JPS626524Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a turbidity meter used for controlling suspended solids in water supply and sewage systems and factory wastewater.

A conventional turbidity meter of this type as shown in FIG. 1 has been known. In FIG. 1, 1 is a light source, 2 is a window through which the light beam from the light source 1 passes, and 3
4 is a liquid to be measured such as wastewater, 4 is a detector that receives transmitted light from the light source 1 and generates an electric signal _I1 proportional to the amount of transmitted light, and 5 receives the output _I1 of the detector 4 and outputs it appropriately. This is a processing circuit that performs processing.

Next, the operation of the turbidity meter shown in FIG. 1 will be explained. The luminous flux emitted by the light source 1 is irradiated onto the liquid 3 to be measured through the window 2 . When the detector 4 receives the transmitted light that is not scattered by the liquid to be measured 3 in this light flux, the output I ₁ of the detector 4 is given by the Lambertian equation I ₁ = I ₀ exp[−Blx] (1) Follow Beer's Law.

Here, B is a constant determined by the absorption and scattering characteristics of the liquid 3 to be measured, I ₀ is the output value l of the detector 4 when the turbidity is zero, and x is the measurement length.

Therefore, by measuring the output _I1 , the turbidity x can be calculated backwards, and the processing circuit 5 performs such processing and outputs the turbidity value.

Since the conventional turbidity meter is configured as described above, there is an optimal measurement range depending on the measurement length l, and outside this range, the output _I1 of the detector 4 may become saturated or cannot be obtained sufficiently. Therefore, accurate measurements could not be made. For this reason, it has been necessary to prepare various optical systems having measurement lengths l depending on the measurement range.

This idea was made in order to eliminate the drawbacks of the conventional ones as mentioned above.The light source can be turned on multiple times, and the first time it is turned on, it emits light at a preset brightness, and the second After the first lighting, the operation of emitting light with a brightness corresponding to the brightness of the transmitted light obtained in the previous lighting is repeated until a constant detector output is obtained. The purpose of this invention is to provide a turbidity meter that can measure all turbidity ranges in a system.

Examples of the turbidity meter of this invention will be described below based on the drawings. FIG. 2 is a block diagram showing the configuration of one embodiment. In this figure 2,
The parts indicated by numerals 1 to 4 are exactly the same as those described in the explanation of the conventional turbidity meter shown in FIG. 1, and the explanation thereof will be omitted.

Reference numeral 6 denotes a pulse lighting circuit for lighting the light source 1 in pulses, which receives a lighting command from a timing circuit 7 to be described later and lights the light source 1 at a lighting level of I ₀ or In.

The timing circuit 7 sends out a pulse lighting command signal until the output value I _N of the hold circuit 8 becomes smaller than the set value I _NR , and sends out a measurement completion signal to the arithmetic circuit 9 .

The hold circuit 8 holds the output of the detector 4 in synchronization with the lighting command signal from the timing circuit 7, and the arithmetic circuit 9 inputs the measurement completion signal from the timing circuit 7 and controls the hold circuit 8 at this time. The turbidity x is calculated from the output I _N of . Reference numeral 10 indicates a control system that brings together the above-mentioned circuits.

The control system 10 includes the pulse lighting circuit 6, the timing circuit 7, the hold circuit 8, and the arithmetic circuit 9.
is configured.

Next, the operation of the turbidity meter of this invention constructed as above will be explained. First, the timing circuit 7 sends a first lighting command signal to the pulse lighting circuit 6. The pulse lighting circuit 6 inputs this signal to the light source 1 at a preset lighting level V ₀ .
lights up.

As a result, as described in the explanation of the operation of the conventional turbidity meter, the detector 4 obtains the output _I1 expressed by equation (1), and outputs it to the hold circuit 8. Since this hold circuit 8 holds the output _I1 of the detector 4 in synchronization with the lighting command from the timing circuit 7, the output of the hold circuit 8 is now the above-mentioned _I1 .

Next, the timing circuit 7 sends a second lighting command signal to the pulse lighting circuit 6 at appropriate intervals. In response to this second lighting command signal, the pulse lighting circuit 6 lights the light source 1 at a light source lighting level V ₁ corresponding to the output value I _N of the hold circuit 8.

That is, the output _I0 of the detector 4 when the turbidity is zero is measured in advance, and the ratio with the output I1 of the detector 4 at the first lighting of the light source ₁ and the first lighting level V are measured. ₀ to V ₁ = I ₁ / I ₀ V ₀ ...(2) Since it lights up at the lighting level V ₁ calculated as
The output I ₂ of the detector 4, which is the second detection signal, is I ₂ = I ₁ exp [−Blx] = I ₀ exp [−Blx] × exp [−Blx] = I ₀ exp [−2Blx] …( 3) According to the relational expression.

Thereafter, at the third lighting, the output I ₂ of the detector 4
The same operation as above, such as obtaining a detector 4 output of _I3 at _a lighting level _V2 corresponding _to This is repeated until the measurement is completed, and when the measurement is completed, a measurement completion signal is input to the arithmetic circuit 9.

At this point, the output I _N of the hold circuit 8 is expressed as I _N =I ₀ exp[-NBlx] (4).

As is clear from the above equation (4), the index part is multiplied by N by N measurements, so the sensitivity to turbidity improves according to N. Based on the above principle, the arithmetic circuit 9 simultaneously receives the measurement completion signal.
Calculate the turbidity x from equation (4) and output it.

In the above embodiment, only the case where only transmitted light is detected has been described, but it can also be used when detecting scattered light scattered by the liquid to be measured 3, as shown in FIG. In this case, until the completion of N measurements, the operation is exactly the same as that described in the above embodiment, and the equation for determining the output I _N of the arithmetic circuit 9 is as follows.

I _N = I ₀ A ^N x ^N exp[-NBlx] (5) where A is a constant.

In addition, as shown in Fig. 4, when detecting transmitted light and scattered light and determining turbidity from the ratio of the two, the characteristics of the light sources 1a and 1b should be made equal, and the hold value of one, for example, the scattered light Measurements are made N times for the outputs I _N a and I _N b shown in equations (4) and (5). Thereafter, when the comparison circuit 11 calculates the ratio of both outputs, a signal with improved sensitivity depending on N is obtained as shown in the following equation, and the turbidity x can be calculated backwards.

I _N c=A ^N x ^N …(6) In this Figure 4, the system of transmitted light is indicated by the subscript “a”
, and the system of scattered light is given the subscript "b". That is, the light source 1a, the detector 4a, the pulse lighting circuit 6a, and the hold circuit 8a represent a system for transmitted light. Further, a light source 1b, a detector 4b, a pulse lighting circuit 6b, and a hold circuit 8b represent a system for scattered light.

Furthermore, the same method can be used to calculate turbidity from the ratio of two scattered lights as shown in Figure 5, or to calculate turbidity from the ratio of two transmitted lights as shown in Figure 6. can. In these cases, the output of the comparison circuit 11 is expressed as I _N c=exp[NBx (l ₁ -l ₂ )] (7), and the sensitivity can be improved according to N.

In addition, in optical systems that use two light sources, measures such as providing a slit or the like to prevent interference with each detector or changing the wavelength of the light source to provide wavelength selectivity on the receiving side are added. You can.

As described above, according to this invention, the light source can be turned on several times, and the first time it is turned on, it emits light at a preset brightness, and from the second time onwards, it emits light at a preset brightness. The light source emits light at a brightness that corresponds to the brightness of the light, and the light source is turned on multiple times depending on the measured value, making it possible to measure a wide range of turbidity with one optical system and at the optimum temperature. There is an effect that a meter can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional turbidity meter, FIG. 2 is a diagram showing the configuration of an embodiment of the turbidity meter of this invention,
FIGS. 3 to 6 are diagrams showing the configurations of other embodiments of the turbidity meter of this invention, respectively. 1, 1a, 1b...Light source, 2...Window, 3...Measurement target liquid, 4, 4a, 4b...Detector, 6, 6
a, 6b...Pulse lighting circuit, 7...Timing circuit, 8, 8a, 8b...Hold circuit, 9...
Arithmetic circuit, 11...comparison circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims for Utility Model Registration] (1) A light source that irradiates light onto a measurement target, a detector that detects the transmitted light of the measurement target, and a detection value of the detector that determines the brightness of the next light emission from the light source. a timing means for lighting the light source multiple times until the detected value obtained as a result becomes equal to or less than an arbitrary value set in advance; a holding means for holding the detection signal of the detector; and the holding means A turbidity meter characterized by being provided with a lighting means for controlling the lighting level of the light source according to the hold value held by the light source, and a calculation means for calculating turbidity by calculation from the number of lighting times of the light source and the hold value. . (2) The turbidity meter according to claim 1, wherein the detector detects light scattered by the object to be measured. (3) Two light sources are provided, each of which irradiates light onto the measurement target, and the detector is configured to detect transmitted light and scattered light, which are transmitted through the measurement target by the irradiated light from the two light sources. Two timing means are provided to turn on each of the two light sources until the detected value by one of the detectors becomes equal to or less than an arbitrary value set in advance, and the hold means is provided to turn on each of the two light sources until the detected value by one of the detectors becomes equal to or less than a preset arbitrary value. There are two lighting devices, each holding the detection value of the device.
Two light sources are provided so as to be controlled according to the lighting level of the light source and the detection value of each of the two detectors,
The turbidity meter according to claim 1, wherein the calculation means calculates the turbidity of the object to be measured from the comparison value obtained by the comparison means and the number of lighting times. (4) The turbidity meter according to claim 3, wherein the detector detects each scattered light from two light sources. (5) The turbidity meter according to claim 3, wherein the detector detects transmitted light from each of two light sources.