KR200261239Y1 - Level detecter by using near infrared laser diode and photodiode - Google Patents

Abstract

The present invention relates to a level detector using a near-infrared laser diode light source and a photodiode. An optical sensor is installed outside the sample tube such that the optical axis of the optical sensor has an inclination angle with the liquid surface inside the sample tube. The refraction property is used to detect and control the position of the liquid surface inside the sample tube.

Description

Level detector by using near infrared laser diode and photodiode

The present invention relates to a level detector using a near-infrared laser diode light source and a photodiode. An optical sensor is installed outside the sample tube such that the optical axis of the optical sensor has an inclination angle with the liquid surface inside the sample tube. The refraction property is used to detect and control the position of the liquid surface inside the sample tube.

The optical sensor that can be used as a sensor of the level detector for detecting the position of the liquid in the sample tube is generally composed of a light transmitting element for irradiating light and a light receiving element for receiving light that transmits or reflects the liquid in the sample tube. . The method of receiving light passing through the liquid in the sample tube is used by detecting the degree of transmission after the liquid absorbs the light. At this time, the sample tube has an upper limit and a lower limit, and a pair of light sources and detectors are installed in accordance with the upper limit, and a pair of light sources and detectors is installed in accordance with the lower limit. However, in this case, it is difficult to deal with the minute change caused by the liquid in the sample tube. The level detector is based on a fiber type optical sensor that has an amplifier part containing an optical sensor and a signal processing circuit and a fiber part that transmits light to a detection location. The level detector utilizes red light (wavelength 660 nm) or green light (wavelength 560 nm) and infrared light. Carry out the presence or absence of an object, detect position, etc. Optical fiber has the most widely used red light because the wavelength transmission efficiency and the red light is visible light, the optical axis is easy to adjust and the position of detection is easy. However, pulse modulated light sources should be used to prevent external noise such as sunlight and incandescent lamps. Green light is mainly used for mark detection or semi-transparent body detection. Light output is weaker than red light, so the detection distance is about 1/10 of red light. Therefore, there is a constraint on where a long detection distance is required. Infrared light has been used for the purpose of detecting a semi-transparent body by detecting a photosensitive film or transmitting a translucent body in combination with a glass fiber or a plastic fiber of 10 cm or less in length.

Even if the translucent liquid is present in the sample tube, the liquid position in the sample tube can be handled by the turbidity and chromaticity without difficulty, and the liquid in the sample tube can handle the minute change. The necessity of the level detector applicable to the industrial site which needs to control the position of the liquid inside the sample tube which requires a long detection distance while preventing the external light noise such as light and incandescent light has increased. The purpose of the present invention is to cope with the necessity, and to detect the position of the liquid contained in the sample tube from outside the sample tube without direct contact with the liquid, thereby preventing contamination of the liquids of the laser diodes and the photodiode. It is possible to measure the position of liquid without chemical reaction between optical sensor and its liquid, It has a level detector with a near infrared laser diode light source and a photo diode to control the value to provide.

1 is a block diagram showing the general configuration of a level detector using a near infrared laser diode light source and a photodiode according to the present invention as an electrical signal.

2 is a block diagram showing an installation configuration of a laser diode and a photodiode, which are optical sensors of a level detector using a near infrared laser diode light source and a photodiode according to the present invention.

<Explanation of symbols for main parts of drawing>

1: power supply

2: laser diode light source

2-1, 2-2: laser diode light source

3: sample tube

4: light detector

4-1, 4-2: photodiode

5: photo amplifier

5-1: Current-to-Voltage Converter Circuit

5-2: OP Amplification Circuit

6: Schmitt trigger circuit

6-1, 6-2: Schmitt trigger circuit

7: display unit

7-1, 7-2: LED

8: digital signal output

9: Negative One-Shot Circuitry

10: upper limit

11: lower limit

12-1, 12-2: Line passing through the laser diode center point

13-1, 13-2: Line through the center of the photodiode

14: motor

15: amplifier

A preferred embodiment of a level detector using a near-infrared laser diode light source and a photodiode according to the present invention will be described with reference to the accompanying drawings.

1 is a block diagram showing the general configuration of a level detector using a near infrared laser diode light source and a photodiode according to the present invention as an electrical signal.

2 is a block diagram showing an installation configuration of a laser diode and a photodiode which are light sensors of a level detector using a near infrared laser diode light source and a photodiode according to the present invention.

1, a level detector using a near-infrared laser diode light source and a photodiode according to the present invention is a laser diode light source 2-1, which is provided from the outside of the sample tube 3 after turning on the power of the power supply unit 1, Photoelectric amplification which detects the position of the liquid in the sample tube 3 as an optical signal through the photodiodes 4-1 and 4-2 and converts the detected optical signal into an electrical signal according to 2-2). The display unit 7 which is on / off according to the electrical signal of the Schmitt trigger circuit unit 6 and the Schmitt trigger circuit unit 6, which receives the electrical signal output from the photoelectric amplifier unit and compares the reference signal with a reference value. ), And a digital signal output unit 8 for outputting with an electrical pulse so as to control the position of the liquid contained in the sample tube 3. Referring to Fig. 2, the sample tube has an upper limit line 10 and a lower limit line 11, and a laser diode 2-2 as a light source is installed above the upper limit line 10, and a photodiode as a detector coincides with the upper limit line 10. A pair of (4-2) is provided, and a laser diode (2-1) as a light source is installed in accordance with the lower limit line (11), and another pair of photodiodes (4-1) as a detector are provided below the lower limit line (11). Install it. A photodiode (4-) parallel to the upper limit line (10) above the upper limit line (10) and coinciding with the upper limit line (12-2) and the upper limit line (10) passing through the center point of the laser diode (2-2). Line 13-2 passing through the center point of 2), line 12-1 passing through the center point of the laser diode 2-1 parallel to the lower limit line 11, and below the lower limit line 11 In Fig. 2, a line 13-1 and the like parallel to the lower limit line 11 and passing through the center point of the photodiode 4-1 are irradiated with a near infrared ray to the liquid in the sample tube with a laser diode. A method of detecting the position of a liquid with or without light reception through a photodiode of refracting light is used.

In addition, near-infrared rays are irradiated to the liquid in the sample tube with a laser diode and light refracted by the liquid is received by the photodiode to detect the position of the liquid, but the photo-amplification part 5 and the current-to-voltage converter circuit part 5-1 ), OP amplifier amplification circuit section 5-2, Schmitt trigger circuit section 6, display section 7, LEDs 7-1, 7-2, digital signal output section 8, negative one-shot circuit section ( 9) The connecting line between the built-in amplifier 15 and the light sensors 2-1, 2-2, 4-1, 4-2 can be more than 2 meters in length, and it can cope with chemicals, heat resistance, In order to reduce the influence of external light noise of incandescent lamps, flexible shield lines are used, and the choice of near-infrared laser diode light sources with a wavelength of 700 nm to 2500 nm can be expanded.

A light detector that provides light to the outside of the sample tube by the laser diode light sources 2-1 and 2-2 of the laser diode light source unit 2 according to the refractive angle of the light in the liquid in the sample tube. The photo-amplification unit 5 is responsible for amplifying and outputting the signal after being detected through the photodiodes 4-1 and 4-2 of 4).

Schmitt trigger circuitry 6 receives the electrical signal output from the photoelectric amplifier 5 and compares with the reference value, the display 7 is on / off according to the voltage output from the Schmitt trigger circuitry (6) Consisting of LEDs 7-1 and 7-2. The negative one-shot circuit unit 9 is a circuit in which an output signal is output in the form of a pulse according to an input signal.

The operation of the level detector using the near infrared laser diode light source and the photodiode according to the present invention configured as described above will be described in detail with reference to FIG. 1.

The position of the liquid flowing into the sample tube 3 is divided into an upper layer and a lower layer. Here, in order to measure the position of the liquid in the lower part of the sample tube 3, the laser diode light source part 2 and the light detection part 4 are fixed to the sample tube 3 outside. Light from the laser diode light sources 2-1 and 2-2 is emitted at a predetermined height above or below the sample tube 3.

The photo-amplification unit 5 is a photodiode after the light of the upper or lower portion of the sample tube 3 is used in accordance with the near-infrared laser diode light sources 2-1 and 2-2 provided from the outside of the sample tube 3. After the position of the liquid in the sample tube 3 is detected as an optical signal through 10, the detected optical signal is converted into an electrical signal using the current-to-voltage converter circuit section 5-1 to operate the OP amplifier. After amplifying by the amplifying circuit unit (5-2) serves to transmit a signal to the display unit (7) consisting of LEDs (7-1, 7-2). Between the sample tube upper limit (10) and the lower limit (11) When the liquid of P crosses the upper limit, the photodiode 4-2 of the photodiode detection unit 4 does not detect near infrared rays. If the photodiode (4-2) is not turned on, the Schmitt trigger circuit unit 6-2 compares the applied voltage with the reference voltage and causes a voltage of 5V to flow toward the LED 7-2 and turns on the LED 7-2. . The negative one-shot circuit unit 9 outputs a pulse signal to the digital signal output unit 8 to stop driving of the motor 14 for controlling the position of the liquid. The negative one-shot circuit unit 9 does not output a pulse signal for driving the motor until the liquid passes below the lower limit again.

When the liquid in the sample tube passes above the upper limit 10 or below the lower limit 11, the photodiode 4-1 or the photodiode 4-2 of the photodetector 4 detects light. . When the photodiode (4-1) or photodiode (4-2) is turned on, the Schmitt trigger circuit 6-1 or Schmitt trigger circuit 6-2 compares the applied voltage with the reference voltage and the voltage is 5V LED. No current flows to the 7-1 or the LED 7-2, so the LED 7-1 or the LED 7-2 is turned off.

The level detector using the near-infrared laser diode light source and the photodiode of the present invention uses a laser diode as a light source and a photodiode as a light detector. Current-to-Voltage Converter circuit part, OP amplifier amplification circuit part, Schmitt trigger circuit part and Negative One-Shot circuit part are used.

The level detector using the near-infrared laser diode light source and the photodiode according to the present invention has superior linearity and intensity than the light emitting diode by using the near-infrared laser diode light source for the light of the upper and lower portions of the sample tube, and the semi-transparent inside the sample tube by using the near infrared ray. Even in the presence of a liquid, it is possible to effectively detect and control the problem while solving a problem of difficult position detection due to turbidity and chromaticity. In addition, laser diodes and photodiodes, which are optical sensors, are free from contamination due to liquid, and the position of the liquid can be measured without chemical reaction with the liquid in the optical sensor and the sample tube. An optical sensor is installed outside the sample tube so that the photodiode can detect the light using the characteristic that the light irradiated from the near-infrared laser diode source is refracted at the liquid surface inside the sample tube, but the optical axis has an inclination angle with respect to the liquid surface inside the sample tube. Install. In this way, a small change in the output signal due to the swelling of the liquid inside the sample tube can be solved with the help of the negative one-shot circuit unit, and an advantage of preventing external light noise such as sunlight and incandescent lamps can be obtained.

Claims (2)

The position of the liquid inside the sample tube is detected as an optical signal using a photodiode of the photo detector according to the near-infrared laser diode light source provided outside the sample tube, and the detected optical signal is converted into a current-to-voltage converter circuit. A photo-amplification unit for converting the signal into an electrical signal using the OP amplifier amplifying circuit unit and outputting the converted signal; A Schmitt trigger circuit unit configured to receive an electrical signal output from the photoelectric amplifier and compare it with a reference value; A display unit turned on / off according to a voltage output from the schmitt trigger circuit unit; A level detector using a near-infrared laser diode light source and a photodiode, comprising a negative one-shot circuit unit in which an output signal is pulsed according to an input signal input from a schmitt trigger circuit unit. The method of claim 1, wherein the laser diode light source and the photodiode emitting near infrared light are fixed to the outside of the sample tube, and a pair of laser diode and photodiode are configured as a pair, and the upper and lower pairs are formed outside the sample tube, and the near infrared laser diode The optical axis connecting the center point of the light source and the center point of the photodiode has an inclination angle with the liquid surface inside the sample tube, and the photodiode can be detected or not by utilizing the property that the light irradiated from the near infrared laser diode light source is refracted at the liquid surface. A level detector using a near-infrared laser diode light source and a photodiode, comprising an optical sensor configured outside the sample tube.