CN1362616A

CN1362616A - Method of measuring level of conducting liquid

Info

Publication number: CN1362616A
Application number: CN 01100074
Authority: CN
Inventors: 王晓峰
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-01-08
Filing date: 2001-01-08
Publication date: 2002-08-07

Abstract

The present invention utilizes conductivity of conductive liquor to convert the resistance of detection electrode into liquid level signal, which is characterized by that the voltage signal applied to detection electrode adopts impulse voltage with a certain width and a certain period. Said method can basically eliminate the corrosion of electrolytic action to detection electrode, and is suitable for controlling liquid level of various conductive liquor.

Description

A kind of method of measuring conducting liquid level

The invention belongs to the liquid level controlling field.

Measurement for conducting liquid level, be extensive use of conductance type, the characteristic of promptly utilizing liquid to conduct electricity, the detecting electrode of the metal manufacturing of two or more mutually insulateds is placed certain position, when detecting electrode immerses liquid, the resistance that immerses between the detecting electrode in the liquid becomes very little, just can learn the liquid level height by the resistance variations of measuring between the detecting electrode like this.For example Granted publication number is the content of describing in 2283274 Chinese patent " electronics level sensor " instructions: the final stage triode of the resistance sizes between the detecting electrode by 555 time base circuits and control thereof is converted to the action of switching signal pilot relay, reaches and detect and the purpose of control water level; And Granted publication number is the content of describing in 2039793 Chinese patent " boiler water level, the vapor pressure automaton " instructions: one group of detecting electrode and water liquid level are formed electric switch, liquid level position is converted to the electric switch signal drive pump motor and realize automatic control to water level.

The method of conductance type measuring liquid level has the advantages that circuit is simple, cost is low, therefore is widely used.But, need between detecting electrode, be applied with certain voltage during owing to the conductance type measuring liquid level, and immerse in the conducting liquid, electrolytic action can be accelerated the corrosion speed of detecting electrode greatly, and detecting electrode was lost efficacy at short notice.

Purpose of the present invention just provides a kind of method of measuring conducting liquid level, adopts this method can eliminate electrolytic action substantially to the detecting electrode influence in serviceable life.

Technical scheme of the present invention is: apply the pulse voltage with certain width and some cycles between the detecting electrode of measuring liquid level, the resistance sizes between the detecting electrode is converted to liquid level signal.

In most of the cases, liquid level is slowly to change, therefore, can between detecting electrode, apply very short pulse voltage of duration with certain cycle, and the duration of voltage, detect liquid level signal, like this, the time that applies voltage between detecting electrode significantly reduces, even can ignore, thereby eliminated electrolytic action substantially to the detecting electrode influence in serviceable life.

The positive negative direction of pulse voltage that is applied between the detecting electrode can be identical, and promptly the positive negative direction of each pulse voltage is identical; Also can be different directions, promptly the positive negative direction of each pulse voltage be inequality.

The width of potential pulse and cycle and ratio thereof can be determined as the case may be.When liquid level change when very fast, the cycle should be shorter, as 0.01 second to 1 second; And when liquid level change was relatively slower, the cycle can be longer, as extremely tens of minutes several seconds; When environmental interference was strong, pulse width was answered broad, and when environmental interference was more weak, pulse width should be narrower; The ratio in pulse width and cycle usually should be as far as possible little, is generally less than 0.02.

After being applied to the voltage employing pulse voltage between the detecting electrode,, thereby can avoid the corrosion of electrolytic action substantially to detecting electrode because it is very short to apply the time of voltage on detecting electrode, even can ignore.Suppose that detecting electrode only is subjected to a kind of corrosion of electrolysis, applying continuously under the voltage condition, life-span is 10 days, if adopt method of the present invention, the ratio that applies pulse width and recurrence interval is 1: 1000 a pulse voltage, then the life-span of this detecting electrode will be increased to 10 days 1000 times, be about 27 years.As seen this method can be eliminated the corrosion of electrolytic action to detecting electrode to greatest extent.

Description of drawings:

Fig. 1 is a technical scheme synoptic diagram of the present invention.

Fig. 2 is the embodiment of the invention 1 synoptic diagram.

Fig. 3 is the embodiment of the invention 2 synoptic diagram.

Fig. 4 is the embodiment of the invention 3 synoptic diagram.

Fig. 5 is the embodiment of the invention 4 synoptic diagram.

Fig. 6 is the process flow diagram of single-chip microcomputer voltage pulse output and measuring liquid level signal.

Be described further below in conjunction with accompanying drawing:

Accompanying drawing 1 is a technical scheme synoptic diagram of the present invention.When liquid level did not arrive the position of detecting electrode 1, the resistance between two detecting electrodes was very big; When liquid level arrived the position of detecting electrode 1, the resistance between two detecting electrodes was very little.Work time pulse is applied between detecting electrode 2 and the detecting electrode 1 towards voltage, the duration of pulse voltage, the resistance sizes between detecting electrode 2 and the detecting electrode 1 is converted to electric signal.If the width of each pulse is very little with respect to the recurrence interval, even can ignore, the temporal summation that then applies voltage between detecting electrode 2 and detecting electrode 1 is also very little with respect to total working time, even can ignore; And electrolytic action is directly proportional with the time that applies voltage between detecting electrode to the extent of corrosion of detecting electrode, and the time that applies voltage is long more, and the degree that detecting electrode is corroded is big more; Otherwise the time that applies voltage is short more, and the degree that detecting electrode is corroded is more little, and therefore, electrolytic action is also very little to the extent of corrosion of detecting electrode, even can ignore; Like this, just eliminated the corrosion of electrolytic action substantially to detecting electrode.

When if detecting electrode is a plurality of, can be with one of them detecting electrode as the common detection electrode, between common detection electrode and other detecting electrode, apply pulse voltage simultaneously, perhaps between other detecting electrode and common detection electrode, apply pulse voltage respectively.

Implementing best way of the present invention is to adopt microcontroller, i.e. single-chip microcomputer.The instruction cycle of most of single-chip microcomputer can both be less than 1 microsecond, control voltage pulse output able to programme, the program flow diagram of voltage pulse output and measuring liquid level signal as shown in Figure 6, delay time wherein can increase or reduce as required.

Embodiment 1: for the single-chip microcomputer that can export enough drive currents, can adopt direct drive mode, as shown in Figure 2: the I/O mouth 4 of single-chip microcomputer 3 links to each other with an end of resistance 6, and the other end of resistance 6 links to each other detecting electrode 8 ground connection with another I/O mouth 5 of detecting electrode 7 and single-chip microcomputer 3.When detecting electrode 7 and detecting electrode 8 immersion liquid, resistance between two detecting electrodes is very little, then the I/O mouth 5 of single-chip microcomputer 3 will be drawn and will be low level, just can learn whether liquid level arrives the position at detecting electrode 7 places as long as judge the level height of the I/O mouth 5 of single-chip microcomputer 3 when I/O mouth 4 output high level.

Embodiment 2: can adopt indirect type of drive for the single-chip microcomputer that can not export enough drive currents, as shown in Figure 3: increase the gauge tap of a triode 10 as power supply 9, I/O mouth 12 by single-chip microcomputer 11 drives triode 10 voltage pulse outputs, and other principle is with embodiment 1.

Embodiment 3: the single-chip microcomputer for built-in A/D converter can adopt mode as shown in Figure 4: an I/O mouth 15 of single-chip microcomputer 18 applies pulse voltage to detecting electrode 17.If detecting electrode 14 immerses in the liquid, because the electric action of liquid, when the I/O of single-chip microcomputer 18 mouth 15 output high level, current flowing resistance 13 is arranged, have certain voltage at resistance 13 two ends, this voltage just can judge according to the value of A/D conversion whether liquid arrives the position of detecting electrode 14 through carrying out the A/D conversion in the 16 input single-chip microcomputers 18 of A/D input port.

Embodiment 4: as accompanying drawing 5: to detecting electrode 23, and another I/O mouth 20 is used to judge whether pulse voltage is arranged on the detecting electrode 22 with I/O mouth 19 voltage pulse outputs of single-chip microcomputer 21.When I/O mouth 19 voltage pulse outputs,, can learn whether liquid arrives the position of detecting electrode 22 according to whether pulse voltage is arranged on the detecting electrode 22.

Claims

A kind of method of measuring conducting liquid level, utilize the electric conductivity of conducting liquid, between the detecting electrode that detects liquid level, apply voltage signal, the size conversion of resistance between the detecting electrode is reflection liquid level electric signal just, and it is characterized in that: the voltage signal employing that is applied on the detecting electrode has the pulse voltage of certain width and some cycles.