JPS6358129A - Turbidity meter - Google Patents

Abstract

PURPOSE:To achieve a higher measuring accuracy eliminating influence of non- uniformity or the like of circuit elements, by providing an input switching circuit to convert received optical signals for detection and reference to a time-series form and a common signal processing system at a rear stage. CONSTITUTION:A light emitting element 3 emits light the quantity of which is proportional to the current from a light emitting current circuit 1. The luminous flux is radiated to sample water 5 and scattered reflection from a suspension 6 is detected with a light receiving element 7. On the other hand, the quantity of light incident on a light receiving element 8 for reference is proportional to the quantity of light emitted. Then, outputs of the elements 7 and 8 are amplified with preamplifiers 9A and 9B and converted to a time-sequential form with an input switching circuit 17. The timing of the conversion is determined by the outputs of a timer circuit 20. Then, the outputs of a detecting section A2 are transmitted to a converter section C2 through a filter circuit 10, a full-wave rectification circuit 11, a voltage-to-current conversion circuit 12 and a transmission cable section B2 and converted into parallel signals with an output switching circuit 18 to be stored into sample holding circuits 19A and 19B. Thereafter, the signal is further inputted into an arithmetic circuit 13 and the results are outputted 14.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application Minute Hand The present invention relates to a turbidity needle that optically measures turbidity during sewage treatment.

B1 Summary of the Invention The present invention provides a scattered light type turbidity meter in which an input switching circuit for converting light reception signals for detection and reference into a time series form is provided in the detection section, and a shared 11! ! By configuring a number system, it is possible to improve accuracy by eliminating the effects of variations in circuit elements, temperature changes, and changes over time, and to facilitate manufacturing.

C0 Conventional Technology Optical methods such as a scattered light method, a transmitted light method, and a transmitted/scattered light comparison method are generally used to measure turbidity.

FIG. 10 is a block diagram showing the configuration of a scattered light type turbidity meter. The light emitting current circuit 1 outputs a current for causing the light emitting element 3 to emit light in an alternating current manner based on the number of firing cycles of the firing cycle wr2. A part of the luminous flux of the light emitting element 30 is emitted to the test water 5 through the glass window 4, and if there is a suspended object 6, it causes scattered reflection light, and a part of it passes through the glass window 4 to the detection light receiving element 7. reach Further, a part of the emitted light beam directly enters the reference light receiving element 8.

A current proportional to the amount of incident light is obtained in the light receiving element 7 (8), and this becomes an input to the preamplifier 9A (9B) and is amplified. The output is 10 filter circuits (1
0B). The filter circuit 10A (IOB) is a bandpass filter that allows only the component that matches the frequency of the flow of the light emission 1 to pass through, and is used to filter external light such as sunlight ([flow]),
The component due to the incidence of fluorescent light (alternating current) emission is excluded.

The output signal of filter circuit 10A (IOB) is all 121E
The rectifier circuit 11A (IIB) converts the voltage to -
The voltage signal is converted into a current signal by the current conversion circuit 12A (12B).

The outputs of both conversion circuits 12A, 12B, that is, the output of the detection section A, are sent to the converter section C via the transmission cable section B.
It is sent to I and becomes an input to the arithmetic circuit 130. Here, VI
JIE is performed, and the output becomes the turbidity output via the output circuit 14. The 60% calculation compensates for the temperature characteristics of the conversion efficiency of the light-emitting element and the light-receiving element, changes over time, changes in temperature of each circuit element, and changes over time. This is done to ensure stable measurements.

Note that the converter section C□ is provided with a power supply circuit 12S, and the detection section A1 is provided with a power supply stabilization circuit 16.

In such a configuration, both the fal detection and the reference signal are current outputs, and since the power supply stabilization circuit 16 is provided in the detection section A1, the voltage is reduced as the transmission cable section B becomes longer distance. No influence of drop (BL detection, reference signal is converted to DC before being transmitted, so even if light emitting current is induced in the transmission cable section Bi or induced from outside, there is no filter on the converter section C1 side. There is an advantage that the effect can be removed by providing a.

D0 Problems to be solved by the invention By the way, in order to accurately measure K using this method, it is necessary that the temperature changes and changes over time of each element of the side-out signal system and the eight-output signal system are exactly the same. Although it is brown in color, even if some of the elements, such as the light-receiving element, are to be selected for summer use, it would be impossible to select all of them because it would be costly and time consuming. Even if elements with exactly the same characteristics are used, the temperature within the detection part will not necessarily be the same. Also, if there is a long distance between the detection part AI and the converter part C1, the cost of installation,
Considering the time and effort involved, it is important that the transmission cable has a small number of cores.

Means for solving the problem of one point between E1 The present invention provides an input switching circuit for converting the received light signal for detection and reference into a time series form in the detection section of a scattered light type turbidity meter, and then A part of the common signal system is provided in the converter section, and an output switching circuit for serial-to-parallel conversion and a timer circuit for generating a switching tie signal are provided in the converter section, and the input switching circuit and the output switching circuit are provided. It is characterized in that a timing signal is applied to perform parallel-to-serial conversion and serial-to-parallel conversion of signals.

70 action. Both light reception signals are applied to an input switching circuit, and a detection signal and a reference signal are alternately selected according to the tireing signal and converted into a time series form. After this, the shared filter circuit, full wave!
It passes through the I current circuit and is transmitted to the converter section via the transmission cable section.

G. Embodiment FIG. 1 shows an embodiment of the present invention, in which 1 is a light emitting current circuit, 2 is an oscillation circuit, and 3 is a light emitting element. A part of the light emitted from the light emitting element 30 is emitted to the test water 5 through the glass window 4, and if there is suspended matter 6, scattered reflected light is generated. 7 is a detection light receiving element, 8 is a reference light receiving element, 9A is a preamplifier connected to the detection light receiving element 7, and 9B is a preamplifier connected to the reference light receiving element 8.

1γ is an input switching circuit (parallel conversion circuit) that converts the output signals of both preamplifiers 9A and 9B from parallel to time-series (serial) format, and at the subsequent stage is a filter circuit 10 and a tray v! A first current circuit 11 and a voltage-current conversion circuit 12 are connected in sequence.

This signal system has the same configuration as the conventional detection or reference signal system (FIG. 10).

1s is an output switching circuit (parallel conversion circuit) provided in the converter section CI, which chronologically converts the output of the voltage-current conversion circuit 12 of the detection section sent via the transmission cable section B. Convert to parallel form.

19A and 19B are sample and hold circuits connected to this output switching circuit 16, and the arithmetic CIII calculation) circuit 13 and output circuit 14 are connected in sequence to the output side thereof. A timer circuit 20 provides a timing signal to the input switching circuit 17, output switching circuit 18, and sample and hold circuits 19A and 19B. In FIG. 1, 15 is a power supply circuit, and 16 is a power supply stabilization circuit.

For example, in the nine preamplifiers (9B), as shown in FIG. 2, a series circuit of resistors 32 and 33 is connected between the negative input terminal and the output terminal of an operational amplifier 31, and a resistor 34 and a capacitor 321 are connected in parallel to this. 1" connection, and the intermediate connection point of the first column circuit is grounded via a capacitor 36. A light receiving element (for example, a photodiode) 7@) is connected to the H input terminal. Note that the positive input terminal is grounded.

The preamplifier with the above configuration has frequency characteristics as shown in FIG.

Next, the operation will be explained with reference to FIG. The light flux is emitted to the sample water 5, and the light scattered and reflected by the Mm object 6 is detected by the detection light receiving element 7.This incident light contains an AC component proportional to the turbidity, a DC component due to sunlight, etc., and a firefly. Contains low-frequency alternating current components from lights, etc.
It changes as shown in FIG. 4 tb+. - 10,000, reference receiving element 80 The amount of incident light is proportional to the amount of emitted light as shown in tK4 diagram fcl.

The outputs of both light receiving elements 7 and 8 are amplified by nine preamplifiers and 9B. In this case, since the amplifier has a filter function, the DC component and low frequency component of the detection signal are removed, resulting in a signal as shown in FIG. 9, 1dl lel. Thereafter, the input switching circuit 17 converts the data into a time series format.

The timing of this conversion is determined by the output of the timer circuit 20 (FIG. 4(f)). For example, when the timing signal is @ l @ (a level), the reference signal, IQ
It becomes a detection signal when it is I (I, level).

At the subsequent stage of the input switching circuit 17, a filter circuit 10
% full wave rectifier circuit 11 and voltage-current converter circuit 12.

At this time, the detection signal and the reference signal appear alternately in the output of the full-wave rectifier circuit 11 as shown in FIG. 4 (1g).

The output of the detection part A is the transmission cable part B! The signals are transmitted to the converter section C1 via the output switching circuit 18, converted into parallel signals, and stored in the sample and hold circuits 19 and 19B, respectively. Thereafter, it is input to the arithmetic circuit 13 and division is performed. The result is output via the output circuit 14.

FIG. 5 shows another embodiment of the present invention, in which a portion of the timing signal of the timer circuit 20 and the output of the oversight circuit 2 are combined into a light emitting current by a light emitting current circuit 1', and a part of the light emitting current is generated on the detection section side. A timing signal separation circuit 2 consisting of a low-pass filter, etc.
1 is provided, and a timing signal is separated from this light emitting current and applied to the input switching circuit 17. The specific circuit is shown in FIG. 6 and the seventh factor. That is, the above-mentioned light emitting current is generated by the output of the oscillation circuit 2 and the timer circuit 2 as shown in FIG.
It is generated by applying a timing signal of 0 to the minus input terminal of the operational amplifier 41, using the amplifier output as a base signal of the transistor 420, and feeding it back from the input terminal to the minus input terminal.

In addition, a voltage follower circuit 43 is provided on the detection section side, and a low-pass filter (or full-wave rectifier circuit) 44 is provided on the output side.
are connected. The low-pass filter 44 has a reduction*W characteristic as shown in FIG.

Figure 9 (a
) to tg+, FIG. 9(a) shows the light emission current (luminous flux) of the light emitting element 30, and when the light emission from the confectionery 30 is emitted to the test water, the amount of incident light on each light receiving element 7.8 is When the received light signal is amplified by the preamplifiers 9A and 9B, it becomes a waveform as shown in FIG. 9 1dl (θ). This waveform is the same as the waveform in the previous embodiment Then, a tying signal as shown in FIG. #I9 ifl is applied to the input switching circuit 17, and as a result, the output of the full-wave rectifier circuit 11 becomes as shown in FIG. 9 1dl.

By making the light emitting current superimposed with the timing signal in this way, the cable of the transmission cable section, 1! ;
The number is smaller than that in the first embodiment.

H0 Effects of the Invention As described above, according to the present invention, an input switching circuit for parallel column conversion of signals is provided in the detection section, and a signal system for both detection and reference is configured at the subsequent stage. The effects of variations in confectionery, temperature changes, and changes over time can be removed by υF, and highly accurate measurements can be expected.

Moreover, selection of circuit components becomes easy. In addition, even if the temperature distribution inside the detection part is uneven, the effect is small.
l! Furthermore, by superimposing the switching timing signal on the light emitting current and transmitting it, it becomes possible to use a cable with a small number of cores.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a turbidity meter according to the present invention, FIGS. 2 and 3 are a circuit diagram and a frequency characteristic diagram of a preamplifier in the same embodiment, and FIG. 4 (11) to +gl are A waveform diagram for explaining the operation, FIG. 5 is a block diagram showing another embodiment of the present invention, and FIGS. 6 and 7 are circuit diagrams of the light emitting current generation section and timing signal separation section in the same embodiment. , FIG. 8 shows the attenuation characteristics of a low-pass filter for separating tied signal, FIG. 9 (al to fg+ are waveform diagrams for explaining the operation, and FIG. 10 is a block diagram showing a conventional example. 1 and 1'... Light emitting current circuit, 2... Oscillation circuit, 3
...Light emitting element, 5...Water test, 6...Suspended matter, 7.
...Detection light receiving element, 8...Reference light receiving element, 9 people and 9B...Preamplifier, 1o...Filter circuit, 1
1...Full wave rectifier circuit, l...Voltage-current conversion circuit,
13... Arithmetic circuit, 14... Output circuit, 17...
Input switching circuit, 18... Output switching circuit, 19A and 1
9B... Sample hold circuit, 20... Timer circuit, 21... Timing signal separation circuit. Figure 2: Circuit diagram of Briaship Figure 3: Frequency comparison characteristics Figure 4: 00 wave diagram of the base moon Input Rainbow Peel Yield [Hz]

Claims (1)

[Claims] (1) Light is emitted into the sample water from a light emitting element driven by alternating current, and the light scattered by the suspended matter is received by a detection light receiving element, while the light from the light emitting element is received by a reference light receiving element. After both received light signals are supplied to the signal system and processed such as removing unnecessary components and converting them to direct current, they are transmitted from this detection section to the exchange section via the transmission cable, where the necessary calculation processing is performed and the turbidity is removed. In a scattered light type turbidity meter that measures the degree of
An input switching circuit is provided in the detection section to convert the received light signals for detection and reference into a time series format, and a shared signal system is configured at the subsequent stage, while an output for serial/parallel conversion is provided in the converter section. A switching circuit and a timer circuit that generates a switching timing signal are provided, and the switching timing signal is applied to the input switching circuit and the output switching circuit to perform parallel-to-serial conversion and serial-to-parallel conversion of signals. Turbidity meter.