JPH034178A - Frequency measuring instrument for high frequency analog signal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a frequency measuring device for high frequency analog signals.
In particular, it relates to a measuring device in which the analog signal is intermittently supplied at predetermined time intervals.

Conventional technology and its challenges When measuring the frequency of an analog signal, the frequency is measured by converting the analog signal into a pulse signal and then counting the number of pulses generated within a predetermined period of time using a counter, etc. Usually, it is measured.

On the other hand, as a means of measuring physical quantities of a rotating body, such as the temperature of a rolling roll or the air pressure of a car tire, a resonant circuit whose resonance frequency changes according to the physical quantity is provided on the rotating body, and the rotation of the rotating body is Accordingly, a receiving circuit that intermittently magnetically couples at predetermined time intervals is provided on the fixed side, the receiving circuit receives a resonant signal that vibrates at the resonant frequency of the resonant circuit, and the physical quantity is measured from the frequency of the resonant signal. That is what is being considered. In such a case, it is necessary to receive sufficient resonance signals for frequency measurement in a relatively short period of time during which the resonant circuit and the receiving circuit are magnetically coupled. It is sometimes necessary to configure a resonant circuit so as to generate a high-frequency resonant signal with a frequency of approximately several hundred kilometres) Iz (period: several microseconds).

However, if you try to count the frequency of high-frequency analog signals that are intermittently supplied in this way using a counter as described above, you will need a complex effective signal discrimination device and a high-speed signal processing device, making the device expensive. There was a problem.

The present invention was made against the background of the above circumstances, and its purpose is to provide an inexpensive device capable of measuring the frequency of an intermittently supplied high-frequency analog signal at a relatively slow signal processing speed. There is a particular thing.

Means for Solving the Problems In order to achieve the object, the present invention provides an apparatus for measuring the frequencies of a series of high-frequency analog signals that are intermittently supplied at predetermined time intervals, comprising: a pulse converter that converts an analog signal into a rectangular pulse signal with a frequency equal to or lower than the frequency of the high-frequency analog signal; (C) a shift register that stores a series of bit signals consisting of two values corresponding to the presence or absence of the pulse signal in synchronization with a shift signal of a constant frequency; The apparatus is characterized by comprising a signal processing means for reading out the bit signal stored in the register and counting the number of consecutive bit signals having the same value.

In such a frequency measuring device, the high-frequency analog signal whose frequency is to be measured is first converted by a pulse converter into a pulse signal with a frequency equal to or lower than that frequency, and the pulse signal is converted into a pulse signal with a predetermined constant frequency. The signals are sequentially stored in the shift register in synchronization with the frequency shift signal. The shift register has two registers corresponding to the presence or absence of a pulse signal.
However, since the frequency of the shift signal is higher than the frequency of the high-frequency analog signal, the two values of the bit signal are the same in number, each corresponding to the pulse width and interval of the pulse signal. Stored continuously. The number n of consecutive same values is 'c', where fc is the frequency of the shift signal and (p is the frequency of the pulse signal).
/2fp, and for example, when the frequency r is 1/2 of the frequency r of the high-frequency analog signal, the number n is f c /
It becomes f.

Then, the bit signals stored in the shift register in this way are read out by the signal processing means during the supply suspension period of the high frequency analog signal, and the number n is counted. This number n is r as described above.

/2f, the frequency fp of the pulse signal can be found by calculating f c /2 n, and from the relationship between the frequency rP by the pulse converter and the frequency
For example, the frequency f of a high frequency analog signal is found.
When the frequency fP is 1/2 of the frequency f as described above, fc/n becomes the frequency f.

As is clear from the above explanation, since the number n corresponds to the period 1/f of the frequency r, it is possible to perform subsequent signal processing etc. based on this number n, and it is not necessary to use the frequency f itself. There's no need to ask.

Effects of the Invention As described above, in the present invention, a pulse signal having a certain relationship with a high frequency analog signal is stored in a -H shift register, and a bit signal representing the stored contents is read from the shift register during a period when the supply of the high frequency analog signal is suspended. number n
, it is possible to measure the frequency of high-frequency analog signals using inexpensive signal processing means with relatively slow signal processing speeds, without necessarily requiring high-speed signal processing. It is.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

First, FIG. 1 is a diagram illustrating the configuration of a physical quantity measuring device for a rotating body including the frequency measuring device of this embodiment, and FIG. 2 is a time chart showing signals of each part in FIG. 1.

In this FIG.
2 is provided. The resonant circuit 12 includes a first coil 14 arranged along the rotation direction of the rotating body 10 and a pair of capacitors 16 and 18 arranged in parallel with each other, and a sensor 20 connected in series to the capacitor 18. It is connected. The sensor 20 has a resistance that changes depending on the physical quantity to be measured, and in this embodiment, a PTC element (positive Characteristic thermistors) and pressure switches are used.

In such a resonant circuit 12, the capacitor 16.1
If the capacitances of sensor 8 are CI and C2, respectively, then sensor 2
When the resistance value of 0 is approximately zero, the capacitance C of the resonant circuit 12 is approximately (C, +Cz), and when the resistance value of the sensor 20 is large and almost no voltage is applied to the capacitor 18, the capacitance C is approximately It becomes C1. Further, the resonant frequency r of the resonant circuit 12 is expressed by the following equation (1), where L is the inductance of the first coil 14, and when the capacitance 1c changes, the resonant frequency f also changes. For example, the capacitances IC1 and C2 are 1000 pF and 3300 pF, respectively.
If the inductance L is 330 μH, the resonant frequency f when the resistance value of the sensor 20 is approximately zero is approximately 133.6 k
Hz, whereas the resonance frequency f when the resistance value of the sensor 20 is large is approximately 277.1 kHz.

f = ... (1) 2πJ
On the other hand, a receiving circuit 22 is provided near the rotating body 10. This receiving circuit 22 is intermittently magnetically coupled to the first coil 14 of the resonant circuit 12 as the rotating body 10 rotates. The second coil 24 is provided with a second coil 24 whose position is fixed, and an excitation pulse DP is supplied from an oscillator 26 to this second coil 24.The excitation pulse DP is supplied with a predetermined constant cycle. The first coil 14 and the second coil 24 are 6nn.
By supplying this excitation pulse DP to the second coil 24 in a caked state, the excitation pulse DP is sent from the second coil 24 to the first coil 14 . and,
When such an excitation pulse DP is supplied to the first coil 14, the resonant circuit 12 is caused to resonate at the resonant frequency f, and a resonant signal SS vibrating at the resonant frequency f is received by the second coil 24. This resonance signal SS corresponds to a high frequency analog signal.

Here, the first coil 14 and the second coil 24 are
The length is determined according to the maximum rotational speed of the rotating body IO so that the magnetic coupling is performed for a time that is twice or more the generation period of the excitation pulse DP. This allows, for example, the second
Even if the first coil 14 and the second coil 24 are magnetically coupled after the generation of one excitation pulse DP, as shown in the figure, the receiving circuit 22 has at least the ability to detect the next excitation pulse DP2. A series of associated resonant signals S
S can be received.

The resonance signal SS is amplified in a waveform shaper 30 and converted into a pulse signal SP having the same frequency as the frequency f, and is supplied to an AND circuit 32 and a monostable multivibrator 34. The armband circuit 32 receives the excitation pulse DP from the microcomputer 28.
gate signal SG for a predetermined period of time in synchronization with
I is supplied with the pulse signal SP
is taken into the microcomputer 2 only while the gate signal SGI is supplied. The microcomputer 28 is supplied with an excitation pulse DP from the oscillator 26, and the gate signal SGI is set at a time interval at which the resonance signal SS is received relatively stably, for example, at the generation interval of the excitation pulse DP. It is output in the center part. By supplying the pulse signal SP to the microcomputer 28, the second coil 24 is supplied with the first coil 1.
4 is located at the magnetic coupling position, and it is detected by the receiving circuit 22 that a valid resonance signal SS is being received.

Further, the pulse signal SP supplied from the waveform shaper 3 "0 to the monostable multivibrator 34 and the flip-flop circuit 36
The pulse signal SPP is converted into a pulse signal SPP whose frequency is 1/2, and then supplied to the shift register 38. In this shift register 38, a clock signal SCA output from a clock signal generator A40 is connected to an AND circuit 42 and an OR circuit 44.
The clock signal SCA
The pulse signal SPP is sequentially stored as a bit signal SB in synchronization with . The clock signal SCA corresponds to a shift signal, and is output at a frequency higher than the frequency f of the resonance signal SS, for example, about IMHz, and the write signal SG2 from the microcomputer 28 is sent to the AND circuit. It is supplied to the shift register 38 only while being supplied to the shift register 42. The write signal SG2 is used only after the pulse signal SPP is stored as the bit signal SB in the shift register 38 until the microcomputer 28 completes the read operation of the bit signal SB from the shift register 38 for frequency calculation. Based on the pulse signal SP being supplied from the AND circuit 32, its output is temporarily stopped. Note that the waveform shaper 30, monostable multipipe rake 34. The flip-flop circuit 36 corresponds to a pulse converter that converts the resonance signal SS, which is a high frequency analog signal, into a pulse signal SPP.

The bit signal SB consists of two values "l" and "0" corresponding to the presence or absence of the pulse signal SPP, and as shown in FIG. 3, corresponds to the pulse width and interval of the pulse signal SPP. “1” and “0” are stored in the shift register 38 in a state in which approximately the same number of consecutive “1”s and “0” are respectively stored.

Since the frequency of the pulse signal SPP is 172 of the frequency f of the pulse signal SP and resonance signal SS, the bit signal S
The value rlJ of B or the number n of consecutive “0”s is:
Corresponding to the period 1/f of the pulse signal SP and resonance signal SS,
When the frequency of the clock signal SCA is fc, the following equation (
2). Therefore, as mentioned above, the frequency f
, is IMH2 and the frequency f is 133.6 kHz, the number n is approximately 7.5, and the value "l" or rQJ of the bit signal SB is continuous in units of 7 or 8. Furthermore, when the frequency f is IMHz and the frequency f is 277.1kHz, the number n is approximately 3.6, and the value rl of the bit signal SB
Three or four consecutive J's or "0's" are present.

n=fc/f (2) The shift register 38 also receives a clock signal SCB having a lower frequency than the clock signal SCA by supplying the read signal SG3 from the microcomputer 28 to the AND circuit 46. is the clock signal generator B41
As a result, the bit signal SB stored in the shift register 38 is sequentially supplied to the microcomputer 28 in synchronization with the clock signal SCB.
is loaded into. The frequency of the clock signal SCB is determined to be, for example, about 1 kHz depending on the performance of the microcomputer 28, and the clock signal SCB has a high frequency of about IMHz.
The bit signal SB stored in the shift register 38 at a high speed according to CA is transferred to the microcomputer 2 at a relatively low speed according to a clock signal SCB having a frequency of about 1 kHz.
8. Note that this clock signal SCB is also supplied to the microcomputer 28.

The microcomputer 28 is CPLJ, RA
M, and a ROM, and performs signal processing according to a program stored in the ROM in advance while utilizing the temporary storage function of the RAM, so that the physical quantities of the rotating body 10, such as temperature and pressure, are determined by the characteristics of the sensor 20. It is determined whether it is higher or lower than a predetermined constant value, and the determination result is displayed on the display 48. A series of signal processing by the microcomputer 28 will be explained below with reference to the flowchart of FIG.

First, in step Sl, the gate signal SGl is outputted to the AND circuit 32 in synchronization with the excitation pulse DP supplied from the oscillator 26, thereby determining whether or not the pulse signal SP is supplied. This pulse signal SP is
During the rotation of the rotating body IO, the excitation pulse DP is sent to the first coil 14 in a state where the first coil 14 and the second coil 24 are magnetically coupled, and the resonant circuit 12 is caused to resonate, and a resonance signal is generated. Since SS is supplied by being received by the receiving circuit 22, for example, when the first coil 14 and the second coil 24 are magnetically coupled after the excitation pulse DP is generated in FIG. Next excitation pulse DP! A pulse signal SP is supplied by outputting a gate signal SGI in synchronization with .

When the pulse signal SP is supplied, step S2 is executed next, and the write signal S output to the AND circuit 42 is
G2 is the excitation pulse D after the pulse signal SP is supplied.
It is stopped immediately before the occurrence of P. This causes the shift register 38 to stop storing, but the shift register 38 contains the pulse signal SP related to the series of resonance signals SS generated in association with the excitation pulse DP.
P is stored as a bit signal SB.

Thereafter, step S3 is executed to output a read signal SG3, and the bit signals SB stored in the shift register 38 are sequentially read, and in step S4, a series of consecutive values rlJ and rQJ of the bit signal SB are set. n is counted, and the average value N of the n is calculated. Then, in the next step S5, from this average value N and the frequency f of the clock signal SC, the (
The frequency f of the resonance signal SS is calculated according to the following equation (3) obtained based on equation 2).

f = f c / N...
(3) Here, in order to improve the calculation accuracy of the frequency f,
It is desirable to read data related to a larger number n, and in this embodiment, the generation period of the excitation pulse DP is set to about 60 μsec in consideration of the rotational speed and frequency f of the rotating body IO. As a result, for example, when the frequency f of the resonance signal SS is about 133.6 kHz (period: about 7.5 μsec) as described above, about 8 pieces of data regarding the number n can be obtained, while the frequency f is about 277 kHz. .1kH
In the case of z (period: about 3.6 μsec), about 16 pieces of data regarding the number n are obtained, and a more accurate frequency f can be calculated. Also, the capacitor 16 of the resonant circuit 12.
18 electrostatic capacitances C2 and Ct and the inductance of the first coil 14, a resonance signal SS sufficient to measure the frequency is generated in the receiving circuit 22 during the period in which the first coil 14 and the second coil 24 are magnetically coupled. As mentioned above, the resonance frequency f is determined to be approximately several hundred kHz in consideration of the rotational speed of the rotating body 10, etc. so that the signal can be received by the following.

Note that since the number n is predicted in advance from the resonance frequency f of the resonance circuit 12, when calculating the average value N, those that are significantly different from the expected number n are removed.

Once the frequency f has been calculated in this manner, step S6 is then executed, and it is determined whether the calculated frequency f is greater than a preset frequency 10 or not. This frequency f0 is determined based on the frequency f of the resonant circuit 12 which is changed by the sensor 20, and for example, if the frequency f is 133.6kHz or 277.1kHz as described above.
z, it is set to about 200 kHz, which is in the middle. This determines whether the physical quantity at the time of measurement is larger than the value of the physical quantity at which the resistance value of the sensor 20 suddenly changes.
In other words, it is determined whether the temperature of the rolling rolls and the air pressure of the tires are higher than predetermined values, and this fact is displayed on the display in step S7 or S8.

Note that steps 33 and subsequent steps need only be executed before the rotating body lO rotates once and the first coil 14 and the second coil 24 are magnetically coupled again. Among a series of signal processing,
The portion that executes steps S3 and S4 above corresponds to a signal processing means.

Here, in the measurement equipment of this embodiment, the resonance signal SS
The data regarding is temporarily stored in the shift register 38,
During one rotation of the rotating body IO, the data is read into the microcomputer 28 and processed, and the frequency r is calculated.
High speed performance is not necessarily required as a function, and the device can be constructed at low cost. That is, the rotating body lO
The resonance signal SS having data regarding the physical quantity is intermittently supplied at predetermined time intervals as the rotating body 10 rotates, so by performing signal processing when the resonance signal SS is not obtained, the physical quantity can be determined. This made it possible to process signals at relatively slow signal processing speeds without affecting measurements in any way.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the above embodiment, the frequency f of the resonance signal SS is 1/
Although the pulse signal SPP with a frequency of 2 is supplied to the shift register 38, it is also possible to supply the pulse signal SP with the same frequency as the frequency f to the shift register 38, or It is also possible to supply a pulse signal with a frequency of /4.

Further, in the above embodiment, writing and reading of the shift register 38 are performed based on separate clock signals SCA and SCB, but if the reading speed of the bit signal SB by the microcomputer 2 is fast enough, the clock signal SCA It's fine just by itself.

Further, in the above embodiment, the excitation pulse DP and the clock signal S
CB is the oscillator 26. Although the signals DP and SCB are obtained from the clock signal generator B41, they may also be generated by a program within the microcomputer 28.

Further, in the above embodiment, the frequency r is calculated from the average value N of the number n of consecutive bit signals SB with the same value, and the frequency r is compared with the frequency 10, but the average value N is As is clear from equation 2), since it corresponds to the period of the resonance signal SS, the magnitude of the physical quantity can also be determined by comparing its average value N with a predetermined number N0.

Further, in the above embodiment, the average value N of a plurality of numbers n is calculated, but it is also possible to calculate the frequency f from only one number n of continuous OJs. .

In addition, in the embodiment, the sensor 20 has a resistance value that suddenly changes when the physical quantity changes beyond a predetermined constant value.
However, the resonant frequency f of the resonant circuit 12 is continuously changed by using a resistor whose resistance value changes continuously in response to changes in the physical quantity, and the physical quantity can be measured extremely precisely. It is also possible to change the resonance frequency f in multiple stages using a plurality of sensors.

In addition, a sensor whose capacitance changes depending on temperature, pressure, etc. may be used instead of the capacitor 18 and sensor 20.
Alternatively, it is also possible to provide the capacitors 16, 18 and the sensor 20 instead.

Further, in the above embodiment, the physical quantity of the rotating body 10 is
Although the present invention is applied to a device that measures based on the resonant frequency f of No. 2, the present invention can be similarly applied to other devices that measure the frequency of high-frequency analog signals supplied at predetermined time intervals. may be applied. The frequency of the high frequency analog signal is not necessarily limited to about several hundred kHz either.

Although other examples are not provided, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the configuration of a physical quantity measuring device including a frequency measuring device, which is an embodiment of the present invention. FIG. 2 is a time chart showing signals of each part in FIG. 1. FIG. 3 is a diagram illustrating an example of the storage contents of the shift register in the apparatus of FIG. 1. FIG. 4 is a flowchart illustrating the operation of the apparatus of FIG. 1. 28: Microcomputer (signal processing means) 38: Shift register SS: Resonance signal (high frequency analog signal) SPP: Pulse signal SCA: Clock signal (shift signal) SB 2-bit signal

Claims (1)

[Claims] A device for measuring the frequency of a series of high-frequency analog signals that are intermittently supplied at predetermined time intervals, the high-frequency analog signal having a frequency that is the same as or lower than the frequency of the high-frequency analog signal. a pulse converter that converts the pulse signal into a rectangular pulse signal, and synchronizes the pulse signal with a shift signal having a predetermined constant frequency higher than the frequency of the high-frequency analog signal to correspond to the presence or absence of the pulse signal. a shift register that stores a series of bit signals consisting of two values; and during a period when the supply of the high-frequency analog signal is suspended, the bit signal stored in the shift register is read out, and the number of successive bit signals of the same value is read out. A frequency measuring device for a high frequency analog signal, characterized in that it has a signal processing means for counting.