CN204258783U - The A/D conversion system of weighing instrument - Google Patents
The A/D conversion system of weighing instrument Download PDFInfo
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- CN204258783U CN204258783U CN201420773744.2U CN201420773744U CN204258783U CN 204258783 U CN204258783 U CN 204258783U CN 201420773744 U CN201420773744 U CN 201420773744U CN 204258783 U CN204258783 U CN 204258783U
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Abstract
The utility model provides a kind of A/D conversion system of weighing instrument, comprise single-chip microcomputer etc., first resistance, second resistance is connected between LOAD CELLS and modulus conversion chip, 3rd resistance is connected between the first resistance and the second resistance, single-chip microcomputer is connected with modulus conversion chip, 4th electric capacity, 15 resistance, 16 resistance is connected successively, 4th electric capacity is connected with LOAD CELLS, integrated switch power voltage stabilizing chip and the 16 resistor coupled in parallel, LOAD CELLS and a positive energize power supply, a negative energize power supply connects, the voltage of positive energize power supply is different from the voltage of negative energize power supply.The utility model is by changing the mode of the positive and negative driving voltage of instrument output, realization can export a high transducer excitation voltage, one can be obtained again and meet the low common-mode voltage input requirements of ∑-△ type ADC, reduce design cost and design difficulty that instrument improves the adaptive capacity of site of deployment.
Description
Technical field
The utility model relates to a kind of A/D conversion system, particularly, relates to a kind of A/D conversion system of weighing instrument.
Background technology
Measurement technology is particularly in Weighing technology, and AD (modulus) technology is a link of most critical.Weighing technology needs the ADC of high-resolution, high integration, high reliability and low price.Over-sampling, filtering extraction and quantized noise shaping three technology combine by ∑-△ switch technology, achieve high integration, high measuring accuracy, just meet these requirements.At present, the ADC of ∑-△ technology to have become in weighing technology AD technology the ADC of most main flow, is widely used in various non-automatic and autoelectrinic weighing apparatus.
In the application, both requirement will have very high measuring accuracy to weighing instrument, and the measurement data simultaneously requiring again instrument to record will have higher stability.Meet above-mentioned requirements, first need the ADC of instrument (analog to digital conversion circuit) will have very high resolution, the input measurement signal needing instrument to accept in addition is large as much as possible.
Weighing instrument adopts ∑-△ type ADC, and it is not in-problem for realizing high-resolution, mainly solves and how to obtain large this problem of input measurement signal.In general, the method obtaining large input signal has two kinds: (1) increases the multiplication factor of input signal amplifying circuit; (2) driving voltage of transducer is improved.The multiplication factor increasing input signal is not optimal mode: because carry out the input signal of sensor in signals transmission, inevitably be applied many noises (interference) signal, when amplifying through signal amplifier, the measuring-signal of input and noise is amplified all simultaneously, no matter amplify how many times, all cannot improve or improve the signal to noise ratio of instrument A/D change-over circuit, reach the object of data stability when realizing high-acruracy survey.And by improving the mode of transducer excitation voltage, only just increase the measuring-signal of input, can not change the size of noise signal, this just improves the signal to noise ratio of instrument A/D change-over circuit virtually, improve the antijamming capability of circuit, improve data stability under high-acruracy survey.
But general ∑-△ type ADC is low voltage operating (+3.3V ~+5V), and the common-mode voltage of input signal is generally the half of operating voltage, reference input voltage is maximum can not more than the operating voltage of ADC.And the signal common-mode voltage that LOAD CELLS exports is the half of transducer excitation voltage, this excitation output voltage just determining weighing instrument can not more than the operating voltage of ADC.This restriction, directly just by the excitation export-restriction of the weighing instrument of the ∑-△ type ADC that samples maximum can only be+5V, for bringing great difficulty by the mode of " improve the mode of transducer excitation voltage and realize data stability under high-acruracy survey ", also considerably increase design cost and design difficulty that this type of instrument improves the adaptive capacity of site of deployment.
Utility model content
For defect of the prior art, the purpose of this utility model is to provide a kind of A/D conversion system of weighing instrument, it is by changing the mode of the positive and negative driving voltage of instrument output, realization can export a high transducer excitation voltage, one can be obtained again and meet the low common-mode voltage input requirements of ∑-△ type ADC, reduce design cost and design difficulty that instrument improves the adaptive capacity of site of deployment.
According to an aspect of the present utility model, a kind of A/D conversion system of weighing instrument is provided, it is characterized in that, comprise single-chip microcomputer, integrated switch power voltage stabilizing chip, modulus conversion chip, LOAD CELLS, first resistance, second resistance, 3rd resistance, 15 resistance, 16 resistance, 4th electric capacity, first resistance, second resistance is connected between LOAD CELLS and modulus conversion chip, 3rd resistance is connected between the first resistance and the second resistance, single-chip microcomputer is connected with modulus conversion chip, 4th electric capacity, 15 resistance, 16 resistance is connected successively, 4th electric capacity is connected with LOAD CELLS, integrated switch power voltage stabilizing chip and the 16 resistor coupled in parallel, LOAD CELLS and a positive energize power supply, a negative energize power supply connects, the voltage of positive energize power supply is different from the voltage of negative energize power supply.
Preferably, the model of described integrated switch power voltage stabilizing chip is LM25965.
Preferably, the model of described modulus conversion chip is ADS1232.
Preferably, described first resistance, the second resistance, the 3rd resistance form resistance network.
Preferably, described 4th electric capacity, the 15 resistance, the 16 resistance form the sluggish start-up circuit that powers on.
Preferably, the 8th resistance, the 9th resistance, the tenth resistance, the 11 resistance, the 12 resistance, the 13 resistance, the 9th electric capacity is provided with between described single-chip microcomputer and modulus conversion chip, parallel with one another between 8th resistance, the 9th resistance, the tenth resistance three, parallel with one another between 11 resistance, the 12 resistance, the 13 resistance three, 8th resistance and the 11 resistant series, 9th resistance and the 12 resistant series, the tenth resistance and the 13 resistant series.
Preferably, described modulus conversion chip is also connected with the first electric capacity, the 3rd electric capacity, the 5th electric capacity, the 11 electric capacity, the 12 electric capacity, the first electric capacity and the 11 Capacitance parallel connection, the 3rd electric capacity and the 12 capacitances in series.
Preferably, described integrated switch power voltage stabilizing chip is connected with diode, the first electrochemical capacitor, inductance, the second electrochemical capacitor.
Preferably, described LOAD CELLS is connected with the 6th electric capacity, the 7th electric capacity, the 8th electric capacity, the 6th resistance, the 7th resistance.
Compared with prior art, the utility model has following beneficial effect: the utility model is by changing the mode of the positive and negative driving voltage of instrument output, realization can export a high transducer excitation voltage, one can be obtained again and meet the low common-mode voltage input requirements of ∑-△ type ADC, reduce design cost and design difficulty that instrument improves the adaptive capacity of site of deployment.The utility model both achieved high-acruracy survey, the high stability of measurement data of having got back.
Accompanying drawing explanation
By reading the detailed description done non-limiting example with reference to the following drawings, other features, objects and advantages of the present utility model will become more obvious:
Fig. 1 is the circuit diagram of the A/D conversion system of the utility model weighing instrument.
Embodiment
Below in conjunction with specific embodiment, the utility model is described in detail.Following examples will contribute to those skilled in the art and understand the utility model further, but not limit the utility model in any form.It should be pointed out that to those skilled in the art, without departing from the concept of the premise utility, some distortion and improvement can also be made.These all belong to protection range of the present utility model.
As shown in Figure 1, the A/D conversion system of the utility model weighing instrument comprises single-chip microcomputer U1, integrated switch power voltage stabilizing chip U2, modulus conversion chip U3, LOAD CELLS U4, first resistance R1, second resistance R2, 3rd resistance R3, 15 resistance R15, 16 resistance R16, 4th electric capacity C4, first resistance R1, second resistance R2 is connected between LOAD CELLS U4 and modulus conversion chip U3, 3rd resistance R3 is connected between the first resistance R1 and the second resistance R2, single-chip microcomputer U1 is connected with modulus conversion chip U3, 4th electric capacity C4, 15 resistance R15, 16 resistance R16 connects successively, 4th electric capacity C4 is connected with LOAD CELLS U4, U2 is in parallel with the 16 resistance R16 for integrated switch power voltage stabilizing chip, a LOAD CELLS U4 and positive energize power supply EX+, a negative energize power supply EX-connects, the voltage of positive energize power supply EX+ is different from the voltage of negative energize power supply EX-.The model of integrated switch power voltage stabilizing chip U2 is LM25965.The model of modulus conversion chip U3 is ADS1232.
Integrated switch power voltage stabilizing chip U2 produces negative energize power supply EX-, integrated switch power voltage stabilizing chip U2 with positive energize power supply EX+ for input power, power output end (the 4th pin) is connected as out-put supply ground with ground wire, the ground terminal (the 3rd pin) of integrated switch power voltage stabilizing chip U2, as the output of U2, realizes the generation of negative energize power supply EX-.
Modulus conversion chip U3 amplifies the analog signal that LOAD CELLS U4 exports and performs A/D conversion.The inside of modulus conversion chip U3 has incorporated amplifier, and multiplication factor is configured by the level state of the 19th pin and 20 pin.The built-in filter circuit of U3 forms complete filter circuit jointly by the 11 electric capacity C11 between the 9th pin and the 10th pin, realizes the filtering to input analog signal.
Single-chip microcomputer U1 mainly controls modulus conversion chip U3 reset (the 22nd pin of modulus conversion chip U3), offset correction (the 23rd pin of modulus conversion chip U3), monitoring A/D transition status (the 24th pin of modulus conversion chip U3), when U3 once converts, read transformation result by control synchronization clock (the 23rd pin of modulus conversion chip U3) from the data output end (the 24th pin) of modulus conversion chip U3, then do further process.
The 8th resistance R8, the 9th resistance R9, the tenth resistance R10, the 11 resistance R11, the 12 resistance R12, the 13 resistance R13, the 9th electric capacity C9 is provided with between single-chip microcomputer U1 and modulus conversion chip U3, parallel with one another between 8th resistance R8, the 9th resistance R9, the tenth resistance R10 three, parallel with one another between 11 resistance R11, the 12 resistance R12, the 13 resistance R13 three, 8th resistance R8 connects with the 11 resistance R11,9th resistance R9 connects with the 12 resistance R12, and the tenth resistance R10 connects with the 13 resistance R13.
Modulus conversion chip U3 is also connected with the first electric capacity C1, the 3rd electric capacity C3, the 5th electric capacity C5, the 11 electric capacity C11, the 12 electric capacity C12.
First electric capacity C1, the 3rd electric capacity C3, the 5th electric capacity C5 form the filter circuit of modulus conversion chip U3 benchmark input, carry out filtering to the reference power supply input of modulus conversion chip U3, to ensure the stable of reference voltage.11 electric capacity C11 is connected across between the 9th pin of U3 and the 10th pin, analog input signal filter in the sheet of cooperation modulus conversion chip U3 inner filter circuit formation modulus conversion chip U3.
Integrated switch power voltage stabilizing chip U2 is connected with diode D1, the first electrochemical capacitor E1, inductance L, the second electrochemical capacitor E2.Second electrochemical capacitor E2 is the input capacitance of integrated switch power voltage stabilizing chip U2, for carrying out filtering to input power; First electrochemical capacitor E1 and inductance L form the output ripple filter circuit of integrated switch power voltage stabilizing chip U2, filtering output ripple; Diode D1 is absorption diode, for the inverse electromotive force that absorption inductor L is operationally produced.
LOAD CELLS U4 is connected with the 6th electric capacity C6, the 7th electric capacity C7, the 8th electric capacity C8, the 6th resistance R6, the 7th resistance R7.
6th electric capacity C6, the 7th electric capacity C7, the 8th electric capacity C8 form the elementary filter circuit of LOAD CELLS U4 output signal.The differential mode interference of the positive negative output signal of the 6th electric capacity C6 and the 8th electric capacity C8 difference filtering, the 7th electric capacity C7 is used for filtering common mode interference signal.Six resistance R6, the 7th resistance R7 are connected on the positive and negative output signal line of transducer respectively; T-shaped filter circuit is jointly formed on the one hand with the 6th electric capacity C6, the 7th electric capacity C7; meanwhile, the signal buffer protection of the input end of analog signal to modulus conversion chip U3 is played.
Excitation power supply of the present utility model adopts asymmetric double Power Management Design, positive energize power supply (positive energize power supply can be connected with first pin of LOAD CELLS U4) adopts DC+10V, negative energize power supply (negative energize power supply can be connected with the tripod of LOAD CELLS U4) adopts DC-5V (DC-5V is produced by the negative voltage circuit for generating being core with integrated switch power voltage stabilizing chip U2), realizes the object of the input of high driving voltage, the output of low common-mode voltage.Adopt this asymmetric double power supply energisation mode, the driving voltage be loaded on LOAD CELLS U4 is+10V-(-5V)=+ 15V, comparison with standard ∑-△ type ADC (for the modulus conversion chip U3 of the 24bit precision of TI in this scheme) generally can only adopt+5V driving voltage, expand three times, achieve the object of high voltage excitation.
LOAD CELLS U4 signal output signal voltage (U
o) be as shown in the formula (1):
U
O＝U
EXC×α……………………………………………………………………(1)
Wherein, U
eXcfor driving voltage, α is the output sensitivity of transducer, because α is a steady state value, so as driving voltage (U
eXc) promote after three times, sensor output signal U
oalso by raising three times.
Simultaneously because adopt+10V and-5V to be used as positive and negative excitation power supply, LOAD CELLS U4 is strain gauge load cell, essence is by four resistance elements---the wheatstone bridge that electric resistance wire strain gauge forms, and crus secunda and the 4th pin of LOAD CELLS U4 are LOAD CELLS positive output signal and negative output signal respectively.Suppose that the resistance value of four strain ga(u)ges is respectively R, when sensor output signal is 0, then the voltage at the crus secunda place of LOAD CELLS U4 is: 10V-(10V-(-5) V) .R/2R=10V-7.5V=2.5V; In like manner, the voltage at the 4th pin place of LOAD CELLS U4 is also 2.5V.It can thus be appreciated that the common-mode voltage that the positive and negative two-way of LOAD CELLS U4 (crus secunda of LOAD CELLS U4 and the 4th pin) outputs signal is+2.5V, this magnitude of voltage meets ∑-△ type ADC common-mode voltage requirement (≤+ 2.5V completely, recommendation+2.5V), achieve the object of low common-mode voltage.
The utility model forms resistance network by the first resistance R1, the second resistance R2, the 3rd resistance R3, produces the problem that meet low motivational feedback voltage that ∑-△ type ADC require under realizing high driving voltage by this resistor network.The resistance of the resistance of the first resistance R1, the resistance of the second resistance R2, the 3rd resistance R3 is equal, by be applied to LOAD CELLS U4 1,3 pin between driving voltage 15V decile, dividing potential drop on 3rd resistance R3 is+5V, the reference voltage input U3-15 (negative benchmark inputs) of the 3rd resistance R3 two ends and modulus conversion chip U3, U3-16 (positive benchmark input) pin are linked, benchmark as modulus conversion chip U3 inputs, and reaches the requirement meeting ∑-△ type ADC reference input voltage (≤+ 5.5V).
The problem meeting the low motivational feedback voltage that ∑-△ type ADC requires is produced under realizing high driving voltage by resistor network.The motivational feedback voltage of weighing instrument is very important, can play " long line compensation " effect that weighing technology is said using motivational feedback voltage as the reference voltage of ADC.But the reference voltage amplitude upper limit of ∑-△ type ADC (for ADS1232) is that there are strict requirements: the analog operation voltage+10% being generally ADC.The driving voltage that LOAD CELLS U4 holds is turned back to weighing instrument by feedback circuit, the resistor network consisted of the first resistance R1, the second resistance R2, the 3rd resistance R3 produces the voltage signal of a road+5V, as the reference input voltage meeting ∑-△ type ADC (for ADS1232) requirement (≤+ 5.5V).
+ 10V power supply is not only as positive energize voltage (EX+), and meanwhile ,+10V produces-5V driving voltage after being input to integrated switch power voltage stabilizing chip U2.5th pin of single-chip microcomputer U1 is output enable control pin, and the sluggish start-up circuit that powers on formed with the 4th electric capacity C4, the 15 resistance R15, the 16 resistance R16 is connected.Before+10V power supply does not also have Establishment of Stable, the sluggish start-up circuit that powers on exports 5th pin of high level to single-chip microcomputer U1, make the output of single-chip microcomputer U1 in high-impedance state, export without-5V, operating state that LOAD CELLS U4 is similar to " open circuit ", so no signal exports, so also just avoid when-5V negative energize voltage is not also accurately set up and cause abnormal the generation ∑-△ type ADC of common-mode voltage to be damaged.Meanwhile, produce negative energize voltage from positive energize voltage, also can ensure the sensor power loop energy power-off in time when positive energize+10V has fault thus avoid unexpected generation.
The problem that the weighing instrument that the utility model solves employing ∑-△ type ADC with cheap, simple circuit can not use high driving voltage to be sensor power, both the output signal of LOAD CELLS had been increased, improve signal to noise ratio, greatly improve the antijamming capability of electronic-weighing instrument and the adaptive capacity to site of deployment; Under high driving voltage, again reduce the common-mode voltage of sensor output signal simultaneously, make it the requirement adapting to ∑-△ type ADC, achieve high-acruracy survey, that is: both ensure that certainty of measurement, in turn ensure that the stable of measurement data.
Above specific embodiment of the utility model is described.It is to be appreciated that the utility model is not limited to above-mentioned particular implementation, those skilled in the art can make various distortion or amendment within the scope of the claims, and this does not affect flesh and blood of the present utility model.
Claims (9)
1. the A/D conversion system of a weighing instrument, it is characterized in that, comprise single-chip microcomputer, integrated switch power voltage stabilizing chip, modulus conversion chip, LOAD CELLS, first resistance, second resistance, 3rd resistance, 15 resistance, 16 resistance, 4th electric capacity, first resistance, second resistance is connected between LOAD CELLS and modulus conversion chip, 3rd resistance is connected between the first resistance and the second resistance, single-chip microcomputer is connected with modulus conversion chip, 4th electric capacity, 15 resistance, 16 resistance is connected successively, 4th electric capacity is connected with LOAD CELLS, integrated switch power voltage stabilizing chip and the 16 resistor coupled in parallel, LOAD CELLS and a positive energize power supply, a negative energize power supply connects, the voltage of positive energize power supply is different from the voltage of negative energize power supply.
2. the A/D conversion system of weighing instrument according to claim 1, is characterized in that, the model of described integrated switch power voltage stabilizing chip is LM25965.
3. the A/D conversion system of weighing instrument according to claim 1, is characterized in that, the model of described modulus conversion chip is ADS1232.
4. the A/D conversion system of weighing instrument according to claim 1, is characterized in that, described first resistance, the second resistance, the 3rd resistance form resistance network.
5. the A/D conversion system of weighing instrument according to claim 1, is characterized in that, described 4th electric capacity, the 15 resistance, the 16 resistance form the sluggish start-up circuit that powers on.
6. the A/D conversion system of weighing instrument according to claim 1, it is characterized in that, the 8th resistance, the 9th resistance, the tenth resistance, the 11 resistance, the 12 resistance, the 13 resistance, the 9th electric capacity is provided with between described single-chip microcomputer and modulus conversion chip, parallel with one another between 8th resistance, the 9th resistance, the tenth resistance three, parallel with one another between 11 resistance, the 12 resistance, the 13 resistance three, 8th resistance and the 11 resistant series, 9th resistance and the 12 resistant series, the tenth resistance and the 13 resistant series.
7. the A/D conversion system of weighing instrument according to claim 1, it is characterized in that, described modulus conversion chip is also connected with the first electric capacity, the 3rd electric capacity, the 5th electric capacity, the 11 electric capacity, the 12 electric capacity, first electric capacity and the 11 Capacitance parallel connection, the 3rd electric capacity and the 12 capacitances in series.
8. the A/D conversion system of weighing instrument according to claim 1, is characterized in that, described integrated switch power voltage stabilizing chip is connected with diode, the first electrochemical capacitor, inductance, the second electrochemical capacitor.
9. the A/D conversion system of weighing instrument according to claim 1, is characterized in that, described LOAD CELLS is connected with the 6th electric capacity, the 7th electric capacity, the 8th electric capacity, the 6th resistance, the 7th resistance.
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| CN201420773744.2U CN204258783U (en) | 2014-12-09 | 2014-12-09 | The A/D conversion system of weighing instrument |
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| CN201420773744.2U CN204258783U (en) | 2014-12-09 | 2014-12-09 | The A/D conversion system of weighing instrument |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105634490A (en) * | 2015-12-28 | 2016-06-01 | 上海耀华称重系统有限公司 | Zener type intrinsically safe analog-to-digital signal conversion circuit |
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2014
- 2014-12-09 CN CN201420773744.2U patent/CN204258783U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105634490A (en) * | 2015-12-28 | 2016-06-01 | 上海耀华称重系统有限公司 | Zener type intrinsically safe analog-to-digital signal conversion circuit |
| CN105634490B (en) * | 2015-12-28 | 2019-01-08 | 上海耀华称重系统有限公司 | Zener type essential safe type analog signal conversion digital signal circuit |
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