CN109633252A - The method and circuit of big small-range segmented A/D acquisition accelerometer current signal - Google Patents
The method and circuit of big small-range segmented A/D acquisition accelerometer current signal Download PDFInfo
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- CN109633252A CN109633252A CN201811481103.9A CN201811481103A CN109633252A CN 109633252 A CN109633252 A CN 109633252A CN 201811481103 A CN201811481103 A CN 201811481103A CN 109633252 A CN109633252 A CN 109633252A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The present invention provides the method and circuit of a kind of big small-range segmented A/D acquisition accelerometer current signal, the actual conditions for being in smaller acceleration condition to the accelerometer most of the time are held, propose the design concept of " amplification low current; guarantee high current ", newly-increased small-range channel, amplify low current as far as possible, it is close to the input requirements of A/D chip full scale, it can guarantee in small-range section, the resolution ratio of A/D chip can make full use of, meanwhile guaranteeing in high current, circuit still can carry out A/D acquisition according to former scheme.The method can effectively improve the A/D acquisition precision of small-range section accelerometer output electric current, and in most runing times of accelerometer measures carrier, acceleration information measurement is more accurate, to improve navigation accuracy.
Description
Technical field
The present invention relates to a kind of method for acquiring accelerometer current signal and circuits more particularly to a kind of big small-range point
The method and circuit of segmentation A/D acquisition accelerometer current signal.
Background technique
Accelerometer is used to acquire the linear acceleration information of carrier, is one of core element of inertial navigation set.Its is defeated
Signal is generally current signal out, characterizes linear acceleration with the size of electric current.For inertial navigation set, the precision of navigation
The precision for depending not only upon inertia sensitive element itself also relies on the precision of Acquisition Circuit.So promoting the acquisition essence of circuit
Degree is to improve one of the important means of navigation equipment navigation accuracy.As inertial navigation set is to digitlization, miniaturization, lightweight
Requirement and control to cost, high-precision A/D acquisition technique be increasingly becoming the development trend of acquisition accelerometer electric current.It is high
Precision A/D acquisition technique has many advantages, such as that dynamic response is fast, sampled point is more, integration degree is high.
It is bigger that accelerometer generally exports electric current, indicates that the acceleration of carrier is bigger.A/D acquisition refers to A/D chip
The digital signal that analog signal (such as current signal of accelerometer output) is converted into binary format, for components such as CPU
It reads.A/D chip requires the magnitude range of input analog signal, i.e., cannot acquire range beyond it.It is defeated to meet
The size for entering analog signal meets the range requirement of A/D chip, the prior art such as " Liang Yuheng high-accuracy data acquisition and DSP
+ FPGA igh-speed wire-rod production line Hardware Design [D] Xian Electronics Science and Technology University master thesis, 2012. " it is usually logical
Prime signal condition is crossed, the accelerometer current signal of input is zoomed in or out in the range ability of A/D chip.A/D core
It is low that the resolution ratio of piece has height to have, such as has 12, there is 24, and 12 refer to there are 2 12 power binary numbers to differentiate
Different analog signals inputs size, this is the inherent characteristic of A/D chip.To reach making full use of for A/D chip resolution, all
It is input requirements of the maximum value close to A/D chip full scale that will input analog signal, to improve A/D chip to defeated
Enter the resolution ratio of analog signal, to improve acquisition precision.And in reality, the carrier as where accelerometer is typically all phase
It is not in the very big situation of acceleration to even running, only under few time and condition, acceleration may reach
To maximum value.But in order to reach the measurement of gamut, the prior art is all the need to ensure that this maximum value is acquired in A/D chip
In range ability.This was resulted within most times that carrier is run, and the resolution ratio of A/D chip has only been used less than half very
To smaller, the waste of A/D chip resolution is caused, the measurement accuracy of the acceleration information during carrier whole service is caused
It influences.
Summary of the invention
In order to solve the problems, such as that acceleration current information measurement accuracy is low, the invention proposes a kind of big small-range segmenteds
The method of A/D (analog/digital) acquisition accelerometer current signal.Signal is amplified again in small-range section, increases small-range
The acquisition precision of section, to improve accelerometer to the measurement accuracy of linear acceleration.Meanwhile giving a kind of this method realized
Circuit.
The technical solution of the invention is as follows provides a kind of big small-range segmented A/D acquisition accelerometer current signal
Method, comprising the following steps:
S1, the output current signal of accelerometer is converted to by the voltage letter that A/D chip can acquire by sampling resistor
Number；
S2, second order active low-pass filtering is carried out to the voltage signal that step S1 is obtained；
S3, by step S2, treated that voltage signal is amplified in the acquisition range ability of A/D chip, and after guaranteeing amplification
Voltage signal maximum value close to A/D chip maximum range, define the channel be wide range acquisition channel；
S4, amplify again after carrying out big small-range division to step S3 treated voltage signal, and guarantee amplified
Maximum range of the maximum value of small-range voltage signal as close possible to A/D chip；Defining the channel is small-range acquisition channel；
S5, the voltage signal that step S3 wide range acquisition channel is obtained and step S4 small-range acquisition channel obtain voltage
Signal distinguishes RC and filters and input the progress A/D conversion of A/D chip；
S6, CPU are read out the transformation result of the step S5 voltage signal obtained respectively, if collected as the result is shown
Accelerometer electric current corresponded in range in small-range voltage signal, then the collection result of small-range acquisition channel is protected
It deposits；If collected accelerometer electric current has exceeded small-range voltage signal and corresponds to range as the result is shown, wide range is adopted
The collection result in collection channel is saved.
It is special the present invention also provides a kind of circuit of big small-range segmented A/D acquisition accelerometer current signal
Place is: including sampling resistor R1, the first filter circuit, wide range voltage signal amplifying circuit, the second filter circuit, a small amount of
Journey voltage signal amplifying circuit, third filter conditioning circuit.
One end of above-mentioned sampling resistor R1 is connect with the input terminal of accelerometer current output terminal and the first filter circuit, sampling
The resistance R1 other end is connect with circuit common；The output end and wide range voltage signal amplifying circuit of above-mentioned first filter circuit
Input terminal connection, above-mentioned wide range voltage signal amplification circuit output end and the second filter circuit input terminal and small-range voltage are believed
The connection of number input amplifier, small-range voltage signal amplification circuit output end connect third filter circuit.
Further, the first filter circuit is second order active low-pass filter circuit；Wide range voltage signal amplifying circuit is
Positive amplifying circuit；Second filter circuit is RC first-order filtering circuit；Small-range voltage signal amplifying circuit is positive amplification electricity
Road；Third filter circuit is RC first-order filtering circuit
Further, used A/D chip is AD7608.
Further, second-order active filter, wide range voltage signal amplifying circuit, small-range voltage signal amplifying circuit institute
The operational amplifier of use is OPA4188.
Further, the power supply of all operational amplifiers is ± 15V.
The beneficial effects of the present invention are:
The present invention has fully considered the practical situations of accelerometer, is in smaller to the accelerometer most of the time and adds
The actual conditions of speed state are held, and are proposed the design concept of " amplification low current, guarantee high current ", are increased small-range newly
Channel, as far as possible amplification low current, are close to the input requirements of A/D chip full scale, it is ensured that in small-range section, A/
The resolution ratio of D chip can make full use of, meanwhile, guarantee in high current, circuit still can carry out A/D according to former scheme and adopt
Collection.The method can effectively improve the A/D acquisition precision of small-range section accelerometer output electric current, in acceleration measuring loading gage
In most runing times of body, acceleration information measurement is more accurate, to improve navigation accuracy.
Detailed description of the invention
Fig. 1 is schematic block circuit diagram of the present invention；
Fig. 2 is circuit structure diagram of the present invention；
Specific embodiment
The present invention is further described through below in conjunction with drawings and the specific embodiments.
Present invention firstly provides a kind of methods of big small-range segmented A/D acquisition accelerometer current signal, largely
The acquisition method of Cheng Tongdao is similarly to the prior art.The acquisition method in wide range channel mainly includes following three step:
Step 1 allows the output electric current of accelerometer to flow through sampling resistor, so that current signal is converted to A/D chip can
With the voltage signal of acquisition；
Step 2 carries out the filtering and conditioning of voltage signal, and voltage signal is zoomed in or out to the collection capacity of A/D chip
Within the scope of journey, and guarantee maximum range of the maximum value as close possible to A/D chip of voltage signal；
Voltage signal RC after conditioning is filtered and is inputted the progress A/D conversion of A/D chip by step 3.
The present invention introduces small-range channel on the basis of above-mentioned three step, i.e., carries out after step 2 to voltage signal
It is artificial to divide, it is divided into wide range voltage signal and small-range voltage signal, and increase small-range all the way newly after step 2 and adopt
Collect channel.Voltage signal after step 2 is amplified again by small-range acquisition channel, and guarantees small-range voltage signal
Maximum value as close possible to A/D chip maximum range, also pass through RC filtering after input A/D chip.Finally, A/D chip
The voltage signal of wide range acquisition channel and small-range acquisition channel is acquired respectively.
After A/D chip completes voltage signal-digital signal conversion, by CPU to wide range voltage signal and small-range voltage
The transformation result of signal is read out respectively, if collected accelerometer electric current is little as the result is shown, in small-range range
It is interior, then the collection result of small-range section is saved；If collected accelerometer electric current is larger as the result is shown, have exceeded
Small-range range then saves the collection result of wide range section.In this manner it is ensured that in small-range section, A/D chip
Resolution ratio can make full use of, to improve the acquisition precision of small-range section.
The present invention has fully considered the practical situations of accelerometer, is in smaller to the accelerometer most of the time and adds
The actual conditions of speed state are held, and are proposed the design concept of " amplification low current, guarantee high current ", i.e., are put as far as possible
Current is close to the input requirements of A/D chip full scale, meanwhile, when guaranteeing high current, circuit still can be according to original
Scheme carries out A/D acquisition.
For example, the common occasion aircraft of accelerometer.Aircraft is very big in the acceleration of that a period of time of takeoff and landing,
It can achieve 3 g (g is acceleration of gravity), and aircraft is all smooth flight in the flight time of other overwhelming majority, acceleration
Hardly more than 1 g.In order to measure accurate aircraft navigation data, should more go to improve this section of state of flight of smooth flight
Acceleration analysis precision.If removing the current information of acquisition aircraft acceleration meter output with the present invention shown in FIG. 1, within general ± 1g
It is considered small-range section, 1g~3g and -3g~-1g is considered wide range section, it is assumed that acceleration is the output of 1g brief acceleration meter
Electric current be about 12mA, the full scale of A/D chip is ± 10V.Selection sampling resistor is 185 Ω, in this way, the corresponding voltage of ± 3g
± 6.66V has been reformed into, then conditioning is filtered to the signal, has been amplified by 1.5 times, the corresponding voltage of ± 3g reforms into
± 9.99V, close to the full scale of A/D chip, the acquisition precision of wide range section is ensured that.And in small-range ± 1g,
After carrying out resistance sampling and 1.5 times of amplifications, small-range acquisition channel is introduced, then carries out 3 times of amplifications, the small-range of general ± 3.33V
Voltage amplification is ± 9.99V, close to the full scale of A/D chip, makes full use of the A/D chip resolution of small-range section, improves small
Range section acquisition precision.Aircraft is improved in the acceleration acquisition precision of other most flight time, is also just improved winged
The navigation accuracy of machine.
Assuming that the electric current that acceleration is the output of 1g brief acceleration meter is about 1.2mA, output area ± 30g, i.e. output electric current
Range is ± 36mA.The above method, circuit theory such as Fig. 2 of big small-range part charge are realized according to this design requirement circuit
It is shown, it mainly include sampling resistor R1, the first filter circuit, wide range voltage signal amplifying circuit, the second filter circuit, a small amount of
Journey voltage signal amplifying circuit, third filter conditioning circuit.One end of sampling resistor R1 and accelerometer current output terminal and first
The input terminal of filter circuit connects, and the sampling resistor R1 other end is connect with circuit common；The output end of first filter circuit with
The connection of wide range voltage signal input amplifier, wide range voltage signal amplification circuit output end and the second filter circuit are defeated
Enter end and the connection of small-range voltage signal input amplifier, small-range voltage signal amplification circuit output end connects third filtering
Circuit.The specific implementation steps are as follows:
S1, sampling resistor R1 are 150 Ω, and ± 36mA the electric current that accelerometer exports can be converted to the voltage of ± 5.4V
Signal；
S2, second order active low-pass filtering is carried out by the first filter circuit to the ± 5.4V voltage signal that step S1 is obtained；
S3,1.5 times are carried out by wide range voltage signal amplifying circuit to the filtered voltage signal that step S2 is obtained
Forward direction amplification, voltage signal becomes ± 8.1V after amplification, and the maximum range of A/D chip is ± 10V, is not above A/D chip
Maximum range；
S4, big small-range division is carried out to the voltage signal that step S3 is obtained, it is believed that the voltage signal within the scope of ± 2.7V
It is wide range voltage signal beyond the range for small-range voltage signal.By small-range voltage signal amplifying circuit to step
The voltage signal that rapid S3 is obtained carries out 3 times of positive amplification again, and small-range voltage signal becomes ± 8.1V after amplification；
S5, the step S3 and step S4 voltage signal obtained is carried out to after RC filtering A/D turns of progress of input A/D chip respectively
It changes, wherein R is 2k Ω, and C is 0.022 μ F；
S6, distinguished by transformation result of the FPGA to the step S5 wide range voltage signal obtained and small-range voltage signal
It is read out, if collected accelerometer electric current is in small-range range of signal as the result is shown, by small-range channel
Collection result is saved；If collected accelerometer electric current has exceeded small-range range as the result is shown, by wide range
The collection result of section is saved.
The technical effect of method proposed by the present invention and circuit is verified, bias instaility is to measure A/D acquisition essence
The important indicator of degree.Under prior art conditions, test is measured in ± 30g, when accelerometer output current scope is ± 36mA
Bias instaility be not more than 6.5 × 10-5g.When using method and circuit of the invention, measure 10g~30g and -30g~-
10g, i.e. wide range section, accelerometer output current scope be 12mA~36mA and -36mA~-12mA when bias instaility and
The prior art is not much different, for no more than 6.5 × 10-5g.And in ± 10g, i.e. small-range section, accelerometer output current scope
Bias instaility when for ± 12mA is not more than 2.6 × 10-5The acquisition precision of g, the larger range of the acquisition precision of small-range improve
2.5 again.
Claims (6)
1. a kind of method of big small-range segmented A/D acquisition accelerometer current signal, which is characterized in that including following step
It is rapid:
S1, the output current signal of accelerometer is converted to by the voltage signal that A/D chip can acquire by sampling resistor；
S2, second order active low-pass filtering is carried out to the voltage signal that step S1 is obtained；
S3, by step S2, treated that voltage signal is amplified in the acquisition range ability of A/D chip, and guarantees amplified electricity
The maximum value of signal is pressed close to the maximum range of A/D chip, defining the channel is wide range acquisition channel；
S4, amplify again after carrying out big small-range division to step S3 treated voltage signal, and guarantee amplified a small amount of
Maximum range of the maximum value of journey voltage signal close to A/D chip；Defining the channel is small-range acquisition channel；
S5, the voltage signal that step S3 wide range acquisition channel is obtained and step S4 small-range acquisition channel obtain voltage signal
RC, which is filtered and inputted A/D chip, respectively carries out A/D conversion；
S6, CPU are read out the transformation result of the step S5 voltage signal obtained respectively, if collected as the result is shown add
Speedometer electric current corresponds in range in small-range voltage signal, then saves the collection result of small-range acquisition channel；Such as
Collected accelerometer electric current has exceeded small-range voltage signal and corresponds to range fruit as the result is shown, then by wide range acquisition channel
Collection result saved.
2. a kind of circuit of big small-range segmented A/D acquisition accelerometer current signal, it is characterised in that: including sampling resistor
R1, the first filter circuit, wide range voltage signal amplifying circuit, the second filter circuit, small-range voltage signal amplifying circuit,
Three filter circuits；
One end of the sampling resistor R1 is connect with the input terminal of accelerometer current output terminal and the first filter circuit, sampling resistor
The R1 other end is connect with circuit common；The output end and wide range voltage signal amplifying circuit of first filter circuit input
End connection, the wide range voltage signal amplification circuit output end are put with the second filter circuit input terminal and small-range voltage signal
Big circuit input end connection, small-range voltage signal amplification circuit output end connect third filter circuit.
3. the circuit of big small-range segmented A/D acquisition accelerometer current signal according to claim 2, feature exist
In: the first filter circuit is second order active low-pass filter circuit；Wide range voltage signal amplifying circuit is positive amplifying circuit；The
Two filter circuits are RC first-order filtering circuit；Small-range voltage signal amplifying circuit is positive amplifying circuit；Third filter circuit
For RC first-order filtering circuit.
4. the circuit of big small-range segmented A/D acquisition accelerometer current signal according to claim 2, feature exist
In: operation amplifier used by second-order active filter, wide range voltage signal amplifying circuit, small-range voltage signal amplifying circuit
Device is OPA4188.
5. the circuit of big small-range segmented A/D acquisition accelerometer current signal according to claim 4, feature exist
In: the power supply of all operational amplifiers is ± 15V.
6. the circuit of big small-range segmented A/D acquisition accelerometer current signal according to claim 5, feature exist
In: used A/D chip is AD7608.
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