JP2675733B2 - Chemical sensing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical sensing device in which a special polymer thin film is formed on the surface of a sensor oscillator and the adsorbed gas is identified by changing the resonance frequency during gas adsorption. Is a high-resolution, high-speed measurement.

[0002]

2. Description of the Related Art Conventionally, the resonance frequency in this type of device has been measured by directly inputting the oscillation frequency of a sensor oscillator to a frequency counter.

[0003]

However, in this type of measurement, it is usually 1H for an absolute value of about 10MHz.
A resolution of about z is required. If an attempt is made to perform this measurement with a frequency counter that counts the number of pulses per unit time, an expensive frequency counter with an extremely wide measurement range is required. Further, in order to increase the resolution, it is necessary to make the measurement time sufficiently long. On the other hand, in a frequency counter that measures the pulse period in order to shorten the measurement time and obtains the frequency from the reciprocal thereof, a clock that counts the period as the absolute value of the frequency to be measured increases as shown in FIG. However, there is a problem that it is difficult to improve the resolution.

The present invention has been made by paying attention to such a conventional problem. The change of the oscillation frequency of the sensor oscillator can be measured at high speed with high resolution, and the frequency measuring system is inexpensively constructed. It is an object of the present invention to provide a chemical sensing device that can be used.

[0005]

In order to solve the above-mentioned problems, the present invention firstly requires that a special polymer film is formed on the surface of a sensor vibrator used as a sensor, and the sensor vibration during gas adsorption. the change in the resonant frequency of the child, in the chemical sensing device for performing identification of adsorbed gas, different resonant frequencies _{(f i: i = 1~n,} n is a natural number of 2 or more)
A plurality (n) of the sensor oscillators, a reference oscillator that generates a reference frequency ( _fr ), an oscillation circuit that oscillates the sensor oscillator and the reference oscillator, respectively. A selector for selecting the oscillation frequency (f _i ) of the sensor oscillator; a sampling circuit for outputting the absolute value of the difference frequency between the oscillation frequency of one sensor oscillator selected by the selector and the reference frequency; A dividing circuit for dividing the difference frequency by a required dividing ratio (N: natural number), a counter for counting the period of the divided output of the dividing circuit using the period of the reference frequency as a clock, and the counter for counting. Formula (1) f _i = (1 + N / C) f _r (f _i > f _r ) = (1−N / C) f is used to calculate the oscillation frequency of the selected sensor vibrator based on the selected period (C). _r (f _i < _fr ) (1) The gist of the present invention is to have an arithmetic unit that is more sought.

Secondly, in a chemical sensing device in which a special polymer film is formed on the surface of a sensor oscillator used as a sensor, and the adsorbed gas is identified by the change in the resonance frequency of the sensor oscillator during gas adsorption. , different resonant frequencies _{(f i: i = 1~n,} n is a natural number of 2 or more) and the sensor oscillator plurality of (n) having, corresponding to respective resonant frequencies of the plurality of sensor transducers Corresponding to a plurality of (n) reference oscillators that generate reference frequencies ( _fri : i = 1 to n, n is a natural number of 2 or more), and oscillation circuits that respectively oscillate the sensor oscillator and the reference oscillator. A plurality of (n output the absolute value of the difference frequency between the oscillation frequency of the sensor oscillator and the reference oscillator and the reference frequency.
Number) of sampling circuits, a selector that selects the difference frequency output of the plurality of sampling circuits, and a frequency dividing circuit that divides the difference frequency selected by the selector by a required frequency division ratio (N: natural number). A counter that counts the frequency of the frequency-divided output of the frequency-dividing circuit using the frequency of one of the reference frequencies, f _rx (x is any one of 1 to n), as a clock, and the counter. period formulas the oscillation frequency of the selected sensor oscillator based on _{(C) (2) f i} = f ri + (N / C) f rx (f i> f ri) = f ri - (N / C ) F _rx (f _i <f _ri ) (2) The calculation device is obtained.

Thirdly, in the above-mentioned first or second configuration, when measuring the oscillation frequency of the selected sensor vibrator for a certain period of time, the arithmetic unit sets the difference frequency value at the time of starting the measurement. Is stored as an initial value, a value obtained by subtracting the initial value from the difference frequency value measured thereafter is obtained, and the values are sequentially plotted to obtain a temporal change in the oscillation frequency of the selected sensor vibrator. The gist is that it is configured as.

[0008]

In the above structure, firstly, by obtaining the difference frequency between the oscillation frequency of the selected sensor vibrator and the reference frequency, the difference frequency becomes a value much smaller than the oscillation frequency. The absolute value of the power frequency can be made extremely small, and high-resolution measurement can be performed without expanding the measurement range. In addition, in order to shorten the measurement time, the difference frequency value is measured by measuring its period and using the method of taking the reciprocal thereof.However, the period after dividing the difference frequency by the required dividing ratio is By measuring, it is possible to secure sufficient resolution without increasing the frequency of the clock by increasing the change in the cycle, and it is possible to use the reference frequency as it is as the clock. Then, the oscillation frequency of the selected sensor vibrator is obtained based on the measured cycle.

Secondly, since the reference frequencies corresponding to the respective resonance frequencies are provided for the respective sensor oscillators, even if there is some difference between the oscillation frequencies of the sensor oscillators, The difference from the reference frequency can be set extremely small, and the frequency to be measured can be further reduced. Therefore, it is possible to further increase the measurement resolution and shorten the measurement time.

Third, when measuring the change in the frequency of the sensor vibrator, by plotting the change from the frequency at the start of measurement, even after the reference frequency fluctuates, the selected sensor vibrator is changed. It is possible to accurately measure the change in the oscillation frequency of.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG.
2 and FIG. 2 are views showing the first embodiment of the present invention. FIG.
In the above, 1 is n sensor vibrators used as sensors. These resonance frequencies are f _{1 to} f _n , and change with time within a certain range due to gas adsorption. Reference numeral 2 is one reference oscillator for generating the reference frequency f _r , and f _r is set to be a value as close as possible to f _{1 to} f _n . 3 is an oscillation circuit for oscillating the oscillator frequency to output a square wave of f ₁ ~f _n and f _r. Reference numeral 4 denotes a selector for switching the output of the sensor vibrator according to a select signal, and 5 denotes a frequency f _i (i is one of 1 to n) of one sensor vibrator selected by the selector and a reference frequency _fr . A sampling circuit that outputs the absolute value f _{d of the} difference, and is composed of, for example, a D-flip-flop. 6 is the period of f _d T _d (T _d =
1 / f _d) the divide-by-N to the divider circuit, the period T _r of the reference frequency f _r is the period N · T _d which is divided by a frequency divider 7 (T _r =
A counter that counts 1 / _fr ) as a clock, 8
Is an arithmetic unit for converting a cycle into a frequency, and for example, a personal computer or the like is used.

Next, the measurement operation of the present invention will be described. Each of the n sensor vibrators 1 is constantly oscillating at a frequency of f _{1 to} f _n , and the output f _{i of} one of them is f _i.
Are selected by the selector 4. This value f _i is compared with the output f _r of the reference oscillator 2 by the sampling circuit 5, and the absolute value f _d = | f _i −f _r | of those differences is output. As the sampling circuit 5, for example, the D-flip-flop is used as described above. Now, as shown in FIG. 2, f _i is input to the D input, and its period is T
a _{i (T i = 1 / f} i), also enter the f _r to T (trigger) input, when the period between _{T r (T r = 1 /} f r), D inputs of the pulse of T _r It will be sampled in cycles. That is, when f _i > _fr (T _i < _Tr ),
When the number of samples until sampling and returning to the initial phase difference is M, M = T _i / (T _r −T _i ), and the cycle of the output Q of the D-flip-flop is T _d (T
_d = 1 / f _d ), T _d = M · T _r

## EQU1 ## T _d = T _i · T _r / (T _r −T _i ), 1 / T
_{d = 1 / T i -1 /} T r Accordingly, f _d = f _i -f _r, and the frequency difference is obtained. Similarly, when f _i <f _r , f _d = f _r −f _i, and therefore f _d = | f _i −f _r |.

Next, the output of the sampling circuit 5 is divided by N by the frequency dividing circuit 6 to obtain f _d / N, and the divided period is counted by the counter 7 using the reference frequency f _r as a clock pulse. If the value of the counter is C, It is. If the value C of the counter is taken into the arithmetic unit 8 and the above calculation is performed, the frequency f of the target sensor vibrator 1 is calculated.
_i is obtained. Here, the frequency dividing circuit 6 is used to increase the resolution of period measurement.

As an example, f _r = 10 MHz and f _i = 1
At 0.05 MHz, f _d = 50 KHz. f
_In order to measure the value of _d with a resolution of 1 Hz, it is necessary to be able to count the change ΔT of the cycle corresponding to 1 Hz with a clock. ΔT = 1 / 50000-1 / 50001
= 4 × 10 ^-10 sec, the clock frequency is 1
/ 4 × 10 ^-10 = 2.5 × 10 ⁹ That is, 2.5 GH
A clock of z or higher is required. It is not easy to generate an extremely high frequency clock. Therefore, f
For example, if _d is _divided by 256, ΔT = 4 × 10 ⁻¹⁰ × 2
56 = 10 ^-7 , so 10 ⁷ or 10 MHz
You can count with the clock. At this time, the value C of the counter is (1/50000) × 256/10 ⁻⁷ = 51200
Since 2 ¹⁶ = 65536, a 16-bit counter is sufficient. Also, the measurement time in this case is
(1/50000) × 256 = 5.12 × 10 ^−3, that is, about 5 msec. If N is increased, the resolution will be improved, but the measurement time will be longer, so an appropriate value is selected in consideration of both factors.

FIG. 3 shows a second embodiment of the present invention. In the figure, 2 'of the sensor transducer 1 the resonance frequency f ₁ ~
There are n reference oscillators provided corresponding to the respective f _n , and the reference frequencies f _{r1 to} f _r are respectively set by the oscillation circuit 3.
Output a rectangular wave of _rn . All other numbers are the same as those in FIG. The sampling circuit 5 uses the resonance frequency f _i of each sensor vibrator 1 and the corresponding reference frequency f _i.
The absolute value of the difference between the _{ri f di = | f i -f} ri | (i = 1~n)
Output. Then, the cycle of one of them and N divides in frequency divider 6 After selected by the selector 4, any one frequency of one cycle reference frequency f _r1 ~f _rn (f _rx) as a clock, The counter 7 counts. The value of the counter 7 is taken into the arithmetic unit 8 and the same calculation as in the first embodiment is performed to obtain the oscillation frequency f _i of the selected sensor vibrator 1. That is, assuming that the value of the counter 7 is C, similar to the first embodiment. It is. In this embodiment, since the reference frequency is provided for each sensor vibrator 1, even if there is some difference between the frequencies of the sensor vibrators 1, the difference from the reference frequency can be set to be extremely small. The frequency to be measured can be lowered. Therefore, it is effective in further increasing the measurement resolution and shortening the measurement time.

Next, in the above first and second embodiments,
A case where the oscillation frequency of the selected sensor vibrator is measured for a certain fixed time will be described. The reference frequency f _r can be regarded as constant for a short time, but may change for a long time due to the influence of temperature and humidity fluctuations. The absolute value f _d of the difference frequency, because given by _{f d = (N / C)} · f r, the reference frequency f _r is the changes by Delta] f _r from the initial setting, variation Delta] f _d of f _d is Δf _d = (N / C) · Δf
_r . As an example, f _d = 50 KHz, f _r = 10
If MHz, N = 256, and Δf _r = 10 KHz, then Δ
When f _d = 50 Hz and f _r changes, the measured value also changes greatly. However, the information to be acquired by this device is the change in the oscillation frequency of the sensor oscillator from the start of measurement. Therefore, in this device, when the frequency of one sensor transducer is measured for a certain period of time, f _d at the measurement start time is measured.
The value is stored as an initial value f _do , and f _d measured thereafter is used.
A value obtained by subtracting f _do from the value is obtained, and the values are sequentially plotted to obtain the temporal change of the frequency of the sensor oscillator. The above calculation is performed using the calculation device 8.

Now, the reference frequency in the first setting is f
_r, the measured values f _do the difference frequency f _d at time t = 0 of the measurement start, the measured values of f _d in t = tau and f _{d tau.} Also, when measuring the same value based on the reference frequency f _r 'after variation, a measurement value of f _d at time t = 0 f
_do and holds the following equation ', t = measured value of f _d f _{d tau} in tau' and.

[0018]

## EQU00002 ## _fd.tau .'- _fdo '= _fd.tau. ( _Fr / _fr ')-
f _do (f _r / f _r ') = (f _{d τ} −f _do ) · (f _r / f _r ′) Here, since f _r / f _r ′ ≈1, f _{d τ} ′ −
f _do '≈ f _{d τ} −f _do , and the change from t = 0 is
The value is almost the same even after the reference frequency fluctuates. As an _{example, f r = 10MHz, f r} '= 10.01MHz,
If f _{d τ} −f _do = 1000 Hz, then f _{d τ} '−
Since f _do '= 999 Hz, an accuracy of 0.1% can be secured.

[0019]

As described above, according to the present invention,
First, the difference frequency between the oscillation frequency of the selected sensor oscillator and the reference frequency is obtained, and the period after dividing the difference frequency by the required frequency division ratio is counted using the period of the reference frequency as a clock. Since the oscillation frequency of the selected sensor oscillator is calculated based on the counted period,
It is possible to perform high-resolution and high-speed measurement without widening the measurement range because the absolute value of the frequency to be measured becomes extremely small. Further, a frequency counter having a wide measuring range is not required, and the frequency measuring system can be constructed at low cost.

Secondly, for each sensor oscillator,
Since a plurality of reference oscillators that generate reference frequencies corresponding to the respective resonance frequencies are provided, even if there is some difference between the oscillation frequencies of the sensor oscillators,
The difference frequency from the reference frequency can be set to be extremely small, the absolute value of the frequency to be measured can be further reduced, and higher resolution and high speed measurement can be performed.

Thirdly, when measuring the time change of the selected sensor oscillator, the change from the frequency at the start of measurement is plotted, so that even if the reference frequency fluctuates, the selection can be made. It is possible to correctly measure the change in the oscillation frequency of the sensor vibrator. Further, it is possible to absorb an error when the reference frequency is initially set, and it is not necessary to carefully set the reference frequency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a chemical sensing device according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the sampling circuit in the first embodiment.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the frequency to be measured and the frequency of the clock with the resolution as a parameter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 sensor oscillator 2, 2'reference oscillator 3 oscillator circuit 4 selector 5 sampling circuit 6 frequency divider circuit 7 counter 8 arithmetic unit

Claims (3)

(57) [Claims] 1. A chemical sensing device in which a special polymer film is formed on the surface of a sensor oscillator used as a sensor, and the adsorbed gas is identified by a change in the resonance frequency of the sensor oscillator during gas adsorption. different resonance frequencies _{(f i: i = 1~n,} n is 2
A plurality of (n) sensor oscillators having the above natural numbers; one reference oscillator that generates a reference frequency ( _fr ); and an oscillation circuit that oscillates the sensor oscillator and the reference oscillator, respectively. A selector for selecting the oscillation frequencies (f _i ) of the plurality of sensor oscillators, and sampling for outputting the absolute value of the difference frequency between the oscillation frequency of one sensor oscillator selected by the selector and the reference frequency A circuit, a frequency dividing circuit for frequency-dividing the difference frequency by a required frequency division ratio (N: natural number), a counter for counting the frequency of the frequency-divided output of the frequency-dividing circuit using the frequency of the reference frequency as a clock, Based on the cycle (C) counted by the counter, the oscillation frequency of the selected sensor oscillator is _expressed by the formula (1) f _i = (1 + N / C) f _r (f _i > f _r ) = (1-N / C) _fr (f _i < _fr ) (1) The chemical sensing device characterized by having the calculating device calculated | required by (1). 2. A chemical sensing device in which a special polymer film is formed on the surface of a sensor oscillator used as a sensor, and the adsorbed gas is identified by a change in resonance frequency of the sensor oscillator during gas adsorption. different resonance frequencies _{(f i: i = 1~n,} n is 2
A plurality (n) of the sensor oscillators having the above natural numbers and reference frequencies (f _ri : i = 1 to n, n is a natural number of 2 or more) corresponding to the resonance frequencies of the plurality of sensor oscillators. A plurality of (n) reference oscillators, an oscillation circuit that oscillates the sensor oscillator and the reference oscillator, and an oscillation frequency and a reference frequency between the corresponding sensor oscillator and the reference oscillator. A plurality of (n) sampling circuits that output the absolute value of the difference frequency, a selector that selects the difference frequency output of the plurality of sampling circuits, and a difference ratio (N: A frequency divider circuit that divides the frequency by a natural number), and the frequency of the frequency division output of the frequency divider circuit is the clock of the frequency f _rx (x is any one of 1 to n) of any one of the reference frequencies. Counting power Counter and the oscillation frequency of the selected sensor oscillator based on the cycle (C) counted by the counter, expressed by the formula (2): f _i = f _ri + (N / C) f _rx (f _i > f _{ri) ) = f ri - (N /} C) f rx (f i <f ri) ( chemical sensing apparatus characterized by comprising a computing device for determining by 2). 3. When the oscillation frequency of the selected sensor oscillator is measured for a certain period of time, the arithmetic unit is
The difference frequency value at the start of measurement is stored as an initial value,
A value obtained by subtracting the initial value from the difference frequency value measured thereafter is obtained, and the values are sequentially plotted to obtain a temporal change in the oscillation frequency of the selected sensor oscillator. The chemical sensing device according to claim 1 or 2, which is characterized.