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 accurately ground voltage.
In order to achieve the above object, the invention provides following technical scheme:
A kind of testing circuit for automobile instrument comprises:
Sensor and processor unit, described sensor is fuel level sensor or cooling-water temperature sensor, described processor unit is connected to the processor reference earth point, be connected to the first data input pin of processor unit behind ground connection termination first resistance of sensor, described data input pin is connected to the first filter capacitor, the ground voltage of described processor unit by sensor and the difference of the reference earth point voltage of processor unit are 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 an 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 connect 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 the processor reference earth point after by the 4th resistance, and is connected to the 3rd filter capacitor.
The testing circuit that is used for automobile instrument that the embodiment of the invention provides, collect the ground voltage of sensor by processor unit, simultaneously, processor unit self also has with reference to ground voltage, the difference of the reference earth point voltage of the ground voltage by sensor and processor unit is determined the ground connection reference voltage of sensor like this, got rid of stake resistance error problem in the 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 that make invention can 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 in the situation of intension of the present invention, so the present invention is not subjected to the restriction of following public specific embodiment.
In the present embodiment, as shown in Figure 2, fuel level sensor Q 1 and cooling-water temperature sensor Q2 have been comprised in the testing circuit, 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 adopt this set to fuel level sensor or cooling-water temperature sensor.
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, receive the data input port ADC2 of single-chip microcomputer U2 behind its current-limiting resistance of the earth terminal A of fuel level sensor Q1 process R3, and ground connection behind the ADC2 termination filter capacitor C4; Similarly, receive the data input port ADC4 of single-chip microcomputer U2 behind its current-limiting resistance of earth terminal B process R6 of cooling-water temperature sensor Q2, and ground connection behind the ADC4 termination filter capacitor C6, like this, collect the ground voltage of fuel level sensor Q1 and cooling-water temperature sensor Q2 by single-chip microcomputer U2, in the present embodiment, the data input port of single-chip microcomputer U2 is the data port of built-in analog to digital converter, it gathers analog quantity and change, certainly, the data input port of single-chip microcomputer also can be 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), and the direct Collect conversion of single-chip microcomputer is the signal of digital quantity.Single-chip microcomputer U2 is connected to the processor reference earth point C of oneself, behind a data input port ECU IN termination current-limiting resistance R7, meet processor reference earth point C, and ground connection behind the 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, the difference of ground voltage that can be by 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 the 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, and C2 is the electric capacity of 1000uF/25Vd.
For fuel level sensor Q1, its output terminal one tunnel connects the output terminal of receiving voltage source U1 behind the biasing resistor R1, and another road of Q1 output terminal connects the data input port ADC1 that receives single-chip microcomputer U2 behind the current-limiting resistance R2, ground connection behind the 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 behind the biasing resistor R4, and another road of Q2 output terminal connects the data input port ADC3 that receives single-chip microcomputer U2 behind the current-limiting resistance R5, ground connection behind the ADC3 termination filter capacitor C5.Fuel level sensor Q1 and cooling-water temperature sensor Q2 are resistance type sensor, behind upper offset resistance R 1, R4, be connected to single-chip microcomputer through current-limiting resistance R2, R5, gather the voltage signal that oil mass and water temperature change, filter capacitor C3, C5 are the spike pulse filter capacitor, with the short 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 100 ohm resistance, 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, those skilled in the art can according to concrete design, choose different numerical value.
The above only is preferred embodiment of the present invention, is not the present invention is done any pro forma restriction.
Although the present invention discloses as above with preferred embodiment, yet is not to limit the present invention.Any those of ordinary skill in the art, do not breaking away from the technical solution of the present invention scope situation, all can utilize method and the technology contents of above-mentioned announcement that technical solution of the present invention is made many possible changes and modification, or be revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not break away from technical solution of the present invention according to any simple modification, equivalent variations and the modification that technical spirit of the present invention is done above embodiment, all still belongs in the scope of technical solution of the present invention protection.