CN1400469A - Anti-jumming measuring circuit - Google Patents

Abstract

The invention discloses a kind of anti-jamming measuring circuit. It can measure the all kinds of physical magnitude and also make the circuit keep the accuracy and the stability of its output signals under the continual change and the external magnetic disturbance.

Description

Anti-jumming measuring circuit

The present invention relates to electronic measuring technology field, specifically a kind of anti-interference metering circuit.

Electronic measurement circuit is generally single channel sample circuit shown in Figure 1, with the example that is measured as of resistance R x, it comprises constant pressure source or constant current source [1], is assumed to be constant pressure source here, A/D converter [2], reference voltage source [2 '], single-chip microcomputer [4], display [5] is formed, as measuring and show the resistance of Rx, then will provide a normal voltage signal by [1], establishing this signal is DC10V, R _1NBe sampling resistor, establish and be taken as 10K Ω, if the A point voltage is 1V, then according to Ohm law, 10V/R _X=1V/R _IN, R _X=10V * 10K Ω/1V=100K Ω.The output valve R ' of A/D converter _X=V _A/ V _{2 '}* 20000, establish reference voltage source [2 '] and be taken as 2.000V, then work as V _ADuring=1V, R ' _X=1V/2V * 20000=10000 needs only and rationally places scaling position, then R when showing _X=R ' _X, promptly the A/D output valve equals actual measured resistance value.In this circuit, require the necessary precision height of constant pressure source (constant current source) [1], and the influence of temperature, humidity extraneous factor not in time,, and the interference of electromagnetic field etc. can not be arranged near the metering circuit, otherwise the accuracy of metering circuit and stability will can not get guaranteeing, become 9.9V as constant pressure source 1 by 10V, then by Ohm law: 9.9V/100K Ω=V _A/ 10K Ω, V _A=9.9V * 10K Ω/100K Ω=0.99V, this moment A/D output valve=0.99V/2V * 20000=9900, the radix point location is after single-chip microcomputer 4 is handled and delivered to the resistance that shows behind the display is 99K Ω, this has just produced the measuring error of 1K Ω.Equally, because the interference of external electromagnetic field also can make V _AValue change, in order to improve the antijamming capability of circuit, metering circuit shown in Figure 2 has been proposed, it is different with Fig. 1 circuit is to have become the two-way sampling by 1 tunnel sampling, and the two-way A/D converter, for convenience of description, supposes R ₀＞＞R ₁At R _X＞＞R _IN, establishing constant pressure source [1] is V, R ₀, R ₁, R _INBe the measuring resistance of known resistance, according to Ohm law, V _A=V/R _X* R _IN, V _B=V/R ₀* R ₁, two formulas are divided by, V _B/ V _A=R _X/ R ₀* R ₁/ R _IN, establish R ₁/ R ₀/ R _IN=C, then R _X=V _B/ V _A* C (1), the composition that in this formula, has not had constant pressure source [1], this just illustrates that the variation of constant pressure source [1] can not influence the accuracy of measurement, and the interference of electromagnetic field on every side also will be slackened equally, the groundwork program of single-chip microcomputer [4] is such, leave a storage unit in after earlier the signal that one road signal such as A/D converter [2] are sent here is handled, handle the signal that A/D converter [3] sends here again and have another storage unit, and then this two paths of signals taken out carry out computing, computing finishes and delivers to display [5] and show.The above-mentioned course of work makes the sampling of two paths of signals produce the mistiming, and general single-chip microcomputer is in order to improve the antijamming capability of circuit, all be added with the program of digital filtering, promptly not to get one but get several when the number of winning the confidence, get its mean value then, this has strengthened the mistiming of two paths of signals virtually, we see the composition that does not have permanent power supply [1] in formula (1), but it has a prerequisite, the constant pressure source (or constant current source) that is the two-way sampling must be to change synchronously, if the sampling time difference of two-way, then because the variation of constant pressure source [1] can cause measuring error, also be random variation from the interference of electromagnetic field on every side equally, this makes the antijamming capability of circuit shown in Figure 2 be subjected to slackening.

The object of the present invention is to provide a kind of circuit, it not only can measure various physical quantitys, and can eliminate from the inside and outside various interference of circuit, and can improve the accuracy and the stability of circuit measuring.

Fig. 3 is a circuit block diagram of the present invention.

Below in conjunction with Fig. 3 most preferred embodiment of the present invention is elaborated, [1] is constant pressure source, and [2] are A/D converter, and [4] are single chip circuit, and [5] are display, R _XBe measured resistance, R ₀, R ₁, R _INBe measuring resistance, A/D converter [2] has two input ends, the 1st, the reference voltage source input end, the 2nd, the measured signal input end all requires the necessary good stability of reference voltage source [1] during conventional the use, in case set up, can not change, temperature drift is little, does not change in time, otherwise the conversion of signals of A/D will produce very big error, and reference voltage source end 1 has exactly inserted transformable signal V among Fig. 3 _A, signal input part has inserted signal V _B, according to the output signal R ' of A/D converter _X=V _B/ V _A* 20000, and change the formula (1) that obtains, R according to Ohm law _X=V _B/ V _A* C is not difficult to find out as long as C gets suitable value, R _X=R ' _X, and V _AWith V _BBe the precise synchronization sampling, almost not free poor, the variation of constant pressure source [1] is eliminated in this circuit, and the extraneous interference of electromagnetic field also is eliminated basically, i.e. stationary state equilibrium conversion by passiveness is more stable and accurate mobile equilibrium.

Also can go out the metering circuit of physical quantitys such as measuring voltage, electric current, temperature, pressure according to above-mentioned principle design.

The present invention is widely used in various measurements, measuring instrument and meter, and it will improve the antijamming capability of instrument and meter greatly, improves the accuracy and the stability of instrument.

Claims (2)

1, a kind of anti-interference metering circuit that is made of two-way sample circuit, single chip circuit and display circuit is characterized in that it also comprises:

A/D converter [2] when measured object is resistance, provides a voltage signal by constant voltage former [1], according to Ohm law R _X=V _B/ V _A* C, wherein C is a setting constant value, the output valve=R ' of A/D converter [2] _X=V _B/ V _A* 20000, rationally choose the value of constant C and the position of rationally placing radix point, then R _X=R ' _X, promptly actual measurand and A/D output valve are in full accord, data are given display [5] again and show after single-chip microcomputer [4] is handled, here V _BWith V _AThe sampling of two paths of signals is carried out synchronously, and is not free poor, eliminated from circuit inside and extraneous various interference, guaranteed the in full accord of displayed value and measurand.

2,, can also be designed to measure or detect the anti-jumming measuring circuit of other physical quantitys such as voltage, electric current, temperature, pressure according to claim 1 described anti-interference metering circuit.