CN1025466C - Pulse width measuring method by serial output resistance method - Google Patents

Abstract

The invention relates to a pulse width measuring method by a serial output resistance method. The method is characterized in that the tested resistors are switched in sequence by the analog multi-way switch and are overlapped with a charging resistor of the RC oscillating circuit, the RC oscillating circuit outputs an electric pulse with the width proportional to the value of the tested resistors, an output signal of the pulse counted by the counter sequentially gates a measuring channel of the analog multi-way switch, the tested resistors are converted into a data pulse train with the corresponding width, and the data pulse train is automatically circulated and output in a serial circulation mode. At the same time, a mark pulse is set in the pulse train to identify the addition starting point, and the data input end of the analog multi-way switch is connected with a standard precision resistor and a zero resistor, besides the measured resistor, for providing a measuring reference value and an additional resistor of the detection quantity circuit, and they are respectively correspondent to a pulse with correspondent width in the data pulse train, so that the measured resistor value can be used as formulaAnd (4) calculating.

The measuring circuit adopting the method of the invention has the advantages of low cost, simple circuit, strong anti-interference performance and high measuring precision.

Description

Measuring method of pulse width with serial output resistance method

The present invention relates to a kind of method of utilizing measured resistance value to carry out DATA REASONING, sampling and remote serial transfer, refer more particularly to a kind of measuring method of pulse width with serial output resistance method.

In order to measure, gather the various parameters in the production runes such as a large amount of temperature, humidity, pressure, brightness, often these non electrical quantities are converted to the variation of resistance value by semiconductor element, calculate non-electrical quantity by measured resistance value then.Usually, for measured resistance value then is converted to voltage or current signal to resistance, is converted to digital quantity through A/D again and gives Computer Processing or show.The also available method that converts resistance value to pulse signal is measured.These methods and present known measurement mechanism all are subjected to the restriction of external condition (temperature, supply voltage, line component parameter etc.) to some extent, cause measuring accuracy not high, simultaneously, when measurement point increases, measuring equipment is also wanted corresponding increase, the transmission lines complexity, disturbing increases, and operational reliability is descended.

In order to improve the anti-interference of measuring circuit, United States Patent (USP) 4513403 has proposed a kind of " digital coding of pulse remote measurement and synchronization " method and circuit, its output waveform is as shown in Figure 1.As shown in Figure 1, this method be the data that will measure be placed on the synchronization pulse and at interval in transmit, form the digital coding spike train, in the data that transmitted, add redundant pulse simultaneously, the antijamming capability when improving data and transmitting.This method has the advantage of identification data-signal from the noise that transmission lines self produces, but do not solve the problem that improves the DATA REASONING precision, do not solve when measuring and transmit data yet, circuit external cause (as temperature, mains fluctuations etc.) disturbs the problem that causes error, simultaneously, it is more to use the device line link that this method makes, and cost is higher.

Task of the present invention provides a kind of measuring method of pulse width with serial output resistance method, to improve the anti-interference problem in DATA REASONING precision and the solution data transmission procedure.

Solution of the present invention is as follows: Fig. 2 is an output waveform figure of the present invention, and Fig. 3 is a schematic circuit of the present invention.By shown in Figure 3, switch measured resistance with the analog multichannel switch order, make the charging resistor R of capacitor C 1 in itself and the RC oscillatory circuit _FStack, the pulse of the corresponding measured resistance of width of oscillator output at this moment, and the back edge of this pulse makes rolling counters forward, the output of counter is as the gating signal of analog multichannel switch, repeat said process, then oscillator is exported a string width spike train corresponding with each measured resistance.At the input end of analog multichannel switch except that by having the measured resistance, also fixing precision resistance and zero resistance that inserts a standard resistance, the pulse of a respectively corresponding respective width in the output spike train, when mains fluctuations or circuit parameter variations, the pulse width of precision resistance correspondence also will change, this just provides reference point to data computation, eliminated of the influence of external interference factor to the data measuring accuracy, additional resistance for circuit itself changes, then detect by the respective pulses width in the zero resistance sky output spike train, and deducted in the computing method of introducing in the back, thereby eliminated the influence of the interference of circuit self, improved the precision of DATA REASONING thus the data measuring accuracy.As shown in Figure 2, for the circulation that guarantees the output spike train sends, in the spike train of measured resistance correspondence, be provided with a mark pulse, show that a data set measurement finishes, begin next cyclic process,, will deliver in the computing machine with formula by the data pulse row of oscillator output

$R_X=\frac{{\mathrm{(W}}_x{\mathrm{-\; W}}_L{\mathrm{)\; ·\; R}}_J}{W_J{\mathrm{-\; W}}_L}$

Calculate formula R _JBe the precision resistance value; R _XBe the measured resistance value; W _LPulse width for zero resistance correspondence in spike train; W _JPulse width for precision resistance correspondence in spike train; W _XBe the pulse width of measured resistance correspondence in spike train, then obtain the exact value of measured resistance, finish the task of DATA REASONING.

The circuit that adopts the method for the invention design as shown in Figure 3, this circuit only can be finished by several commercially available integrated circuit, circuit is simple, and is with low cost, not only improved antijamming capability and measuring accuracy, and easy to utilize.

Fig. 3 has represented one embodiment of the present of invention, and it is by analog multichannel switch (1), code translator (2), counter (3), delay circuit (5), (6), time base circuit (4) and discharge resistance R _FWith the oscillator that capacitor C 1 constitutes, measured resistance (7), precision circuit R _J, zero resistance R0 forms, and after the circuit energized, the output signal of counter (3) is delivered to the input end of analog multichannel switch (1) through code translator (2), makes working power by power Vcc ₂Through current-limiting resistance R _FMeasured resistance (7), the resistance R of the public output of analog multichannel switch (1) _RTo capacitor C 1 charging, make the pulse of the oscillatory circuit measured resistance of forming by time base circuit (4) of correspondence of output (7), this pulse can be imported computing machine and carry out data processing, and the back of this pulse given counter (3) along loopback, makes counter (3) output add " 1 ", analog multichannel switch (1) switches to the next passage of measuring, circulation successively, capacitor C 1 are charged to and begin discharge behind the setting, and its, length just determined the recurrent interval discharge time.

When measured resistance (7) not during place in circuit, when being measured resistance value infinity, 1 duration of charging of capacitor C is very long, and delay circuit this moment (5) is according to the time action of adjusting in advance, substitute original charge circuit, make the pulse W ∞ of a fixed width of time base circuit (4) output.

After all measured resistance all circulate measurement, counter (3) carry, its output is blocked delay circuit (5) like this because of there not being tested passage to connect, 1 duration of charging of capacitor C is very long, and then delay circuit (6) is by the time action of adjusting in advance, and its output makes counter (3) clear " 0 ", show a loop ends, beginning is circulation next time, at this moment, and the next mark pulse W of time base circuit (4) output _R, its width generally when adjusting circuit, gets final product Wn＞1.3W ∞ greater than W ∞.

In order to improve the anti-interference of measuring accuracy and circuit, with a precision resistance R _JInsert the input end of analog multichannel switch with a short circuit zero resistance R0 and measured resistance (7), after a complete measuring process finishes, just can obtain the oscillogram of output data spike train as shown in Figure 2 like this.

After DATA REASONING is finished, then can be according to formula

$R_x=\frac{W_x{\mathrm{＇\; ·\; R}}_J}{\mathrm{W\; J}}$

In computing machine, calculate each measured resistance value, in the formula: W _LBe the corresponding width of zero resistance in spike train; R _JBe the precision resistance value; W _X'=W _X-W _LBe the respective pulses width of measured resistance value in spike train; W _J'=W _J-W _LBe the respective pulses width of precision resistance value in spike train.

Adopt the DATA REASONING of the method for the invention and used equipment, have following advantage and good effect:

1. the data pulse of measuring row is classified the automatic cycle serial as and is sent, and does not need to add in addition addressing and enabling signal, and remote transmission need only two holding wires, and cost reduces greatly.

2. the measurement reference point is provided, and has eliminated the impact that measurement and transmission lines additional resistance disturb with the mode of zero resistance, certainty of measurement and anti-interference are increased.

3. provide simple method, namely

$R_X=\frac{{\mathrm{(W}}_x{\mathrm{-\; W}}_L{\mathrm{)\; ·\; R}}_J}{W_J{\mathrm{-\; W}}_L}$

4. because circuit of the present invention only is made of several commercially available integrated circuit connections, apply in the production run of being more convenient for, economic benefit is considerable.

Claims (1)

1, a kind of measuring method of pulse width with serial output resistance method is characterized in that:

A. switch measured resistance with the analog multichannel switch order, make the charging resistor stack of itself and RC oscillatory circuit, make width of RC oscillatory circuit output and measured resistance be worth proportional pulse, the output signal of this pulse after rolling counters forward be the measurement passage of gating analog multichannel switch successively, a plurality of measured resistance values are converted to the data pulse row of corresponding width, Automatic Cycle, serial output

B. be provided with the starting point that a mark pulse comes the identification pulse row in the data pulse of the described output row,

C. at the data input pin of analog multichannel switch except that being connected to measured resistance, also be connected to a universal standard precision resistance, the measurement reference point is provided,

D. the data input pin of analog multichannel switch also is connected to a zero resistance, is used for detecting the additional resistance of measurement itself,

E. measured resistance value formula

$R_X=\frac{{\mathrm{(W}}_x{\mathrm{-\; W}}_L{\mathrm{)\; ·\; R}}_J}{W_J{\mathrm{-\; W}}_L}$

Calculate, in the formula:

R in the formula _JBe precision resistance value, R _xBe measured resistance value, W _LBe zero resistance corresponding pulse width in the data pulse row, W _JBe precision resistance corresponding pulse width in the data pulse row, W _XBe each measured resistance corresponding pulse width in the data pulse row.

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