CN102879648B - Thin film resistive gas sensor changes in resistance pick-up unit - Google Patents
Thin film resistive gas sensor changes in resistance pick-up unit Download PDFInfo
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- CN102879648B CN102879648B CN201210374158.6A CN201210374158A CN102879648B CN 102879648 B CN102879648 B CN 102879648B CN 201210374158 A CN201210374158 A CN 201210374158A CN 102879648 B CN102879648 B CN 102879648B
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Abstract
The invention belongs to technical field of integrated circuits, be specially a kind of thin film resistive gas sensor changes in resistance pick-up unit.The invention provides pick-up unit to comprise: external thin film resistive gas sensor, programmable current source, programmable resistance module, reference voltage source, low noise instrument amplifier, programmable gain amplifier, analog to digital converter, built-in temperature sensor, register, SPI interface, external processor MCU, external Temperature Humidity Sensor.Adopt this pick-up unit, can follow the tracks of the carrying out of the baseline electrical resistance Rb of external thin film resistive gas sensor and eliminate, realize changes in resistance ground high-acruracy survey; In addition, can detect by MCU compensation deals after the environment parameter of external thin film resistive gas sensor place environment in real time, the result after process realizes real-Time Compensation function after forming closed-loop control by register and SPI interface.
Description
Technical field
The invention belongs to technical field of integrated circuits, be specifically related to a kind of thin film resistive gas sensor changes in resistance pick-up unit.
Background technology
In recent years, along with the development of sensor technology, increasing gas sensor is used to the detection of the aspects such as gas concentration, humidity, temperature.Thin film resistive gas sensor can realize microminiaturization because of it and not need high-temperature heating and be widely used in gas sensor detection field.From the angle of electricity, the output of thin film resistive gas sensor can be equivalent to a resistance Re, and this equivalent resistance Re is made up of baseline electrical resistance Rb and changes in resistance dR.For different thin film resistive gas sensors, the variation range of baseline electrical resistance Rb is very large, its scope be probably ten kilohms to tens megohms, the change of changes in resistance dR then measurement tested with gas is relevant.As a rule, the ratio of changes in resistance dR and baseline electrical resistance Rb is very little.Therefore, for different thin film resistive sensors, how to detect that the very little changes in resistance dR of change is a present design difficulty accurately.In addition, baseline electrical resistance Rb can change along with the change of the environmental variances such as the humiture of time, periphery, and this will cause measuring accuracy not high, and this just proposes the requirement of real-Time Compensation to whole signal conditioning circuit.
Summary of the invention
The present invention aims to provide one and can measure accurately changes in resistance, and the pick-up unit of the thin film resistive gas sensor changes in resistance that can compensate in real time.
The pick-up unit of thin film resistive gas sensor changes in resistance provided by the invention, comprising: external thin film resistive gas sensor, programmable current source, programmable resistance module, reference voltage source, low noise instrument amplifier IA, programmable gain amplifier PGA, analog to digital converter ADC, built-in temperature sensor, register, SPI interface, external processor MCU, external Temperature Humidity Sensor, wherein, external thin film resistive gas sensor is connected with programmable resistance module, programmable resistance module and reference voltage source are connected with negative input with the positive input of low noise instrument amplifier IA respectively, low noise instrument amplifier IA is connected with programmable gain amplifier PGA, programmable gain amplifier PGA and analog to digital converter ADC is linked in sequence, programmable current source, programmable resistance module, reference voltage source, low noise instrument amplifier IA, programmable gain amplifier PGA, analog to digital converter ADC, built-in temperature sensor and register are connected register respectively and are connected with SPI interface, SPI interface is connected with external processor MCU, external Temperature Humidity Sensor is connected with external processor MCU.
In the present invention, described programmable resistance module is made up of two programmable resistor array R1 and R2.Two electric resistance array R1 and R2 form by 16 × 16 resistance, and adopt 8 segmented decodings modes, its minimum bit is 15.625K Ω.Fig. 2 shows the implementation of programmable resistor array, and when input 8 bit data decoding, high 4 correspond to row address, and low 4 correspond to column address, then by respectively to the control realization of each switch in ranks to the programming of resistance.
In the present invention, equivalent resistance Re and programmable resistor array R1 and the R2 of described external thin film resistive gas sensor have 8 kinds of integrated modes, be respectively: (1) Re+R1+R2, (2) Re+R1, (3) Re+ (R1 ∥ R2), (4) Re ∥ R1 ∥ R2, (5) (Re+R1) ∥ R2, (6) Re ∥ (R1+R2), (7) Re, (8) reserve pattern.
In the present invention, the electric current that described programmable current source produces flows through baseline electrical resistance Rb and the rear resistance R3 produced of programmable resistor array R1 and R2 combination of external thin film resistive gas sensor, the voltage difference V1 that the voltage produced and reference voltage source produce at low noise instrument amplifier IA input end is less than threshold V T, voltage difference V1 exports as DC voltage Vdc after low noise instrument amplifier IA, programmable gain amplifier PGA amplify, and this voltage meets the requirement of DC voltage bias; Simultaneously, the electric current that programmable current source produces flows through changes in resistance dR and the rear resistance R4 produced of programmable resistor array R1 and R2 combination of external thin film resistive gas sensor, the voltage produced exports as alternating voltage Vac after low noise instrument amplifier IA, programmable gain amplifier PGA amplify, and this voltage can be detected by analog to digital converter ADC7.
In the present invention, the equivalent resistance Re of programmable current source size of current, programmable resistor array R1 resistance and R2 resistance, external thin film resistive gas sensor can carry out communicating or configuring with register with the integrated mode of programmable resistor array R1 and R2, the enlargement factor of low noise instrument amplifier IA, programmable gain amplifier PGA enlargement factor, analog to digital converter ADC, built-in temperature sensor, and register to communicate with external processor MCU by SPI interface and is configured.
In the present invention, built-in temperature sensor or external Temperature Humidity Sensor obtain the environment parameter of external thin film resistive gas sensor surrounding environment, environment parameter, after external processor MCU compensation deals, realizes real-Time Compensation function after forming closed-loop control by SPI interface.
The beneficial effect that the present invention has is:
1, by following the tracks of the technology eliminated to external thin film resistive gas sensor baseline electrical resistance Rb, realize changes in resistance ground high-acruracy survey;
2, by after the environment parameter that detects in real time external thin film resistive gas sensor place environment through MCU compensation deals, then realize real-Time Compensation function after forming closed-loop control by register and SPI interface.
Accompanying drawing explanation
Fig. 1 is theory diagram of the present invention.
Fig. 2 is the implementation of programmable resistance of the present invention.
Fig. 3 is the schematic diagram of baseline electrical resistance of the present invention and programmable resistance integrated mode.
Fig. 4 is the schematic diagram of DC voltage Vdc of the present invention.
Fig. 5 is the schematic diagram of alternating voltage Vac of the present invention.
Embodiment
Below in conjunction with drawings and Examples, the invention will be further described:
In FIG, the pick-up unit of thin film resistive gas sensor changes in resistance, comprises external thin film resistive gas sensor 1, programmable current source 2, programmable resistance module 3, reference voltage source 4, low noise instrument amplifier IA5, programmable gain amplifier PGA6, analog to digital converter ADC7, built-in temperature sensor 8, register 9, SPI interface 10, external processor MCU 11, external Temperature Humidity Sensor 12, external thin film resistive gas sensor 1 is connected with programmable resistance module 3, programmable resistance module 3 and reference voltage source 4 are connected with negative input with the positive input of low noise instrument amplifier IA5 respectively, low noise instrument amplifier IA5 is connected with programmable gain amplifier PGA6, programmable gain amplifier PGA6 and analog to digital converter ADC7 is linked in sequence, programmable current source 2, programmable resistance module 3, reference voltage source 4, low noise instrument amplifier IA5, programmable gain amplifier PGA6, analog to digital converter ADC7, built-in temperature sensor 8 is connected respectively with register 9, register 9 is connected with SPI interface 10, SPI interface 10 is connected with external processor MCU 11, external Temperature Humidity Sensor 12 is connected with external processor MCU 11.
Programmable current source 2 has 3 kinds of output currents, is respectively 25.6uA, 3.2uA and 0.4uA.
Programmable resistance module 3 is made up of two programmable resistor array R1 and R2, and two electric resistance arrays form by 16 × 16 resistance, and adopt 8 segmented decodings modes, its minimum bit is 15.625K Ω.Fig. 2 shows the implementation of programmable resistor array, and when input 8 bit data decoding, high 4 correspond to row address, and low 4 correspond to column address, then by respectively to the control realization of each switch in ranks to the programming of resistance.
The baseline electrical resistance Re of external thin film resistive gas sensor 1 and programmable resistor array R1 and R2 has 8 kinds of integrated modes, be respectively: (1) Re+R1+R2, (2) Re+R1, (3) Re+ (R1 ∥ R2), (4) Re ∥ R1 ∥ R2, (5) (Re+R1) ∥ R2, (6) Re ∥ (R1+R2), (7) Re, (8) reserve pattern.In figure 3, S1 ~ S10 is switch, can be determined the integrated mode of baseline electrical resistance Rb and programmable resistor array R1 and R2 by the on off state arranging S1 ~ S10, as shown in table 1 below:
Table 1 on off state is corresponding with integrated mode to be shown
。
Reference voltage source 4 exports the reference voltage of 1.2V, and the enlargement factor of low noise instrument amplifier IA5 is 1 to 128 times, and programmable gain amplifier PGA6 enlargement factor is 10 to 100 times, analog to digital converter ADC is 21 high precision converters.
In the diagram, the electric current that programmable current source 2 produces flows through baseline electrical resistance Rb and the rear resistance R3 produced of programmable resistor array R1 and R2 combination of external thin film resistive gas sensor 1, the voltage difference V1 that the voltage produced and reference voltage source 4 produce at low noise instrument amplifier IA5 input end is less than threshold V T, and this threshold V T is less than 50mV; Voltage difference V1 exports as DC voltage Vdc after low noise instrument amplifier IA5, programmable gain amplifier PGA6 amplify, and this voltage meets the requirement of DC voltage bias; Simultaneously, the electric current that programmable current source 2 produces flows through changes in resistance dR and the rear resistance R4 produced of programmable resistor array R1 and R2 combination of external thin film resistive gas sensor 1, the voltage produced exports as alternating voltage Vac after low noise instrument amplifier IA5, programmable gain amplifier PGA6 amplify, this voltage can be detected by analog to digital converter ADC7, as shown in Figure 5.
The equivalent resistance Re of programmable current source 2 size of current, programmable resistor array R1 resistance and R2 resistance, external thin film resistive gas sensor 1 can carry out communicating or configuring with register 9 with the integrated mode of programmable resistor array R1 and R2, the enlargement factor of low noise instrument amplifier IA5, programmable gain amplifier PGA6 enlargement factor, analog to digital converter ADC7, built-in temperature sensor 8, and register 9 to communicate with external processor MCU 11 by SPI interface 10 and is configured.
Table 2 baseline electrical resistance Rb follows the tracks of and eliminates certain embodiments
| Iref | 0.4uA | 3.2uA | 25.6uA |
| Rid | 3MΩ | 375KΩ | 46.875KΩ |
| Rb Range | 1~9MΩ | 125KΩ~1125KΩ | 15.625KΩ~140.625KΩ |
| Rb compensation precision | 15.625KΩ | 15.625KΩ | 2KΩ |
| Max V1 | 6.25mV | 50mV | 50mV |
Certain embodiments for baseline electrical resistance Rb tracking elimination as shown in table 2, in table, Iref is the electric current that programmable current source 2 produces, and Rid is the ideal value of resistance R3, and Rb compensation precision is the compensation precision after resistance through selecting suitable resistance R1 resistance, R2 and integrated mode.
From the above mentioned, external processor MCU 11 selects enlargement factor and the programmable gain amplifier PGA6 enlargement factor of programmable current source 2 size of current, resistance R1 resistance, R2 resistance, integrated mode, low noise instrument amplifier IA5 suitably automatically by SPI interface and register, the voltage difference V1 of generation is made to be less than threshold V T, the tracking realizing baseline electrical resistance Rb is eliminated, and the DC voltage Vdc produced and alternating voltage Vac can try to achieve changes in resistance dR after sending the process of external processor MCU 11 to by register 9 and SPI interface 10.
Built-in temperature sensor 8 or external Temperature Humidity Sensor 12 obtain the environment parameter of external thin film resistive gas sensor 1 surrounding environment, environment parameter, after the compensation deals of external processor MCU 11, realizes real-Time Compensation function after forming closed-loop control by SPI interface 10.
Claims (5)
1. a pick-up unit for thin film resistive gas sensor changes in resistance, comprises external thin film resistive gas sensor, programmable current source, programmable resistance module, reference voltage source, low noise instrument amplifier IA, programmable gain amplifier PGA, analog to digital converter ADC, built-in temperature sensor, register, SPI interface, external processor MCU, external Temperature Humidity Sensor; Wherein, external thin film resistive gas sensor is connected with programmable resistance module, programmable resistance module and reference voltage source are connected with negative input with the positive input of low noise instrument amplifier IA respectively, low noise instrument amplifier IA is connected with programmable gain amplifier PGA, and programmable gain amplifier PGA and analog to digital converter ADC is linked in sequence; Programmable current source, programmable resistance module, reference voltage source, low noise instrument amplifier IA, programmable gain amplifier PGA, analog to digital converter ADC, built-in temperature sensor are connected register respectively with register and are connected with SPI interface, SPI interface is connected with external processor MCU, and external Temperature Humidity Sensor is connected with external processor MCU;
It is characterized in that: described programmable resistance module is made up of two programmable resistor array R1 and R2, two electric resistance array R1 and R2 form by 16 × 16 resistance, adopt 8 segmented decodings modes, when input 8 bit data decoding, high 4 correspond to row address, low 4 correspond to column address, then by respectively to the control realization of each switch in ranks to the programming of resistance.
2. the pick-up unit of thin film resistive gas sensor changes in resistance according to claim 1, it is characterized in that: equivalent resistance Re and programmable resistor array R1 and the R2 of described external thin film resistive gas sensor have 8 kinds of integrated modes, be respectively: (1) Re+R1+R2, (2) Re+R1, (3) Re+ (R1 ∥ R2), (4) Re ∥ R1 ∥ R2, (5) (Re+R1) ∥ R2, (6) Re ∥ (R1+R2), (7) Re, (8) reserve pattern.
3. the pick-up unit of thin film resistive gas sensor changes in resistance according to claim 2, it is characterized in that: the electric current that described programmable current source produces flows through baseline electrical resistance Rb and the rear resistance R3 produced of programmable resistor array R1 and R2 combination of external thin film resistive gas sensor, the voltage difference V1 that the voltage produced and reference voltage source produce at low noise instrument amplifier IA input end is less than threshold V T, voltage difference V1 is through low noise instrument amplifier IA, export after programmable gain amplifier PGA amplifies as DC voltage Vdc, this voltage meets the requirement of DC voltage bias, simultaneously, the electric current that programmable current source produces flows through changes in resistance dR and the rear resistance R4 produced of programmable resistor array R1 and R2 combination of external thin film resistive gas sensor, the voltage produced exports as alternating voltage Vac after low noise instrument amplifier IA, programmable gain amplifier PGA amplify, and this voltage can be detected by analog to digital converter ADC7.
4. the pick-up unit of thin film resistive gas sensor changes in resistance according to claim 3, it is characterized in that: programmable current source size of current, programmable resistor array R1 resistance and R2 resistance, the equivalent resistance Re of external thin film resistive gas sensor and the integrated mode of programmable resistor array R1 and R2, the enlargement factor of low noise instrument amplifier IA, programmable gain amplifier PGA enlargement factor, analog to digital converter ADC, built-in temperature sensor can carry out communicating or configuring with register, register to communicate with external processor MCU by SPI interface and is configured.
5. the pick-up unit of thin film resistive gas sensor changes in resistance according to claim 4, it is characterized in that: built-in temperature sensor or external Temperature Humidity Sensor obtain the environment parameter of external thin film resistive gas sensor surrounding environment, environment parameter, after external processor MCU compensation deals, realizes real-Time Compensation function after forming closed-loop control by SPI interface.
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| CN104597383A (en) * | 2014-12-08 | 2015-05-06 | 惠州市亿能电子有限公司 | Controllable resistance output device, method thereof and application |
| US10429330B2 (en) | 2016-07-18 | 2019-10-01 | Stmicroelectronics Pte Ltd | Gas analyzer that detects gases, humidity, and temperature |
| US10557812B2 (en) | 2016-12-01 | 2020-02-11 | Stmicroelectronics Pte Ltd | Gas sensors |
| TWI648528B (en) | 2017-11-23 | 2019-01-21 | 財團法人工業技術研究院 | Resistive gas sensor and gas sensing method thereof |
| CN110940861B (en) * | 2019-12-10 | 2022-02-18 | 江苏智闻智能传感科技有限公司 | Resistance testing circuit and resistance testing method of gas sensor |
| CN112816784B (en) * | 2020-12-31 | 2024-07-19 | 广电计量检测（成都）有限公司 | Resistance test circuit and system |
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