Photoelectric flow meter circuit and photoelectric flow meter

Abstract

This invention discloses a photoelectric flow meter circuit and a photoelectric flow meter. The photoelectric flow meter circuit includes: a light-emitting element, a phototransistor, and a DC blocking circuit. The circuit power supply terminal is electrically connected to one end of the light-emitting element and the collector of the phototransistor, respectively. The other end of the light-emitting element and the emitter of the phototransistor are grounded. The collector of the phototransistor is electrically connected to the circuit output terminal through the DC blocking circuit. By adding a DC blocking circuit, this invention eliminates the DC bias voltage, thus enabling the output of a standard level signal even when scale buildup adheres to the flow meter housing or the light intensity of the photoelectric emitter gradually weakens due to long-term operation. This allows the flow meter to withstand more severe scale buildup and extends its service life.

Description

Technical Field

[0001] This invention relates to the technical field of measuring equipment, and in particular to a photoelectric flow meter circuit and a photoelectric flow meter. Background Technology

[0002] Existing photoelectric flow meters use light-emitting diodes (LEDs) to emit light, which is received by a phototransistor. An impeller is located between the LED and the phototransistor. Driven by the liquid, the impeller intermittently blocks the light path between the LED and the phototransistor, causing the phototransistor to output a corresponding signal. Its circuit diagram is shown below. Figure 1 and Figure 2 As shown.

[0003] An existing photoelectric flow meter circuit, such as Figure 1 As shown, the power supply terminal 1' of the circuit is electrically connected to the collectors of the light-emitting diode D1' and the phototransistor Q1' through resistors R1' and R2' respectively. The other end of the light-emitting diode D1' and the emitter of the phototransistor Q1' are connected to ground VSS. Resistor R2' is used as a pull-up resistor. The signal output is directly led out from the collector of the phototransistor Q1' through terminal 2', and the output signal is acquired by the microcontroller unit (MCU).

[0004] Another existing photoelectric flow meter circuit, such as Figure 2 As shown, the circuit power supply terminal 1' is electrically connected to the collectors of LED D1' and phototransistor Q1' through resistors R1' and R2' respectively. The other end of LED D1' and the emitter of phototransistor Q1' are connected to ground VSS. Resistor R2' serves as a pull-up resistor. The collector of phototransistor Q1' is connected to the base of phototransistor Q2' after voltage division through resistors R3' and R4'. The circuit power supply terminal 1' is connected to the collector of phototransistor Q2' through resistor R5'. The output signal is led out from the collector of phototransistor Q2' through terminal 2' and is acquired by the microcontroller unit (MCU).

[0005] However, due to water quality issues or the photoelectric emitter's luminous intensity gradually weakening due to long-term operation, existing photoelectric flow meters fail when the light-transmitting part of the flow meter housing is covered with scale, causing the photoelectric emitter's luminous intensity to gradually weaken due to long-term operation, resulting in an increase in signal trough.

[0006] like Figure 3The diagram shows the output waveform of a scale-free casing in existing technology. The output is a TTL pulse signal, where the high level is 2.5V and the low level is 0.08V. Existing microcontrollers use Schmitt triggering at the input. The rule for TTL level judgment is: less than 0.8V is low level, and greater than 2V is high level. However, with Schmitt triggering, when the level is higher than 2V (triggering high threshold), it is high. Afterward, unless the level drops below 0.8V, triggering the low threshold voltage and becoming low, it remains high. Therefore, for Schmitt triggering, 0.8–5V is high. Conversely, when at a low level, it only becomes high when the voltage increases above 2V, triggering the high level threshold; that is, 0–2V is low. Therefore, when the initial position of the light-blocking rotor is such that the input voltage is 0.5V (low level), water is injected and the rotor continues to rotate. When the light is completely blocked, the receiving tube is cut off. Due to the pull-up resistor, the output is 5V (high level). The rotor continues to rotate, and the light received by the receiving tube gradually becomes stronger, that is, it gradually conducts. However, due to the scale, the lowest point of the wave is >0.8V, which cannot trigger the Schmitt low threshold. The output voltage detected by the microcontroller unit is still high level.

[0007] Therefore, when the microcontroller detects an output voltage above 1.2V, it interprets it as a high level. However, if... Figure 4 The diagram shows the output waveform of a prior art casing with scale buildup. Scale buildup causes a DC bias voltage. When this voltage exceeds 1.2V, the trough of the output waveform will also exceed 1.2V. In this case, the microcontroller will mistakenly interpret a low level as a high level, thus malfunctioning. Summary of the Invention

[0008] Based on this, it is necessary to address the technical problem of existing photoelectric flow meters where the light-transmitting part of the flow meter housing gradually weakens due to scale buildup or the photoelectric emitting tube gradually weakens due to long-term operation, leading to an increase in signal trough and eventual failure. Therefore, a photoelectric flow meter circuit and a photoelectric flow meter should be provided.

[0009] This invention provides a photoelectric flow meter circuit, comprising: a light-emitting element, a phototransistor, and a DC blocking circuit. The power supply terminal of the circuit is electrically connected to one end of the light-emitting element and the collector of the phototransistor, respectively. The other end of the light-emitting element and the emitter of the phototransistor are grounded. The collector of the phototransistor is electrically connected to the output terminal of the circuit through the DC blocking circuit.

[0010] Furthermore, the DC blocking circuit includes a high-pass filter circuit, one end of which is electrically connected to the collector of the phototransistor, and the other end of which is electrically connected to the output terminal of the circuit.

[0011] Furthermore, the high-pass filter circuit includes a filter capacitor and a filter resistor. One end of the filter capacitor is electrically connected to the collector of the phototransistor, and the other end is grounded through the filter resistor. The connection point between the filter capacitor and the filter resistor is electrically connected to the output terminal of the circuit.

[0012] Furthermore, the DC blocking circuit also includes a clamping diode, one end of which is electrically connected to the output terminal of the circuit, and the other end is grounded.

[0013] Furthermore, it also includes an amplifier circuit, and the DC blocking circuit is electrically connected to the output terminal of the circuit through the amplifier circuit.

[0014] Furthermore, the amplification circuit includes a signal output transistor, one end of the DC blocking circuit is electrically connected to the collector of the phototransistor, and the other end is electrically connected to the base of the signal output transistor. The collector of the signal output transistor is electrically connected to the output terminal of the circuit.

[0015] Furthermore, the amplification circuit also includes a first resistor and a second resistor. The power supply terminal of the circuit is electrically connected to the collector of the signal output transistor through the first resistor, and the other end of the DC blocking circuit is electrically connected to the base of the signal output transistor through the second resistor.

[0016] Furthermore, the power supply terminal of the circuit is electrically connected to the collector of the phototransistor through a third resistor, and the power supply terminal of the circuit is electrically connected to the light-emitting element through a fourth resistor.

[0017] Furthermore, the light-emitting element is a light-emitting diode (LED).

[0018] The present invention provides a photoelectric flow meter, including a flow meter housing and a photoelectric flow meter circuit as described above, wherein the photoelectric flow meter circuit is housed within the flow meter housing.

[0019] This invention eliminates the DC bias voltage by adding a DC blocking circuit, so that even when scale adheres to the flow meter housing or the photoelectric emitter's light intensity gradually weakens due to long-term operation, it can still output a standard level signal, withstand more severe scale adhesion, and extend the flow meter's service life. Attached Figure Description

[0020] Figure 1 This refers to an existing photoelectric flow meter circuit;

[0021] Figure 2 This is another existing photoelectric flow meter circuit;

[0022] Figure 3 A schematic diagram of the output waveform of the existing technology with a scale-free casing;

[0023] Figure 4 This is a schematic diagram of the output waveform for a casing with scale in existing technology.

[0024] Figure 5 This is a circuit diagram of a photoelectric flow meter circuit according to an embodiment of the present invention;

[0025] Figure 6 This is a circuit diagram of a photoelectric flow meter circuit according to another embodiment of the present invention;

[0026] Figure 7 This is a waveform diagram of an embodiment of the present invention before passing through the DC blocking circuit when there is scale present.

[0027] Figure 8 This is a schematic diagram of the waveform after passing through the DC blocking circuit in an embodiment of the present invention when there is scale.

[0028] Figure 9 This is a schematic diagram of the waveform after passing through an amplification circuit in an embodiment of the present invention when there is scale present;

[0029] Figure 10 This is a schematic diagram of the structure of a photoelectric flow meter according to the present invention;

[0030] Figure 11 This is a front view of a photoelectric flow meter according to the present invention;

[0031] Figure 12 This is a cross-sectional view of a photoelectric flow meter according to the present invention.

[0032] Marker description

[0033] 1-Light-emitting element; 11-Fourth resistor; 2-Phototransistor; 21-Third resistor; 3-DC blocking circuit; 31-High-pass filter circuit; 311-Filter capacitor; 312-Filter resistor; 32-Clamping diode; 4-Circuit power supply terminal; 5-Circuit output terminal; 6-Amplifier circuit; 61-Signal output transistor; 62-First resistor; 63-Second resistor; 7-Photoelectric flow meter; 71-Transmitter head; 72-Receiver head; 73-Impeller rotor; 74-Flow meter housing; 75-Pipeline. Detailed Implementation

[0034] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Identical components are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0035] like Figure 5The diagram shows a schematic of a photoelectric flow meter circuit according to an embodiment of the present invention, including: a light-emitting element 1, a phototransistor 2, and a DC blocking circuit 3. The circuit power supply terminal 4 is electrically connected to one end of the light-emitting element 1 and the collector of the phototransistor 2, respectively. The other end of the light-emitting element 1 and the emitter of the phototransistor 2 are grounded. The collector of the phototransistor 2 is electrically connected to the circuit output terminal 5 through the DC blocking circuit 3.

[0036] Specifically, the circuit power supply terminal 4 is electrically connected to one end of the light-emitting element 1 and the collector of the phototransistor 2, respectively. The other end of the light-emitting element 1 and the emitter of the phototransistor 2 are electrically connected to ground VSS. The circuit power supply terminal 4 is preferably a 5V power supply. The circuit power supply terminal 4 supplies power to the light-emitting element 1, causing it to emit light. When the phototransistor 2 receives light, it conducts, and its collector outputs a signal. The output signal of the phototransistor 2 is still a TTL waveform pulse signal. Preferably, the high level is 1.2–5V and the low level is 0–0.8V. The signal is de-biased by the DC blocking circuit 3 and output from the terminal block that serves as the circuit output terminal 5.

[0037] When scale builds up or the photoelectric emitter's light intensity gradually weakens due to prolonged operation, the received light becomes weaker. Since the receiver is a photoelectric receiver, its conduction and cutoff are controlled by the light intensity, which will lead to an increase in the signal trough.

[0038] The following explanation uses scale buildup as an example. The same issue causes the light intensity of a photoelectric emitter to gradually weaken due to long-term operation.

[0039] Without scale, the receiver tube will eventually experience two states: complete light blocking and complete light exposure, i.e., saturated conduction (where the resistance at the receiver tube's base and emitter terminals is extremely low) and cutoff, due to the water flow driving the rotor. With scale, the light intensity at complete light exposure is insufficient to fully activate the receiver tube, resulting in unsaturated conduction (where the resistance at the receiver tube's base and emitter terminals increases). In this case, the voltage is divided by the pull-up resistor, and the trough of the signal is the voltage division value at this point.

[0040] like Figure 7 The diagram shown is a waveform representation of this embodiment before passing through the DC blocking circuit 3 when scale is present. Figure 8 As shown, in this embodiment, when there is scale, after the DC bias voltage is eliminated by the DC blocking circuit 3, the trough of the waveform is reduced to 0V, thereby preventing the trough from being misjudged as a high level.

[0041] This invention eliminates the DC bias voltage by adding a DC blocking circuit, so that it can still output a standard level signal when scale adheres to the flowmeter housing, can withstand more severe scale buildup, and improves the service life of the flowmeter.

[0042] like Figure 5 The diagram shown is a circuit diagram of a photoelectric flow meter circuit according to another embodiment of the present invention, including: a light-emitting element 1, a phototransistor 2, and a DC blocking circuit 3. The circuit power supply terminal 4 is electrically connected to one end of the light-emitting element 1 through a fourth resistor 11 and to the collector of the phototransistor 2 through a third resistor 21. The other end of the light-emitting element 1 and the emitter of the phototransistor 2 are grounded. The collector of the phototransistor 2 is electrically connected to the circuit output terminal 5 through the DC blocking circuit 3. The light-emitting element 1 is a light-emitting diode.

[0043] The DC blocking circuit 3 includes a high-pass filter circuit 31 and a clamping diode 32. One end of the high-pass filter circuit 31 is electrically connected to the collector of the phototransistor 2, and the other end of the high-pass filter circuit 31 is electrically connected to the circuit output terminal 5. The high-pass filter circuit 31 includes a filter capacitor 311 and a filter resistor 312. One end of the filter capacitor 311 is electrically connected to the collector of the phototransistor 2, and the other end is grounded through the filter resistor 312. The connection point of the filter capacitor 311 and the filter resistor 312 is electrically connected to the circuit output terminal 5. One end of the clamping diode 32 is electrically connected to the circuit output terminal 5, and the other end is grounded.

[0044] Specifically, the circuit power supply terminal 4 is electrically connected to one end of the light-emitting element 1 through a fourth resistor 11 and to the collector of the phototransistor 2 through a third resistor 21. The other end of the light-emitting element 1 and the emitter of the phototransistor 2 are electrically connected to ground VSS. The circuit power supply terminal 4 is preferably a 5V power supply. The light-emitting element 1 is a light-emitting diode (LED). The circuit power supply terminal 4 supplies power to the light-emitting element 1, causing it to emit light. When the phototransistor 2 receives light, it conducts. The circuit power supply terminal 4 is electrically connected to the collector of the phototransistor 2 through the third resistor 21, which acts as a pull-up resistor. The collector of the phototransistor 2 outputs a signal. The output signal of the phototransistor 2 is still a TTL signal. Preferably, the high level is 1.2–5V and the low level is 0–0.8V. The signal is de-biased by the DC blocking circuit 3 and output from the terminal block, which serves as the circuit output terminal 5.

[0045] The DC blocking circuit 3 includes a high-pass filter circuit 31, which eliminates the DC bias voltage in the collector output signal of the phototransistor 2. The collector output signal of the phototransistor 2 passes through the high-pass filter circuit 31, composed of a filter capacitor 311 and a filter resistor 312. The high-pass filter circuit 31 eliminates the DC bias voltage, and then the signal passes through a clamping diode 32 to clamp the reverse voltage. The waveform at point A when there is scale is as follows... Figure 7 As shown, after passing through the high-pass filter circuit 31, the waveform at point B is as follows: Figure 8As shown in the figure. In this embodiment, when there is scale, after the DC bias voltage is eliminated by the DC blocking circuit 3, the trough of the waveform is reduced to 0V, thereby preventing the trough from being misinterpreted as a high level.

[0046] This embodiment eliminates the DC bias voltage through a high-pass filter circuit with a DC blocking circuit, and simultaneously clamps the reverse voltage through a clamping diode. Therefore, even when scale builds up on the flowmeter housing or the photoelectric emitter's light intensity gradually weakens due to prolonged operation, it can still output a standard level signal. This embodiment features a simple circuit, requires fewer electronic components, and does not necessitate modifications to the flowmeter structure. The circuit in this embodiment can withstand more severe scale buildup, extending the flowmeter's lifespan.

[0047] like Figure 6 The diagram shows a photoelectric flow meter circuit according to another embodiment of the present invention, comprising: a light-emitting element 1, a phototransistor 2, a DC blocking circuit 3, and an amplifier circuit 6. The circuit power supply terminal 4 is electrically connected to one end of the light-emitting element 1 through a fourth resistor 11 and to the collector of the phototransistor 2 through a third resistor 21. The other end of the light-emitting element 1 and the emitter of the phototransistor 2 are grounded. The collector of the phototransistor 2 is electrically connected to the circuit output terminal 5 through the DC blocking circuit 3 and the amplifier circuit 6 in sequence. The light-emitting element 1 is a light-emitting diode.

[0048] The DC blocking circuit 3 includes a high-pass filter circuit 31 and a clamping diode 32. One end of the high-pass filter circuit 31 is electrically connected to the collector of the phototransistor 2, and the other end of the high-pass filter circuit 31 is electrically connected to the circuit output terminal 5. The high-pass filter circuit 31 includes a filter capacitor 311 and a filter resistor 312. One end of the filter capacitor 311 is electrically connected to the collector of the phototransistor 2, and the other end is grounded through the filter resistor 312. The connection point of the filter capacitor 311 and the filter resistor 312 is electrically connected to the circuit output terminal 5. One end of the clamping diode 32 is electrically connected to the circuit output terminal 5, and the other end is grounded.

[0049] The amplifier circuit 6 includes a signal output transistor 61. One end of the DC blocking circuit 3 is electrically connected to the collector of the phototransistor 2, and the other end is electrically connected to the base of the signal output transistor 61 through a second resistor 63. The circuit power supply terminal 4 is electrically connected to the collector of the signal output transistor 61 through a first resistor 62. The collector of the signal output transistor 61 is electrically connected to the circuit output terminal 5.

[0050] Specifically, the circuit power supply terminal 4 is electrically connected to one end of the light-emitting element 1 through a fourth resistor 11 and to the collector of the phototransistor 2 through a third resistor 21. The other end of the light-emitting element 1 and the emitter of the phototransistor 2 are electrically connected to ground VSS. The circuit power supply terminal 4 is preferably a 5V power supply. The light-emitting element 1 is a light-emitting diode (LED). The circuit power supply terminal 4 supplies power to the light-emitting element 1, causing it to emit light. When the phototransistor 2 receives light, it conducts. The circuit power supply terminal 4 is electrically connected to the collector of the phototransistor 2 through the third resistor 21, which acts as a pull-up resistor. The collector of the phototransistor 2 outputs a signal. The output signal of the phototransistor 2 is still a TTL waveform pulse signal. Preferably, the high level is 1.2–5V and the low level is 0–0.8V. The signal is blocked by a DC blocking circuit 3 to eliminate the DC bias voltage, and then amplified by an amplifier circuit 6 before being output from the terminal block 5, which serves as the circuit output terminal.

[0051] The DC blocking circuit 3 includes a high-pass filter circuit 31, which eliminates the DC bias voltage in the collector output signal of the phototransistor 2. The collector output signal of the phototransistor 2 passes through the high-pass filter circuit 31, composed of a filter capacitor 311 and a filter resistor 312. The high-pass filter circuit 31 eliminates the DC bias voltage, and then the signal passes through a clamping diode 32 to clamp the reverse voltage. The waveform at point A when there is scale is as follows... Figure 7 As shown, after passing through the high-pass filter circuit 31, the waveform at point B is as follows: Figure 8 As shown in the figure. In this embodiment, when there is scale, after the DC bias voltage is eliminated by the DC blocking circuit 3, the trough of the waveform is reduced to 0V, thereby preventing the trough from being misinterpreted as a high level;

[0052] Finally, the output is a standard TTL level, such as... Figure 9 As shown. The amplifier circuit 6 includes a signal output transistor 61. In this embodiment, under the condition of scale buildup, the signal output transistor 61 only amplifies the pulse signal.

[0053] This embodiment uses a high-pass filter circuit with a DC blocking circuit to eliminate the DC bias voltage, and a clamping diode to clamp the reverse voltage. This allows for the output of a standard voltage level signal even when scale adheres to the flowmeter housing. The pulse signal is amplified by an amplifier circuit for subsequent detection by the microcontroller unit. This embodiment features a simple circuit, requires fewer electronic components, and does not require modifications to the flowmeter structure. The circuit in this embodiment can withstand more severe scale buildup, extending the flowmeter's lifespan.

[0054] like Figures 10 to 12 As shown, an embodiment of the present invention provides a photoelectric flow meter, including a flow meter housing and a photoelectric flow meter circuit as described above, wherein the photoelectric flow meter circuit is housed within the flow meter housing.

[0055] Specifically, such as Figures 10 to 12 The photoelectric flow meter 7 shown includes a flow meter housing 74, within which an impeller rotor 73 and a pipe 75 are disposed. The flow meter housing 74 is equipped with a transmitter 71 and a receiver 72. The transmitter 71 houses the light-emitting element 1, and the receiver 72 houses the phototransistor 2. The light-emitting element 1 in the transmitter 71 emits infrared light, and the phototransistor 2 in the receiver 72 outputs a low level when it receives light and a high level when it does not receive light.

[0056] When water is injected from pipe 75, it drives impeller rotor 73 to rotate, at which time an approximate square wave signal is output.

[0057] When scale adheres to the middle position between the transmitter 71 and the receiver 72, the light received by the receiver 72 becomes weaker, and the voltage trough is raised.

[0058] This invention eliminates the DC bias voltage by adding a DC blocking circuit, so that even when scale adheres to the flow meter housing or the photoelectric emitter's light intensity gradually weakens due to long-term operation, it can still output a standard level signal, withstand more severe scale adhesion, and extend the flow meter's service life.

[0059] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An optical flowmeter circuit, comprising: include: The light-emitting element (1), the phototransistor (2), and the DC blocking circuit (3) are provided. The power supply terminal (4) of the circuit is electrically connected to one end of the light-emitting element (1) and the collector of the phototransistor (2), respectively. The other end of the light-emitting element (1) and the emitter of the phototransistor (2) are grounded. The collector of the phototransistor (2) is electrically connected to the output terminal (5) of the circuit through the DC blocking circuit (3).

2. The optical flowmeter circuit of claim 1, wherein, The DC blocking circuit (3) includes a high-pass filter circuit (31), one end of which is electrically connected to the collector of the phototransistor (2), and the other end of which is electrically connected to the circuit output terminal (5).

3. The optical flow meter circuit of claim 2, wherein, The high-pass filter circuit (31) includes a filter capacitor (311) and a filter resistor (312). One end of the filter capacitor (311) is electrically connected to the collector of the phototransistor (2), and the other end is grounded through the filter resistor (312). The connection point of the filter capacitor (311) and the filter resistor (312) is electrically connected to the output terminal (5) of the circuit.

4. The optical flowmeter circuit of claim 2, wherein, The DC blocking circuit (3) also includes a clamping diode (32), one end of which is electrically connected to the output terminal (5) of the circuit, and the other end is grounded.

5. The optical flowmeter circuit of claim 1, wherein, It also includes an amplifier circuit (6), and the DC blocking circuit (3) is electrically connected to the output terminal (5) of the circuit through the amplifier circuit (6).

6. The optical flow meter circuit of claim 5, wherein, The amplifier circuit (6) includes a signal output transistor (61). One end of the DC blocking circuit (3) is electrically connected to the collector of the phototransistor (2), and the other end is electrically connected to the base of the signal output transistor (61). The collector of the signal output transistor (61) is electrically connected to the circuit output terminal (5).

7. The photoelectric flowmeter circuit according to claim 6, characterized in that, The amplifier circuit (6) further includes a first resistor (62) and a second resistor (63). The power supply terminal (4) of the circuit is electrically connected to the collector of the signal output transistor (61) through the first resistor (62). The other end of the DC blocking circuit (3) is electrically connected to the base of the signal output transistor (61) through the second resistor (63).

8. The photoelectric flow meter circuit according to any one of claims 1 to 7, characterized in that, The power supply terminal (4) of the circuit is electrically connected to the collector of the phototransistor (2) through the third resistor (21), and the power supply terminal (4) of the circuit is electrically connected to the light-emitting element (1) through the fourth resistor (11).

9. The photoelectric flow meter circuit according to any one of claims 1 to 7, characterized in that, The light-emitting element (1) is a light-emitting diode.

10. A photoelectric flow meter, characterized in that, It includes a flow meter housing and a photoelectric flow meter circuit as described in any one of claims 1 to 9, wherein the photoelectric flow meter circuit is housed within the flow meter housing.

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