CN104089877B - A kind of wide-range scope turbidimeter - Google Patents

Abstract

The invention discloses a turbidimeter with a wide measuring range, which is composed of a variable angle mechanism, an adjustable luminous flux attenuator, a light source emitter and a sample pool. When measuring low turbidity samples, the scattered light intensity is relatively weak, and the variable angle mechanism is used for measurement, which can increase the measurable scattered light intensity by increasing the area of measurable scattered light; when measuring high turbidity samples, too high The intensity of scattered light will cause overflow of the detector signal, and the correct turbidity value cannot be obtained. At this time, an adjustable light attenuator is used to adjust the light flux entering the sample cell, reduce the intensity of scattered light, and increase the measurable turbidity range. The turbidity of the sample is determined by the transmitted light intensity, and the corresponding attenuator aperture is selected through the corresponding signal feedback mechanism. The invention adopts different measurement methods for samples with different turbidities, and finally realizes the purpose of wide range and accurate measurement.

Description

A wide range turbidimeter

technical field

The invention belongs to the technical field of optical measuring instruments, and in particular relates to a turbidimeter with a wide measuring range.

Background technique

Turbidity, that is, the turbidity of water, is caused by a small amount of insoluble suspended matter and colloidal matter in the water. The turbidity meter, also known as the turbidity meter, can be used to test the turbidity of water samples in water plants, power plants, industrial and mining enterprises, laboratories and field sites. The measurement of turbidity is of great significance in people's life and industrial production. Especially in environmental monitoring, food, medicine, electronics and energy industries, the turbidity of the medium must be monitored in the production process to achieve the purpose of controlling the production process and improving product quality.

With the development of science and technology and people's emphasis on health, when testing water quality, the requirements for turbidity value measurement are gradually increasing, so the design of a new type of turbidity meter is quite necessary. In conventional optical turbidimeters, the measurement angle (detector) of scattered light is generally 90 degrees perpendicular to the incident light source. In this way, for low-concentration samples, the area for receiving scattered light is small, so it is not easy to give An accurate measurement result; for high turbidity samples, the intensity of received scattered light is too large to exceed the detection range of the detector and cannot be measured. The present invention is designed to solve these problems.

Contents of the invention

In order to solve the above problems, the present invention provides a turbidimeter with a wide measuring range. It adopts the scattered light measurement method, and adopts different measurement methods through the turbidimeter according to the level of turbidity. The utility model has the advantages of simple structure, ingenious conception, simple method for turbidity measurement, suitable for wide range measurement, and accurate measurement result.

The wide-range turbidimeter of the present invention adopts the design of variable angle mechanism and adjustable optical attenuator; the variable angle mechanism is used for the detection of low turbidity samples, which controls the angle between the incident beam and the scattered beam to be 90-180 degrees Between, the lower the turbidity, the smaller the angle, so as to ensure a large detection area and strong detection signal intensity, so as to achieve the purpose of accurate measurement; the adjustable light attenuator is used for the detection of high turbidity samples, which can effectively reduce the amount of incoming samples Light intensity, reduce scattered light intensity, increase sample turbidity measurement range. When measuring high turbidity samples, the angle between the incident beam and the scattered beam is controlled to be 90 degrees.

The technical solution of the present invention is specifically introduced as follows.

A turbidimeter with a wide range, which is composed of a variable angle mechanism, an adjustable luminous flux attenuator, a light source emitter and a sample cell; wherein:

The variable angle mechanism includes a stepper motor, a bevel worm, a crank rocker mechanism and a detector; a bevel gear is fixedly arranged on the shaft of the stepper motor through a top screw, and the gear of the bevel gear and the bevel worm is externally meshed; The crank-rocker mechanism includes a fixed base for the active part, a fixed base for the driven part, a crank, a connecting rod, a rocker and a 1/4 arc; a fixed base for the active part, a fixed base for the driven part and 1/4 The arc part is placed on the horizontal plane; the connecting rod is respectively connected to the crank and the rocker through the hinge, and the screw transmission is used between the crank and the bearing of the fixed base of the active part, and between the bearings of the rocker and the fixed base of the follower; Screw transmission between one end of the cone worm and the bearing of the fixed base of the active part in the crank-rocker mechanism; the center of the 1/4 arc part is the connection point between the rocker and the fixed base bearing of the driven part, and the radius is The length of the rocker, a chute is provided on the surface of the 1/4 arc piece; the detector is placed in the chute of the 1/4 arc piece, and its bottom is fixedly connected with the rocker; the light source emitter is arranged on the crank between the fixed base of the active part and the fixed base of the driven part of the rod mechanism, and located on the side close to the fixed base of the active part; the sample pool is fixedly arranged above the fixed base of the driven part; the adjustable luminous flux The attenuator is placed between the light source emitter and the sample cell.

The above-mentioned adjustable luminous flux attenuator is placed on a liftable and fixed base.

The above-mentioned adjustable luminous flux attenuator is a mechanical sheet light-shielding attenuator.

The beneficial effects of the present invention are: the present invention is simple in structure and ingenious in conception. Through the structural design of the variable angle mechanism and the adjustable optical attenuator, different measurement methods are adopted for samples with different turbidities, and finally a wide range range, for precise measurement purposes.

Description of drawings

Fig. 1 is a schematic diagram of the structure of a wide range turbidimeter in the present invention.

Fig. 2 is a schematic diagram of the principle of variable angle scattering measurement of turbidity in the present invention.

Fig. 3 is a schematic diagram of the transmission structure of the crank-rocker mechanism in the variable-angle mechanism design system of the present invention.

Fig. 4 is a schematic diagram of the signal flow of the stepping motor in the variable angle mechanism design system of the present invention.

Fig. 5 is a schematic structural diagram of the adjustable attenuator VOA in the present invention.

Fig. 6 is a working flowchart of the adjustable attenuator VOA in the present invention.

Symbols in the figure: 1-stepping motor; 2-bevel gear; 3-cone worm; 4-crank rocker mechanism; 5-light source emitter; Sample pool; 9-detector; 40-active part fixed base; 41-follower fixed base; 42-crank; 43-connecting rod; 44-rocker; 45-1/4 arc piece.

detailed description

In order to further describe the specific content of the present invention in detail, the following examples are listed, and the detailed description is as follows in conjunction with the accompanying drawings.

Example 1

Fig. 1 is a schematic diagram of the structure of a wide range turbidimeter in the present invention.

The stepping motor 1 is used as the power element of the entire turbidimeter, and the shaft of the stepping motor 1 is fixed with a bevel gear 2 through a top screw, and the bevel gear 2 and the gear of the bevel worm 3 are externally meshed; the bearing of the bevel worm 3 is in contact with the stepping motor The orbiting bearing space of 1 is vertical, and is used for slowing down the output power of stepping motor 1.

Crank and rocker mechanism 4 is made up of active part fixed base 40, follower fixed base 41, crank 42, connecting rod 43, rocking bar 44 and 1/4 arc part 45. The connecting rod 43 in the crank-rocker mechanism connects the crank 42 and the rocking bar 44 through a hinge. Between crank 42 and the bearing of driving part fixed base 40, and between the bearing of rocking bar 44 and follower fixed base 41, spiral rotation, the threaded bearing end of bevel worm screw 3 and crank rocker mechanism 4 The shaft of the active part fixes the base 40 to rotate helically.

The sample cell 8 is fixed on the follower fixing base 41 . The light source emitter 5 is located between the fixed base 40 of the active part and the fixed base 41 of the driven part in the crank rocker mechanism 4, close to the side of the fixed base 40 of the active part, and the light beam emitted by the light source emitter 5 is parallel to the sample cell 8 The connecting line with the fixed base 40 of the active part.

The 1/4 arc part 45 is a 90-degree to 180-degree thin arc made with the rocker 44 as the radius and the connection point between the follower fixing base 41 and the rocker 44 as the center of the circle, and the 1/4 arc A chute is set on the part 45, and the detector 9 is placed in the chute, and is connected with the rocker 44 in the crank-rocker mechanism 4, and with the reciprocating swing of the crank-rocker mechanism 4, the detector 9 is in the 1/4 arc Slide on the piece 45 to realize the variable angle detection of the sample turbidity of the detector 9 to obtain the sample turbidity value.

The adjustable luminous flux attenuator 6 is arranged between the light source emitter 5 and the sample cell 8 ; at the same time, the adjustable luminous flux attenuator 6 can be placed on the liftable base 7 . When the turbidity of the sample is large and the light intensity of the incident light beam needs to be attenuated, manually press the up button of the liftable base 7 to make the light beam attenuate through the adjustable luminous flux attenuator 6 before reaching the sample cell; when the sample is turbid When the light intensity is small and there is no need to attenuate the light intensity of the incident beam, manually press the lower button of the liftable base 7 to make the beam directly reach the sample cell 8.

During detection, the operator needs to analyze the turbidity value signal to see if the turbidity value is within the detection range and whether it is the correct turbidity value, and then decide whether to change the detection angle of the detector 9, whether it is necessary to add an adjustable luminous flux attenuator 5 and carry out adjust.

The following will describe in detail how to perform turbidity detection on samples with a wide range for the design of the variable angle mechanism and the design of the adjustable luminous flux attenuator 5 respectively.

1. Design of variable angle mechanism

In the present invention, a variable angle mechanism design is adopted to detect low turbidity samples. It utilizes the principle of variable angle scattering to measure turbidity, as shown in Figure 2.

The reason for using variable angle scattering is that the detection area is different for different incident angles. Figure 2a and Figure 2b are comparisons of the scattered light area in the sample received by the detector under different scattering angles. Assuming that the width of the incident light is 1, the width of the optical path of the scattered light entering the detector is also 1:

=1 1=1

= L 1= 1 0< <1 >1 ie >

Such as: when =120 degrees, =1 1=2>

when =110 degrees, =1 1=1.06>

It can be seen from the above formula that the sample area corresponding to the light passing through the 90-180 degree variable angle scattered light is larger than the sample area corresponding to the light passing through when the scattered light is 90 degrees perpendicular, so that the turbidity measurement value obtained in this way is more accurate, and the variable angle scattered light ratio Right-angle scattered light is more advantageous in turbidity measurement. In the range of low turbidity, different measurement angles can be used for samples with different turbidity. Samples with high turbidity use a large measurement angle; water bodies with low turbidity use a small measurement angle to ensure a large detection area. , to ensure the strength of the detection signal.

In the variable angle mechanism design system of the present invention, the bevel worm 3 is a reduction mechanism. Conical worm transmission is suitable for cross-shaft transmission with a transmission ratio greater than 10 (it may not be 90 degrees). The bevel worm 3 is easy to manufacture and assemble, and the axial displacement of the bevel worm does not destroy the tooth surface conjugation. The conical worm has stable transmission, large load capacity, high efficiency, compact structure when the transmission ratio is large, and self-locking when the worm reverses stroke, suitable for turbidimeter measurement, and can also fix the angle through such a mechanical structure.

The structural diagram of the crank rocker mechanism 4 in the variable angle mechanism design system of the present invention is shown in FIG. 3 . The crank-rocker mechanism 4 is an actuator in the mechanical system, and the crank-rocker mechanism 4 has a snap-back characteristic, which shortens the non-measurement time and shortens the overall measurement time of the sample. Considering that the target object measured by the turbidity meter contains acid and alkali substances, the material of the crank rocker mechanism 4 should be selected from materials with good mechanical properties, moisture resistance and corrosion resistance.

The flow diagram of the stepper motor 1 signal in the variable angle mechanism design system of the present invention is shown in FIG. 4 .

The stepper motor 1 is the control mechanism in the mechanical system. It converts the electric pulse signal into an open-loop control element of angular displacement or linear displacement. When the stepper driver receives a pulse signal, it drives the stepper motor 1 according to the setting. Rotate a fixed angle in a given direction, called "step angle θ", θ=360 degrees/(number of rotor teeth)*number of operating pulses, and its rotation runs step by step at the step angle θ. The angle at which the detector 9 is located is the best measurement angle when the detector receives the largest signal and no signal overflows. Every time the detector 9 passes through the angle of a specific distance, it will pause due to the characteristics of the stepping motor, and record the turbidity value detected by a detector at this time.

When the variable angle mechanism is used to detect low turbidity samples, the detector 9 is first placed at the maximum angle of nearly 180 degrees (ie close to the horizontal position) to obtain a maximum reference turbidity value. Then first judge whether the signal overflow occurs in the detector 9. The judgment method is to adjust the number of pulses sent by the stepper motor 1 to form a large-angle step angle, and order the stepper motor 1 to work again, which is equivalent to coarse adjustment. After the angle step angle, stop again according to the characteristics of the stepping point machine 1, and record the detected turbidity value. If the obtained turbidity value is consistent with the maximum reference turbidity value, it means that the signal of the detector 9 overflows, and the detection angle needs to be reduced again, and so on, until the measured turbidity value is just lower than the maximum reference turbidity value, which is Check the turbidity value. If the obtained turbidity value is smaller than the maximum reference turbidity value, it means that the signal of the detector 9 does not overflow. At this time, the stepping motor 1 needs to send a pulse signal for a unit angle to increase the detection angle and order the stepping machine to work again. For fine adjustment, after walking a unit angle again, stop again according to the characteristics of the stepper, record the turbidity value detected at this time, and compare it with the maximum reference turbidity value, repeat the above steps until the measured turbidity value The turbidity value is just lower than the maximum reference turbidity value, which is the detection turbidity value. In short, the turbidity value obtained by rough adjustment first and then fine adjustment just does not increase due to the increase of the detection angle is the measured turbidity value of the sample.

In the present invention, the setting of the adjustable luminous flux attenuator 6 is used for testing high turbidity samples. The adjustable optical attenuation reducer 6 adopts the adjustable attenuator VOA as shown in Figure 5. This optical attenuator has the advantages of mature technology, good optical characteristics, low insertion loss, small polarization-dependent loss, and no need for temperature control. It can effectively reduce the light intensity entering the sample, reduce the scattered light intensity, prevent the light receiver from being saturated, and keep the scattered light within the detection range of the detector 9 .

The working flow chart of the adjustable attenuator VOA is shown in Figure 6. Different apertures on the adjustable attenuator VOA represent different attenuation coefficients. The selection of the attenuation coefficient refers to the transmitted light intensity, that is, to set a certain transmitted light intensity. If it is lower than the measured threshold, it means that the turbidity of the sample is high, and an attenuator needs to be added. If it is lower than a certain threshold, it means that the turbidity of the sample is relatively low, and there is no need to attenuate the light source.

When the adjustable luminous flux attenuator 6 is used for the detection of high turbidity samples, the variable angle mechanism is adjusted to 90 degrees (that is, the detector 9 is located at the highest point of the 1/4 arc piece 45), and the sample is assumed to be the maximum turbidity , choose the smallest aperture with the smallest attenuation coefficient, the smallest transmitted light intensity, and the largest scattered light intensity to obtain the largest reference turbidity value. Then determine whether the detector 9 has signal overflow, the determination method is to select a larger aperture, obtain a turbidity value, and compare it with the maximum reference turbidity value. If it is consistent with the maximum reference turbidity value, it means that the signal overflows. At this time, it is necessary to select a larger aperture and perform a rough adjustment, and compare the obtained turbidity value with the maximum reference turbidity value again, and repeat the above steps; If the value is small, it is necessary to select a smaller aperture and fine-tune it until the obtained turbidity value does not change due to the change of the aperture. The turbidity value does not become smaller due to the increase of the pore size, and the turbidity value obtained at this time is the measured turbidity value.

Claims (3)

1. A wide range turbidimeter is characterized in that: it is made up of a variable angle mechanism, an adjustable luminous flux attenuator, a light source emitter and a sample cell; wherein: The variable angle mechanism includes a stepper motor, a bevel worm, a crank rocker mechanism and a detector; a bevel gear is fixedly arranged on the shaft of the stepper motor through a top screw, and the gear of the bevel gear and the bevel worm is externally meshed; The crank-rocker mechanism includes a fixed base for the active part, a fixed base for the driven part, a crank, a connecting rod, a rocker and a 1/4 arc; a fixed base for the active part, a fixed base for the driven part and 1/4 The arc part is placed on the horizontal plane; the connecting rod is respectively connected to the crank and the rocker through the hinge, and the screw transmission is used between the crank and the bearing of the fixed base of the active part, and between the bearings of the rocker and the fixed base of the follower; A screw transmission is adopted between one end of the cone worm and the bearing of the fixed base of the active part in the crank-rocker mechanism; For the length of the rocker, a chute is provided on the surface of 1/4 arc; the detector is placed in the chute of 1/4 arc, and its bottom is fixedly connected with the rocker; the light source emitter is arranged on the crank between the fixed base of the active part and the fixed base of the driven part of the rocker mechanism, and is located on the side close to the fixed base of the active part; the sample pool is fixedly arranged above the fixed base of the driven part; the adjustable A luminous flux attenuator is placed between the light source emitter and the sample cell. 2. The wide-range turbidimeter according to claim 1, characterized in that: the adjustable luminous flux attenuator is placed on a liftable and fixed base. 3. The wide range turbidimeter according to claim 1 or 2, characterized in that: the adjustable luminous flux attenuator is a mechanical sheet light-blocking attenuator.