the differential filtering module 12 according to a first control signal and electrically connect a pair of corresponding filtering input ends of the differential filtering module 12 with a pair of power signal output ends according to a second control signal; the input end of the analog-to-digital converter 13 is electrically connected with the filtering output end of the differential filtering module 12; and the controller 14 is electrically connected with the output end of the analog-to-digital converter 13 and is used for generating a first control signal and a second control signal so as to calibrate the weight formula of the corresponding variable bridge.
Specifically, as shown in fig. 1, the strain bridge includes four bridge arms and six bridge armsThe six ports are respectively a pair of power signal input ends (EX +, EX-) and two pairs of differential signal output ends, the two pairs of differential signal output ends are respectively a pair of excitation voltage differential signal output ends (SEX +, SEX-) and a pair of strain voltage differential signal output ends (SIG +, SIG-), and are electrically connected with the structure shown in the figure 1, the working principle of the strain bridge is well known by persons skilled in the art, and the description is omitted; of course, in this embodiment, a six-wire strain bridge is taken as an example, and when the strain bridge is a four-wire strain bridge, the pair of excitation voltage differential signal output terminals (SEX +, SEX-) does not exist in the strain bridge; the weight formula of the strain bridge is W ═ K ═ U (U)SEX+/SEX-÷USIG+/SIG-) + B, where W is the weight, K and B are fixed values provided by the producer of the strain bridge, USEX+/SEX-Is the voltage value output by a pair of excitation voltage differential signal output ends (SEX +, SEX-) of a strain bridgeSIG+/SIG-When the strain bridge is input into the sampling circuit without error, the code value acquired by the control signal can correspond to the USEX+/SEX-And USIG+/SIG-But the code value collected by the controller 14 may not correspond to U due to the introduction of the differential filtering module and due to the influence of line resistance and the likeSEX+/SEX-And USIG+/SIG-Resulting in errors in the measurement.
The switch module 11 is arranged in this embodiment, and can calibrate a weight formula of the strain bridge, the output voltage of the differential signal output end of the strain bridge and a code value (digital form of voltage) acquired by the controller are in a linear relationship, and the influence relationship (namely, a preset formula) is U ═ k × ADC + b, where U is a voltage value corresponding to the differential signal output end of the strain bridge, and ADC is a code value acquired by the controller; when the controller 14 outputs a first control signal, the switch module 11 controls the two filtering input ends of the corresponding differential filtering module 12 to be in short circuit, at this time, the filtering input ends of the differential filtering module 12 are equivalent to signals with an input voltage value of 0, after the signals are converted into digital signals by the analog-to-digital converter 13, the controller 14 acquires code values of the signals to obtain a group of corresponding relations, and at this time, the corresponding relation is the minimum value of the measuring range of the strain bridge (zero calibration); in addition, theWhen the controller 14 outputs the second control signal, the switch module 11 controls the pair of filter input ends of the corresponding differential filter module 12 to be electrically connected with the pair of power signal output ends, which is equivalent to that the pair of filter output ends of the differential filter module 12 is directly connected to the maximum voltage value that can be output by the strain bridge, the maximum voltage value is set by a user, for example, set to VCC, and after being converted into a digital signal by the analog-to-digital converter 13, the controller 14 acquires the code value thereof to obtain another set of corresponding relationship, and at this time, the corresponding maximum value is the maximum value of the range of the strain bridge (full-range calibration); substituting the two groups of corresponding relations into a preset formula to obtain the values of k and b, so as to obtain USEX+/SEX-Correction is k0*ADC0X+b0(ii) a And/or, mixing USIG+/SIG-Correction is k1*ADC1Y+b1(ii) a It should be noted that, when the strain bridge sampling input circuit only includes a pair of feedback signal input terminals, if the feedback signal input terminal corresponds to the excitation voltage differential signal output terminal (SEX +, SEX-) of the strain bridge, the final correction is USEX+/SEX-The formula of the corrected weight is W ═ K ═ U (U)SEX+/SEX-÷USIG+/SIG-)+B＝K*((k0*ADC0X+b0)÷USIG+/SIG-) + B; if the feedback signal input end corresponds to the strain voltage differential signal output end (SIG +, SIG-) of the strain bridge, the final correction is that U is correctedSIG+/SIG-The formula of the corrected weight is W ═ K ═ U (U)SEX+/SEX-÷USIG+/SIG-)+B＝K*(USEX+/SEX-÷(k1*ADC1Y+b1) + B, wherein, in order to convert USEX+/SEX-And USIG+/SIG-Corresponding preset formula is distinguished, and U is setSEX+/SEX-＝k0*ADC0X+b0，USIG+/SIG-＝k1*ADC1Y+b1(ii) a When the strain bridge input sampling circuit comprises two pairs of feedback signal input ends, the two pairs of feedback signal input ends respectively correspond to an excitation voltage differential signal output end (SEX +, SEX-) and a strain voltage differential signal output end (SIG +, SIG-) of the strain bridge, so that the pair of U is pairedSEX+/SEX-And USIG+/SIG-All were calibrated and the final weight formula was W ═ K ═ U (U)SEX+/SEX-÷USIG+/SIG-)+B＝K*((k0*ADC0X+b0)÷(k1*ADC1Y+b1) + B); therefore, the weight formula of the strain bridge can be calibrated through the embodiment, so that the strain bridge input sampling circuit can acquire the accurate voltage value output by the strain bridge, and preferably, the strain bridge input sampling circuit is calibrated before each measurement, thereby greatly improving the measurement accuracy.
According to the technical scheme of the embodiment, the strain bridge input sampling circuit comprises: the pair of power supply signal output ends are used for being electrically connected with the power supply signal input end of the strain bridge; at least one pair of feedback signal input ends which are correspondingly and electrically connected with a pair of differential signal output ends of the strain bridge; at least one switch module and at least one differential filter module corresponding to at least one pair of feedback signal input ends; the switch module is used for short-circuiting a pair of filtering input ends of the differential filtering module according to the first control signal and connecting the corresponding pair of filtering input ends of the differential filtering module with a pair of power signal output ends according to the second control signal; the input end of the analog-to-digital converter is electrically connected with the filtering output end of the differential filtering module; and the controller is electrically connected with the output end of the analog-to-digital converter and is used for generating a first control signal and a second control signal so as to calibrate the weight formula of the strain bridge. The controller outputs the first control signal and the second control signal, so that zero point calibration and full-scale calibration can be performed on the weight formula of the strain bridge, the weight formula of the strain bridge after calibration is obtained, and the accuracy of weight measurement is greatly improved.
Optionally, the controller 14 is configured to calibrate voltage values corresponding to at least one pair of differential signal output terminals of the strain bridge, and the calibrating step includes: s101, generating a first control signal, and collecting a zero code value corresponding to a feedback signal input end; s102, generating a second control signal, and collecting a full-scale code value corresponding to the input end of the feedback signal; s103, substituting the zero code value, a first preset voltage value corresponding to the zero code value, the full-scale code value and a second preset voltage value corresponding to the full-scale code value into a preset formula to obtain a constant of the preset formula, wherein the preset formula is U-k-ADC + b, and the constants in the preset formula are k and b; u is the voltage value that the difference signal output terminal of straining bridge corresponds, and the ADC is the code value that the feedback signal input terminal that the controller gathered obtained corresponds.
Specifically, in this embodiment, the first preset voltage value is also referred to as "0" voltage, and the second preset voltage value is also referred to as VCC; the execution sequence of step S101 and step S102 is not particularly limited, and step S101 may be executed first, and then step S102 may be executed; alternatively, step S101 may be performed after step S102 is performed.
Optionally, with continued reference to fig. 1, the strain bridge input sampling circuit includes a pair of excitation voltage feedback signal input ends (ISEX +, ISEX-) and a pair of strain voltage feedback signal input ends (ISIG +, ISIG-), the excitation voltage feedback signal input ends (ISEX +, ISEX-) are electrically connected to the excitation voltage differential signal output ends (SEX +, SEX-) of the strain bridge correspondingly, and the strain voltage feedback signal input ends (ISIG +, ISIG-) are electrically connected to the strain voltage differential signal output ends (SIG +, SIG-) of the strain bridge correspondingly; the at least one switch module 11 comprises a first switch module 111, a second switch module 112; the at least one differential filtering module 12 comprises a first differential filtering module 121 and a second differential filtering module 122; the first switch module 111 is configured to short-circuit the pair of filter input ends of the first differential filter module 121 according to a first control signal, and electrically connect the pair of filter input ends of the first differential filter module 121 to the pair of power signal output ends according to a second control signal; the second switch module 112 is configured to short-circuit the pair of filtering input terminals of the second differential filtering module 122 according to the first control signal, and electrically connect the pair of filtering input terminals 122 of the second differential filtering module with the pair of power signal output terminals according to the second control signal.
Specifically, in this embodiment, two switch modules 11 and two differential filter modules 12 are provided, and the strain bridge input sampling circuit includes two pairs of feedback signal input terminals respectively corresponding to the excitation voltage differential signal output terminal (SEX +, SEX-) and the strain voltage differential signal output terminal (SEX +, SEX-) of the strain bridge, so that the pair U is paired with the pair USEX+/SEX-And USIG+/SIG-All were calibrated and the final weight formula was W ═ K ═ U (U)SEX+/SEX-÷USIG+/SIG-)+B＝K*((k0*ADC0X+b0)÷(k1*ADC1Y+b1) + B, namely the most accurate weight formula of the strain bridge can be obtained, thereby improving the accuracy of weight measurement to a greater extent.
With continued reference to fig. 1, the strain bridge input sampling circuit further includes an input driving module 15, an output terminal of the input driving module 15 is electrically connected to a pair of power signal output terminals (IEX +, IEX-), and an input terminal of the input driving module 15 is electrically connected to the analog power supply terminals (AVDD, GND).
Specifically, the analog power terminals (AVDD, GND) are used for externally connecting an analog voltage to supply power to the input driving module 15, the input driving module 15 can generate a power supply voltage (VCC, GND) adapted to the strain bridge, and the power supply voltage is supplied to the strain bridge, the first switching module 111 and the second switching module 112 on the one hand, so as to calibrate the weight formula of the strain bridge. It should be noted that the analog power supply terminals (AVDD, GND) may also be electrically connected to the analog power supply signal input terminal of the analog-to-digital converter, so as to provide an analog voltage for the analog-to-digital converter 13, and the analog power supply terminals may also be connected to the first filter capacitor C1, so as to filter out interference signals; the strain bridge input sampling circuit may further include digital power supply terminals (DVDD, GND) for electrically connecting with the digital power supply input terminal of the analog-to-digital converter 13 and the digital power supply terminals of the controller 14, for supplying a digital voltage; the digital power supply end can also be connected with a second filter capacitor C2 for filtering interference; the reference voltage input end refut of the analog-to-digital converter is electrically connected with the reference voltage input end VREF, and the reference voltage input end VREF can also be connected to a third filter capacitor C3 for filtering interference. In addition, the GND in the embodiment is connected to a reference ground; the differential filtering module 12 may perform filtering by using an operational amplifier, or perform filtering by using a resistor RC, for example, and the specific filtering manner and circuit structure thereof are well known to those skilled in the art and will not be described herein again. The controller 14 may be, for example, a single chip microcomputer or an FPGA.
Alternatively, fig. 3 is a schematic circuit structure diagram of another strain bridge input sampling circuit according to an embodiment of the present invention, and referring to fig. 3, the first switch module 111 includes a first analog switch T1, a second analog switch T2, and a third analog switch T3; a normally open terminal of the first analog switch T1 is electrically connected to one of the pair of power supply signal input terminals, a normally closed terminal of the first analog switch T1 is electrically connected to one of the pair of excitation voltage feedback signal input terminals, and a common terminal of the first analog switch T1 is electrically connected to a normally closed terminal of the third analog switch T3; a normally open terminal of the second analog switch T2 is electrically connected to the ground terminal of the pair of power signal input terminals, a normally closed terminal of the second analog switch T2 is electrically connected to the other of the pair of driving voltage feedback signal input terminals, and a common terminal of the second analog switch T2 is electrically connected to a normally open terminal of the third analog switch T3; a common terminal of the third analog switch T3 is electrically connected to one of the pair of filter input terminals of the first differential filter module, and a normally open terminal of the third analog switch T3 is also electrically connected to the other of the pair of filter input terminals of the first differential filter module.
Specifically, the first analog switch T1, the second analog switch T2, and the third analog switch T3 may be in the form of a relay, for example, a control port (IO1, IO2, IO3) of the controller 14 controls states of the first analog switch T1, the second analog switch T2, and the third analog switch T3, respectively, when the controller 14 outputs a first control signal, a common terminal of the third analog switch T3 is conducted with a normally open terminal of the third analog switch T3, so that two filter input terminals of the first differential filter module 121 are short-circuited, which is equivalent to the connection voltage "0", that is, zero calibration is performed; when the controller 14 outputs the second control signal, the common terminal of the third analog switch T3 is conducted with the normally-off terminal of the third analog switch T3, the common terminal of the first analog switch T1 is conducted with the normally-open terminal of the first analog switch, and the normally-open terminal of the second analog switch T2 is conducted with the common terminal of the second analog switch T2, so that the two filter input terminals of the first differential filter module 121 are respectively connected to VCC and GND, and the strain bridge input sampling circuit completes full-scale calibration. In this embodiment, the function of the first switch module can be realized by adopting three analog switches, the circuit structure is simple, the complexity of the strain bridge input sampling circuit is favorably reduced, and the cost is reduced.
Optionally, the controller 14 is configured to output a third control signal to the first switch module 111 after calibrating the weight formula of the strain bridge if the strain bridge is a six-wire strain bridge, where the first switch module 111 is configured to connect a pair of excitation voltage feedback signal input ends (ISEX +, ISEX-) with a pair of filter input ends of the first differential filter module according to the third control signal; if the strain bridge is a four-wire strain bridge, the second control signal is output to the first switch module 111 after the weight formula of the strain bridge is calibrated.
Specifically, if the strain bridge is a six-wire strain bridge, that is, the strain bridge has a pair of excitation voltage differential signal output ends (SEX +, SEX-) in fig. 1, after the weight formula of the strain bridge is calibrated, a pair of excitation voltage feedback signal input ends (ISEX +, ISEX-) of the strain bridge input sampling circuit may be directly controlled to be conducted with the corresponding filter input end of the first differential filter module 121, so that the excitation voltage differential signal output ends (SEX +, SEX-) of the strain bridge are conducted with the pair of filter input ends of the first differential filter module 121; more specifically, the first switch module 111 may conduct the common terminal of the first analog switch T1 with the normally-closed terminal of the first analog switch T1 according to a third control signal, the second analog switch T2 conducts the common terminal thereof with the normally-closed terminal thereof according to the third control signal, and the third analog switch T3 conducts the common terminal thereof with the normally-closed terminal thereof according to the third control signal; if the strain bridge is of a four-wire system, the strain bridge does not have the pair of excitation voltage differential signal output ends (SEX +, SEX-) shown in fig. 1, and at this time, when weighing is performed, the second control signal can be continuously output to the first switch module 11 through the controller, so that the pair of filter input ends of the first differential filter module 121 is connected to VCC and GND. Through this embodiment, can control strain bridge input sampling circuit and match four-wire system strain bridge or six-wire system strain bridge, can improve strain bridge input sampling circuit's compatibility.
Optionally, with continued reference to fig. 2, the second switch module 112 includes a fourth analog switch T4, a fifth analog switch T5, and a sixth analog switch T6; a normally open terminal of the fourth analog switch T4 is electrically connected to one of the pair of power supply signal input terminals, a normally closed terminal of the fourth analog switch T4 is electrically connected to one of the pair of strain voltage feedback signal input terminals, and a common terminal of the fourth analog switch T4 is electrically connected to a normally closed terminal of the sixth analog switch T6; a normally open terminal of the fifth analog switch T5 is electrically connected to the ground terminal GND of the pair of power signal input terminals, a normally closed terminal of the fifth analog switch T5 is electrically connected to the other of the pair of strain voltage feedback signal input terminals, and a common terminal of the fifth analog switch T5 is electrically connected to the normally open terminal of the sixth analog switch T6; a common terminal of the sixth analog switch T6 is electrically connected to one of the pair of filter input terminals of the second differential filter module 122, and a normally open terminal of the sixth analog switch T6 is also electrically connected to the other of the pair of filter input terminals of the second differential filter module 122.
Specifically, the fourth analog switch T4, the fifth analog switch T5, and the sixth analog switch T6 may be in the form of a relay, for example, a control port (IO4, IO5, IO6) of the controller 14 controls states of the fourth analog switch T4, the fifth analog switch T5, and the sixth analog switch T6, respectively, when the controller 14 outputs the first control signal, a common terminal of the sixth analog switch T6 is conducted with a normally open terminal of the sixth analog switch T6, so that two filter input terminals of the second differential filter module 122 are short-circuited, which is equivalent to the connection voltage "0", that is, zero calibration is performed; when the controller 14 outputs the second control signal, the common terminal of the sixth analog switch T6 is conducted with the normally-closed terminal of the sixth analog switch T6, the common terminal of the fourth analog switch T4 is conducted with the normally-open terminal of the fourth analog switch T4, and the normally-open terminal of the fifth analog switch T5 is conducted with the common terminal of the fifth analog switch T5, so that the two filter input terminals of the second differential filter module 122 are respectively connected to VCC and GND, and the strain bridge input sampling circuit completes full-scale calibration. In this embodiment, the function of the second switch module can be realized by using three analog switches, and the circuit structure is simple, thereby being beneficial to reducing the complexity of the strain bridge input sampling circuit and reducing the cost. More preferably, the controller 14 is configured to output a third control signal to the second switch module 112 after calibrating the weight formula of the strain bridge, and the second switch module 112 is configured to turn on the pair of strain voltage feedback signal inputs (ISIG +, ISIG-) and the pair of filter inputs of the second differential filter module 122 according to the third control signal; more specifically, the second switch module 112 may conduct the common terminal of the fourth analog switch T4 with the normally-closed terminal of the fourth analog switch T4 according to the third control signal, conduct the common terminal of the fifth analog switch T5 with the normally-closed terminal thereof according to the third control signal, and conduct the common terminal of the sixth analog switch T6 with the normally-closed terminal thereof according to the third control signal, so that the filtering input terminal of the second differential filtering module 122 is connected to the strain voltage signal of the strain bridge.
The embodiment of the invention also provides a weighing system, which comprises a strain bridge and the strain bridge input sampling circuit provided by any embodiment of the invention; the strain bridge may be a four-wire system or a six-wire system, and the specific connection relationship may refer to the description of the strain bridge input sampling circuit portion of the present invention, and since the strain bridge input sampling circuit includes the strain bridge input sampling circuit provided in any embodiment of the present invention, the same advantageous effects are also provided, and details are not repeated herein.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A strain bridge input sampling circuit, comprising:
the pair of power supply signal output ends are used for being electrically connected with the power supply signal input end of the strain bridge;
at least one pair of feedback signal input ends which are correspondingly and electrically connected with a pair of differential signal output ends of the strain bridge;
at least one switch module and at least one differential filter module corresponding to the at least one pair of feedback signal input terminals; the switch module is used for short-circuiting a pair of filtering input ends of the differential filtering module according to a first control signal and connecting a pair of corresponding filtering input ends of the differential filtering module with a pair of power signal output ends according to a second control signal;
the input end of the analog-to-digital converter is electrically connected with the filtering output end of the differential filtering module;
and the controller is electrically connected with the output end of the analog-to-digital converter and is used for generating the first control signal and the second control signal so as to calibrate the weight formula of the strain bridge.
2. The strain bridge input sampling circuit of claim 1, wherein the weight formula of the strain bridge is W-K (U)SEX+/SEX-÷USIG+/SIG-) + B, where W is the weight, K and B are fixed values, USEX+/SEX-And USIG+/SIG-The voltage values corresponding to the two pairs of differential signal output ends of the strain bridge are obtained; the controller is configured to calibrate voltage values corresponding to at least one pair of differential signal output ends of the strain bridge, and the calibrating step comprises the following steps:
generating a first control signal, and collecting a zero code value corresponding to the input end of the feedback signal;
generating a second control signal, and collecting a full-scale code value corresponding to the input end of the feedback signal;
substituting the zero code value, a first preset voltage value corresponding to the zero code value, a full-scale code value and a second preset voltage value corresponding to the full-scale code value into a preset formula to obtain a constant of the preset formula, wherein the preset formula is U-k ADC + b, and the constants in the preset formula are k and b; u is the voltage value that difference signal output terminal of straining bridge corresponds, and the ADC is the code value that feedback signal input terminal that the controller gathered obtained corresponds.
3. The strain bridge input sampling circuit of claim 1, wherein the strain bridge input sampling circuit comprises two pairs of feedback signal inputs, an excitation voltage feedback signal input for electrical connection with an excitation voltage differential signal output of the strain bridge and a strain voltage feedback signal input for electrical connection with a strain voltage differential signal output of the strain bridge;
the at least one switch module comprises a first switch module and a second switch module; the at least one differential filtering module comprises a first differential filtering module and a second differential filtering module;
the first switch module is used for short-circuiting a pair of filtering input ends of the first differential filtering module according to a first control signal and connecting the pair of filtering input ends of the first differential filtering module with the pair of power signal output ends according to a second control signal;
the second switch module is used for short-circuiting the pair of filtering input ends of the second differential filtering module according to a first control signal and connecting the pair of filtering input ends of the second differential filtering module with the pair of power signal output ends according to a second control signal.
4. The strain bridge input sampling circuit of claim 3, wherein the first switching module comprises a first analog switch, a second analog switch, and a third analog switch;
a normally open end of the first analog switch is electrically connected to one of the pair of power signal input terminals, a normally closed end of the first analog switch is electrically connected to one of the pair of excitation voltage feedback signal input terminals, and a common end of the first analog switch is electrically connected to a normally closed end of the third analog switch;
a normally open end of the second analog switch is electrically connected to a ground terminal of the pair of power signal input terminals, a normally closed end of the second analog switch is electrically connected to the other of the pair of driving voltage feedback signal input terminals, and a common terminal of the second analog switch is electrically connected to a normally open end of the third analog switch;
the common end of the third analog switch is electrically connected with one of the pair of filter input ends of the first differential filter module, and the normally open end of the third analog switch is also electrically connected with the other of the pair of filter input ends of the first differential filter module.
5. The strain bridge input sampling circuit of claim 4, wherein the first switch module is configured to conduct a common terminal of the third analog switch with a normally-open terminal of the third analog switch according to a first control signal; the first switch module is further configured to conduct a normally-open end of the first analog switch with a common terminal of the first analog switch, conduct a normally-open end of the second analog switch with a common terminal of the second analog switch, and conduct a normally-closed end of the third analog switch with a common terminal of the third analog switch according to the second control signal.
6. The strain bridge input sampling circuit of claim 4, wherein the controller is configured to output a third control signal to a first switch module after calibrating the weight equation for the strain bridge if the strain bridge is a six-wire strain bridge, the first switch module being configured to conduct the pair of excitation voltage feedback signal inputs with the pair of filter inputs of the first differential filter module according to the third control signal; and if the strain bridge is a four-wire strain bridge, the second control signal is output to the first switch module after the weight formula of the strain bridge is calibrated.
7. The strain bridge input sampling circuit of claim 3, wherein the second switch module comprises a fourth analog switch, a fifth analog switch, and a sixth analog switch;
a normally open end of the fourth analog switch is electrically connected to one of the pair of power signal input terminals, a normally closed end of the fourth analog switch is electrically connected to one of the pair of strain voltage feedback signal input terminals, and a common end of the fourth analog switch is electrically connected to a normally closed end of the sixth analog switch;
a normally open end of the fifth analog switch is electrically connected to a ground terminal of the pair of power signal input terminals, a normally closed end of the fifth analog switch is electrically connected to the other of the pair of strain voltage feedback signal input terminals, and a common terminal of the fifth analog switch is electrically connected to a normally open end of the sixth analog switch;
and the common end of the sixth analog switch is electrically connected with one of the pair of filter input ends of the second differential filter module, and the normally open end of the sixth analog switch is also electrically connected with the other of the pair of filter input ends of the second differential filter module.
8. The strain bridge input sampling circuit of claim 7, wherein the second switch module is configured to conduct a common terminal of the sixth analog switch with a normally-open terminal of the sixth analog switch according to a first control signal; the second switch module is further configured to conduct a normally-open end of the fourth analog switch with the common terminal of the fourth analog switch, conduct a normally-open end of the fifth analog switch with the common terminal of the fifth analog switch, and conduct a normally-closed end of the fifth analog switch with the common terminal of the fifth analog switch according to the second control signal; the controller is configured to output a third control signal to a second switch module after calibrating the weight formula of the strain bridge, the second switch module being configured to turn on the pair of strain voltage feedback signal inputs and a pair of filter inputs of the second differential filter module according to the third control signal.
9. The strain bridge input sampling circuit of claim 1, further comprising an input drive module, an output of the input drive module being electrically connected to the pair of power signal outputs, an input of the input drive module being electrically connected to an analog power supply terminal.
10. A weighing system comprising a strain bridge and a strain bridge input sampling circuit according to any one of claims 1 to 9.
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