CN212082483U - High-precision hydrogen flow detection circuit - Google Patents
High-precision hydrogen flow detection circuit Download PDFInfo
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- CN212082483U CN212082483U CN202020818786.9U CN202020818786U CN212082483U CN 212082483 U CN212082483 U CN 212082483U CN 202020818786 U CN202020818786 U CN 202020818786U CN 212082483 U CN212082483 U CN 212082483U
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 31
- 239000001257 hydrogen Substances 0.000 title claims abstract description 31
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 31
- 238000001514 detection method Methods 0.000 title claims abstract description 16
- 238000007796 conventional method Methods 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 238000001595 flow curve Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000026058 directional locomotion Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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Abstract
The utility model provides a high accuracy hydrogen flow detection circuitry is applied to between hydrogen flow sensor and the back level ADC, include: the circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, an operational amplifier and a reference voltage power supply; wherein: the first end of the first resistor is connected with the output end of the hydrogen flow sensor; the second end of the first resistor is connected with the positive phase input end of the operational amplifier; the first end of the second resistor is connected with the second end of the first resistor, and the second end of the second resistor is grounded; the first end of the third resistor is connected with a reference voltage power supply, and the second end of the third resistor is connected with the inverting input end of the operational amplifier; the first end of the fourth resistor is connected with the inverting input end of the operational amplifier, and the second end of the fourth resistor and the output end of the operational amplifier are both connected to the rear-stage ADC. The detection circuit has the characteristics of simple and convenient adjustment and maximized utilization of the range and resolution of the rear-stage ADC.
Description
Technical Field
The utility model relates to an automatic and instrument and meter detection area, concretely relates to high accuracy hydrogen flow detection circuitry.
Background
Hydrogen flow sensors, such as the universal detector FID (flame ionization detector), use hydrogen as the combustion gas and sample molecules of organic compounds are ionized by a oxyhydrogen flame to form charged particles. The charged particles have a directional motion in the dc electric field, thereby forming a current. By measuring the current intensity, the mass of the measured substance entering the detector can be calculated, and the concentration of the measured sample can be calculated by combining the sample injection amount.
In a gas flow detection scene, the general hydrogen flow sensor has wide application and large total flow range, and can be applied to different flow occasions. Because the output voltage span of the sensor cannot exactly match the input voltage span of the subsequent ADC, the output voltage of the hydrogen flow sensor needs to be scaled and then sent to the subsequent ADC.
When the general hydrogen flow sensor is applied to a small flow range use scene, the non-zero phenomenon of the initial DC voltage of the sensor is common. Here, the sensor start DC voltage is a sensor start voltage corresponding to a start minimum value of an actual flow rate range. If the flow range starts from the zero flow of the sensor, the corresponding sensor voltage at the zero flow is the initial voltage of the sensor; and if the flow range starts from the middle flow of the sensor, the sensor voltage corresponding to the middle minimum initial flow is the sensor initial voltage.
When the initial voltage is not zero, if the offset processing is not performed, the initial voltage and the net signal are sent to the rear-stage ADC together, and the limited range of the ADC is wasted. Particularly, when the actual flow using range is smaller than the full range of the sensor, the initial voltage may be close to 80% -90% of the total signal amplitude, the capacity of the rear stage ADC for processing the net signal is almost compressed to the unusable step, a large amount of ranges are occupied, and the limited ADC resolution cannot process the net signal with too small a ratio.
SUMMERY OF THE UTILITY MODEL
To the defects in the prior art, the present invention provides a high-precision hydrogen flow rate detection circuit to solve the problem of low hydrogen flow rate control precision caused by low resolution of the output signal of the hydrogen flow rate sensor. The technical scheme of the utility model as follows:
a high-precision hydrogen flow detection circuit is applied between a hydrogen flow sensor and a rear-stage ADC, and comprises: the circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, an operational amplifier and a reference voltage power supply; wherein:
the first end of the first resistor is connected with the output end of the hydrogen flow sensor; the second end of the first resistor is connected with the positive phase input end of the operational amplifier;
the first end of the second resistor is connected with the second end of the first resistor, and the second end of the second resistor is grounded;
the first end of the third resistor is connected with a reference voltage power supply, and the second end of the third resistor is connected with the inverting input end of the operational amplifier;
the first end of the fourth resistor is connected with the inverting input end of the operational amplifier, and the second end of the fourth resistor and the output end of the operational amplifier are both connected to the rear-stage ADC.
Optionally, the first resistor and the third resistor have equal resistance values; the resistance values of the second resistor and the fourth resistor are equal; and satisfies the following conditions:
wherein, R1, R2, R3 and R4 are respectively a first resistor, a second resistor, a third resistor and a fourth resistor; vin is the output voltage of the hydrogen flow sensor, Vref is the reference voltage output by the reference voltage power supply, and Vo is the output voltage of the operational amplifier.
Compared with the prior art, the utility model discloses following beneficial effect has:
the detection circuit has the characteristics of simple and convenient adjustment and maximized utilization of the range and resolution of the rear-stage ADC.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic diagram illustrating a connection of a high-precision hydrogen flow rate detection circuit according to a first embodiment of the present invention;
fig. 2 is an output voltage-current curve of a hydrogen flow rate sensor according to a first embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to the following embodiments. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that various changes and modifications can be made by one skilled in the art without departing from the spirit of the invention. These all belong to the protection scope of the present invention.
The first embodiment:
in the present embodiment, a calculation will be given for a non-zero value of the starting voltage (dc bias voltage), and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments.
As shown in fig. 1, the present embodiment discloses a high-precision hydrogen flow rate detection circuit applied between a hydrogen flow rate sensor and a post-stage ADC, including: the circuit comprises a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, an operational amplifier U1 and a reference voltage power supply; wherein:
a first end of the first resistor R1 is connected with an output end of the hydrogen flow sensor; the second end of the first resistor R1 is connected with the non-inverting input end of an operational amplifier U1;
a first end of the second resistor R2 is connected with a second end of the first resistor R1, and a second end of the second resistor R2 is grounded;
a first end of the third resistor R3 is connected with a reference voltage power supply, and a second end of the third resistor R3 is connected with an inverting input end of the operational amplifier U1;
the first end of the fourth resistor R4 is connected to the inverting input end of the operational amplifier U1, and the second end of the fourth resistor R4 and the output end of the operational amplifier U1 are both connected to the next stage ADC.
The resistance values of the first resistor R1 and the third resistor R3 are equal; the resistance values of the second resistor R2 and the fourth resistor R4 are equal; and satisfies the following conditions:
wherein, R1, R2, R3 and R4 are respectively a first resistor, a second resistor, a third resistor and a fourth resistor; vin is the output voltage of the hydrogen flow sensor, Vref is the reference voltage output by the reference voltage power supply, and Vo is the output voltage of the operational amplifier, i.e., the input signal of the post-stage ADC. Where Vin comprises a starting voltage (dc bias voltage); the reference voltage represented by Vref is equal to the zero voltage (dc bias voltage) output from the hydrogen flow rate sensor.
In this embodiment, the hydrogen flow sensor is a honeywell AWM43300V gas flow sensor, the range of the gas flow sensor is 0sccm to 1000sccm, the output voltage-flow curve is known, referring to fig. 2, the zero flow voltage is 1Vdc, the gas flow range is 0sccm to 80sccm, when in actual use, the user is not sensitive to the flow value outside the actual range, and the reference voltage of the rear-stage 16-bit ADC is 2.5 Vdc.
It can be seen that the actual use range of the sensor is less than one tenth of the full range of the sensor, and the flow range of 0sccm to 100sccm can be approximately considered to correspond to the output range of 1Vdc to 2.5Vdc of the sensor, and the actual initial voltage 1Vdc corresponding to 0 sccm; the conventional method inputs the output signal of the sensor (containing the actual initial voltage 1Vdc) into the subsequent stage ADC, so that the actual usable range of the subsequent stage ADC is in the range of 1 Vdc-2.5 Vdc, the amplitude is 1.5Vdc,the flow rate accuracy corresponding to the minimum unit is
With the detection circuit of this embodiment, in fig. 1, appropriate resistance values and reference voltages can be taken to eliminate the influence of the non-zero starting voltage, for example, when R1-R3-10K, R2-R4-1.66K, Vref-1 Vdc, the operational amplifier output signal voltage corresponding to the flow rate of 0sccm is taken as
The output signal voltage of the operational amplifier corresponding to the flow of 100sccm is
After the signals are sent to the rear-stage ADC, the actual available range of the rear-stage ADC is within the range of 0 Vdc-2.5 Vdc, the amplitude is 2.5Vdc, the actual available range of the ADC is 1.67 times that of the conventional method, and the flow precision corresponding to the minimum unit is
The precision is also 1.67 times that of the conventional method.
The basic principle of the detection circuit of the embodiment is to make a differential circuit (a negative offset homodromous attenuator) by using an integrated operational amplifier: the output signal of the flow sensor is differenced with a reference voltage to eliminate the influence of the non-zero value of the initial voltage (DC bias voltage), and then the difference value is amplified and sent to the rear-stage ADC, so that the range and the resolution of the rear-stage ADC are utilized to the maximum extent. According to different use scenes, the resistor and the reference voltage can be conveniently replaced to meet actual requirements. It should be noted that the ADC in the later stage has to have a suppression capability for the possible phenomenon that the operational amplifier is output to the negative rail due to the introduction of the negative offset.
Second embodiment:
in this embodiment, the starting point of the actual use range is located at the middle position of the full scale of the sensor, and the actual use range occupies a smaller proportion than the full scale of the sensor.
It is known that the hydrogen flow sensor (hounwell AWM43300V gas flow sensor) has a measuring range of 0sccm to 1000sccm, an output voltage-flow curve is known, referring to fig. 2, a zero flow voltage is 1Vdc, a gas flow use range is 400sccm to 600sccm, a user is not sensitive to a flow value outside the actual use range during actual use, and a post-stage 16-bit ADC reference voltage is 2.5 Vdc.
The flow range of 400 sccm-600 sccm can be approximately considered to correspond to the output range of 4.2 Vdc-4.7 Vdc of the sensor, and the actual initial voltage corresponding to 400sccm is 4.2 Vdc; the conventional method divides the output signal of the sensor (including the actual initial voltage of 4.2Vdc) and inputs the divided signal into the rear-stage ADC after the divided signal is followed, and in order to not exceed the ADC range (2.5Vdc), the divided signal of the output signal of the sensor can be divided by half, namely, the voltage range of the signal input by the rear-stage ADC is 2.1 Vdc-2.35 Vdc, the amplitude is 0.25Vdc, and the flow precision corresponding to the minimum unit is 2.1 Vdc-2.35 Vdc
The detection circuit of this embodiment is similar to the circuit shown in fig. 1, wherein appropriate resistance and reference voltage can be obtained, for example, when R1-R3-10K, R2-R4-50K, Vref-4.2 Vdc is adopted, and the output signal voltage of the operational amplifier corresponding to 400sccm flow is equal to Vref
The output signal voltage of the operational amplifier corresponding to the flow of 600sccm is
After the signals are sent to the rear-stage ADC, the actual available range of the rear-stage ADC is 0 Vdc-2.5 Vdc, the amplitude is 2.5Vdc, the actual available range of the ADC is 10 times that of the conventional method, and the flow precision corresponding to the minimum unit is
The accuracy is also 10 times that of the conventional method.
The foregoing description of the specific embodiments of the invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (2)
1. A high-precision hydrogen flow detection circuit is applied between a hydrogen flow sensor and a rear stage ADC, and comprises: the circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, an operational amplifier and a reference voltage power supply; wherein:
the first end of the first resistor is connected with the output end of the hydrogen flow sensor; the second end of the first resistor is connected with the positive phase input end of the operational amplifier;
the first end of the second resistor is connected with the second end of the first resistor, and the second end of the second resistor is grounded;
the first end of the third resistor is connected with a reference voltage power supply, and the second end of the third resistor is connected with the inverting input end of the operational amplifier;
the first end of the fourth resistor is connected with the inverting input end of the operational amplifier, and the second end of the fourth resistor and the output end of the operational amplifier are both connected to the rear-stage ADC.
2. The circuit of claim 1, wherein the first resistor and the third resistor have equal resistance values; the resistance values of the second resistor and the fourth resistor are equal; and satisfies the following conditions:
wherein, R1, R2, R3 and R4 are respectively a first resistor, a second resistor, a third resistor and a fourth resistor; vin is the output voltage of the hydrogen flow sensor, Vref is the reference voltage output by the reference voltage power supply, and Vo is the output voltage of the operational amplifier.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020818786.9U CN212082483U (en) | 2020-05-15 | 2020-05-15 | High-precision hydrogen flow detection circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202020818786.9U CN212082483U (en) | 2020-05-15 | 2020-05-15 | High-precision hydrogen flow detection circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112697976A (en) * | 2020-12-18 | 2021-04-23 | 汉威科技集团股份有限公司 | Gas path flow real-time dynamic adjusting method, system and storage medium |
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- 2020-05-15 CN CN202020818786.9U patent/CN212082483U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112697976A (en) * | 2020-12-18 | 2021-04-23 | 汉威科技集团股份有限公司 | Gas path flow real-time dynamic adjusting method, system and storage medium |
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Address after: 310053 Room 301, floor 3, building 3, No. 611, Dongguan Road, Binjiang District, Hangzhou, Zhejiang Province Patentee after: Zhongkong Quanshi Technology (Hangzhou) Co.,Ltd. Address before: 310053 Room B3155, 3rd floor, 368 Liuhe Road, Binjiang District, Hangzhou City, Zhejiang Province Patentee before: ZHEJIANG TRACETECH TECHNOLOGY CO.,LTD. |
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