Summary of the invention
Based on the problems referred to above, the invention provides a kind of testing circuit for automobile instrument, for automobile instrument provides ground voltage accurately.
In order to achieve the above object, the invention provides following technical scheme:
A testing circuit for automobile instrument, comprising:
Sensor and processor unit, described sensor is fuel level sensor or cooling-water temperature sensor, described processor unit is connected to processor reference earth point, after ground connection termination first resistance of sensor, be connected to the first data input pin of processor unit, described data input pin is connected to the first filter capacitor, described processor unit, by the difference of the ground voltage of sensor and the reference earth point voltage of processor unit, is determined the ground connection reference voltage of sensor.
Alternatively, also comprise: voltage source and the second resistance, the 3rd resistance and the second filter capacitor, the output terminal of described sensor connects respectively one end of the second resistance and the 3rd resistance, the output terminal of another termination voltage source of the second resistance, the other end of the 3rd resistance connects respectively the second data input pin of the second filter capacitor and processor unit.
Alternatively, described voltage source is comprised of the filter capacitor in voltage of voltage regulation source and voltage of voltage regulation source.
Alternatively, described voltage of voltage regulation source is output as 9V, and described the first resistance is 10k ohm, and described the second resistance is 100 ohm, and described the 3rd resistance is 10k ohm.
Alternatively, described processor unit is connected to processor reference earth point after by the 4th resistance, and is connected to the 3rd filter capacitor.
The testing circuit for automobile instrument that the embodiment of the present invention provides, by processor unit, collect the ground voltage of sensor, simultaneously, processor unit self also has with reference to ground voltage, by the difference of the ground voltage of sensor and the reference earth point voltage of processor unit, determine like this ground connection reference voltage of sensor, got rid of stake resistance error problem in batch production, improved measuring accuracy, for the application of other instrument and meters provides more accurate data-signal.
Embodiment
For above-mentioned purpose, the feature and advantage of invention can be become apparent more, below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in detail.
A lot of details have been set forth in the following description so that fully understand the present invention, but the present invention can also adopt other to be different from alternate manner described here and implement, those skilled in the art can do similar popularization without prejudice to intension of the present invention in the situation that, so the present invention is not subject to the restriction of following public specific embodiment.
In the present embodiment, as shown in Figure 2, testing circuit has comprised fuel level sensor Q 1 and cooling-water temperature sensor Q2, the earth terminal of these two kinds of sensors has all been received processor unit, be used for comparing with the earth point voltage of processor unit self, obtain ground connection reference voltage separately, improve the measuring accuracy of oil level and water temperature.Certainly, in other embodiments, can, according to concrete needs, in testing circuit, only to fuel level sensor or cooling-water temperature sensor, adopt this set.
As shown in Figure 2, in this specific embodiment, processor unit adopts MCU(Micro Control Unit) single-chip microcomputer U2, this single-chip microcomputer U2 has a plurality of ADC(analog to digital converters) data input port ADC1 ... ADC4.., connect respectively earth terminal A, B and the output terminal of fuel level sensor Q1 and cooling-water temperature sensor Q2, wherein, single-chip microcomputer U2 is connected to the processor reference earth point C of oneself.
Particularly, the earth terminal A of fuel level sensor Q1 receives the data input port ADC2 of single-chip microcomputer U2 after its current-limiting resistance R3, and ground connection after ADC2 termination filter capacitor C4, similarly, the earth terminal B of cooling-water temperature sensor Q2 receives the data input port ADC4 of single-chip microcomputer U2 after its current-limiting resistance R6, and ground connection after ADC4 termination filter capacitor C6, like this, by single-chip microcomputer U2, collect the ground voltage of fuel level sensor Q1 and cooling-water temperature sensor Q2, in the present embodiment, the data port that the data input port of single-chip microcomputer U2 is built-in analog to digital converter, it gathers analog quantity and change, certainly, the data input port of single-chip microcomputer can be also digital input port, analog quantity can be linked into the numerical data mouth of single-chip microcomputer afterwards through analog to digital converter (scheming not shown), the signal that the direct Collect conversion of single-chip microcomputer is digital quantity.Single-chip microcomputer U2 is connected to the processor reference earth point C of oneself, after a data input port ECU IN termination current-limiting resistance R7, meet processor reference earth point C, and ground connection after ECU IN termination filter capacitor C7, R7 adopts the resistance of 6.8k ohm, and C7 adopts the electric capacity of 100uF.Like this, single-chip microcomputer can collect the ground voltage of fuel level sensor Q1 and cooling-water temperature sensor Q2, can be by the difference of the ground voltage of sensor and the reference earth point voltage of processor unit, determine respectively the ground connection reference voltage of oil level and cooling-water temperature sensor, and offer processor and do other purposes, for example do application of further data operation and other instrument and meters etc., got rid of stake resistance error problem in batch production, improved measuring accuracy.
This single-chip microcomputer U2 can also be used to gather the output valve of fuel level sensor Q1 and cooling-water temperature sensor Q2, particularly, in this testing circuit, also include voltage source U1, in one embodiment, this voltage source is the source of stable pressure of 9V, output terminal is connected to filter capacitor C1 and electrochemical capacitor C2, the electric capacity that C2 is 1000uF/25Vd.
For fuel level sensor Q1, its output terminal one tunnel connects the output terminal of receiving voltage source U1 after biasing resistor R1, and another road of Q1 output terminal connects the data input port ADC1 that receives single-chip microcomputer U2 after current-limiting resistance R2, ground connection after ADC1 termination filter capacitor C3; Similarly, for cooling-water temperature sensor Q2, its output terminal one tunnel connects the output terminal of receiving voltage source U1 after biasing resistor R4, and another road of Q2 output terminal connects the data input port ADC3 that receives single-chip microcomputer U2 after current-limiting resistance R5, ground connection after ADC3 termination filter capacitor C5.Fuel level sensor Q1 and cooling-water temperature sensor Q2 are resistance type sensor, after upper offset resistance R 1, R4, through current-limiting resistance R2, R5, be connected to single-chip microcomputer, gather the voltage signal that oil mass and water temperature change, filter capacitor C3, C5 are spike pulse filter capacitor, with the shorter disturbing pulse of filtering time constant.In this specific embodiment, current-limiting resistance R2, R3, R5, R6 adopt the resistance of 10k ohm, and upper offset resistance R 1, R4 adopt the resistance of 100 ohm, and filter capacitor C3-C7 adopts the electric capacity of 100uF.
Be understandable that, the value of above resistance, power supply and electric capacity is just as example, and those skilled in the art can, according to concrete design, choose different numerical value.
The above, be only preferred embodiment of the present invention, not the present invention done to any pro forma restriction.
Although the present invention discloses as above with preferred embodiment, yet not in order to limit the present invention.Any those of ordinary skill in the art, do not departing from technical solution of the present invention scope situation, all can utilize method and the technology contents of above-mentioned announcement to make many possible changes and modification to technical solution of the present invention, or be revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not depart from technical solution of the present invention,, all still belongs in the scope of technical solution of the present invention protection any simple modification made for any of the above embodiments, equivalent variations and modification according to technical spirit of the present invention.