JPS5972205A - Frequency varying method of lc oscillator for analog value detection - Google Patents

Abstract

PURPOSE:To eliminate a decrease and variance in detection sensitivity and to improve the stability of an oscillation frequency and temperature characteristics by controlling the phase characteristics of the amplifying element of an oscillator through a variable capacitor and varying the oscillation frequency. CONSTITUTION:The series circuit of an inductor L1 and capacitors C1 and C2 constitutes an LC parallel resonance circuit. The LC parallel resonance circuit is connected to the collector of a transistor (TR) Q for amplification and a feedback path F for oscillation is provided from the connection point between the capacitors C1 and C2 to the emitter of the TRQ. Further, resistances R1-R3 are applied with the bias of the TRQ and a coupling capacitor C4 cuts the DC component in the output of an oscillator. A capacitor C3 for adjustment is provided between the collector and base of the TRQ. Then, the TRQ varies in phase shift amount with the value of a capacitor C3, so the oscillation frequency is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a frequency variable method KrJA suitable for an LC oscillator for analog quantity detection.

As a method of detecting an analog quantity, the inductor or gear/4' shifter for determining the oscillation frequency of the 50 oscillator is used as a detection element and is changed in accordance with the analog quantity, and the resulting change in oscillation frequency is detected and the analog quantity is detected. Methods for detecting are conventionally known.

For example, a button that uses an inductor L as a detection element can be used to detect the concentration of a developer in a copying machine that consists of two components, toner and a magnetic carrier, or to detect the presence or absence of a metal piece and the distance from it. Detection elements include gap bone measurement using capacitance, proximity switches, and the like.

In such an analog quantity detection method in which the inductor L and capacitor C for determining the oscillation frequency of the LC oscillator are used as detection elements, the oscillation frequency of the LC oscillator before measuring the analog quantity to be measured is a specified value, that is, the measuring device must be calibrated to point to the zero scale. This is done by adding an inductor or capacitor for calibration and adjustment of this oscillation frequency.

Figure 1 shows the circuit diagram of a secondary I and C oscillator using a compensation inductor. There are 6 types showing the 71 number variable system.

In the figure, LI is an inductor for analog quantity detection and frequency determination, an inductor for adjusting R2 and ε, and cl.

C2 is for frequency determination and return meter determination, 41 positions, Q
are amplification elements consisting of transistors, R1, R,.

R3 is a bias resistor and a Vcc power supply, forming a horn-shaped oscillator as a whole. The oscillation output is supplied to a control device (not shown) via a coupling element C4. The resonant frequency or oscillation frequency is adjusted by changing the tuning inductor L2.

In this conventional method, only Ll changes depending on the analog quantity of the detection pair i, and the adjustment inductor L2 changes depending on the analog quantity of the detection pair i. Since the detection of the analog quantity is not performed, the detection sensitivity of the analog quantity decreases. If the value of Ll is adjusted so that the oscillator reaches a predetermined frequency by absorbing the variations in L I * C1 + C2, the inductance value of Lll will fluctuate after adjustment, so the detection sensitivity will vary. Become Keihei. Furthermore, the composition ratio of inductors L1 and R2 is different, and it is often impossible to make the temperature characteristics of both Ll and R2 the same due to the relationship with the characteristics of the detection target. , temperature compensation of the oscillation circuit is a problem. In addition, it is practically inconvenient to use a non-magnetic driver to adjust the adjustment inductor L2, and the inductance is affected by nearby magnetic or metal objects, resulting in changes in the inductance value and detection sensitivity. There are many problems, such as implementation limitations due to a decrease in performance.

On the other hand, it is also possible to use the same circuit shown in FIG. 1, to use the capacitor C2 as a detection element, and to use Ll as an adjustment inductor. In this case, although the problem of a decrease in detection sensitivity due to the presence of the adjustment inductor 2 and the problem of variation in detection sensitivity after adjustment does not occur, other drawbacks still remain.

FIG. 2 shows a conventional LCC oscillator frequency variable system using an adjustment capacitor.

In the figure, the configuration is the same as that of the circuit shown in FIG. 1 except that an adjustment capacitor C1 is provided in parallel with the capacitor C instead of the adjustment inductor 2. First, if the inductor L1 is used as a detection element, there will be no problem of a decrease in detection sensitivity or a 9.
If there is a difference in the temperature characteristics of 1*C2, there will be a -9 deviation in the temperature characteristics after adjustment, making temperature compensation difficult. Also, if the required frequency variable range is large, the capacitance value of C3 needs to be increased, which requires large components, and if a small ceramic trimmer capacitor with a wide variation range is used,
There are problems such as the inability to obtain products with good temperature characteristics.

Furthermore, if the capacitor C2 is used as a detection element in the circuit shown in Figure 2, the detection sensitivity will decrease or become unstable, similar to the explanation for the circuit shown in Figure 1, and if the inductor L1 is used as the detector. The same problem will arise.

The present invention eliminates the drawbacks of the above-mentioned prior art, and solves the problem of low detection sensitivity,
It has a wide frequency variable range that does not cause fluctuations or fluctuations.
The purpose of the present invention is to provide a method of varying the frequency of an LC oscillator for analog quantity detection, which has good oscillation frequency stability and temperature characteristics, and can be adjusted due to oscillator mounting limitations and a magnetic driver.

To achieve this objective, the present invention proposes a frequency determining element (Ll, self) of the LC parallel resonant circuit of the oscillator.

The present invention is characterized in that the oscillation frequency is changed by controlling the phase characteristics of the amplification element of the oscillator using a variable capacitor without adjusting the oscillator (Cz).

An embodiment of the present invention will be described below with reference to FIG.

FIG. 3 shows an analog quantity detection LC according to an embodiment of the present invention.
This figure shows a configuration diagram of an oscillator. In the figure, J
An LC parallel resonant circuit is constructed.

Q is an amplification element consisting of a transistor, the collector of which is connected to an LC parallel resonant circuit, and the canopy transistors C and C2.
A feedback path F for stopping oscillation is provided from the connection point of the transistor Q to the emitter of the transistor Q. R.I.

R2TR3 is a bias resistor that applies a bias to the transistor Q and determines the operating point. C4 is a coupling capacitor that converts the DC component from the output of the oscillator and supplies only the oscillation frequency component to a control device (not shown). The control device converts an analog signal consisting of a change in oscillation frequency into an electrical signal and outputs the electrical signal. C.

is a regulating capacitor consisting of a variable capacitor connected between the collector and pace of transistor Q, and vce is the power supply voltage.

With the above configuration, the oscillator oscillates under the condition that the sum of the phase shift of the feedback path due to the frequency determining element and the phase shift of the amplification element is 2π. Therefore, the oscillation frequency is adjusted by changing the phase shift of the amplification element. That is, in the circuit configuration shown in the figure, when the adjustment capacitor C3 is changed, the amount of phase shift of the transistor Q, which is an amplification element, changes. Therefore, by changing the adjustment capacitor C3, 5,L
The oscillation frequency of the oscillator can be adjusted even if the resonant frequency of the C parallel resonant circuit (Ll + CIr cm) remains constant.

Figure 4 shows that in the circuit of Figure 3, self = 0.015/
JF, C snow = 3300pF, T, = 6
00/lH, and the relationship between the capacitance value of the adjustment capacitor C3 and the oscillation frequency when C3 is changed from 0 to 60 pF. Adjustment capacitor C3 to 0
By changing 60 pF from
It can be changed from 125.3 kHz to 115.9 kHz, about 8%.

In the case of the frequency variable method as shown in FIG. 2, the resonant frequency f of the LC resonant circuit. is given by the following equation.

/, = -; Hole "G tatashi, Ct is the composition of Kya/4'shita cl, c.

(9h6 to change fo by 8% by changing 4)
K % Ct needs to be varied by about 16 inches. To find the approximate value, use Cl ki C! If you look at it, C3=6
Since it is 0 pF, it is necessary to change it by about 500 pF, so C5=500 pF.

According to this embodiment, since C3=60pF, the second
The capacity required is approximately 1/10 compared to the conventional method shown in the figure.

Also, the frequency determining element (Ll) of the LC resonant circuit.

Since there is no change in CIrC*), when the analog detection element to be detected or C2 undergoes a change, the LC
The degree of influence on the resonance circuit is determined by the adjustment capacitor C3.
Since it will be the same regardless of the E circumference adjustment cap... or Sita C3
Even if the detection sensitivity is changed, there is no decrease in detection sensitivity or variation.

Further, since the adjustment capacitor requires a small capacity, it becomes easier to obtain a small and large capacitor with good temperature characteristics, and the temperature characteristics of the oscillator can be improved.

Furthermore, since it is not affected by the surrounding magnetic material, there are fewer restrictions on mounting the oscillator, and W1' due to the magnetic driver
4 adjustments are possible.

Note that the amplifying element in the above embodiments may be replaced with an electron tube in addition to each type of transistor. Further, in the above embodiment, a Colpitts type oscillator was used as an example of the oscillator, but the oscillator type is not limited to the Colpitts type, and other types of LC parallel co-photography circuits such as the Hartley type can be used to determine the frequency. Of course, it can be applied to the LC oscillator as an element.

As described above, according to the present invention, there is no decrease in detection sensitivity or variation due to adjustment, it is small, the frequency can be varied over a wide range, and the stability of the engagement frequency and temperature characteristics are good. Many excellent effects can be obtained, such as fewer restrictions on the implementation of the excavator and easier adjustment.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a conventional method of varying the frequency of an LC oscillator using an adjustment inductor, Figure 2 is an explanatory diagram of a conventional method of varying the frequency of an LC oscillator using an adjustment capacitor, and Figure 3 is an illustration of the present invention. FIG. 4 is an explanatory diagram of a method of varying the frequency of the r and c oscillators showing one embodiment of the present invention, and FIG. 4 is a diagram showing the change characteristics of the adjustment capacitor and the oscillation frequency according to the method of FIG. Rs TR, IRs...Bias resistance, LL...
Capacitor C3 for oscillation frequency and feedback amount determination. CIr...adjustment capacitor, C4...coupling capacitor, Q...transistor as amplification element, V
cc...Power supply. Figure 7 Figure 3 Figure 4 °1 Capacity ρF□

Claims (2)

[Claims] (1) An LC oscillator for analog quantity detection that uses an LC parallel resonant circuit as a frequency determining element, which is characterized in that the oscillation frequency is changed by controlling the phase characteristics of the amplification elements that constitute the LC oscillator. How to vary the frequency of an oscillator. (2) A Corvitz oscillator is used as the LC oscillator for analog quantity detection, and the amplification element of this oscillator is
An adjustment capacitor made of a variable capacitor is connected between the collector of the trans-Zostor and an electrode corresponding to the pace or electrode, and by changing the capacitance of the adjustment capacitor, the phase characteristics of the amplification element can be adjusted. [JCC oscillator frequency variable method for analog detection, which is characterized by controlling the oscillation frequency and changing the oscillation frequency.