JPH0743400B2 - Low frequency signal processing circuit from analyzer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a circuit for processing a low frequency signal such as a detector output of an infrared analyzer.

[Prior Art] Generally, in an infrared analyzer, the detector output is
Depending on the S / N and the modulation means, it is modulated at a low frequency such as 1 Hz or 2 Hz. This is because the amount of signal per unit time can be increased by performing modulation at such a low frequency.

By the way, since the detector output is a so-called low-frequency signal, in order to convert it into a DC signal, after amplification, full-wave rectification is input to the capacitor smoothing circuit for signal processing. Then, when a high speed response is required especially, after amplification, Vf conversion or AD conversion is performed and digital processing is performed.

[Problems to be solved by the invention]

However, when a signal smoothing process is performed using a capacitor smoothing circuit, if the frequency of the signal is low, the capacitance of the capacitor required for smoothing becomes large, which causes a drawback that the response speed becomes slow. Also, V-f conversion and A-
When performing D conversion, an additional conversion circuit, processing circuit, etc. are required, which complicates the configuration of the processing system,
It has the drawback that it tends to be expensive.

The present invention has been made in consideration of the above matters, and a low-frequency signal processing circuit from a circuit analyzer capable of processing a low-frequency signal output from the analyzer at high speed with a simple structure (hereinafter, The purpose is to simply provide a signal processing circuit).

[Means for solving problems]

In the present invention, the output side is provided with a full-wave rectification unit, and the low-frequency signal from the analyzer to be input is
/ n (where n is an integer greater than or equal to 2), n-1 phase-adjusting units connected in parallel to each other for performing phase shifts, and the low-frequency components are connected in parallel to each other. A signal processing circuit is configured by a full-wave rectification unit to which a signal is input, an addition unit that adds the outputs of the respective full-wave rectification units, and a circuit that smoothes the output of the addition unit.

[Action]

In the signal processing circuit configured as described above, the low frequency signal from the analyzer is input in parallel to the n branch circuits. In the n−1 branch circuits, the input low-frequency signal is phase-shifted by π / n, and
It is full-wave rectified, and each output is added to the output obtained by full-wave rectifying the input low frequency signal as it is.

This makes the frequency of the combined output after addition n times the frequency of the input low-frequency signal, reduces the difference between the peak value and the bottom value, and significantly reduces the specific number in the smoothing process. Therefore, signal processing with a fast response can be performed.

〔Example〕

FIG. 1 shows an example of the signal processing circuit of the present invention. In this figure, T ₁ is an input terminal to which a low-frequency signal from a detector (not shown) of an infrared analyzer is inputted,
Two branch circuits 1 and 2 are connected in parallel with each other. One of the branch circuits 1 is provided with a phase adjuster 10 and a full-wave rectifier 20 that receives the output of the phase adjuster 10 and performs full-wave rectification. Further, only the full-wave rectifying unit 20 is provided in the other branch circuit 2.

The phase adjustment unit 10 includes, for example, a capacitor 12 and a variable resistor.
A phase adjuster 11 in which 13 and 13 are connected in series, an amplifier 14, and a resistor.
It consists of 16 and. Then, the phase of the low frequency signal from the input terminal T ₁ is π / 2 (= 90
゜) is shifted.

The full-wave rectifying unit 20 is composed of, for example, an amplifier 21, rectifying elements 22 and 23, resistors 24, 25, 26, 27 and 28. Note that the resistance values of the resistors 24 to 27 are equal to each other and are set to twice the resistance value of the resistor 28.

Reference numeral 30 denotes an adder that adds the outputs of the full-wave rectifiers 20 in the branch circuits 1 and 2, and is composed of, for example, an adder 31.

Reference numeral 40 denotes a filter and a zero / span adjusting unit provided on the output side of the adding unit 30, which includes an amplifier 41, a filter 42 including a condenser, a zero adjusting volume 43, a span adjusting volume 44, and the like.

T ₀ is an output terminal, and 50 is a capacitor that is provided to cut off a direct current component.

Next, the operation of the signal processing circuit configured as described above is
Description will be given with reference to FIG. This FIG. 3 shows the waveform of one cycle of the low frequency signal.

Now, when the low frequency signal a as shown in FIG. 3 (a) is input through the input terminal T ₁ , the full-wave rectification section on the side of the branch circuit 2 produces a signal as shown in FIG. 3 (b). Output b is output. On the other hand, since the branch circuit 1 is provided with the phase adjusting unit 10 that shifts the phase of the low-frequency signal a by π / 2, the phase adjusting unit 10 outputs the phase adjusting unit 10 as shown in FIG. Output c
Is output, and this is input to the full-wave rectification unit 20. Then, from the full-wave rectification unit 20 on the side of the branch circuit 1, FIG.
The output d as shown in is output.

The outputs b, c, d are input to the adder 30, and the adder 30 outputs an output e as shown in FIG. 3 (e). The output e is waveform-shaped by passing through the filter and the zero / span adjuster 40, and is shown in FIG.
A direct current output f as shown in ( ₃₎ is output to the output terminal T ₀ .

In the above embodiment, two branch circuits are provided at the input terminal T _1.
Although 1 and 2 are connected in parallel, the present invention is not limited to this, and as shown in FIG. 2, n branch circuits 1 to n are connected in parallel and n-1 Branch circuit 1
To n-1 are respectively provided with a phase adjustment unit 10 and a full-wave rectification unit 20 connected in series, and the phase adjustment unit 10 outputs the input low frequency signal a by π / n (where n is 2 or more integer)
The phase shift may be performed so as to be different from each other, and only the full-wave rectification unit 20 may be provided in the remaining branch circuits n.

Figure 4 is a waveform diagram showing that the output changes from the adding section 30 by the number of branch circuits, enter the low frequency signal as shown in FIG. 4 (a) to the input terminal T _1, the branch circuit To 2
Outputs from the adder unit 30 when three, four, five are provided are as shown in FIGS. 4 (b), (c), (d), and (e), respectively, and many branch circuits are provided. The frequency of the combined output after addition increases (n times the input original frequency),
The difference between the peak value and the bottom value becomes smaller. Therefore,
It becomes possible to reduce the time constant required for smoothing, and the response speed becomes faster accordingly.

〔The invention's effect〕

As described above, in the signal processing circuit of the present invention, the low frequency signal from the analyzer is phase-shifted in the n branch circuits connected in parallel, the outputs after the phase shift are added, and then the Since the output obtained by this addition is configured to be smoothed, the configuration is simpler and the cost can be reduced as compared with the conventional signal processing circuit. Then, since the time constant required for smoothing is greatly reduced, the response speed is significantly improved.

Further, in the present invention, since the output obtained by the addition is smoothed, the signal is substantially amplified, and therefore, like the detector output of the analyzer,
It is especially effective for objects with large waveform distortion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of the present invention and showing a configuration example in the case of using two branch circuits. FIG. 2 is a block diagram showing another embodiment of the present invention and showing a configuration example in the case of using n branch circuits. 3 and 4 are waveform charts for explaining the operation. 10 …… Phase adjuster, 20 …… Full wave rectifier, 30 …… Adder,
a: Low frequency signal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadao Nakamura 2 Higashi-cho, Kichijoin-miya, Minami-ku, Kyoto-shi, Kyoto Prefecture Horiba Seisakusho Co., Ltd. (56) References JP-A-50-61265 (JP, A) JP-A Sho 52-103657 (JP, A) JP-A-52-102553 (JP, A) Actually opened 50-93244 (JP, U) Actually opened 52-136128 (JP, U)

Claims (1)

[Claims] 1. A full-wave rectifier is provided on each output side, and phase shift is performed such that a low-frequency signal from an analyzer to be input is different by π / n (where n is an integer of 2 or more). -One phase-adjusting section connected in parallel with each other, a full-wave rectifying section that is connected in parallel with each of the phase adjusting sections and receives the low-frequency signal, and outputs of the full-wave rectifying sections A low-frequency signal processing circuit from an analyzer, comprising: an adding unit for performing the smoothing and a circuit for smoothing the output of the adding unit.