Piecewise linearization correction circuit with temperature compensation function

Abstract

The utility model discloses a piecewise linearization correction circuit with a temperature compensation function. The correction circuit comprises a gain selection circuit and an operational amplifier, the gain selection circuit comprises a plurality of gain selection channels, and each gain selection channel corresponds to a gain multiple; the positive input end of the operational amplifier is connected with the output end of a sensor, and the operational amplifier is used for receiving sensing signals collected by the sensor. The reverse input end of the operational amplifier is connected with the output end of the gain selection circuit, the gain of the operational amplifier is determined based on the conduction condition of the plurality of gain selection channels, and the conduction condition of the gain selection channels is determined based on the size of the sensing signal. The piecewise linearization correction circuit with the temperature compensation function not only can carry out piecewise linearization correction on signals with nonlinear characteristics, but also has the temperature compensation function, and can have stable output in a wide temperature range.

Description

Technical Field

[0001] The present application relates to the technical field of temperature compensation, and in particular to a piecewise linearization correction circuit with a temperature compensation function. Background Art

[0002] When using a platinum resistance thermal mass flowmeter to collect flow signals, the output signal of the resistor is a nonlinear signal as the flow changes, while the 4-20mA signal received by the DCS (Distributed Control System) industrial control system used in conventional industrial sites is linear, so the nonlinear signal of the sensor needs to be converted into a linear signal. At the same time, because the environment in which conventional integrated industrial instruments are located changes drastically, temperature sensitivity will cause large instrument measurement errors. Utility Model Content

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a piecewise linearization correction circuit with a temperature compensation function, so as to solve at least one problem existing in the prior art.

[0004] In order to achieve the above-mentioned object and other related objects, the utility model provides a piecewise linearization correction circuit with temperature compensation function, the correction circuit comprising: a gain selection circuit and an operational amplifier;

[0005] The gain selection circuit includes a plurality of gain selection channels, each of which corresponds to a gain multiple;

[0006] The positive input terminal of the operational amplifier is connected to the output terminal of the sensor, and is used to receive the sensing signal collected by the sensor; the reverse input terminal of the operational amplifier is connected to the output terminal of the gain selection circuit, and the gain of the operational amplifier is determined based on the conduction conditions of the multiple gain selection channels, and the conduction conditions of the gain selection channels are determined based on the size of the sensing signal;

[0007] The sensing signal includes a front-end signal, a middle-end signal, and a final-end signal, wherein the slope of the front-end signal gradually increases, and the slope of the final-end signal gradually decreases; the multiple gain selection channels include a first gain selection unit and a second gain selection unit; when the sensor collects the front-end signal, one or more gain selection channels in the first gain selection unit are turned on; when the sensor collects the final-end signal, one or more gain selection channels in the second gain selection unit are turned on;

[0008] The gain selection channel of the first gain selection unit comprises: a first transistor, whose collector is connected to a first voltage, whose emitter is connected to a second voltage via a resistor, and whose base is connected to a first bias voltage;

[0009] The gain selection channel of the second gain selection unit includes: a third transistor, an emitter of which is connected to a third voltage via a resistor, a collector of which is connected to a fourth voltage, and a base of which is connected to a second bias voltage.

[0010] Optionally, the gain selection channel of the first gain selection unit further includes:

[0011] The base of the second transistor is connected to the emitter of the first transistor, the collector of the second transistor is connected to the second voltage, and the emitter of the second transistor is connected to the reverse input terminal of the operational amplifier via a resistor.

[0012] Optionally, the first transistor is an NPN transistor, and the second transistor is a PNP transistor.

[0013] Optionally, the gain selection channel of the second gain selection unit further includes:

[0014] The fourth transistor has a base connected to the emitter of the third transistor, a collector connected to the third voltage, and an emitter connected to the inverting input terminal of the operational amplifier via a resistor.

[0015] Optionally, the third transistor is a PNP transistor, and the fourth transistor is an NPN transistor.

[0016] Optionally, the correction circuit further includes: a plurality of voltage-dividing resistors and a reference voltage source, wherein the plurality of voltage-dividing resistors are connected in series and then connected in parallel with the reference voltage source; and one or more of the voltage-dividing resistors provide a turn-on voltage for the plurality of gain selection channels.

[0017] Optionally, the correction circuit further includes:

[0018] The gain resistor is connected in parallel between the output terminal and the inverting input terminal of the operational amplifier.

[0019] As described above, the present application provides a piecewise linearization correction circuit with temperature compensation function, which has the following beneficial effects:

[0020] The utility model discloses a piecewise linearization correction circuit with a temperature compensation function, the correction circuit comprising: a gain selection circuit and an operational amplifier; the gain selection circuit comprises a plurality of gain selection channels, each of which corresponds to a gain multiple; the positive input end of the operational amplifier is connected to the output end of the sensor, for receiving the sensing signal collected by the sensor; the reverse input end of the operational amplifier is connected to the output end of the gain selection circuit, the gain of the operational amplifier is determined based on the conduction conditions of the plurality of gain selection channels, and the conduction conditions of the gain selection channels are determined based on the size of the sensing signal. The utility model discloses a piecewise linearization correction circuit with a temperature compensation function, which can perform piecewise linearization correction on signals with nonlinear characteristics, and also has a temperature compensation function, and can have a stable output within a wide temperature range.

[0021] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0023] Figure 1 A schematic diagram of a signal collected by a sensor according to an embodiment of the present application;

[0024] Figure 2 This is a schematic diagram of a piecewise linearization correction circuit with a temperature compensation function according to an embodiment of the present application;

[0025] Figure 3 A circuit diagram of a piecewise linearization correction circuit with a temperature compensation function according to an embodiment of the present application;

[0026] Figure 4 FIG. 4 is a schematic diagram of a compensated signal according to an embodiment of the present application. DETAILED DESCRIPTION

[0027] The following describes the implementation of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0028] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed at will, and the component layout may also be more complicated.

[0029] Although the terms "first", "second", "A", "B", etc. may be used herein to describe various elements, these elements should not be limited by these terms and are only used to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the following technology. The term "and / or" includes a combination of multiple related items or any item in the multiple related items.

[0030] As used herein, unless the context indicates otherwise, the singular form is intended to include the plural form, and it will be understood that the term "comprising" means the presence of stated features, quantities, steps, operations, elements, or combinations thereof, but does not exclude the presence or addition of one or more other features, quantities, steps, operations, elements, components, or combinations thereof.

[0031] Before describing the drawings in detail, it is intended to clarify that the division of components in this specification is divided only by the main function of each component. That is, two or more components to be described below can be combined into one component, or can be divided into two or more components according to more detailed functions. In addition to the main function of the component, each component to be described below can also perform some or all of the functions of other components, and some of the main functions of each component can be exclusively performed by other components.

[0032] When using a platinum resistance thermal mass flowmeter to collect flow signals, the output signal of the resistor is a nonlinear signal as the flow changes, while the 4-20mA signal received by the DCS (Distributed Control System) industrial control system used in conventional industrial sites is linear, so the nonlinear signal of the sensor needs to be converted into a linear signal. At the same time, because the environment in which conventional integrated industrial instruments are located changes drastically, temperature sensitivity will cause large instrument measurement errors.

[0033] See also Figure 1 , Figure 1 is the sensor input signal diagram, Figure 1 It can be seen that the overall slope of the sensor's input signal first increases from small, the linearity is approximately unchanged in the middle section, and finally decreases from large to small. In order to linearize the overall signal, the nonlinear parts on both sides can be linearized based on the middle section. According to the characteristics of the sensor, it is necessary to provide a larger gain at the beginning of the first half and then gradually reduce it. As the signal reaches the linear region, the gain remains unchanged, and the gain in the second half increases from small to large. Based on this, the present application proposes a piecewise linearization correction circuit with a temperature compensation function. In addition to being able to perform piecewise linearization correction on signals with nonlinear characteristics, it also has a temperature compensation function and can have a stable output within a wide temperature range. At the same time, compared with linearization correction circuits using multiplexers and multiple groups of operational amplifiers and analog switches, the utility model reduces the number of components used and improves the overall reliability of the circuit.

[0034] See also Figure 2 , Figure 2 A piecewise linearization correction circuit with a temperature compensation function according to an embodiment of the present application includes: a gain selection circuit and an operational amplifier;

[0035] The gain selection circuit includes a plurality of gain selection channels, each of which corresponds to a gain multiple;

[0036] The positive input terminal of the operational amplifier is connected to the output terminal of the sensor for receiving the sensing signal collected by the sensor; the reverse input terminal of the operational amplifier is connected to the output terminal of the gain selection circuit, and the gain of the operational amplifier is determined based on the conduction conditions of the multiple gain selection channels, and the conduction conditions of the gain selection channels are determined based on the size of the sensing signal.

[0037] In one embodiment, the sensing signal includes a front-end signal, a middle-end signal, and a final-end signal, the slope of the front-end signal gradually increases, and the slope of the final-end signal gradually decreases; the multiple gain selection channels include a first gain selection unit and a second gain selection unit; when the sensor collects the front-end signal, one or more gain selection channels in the first gain selection unit are turned on; when the sensor collects the final-end signal, one or more gain selection channels in the second gain selection unit are turned on.

[0038] It should be noted that the correction circuit selects one or more gain selection channels from multiple compensation modules as target gain selection channels according to the slope of the voltage amplitude of the sensing signal. For example, at the beginning of the signal, that is, the slope of the front signal increases from a small value, and a larger gain needs to be provided, and then gradually decreases. Therefore, more gain selection channels are used as target gain selection channels, and corresponding gain multiples are provided through the target gain selection channels; as the slope of the sensing signal gradually increases, the gain provided by the corresponding correction circuit needs to be reduced. Therefore, three gain selection channels are used as target gain selection channels. As the time of using the signal increases, fewer and fewer gain selection channels are required. Similarly, for the last signal, its correction method is similar to that of the front signal, and will not be repeated here.

[0039] In one embodiment, the gain selection channel of the first gain selection unit includes:

[0040] The first transistor has a collector connected to a first voltage, an emitter connected to a second voltage via a resistor, and a base connected to a first bias voltage.

[0041] It should be noted that the first transistor can be called a gain switching transistor, which is used for gain selection. When the first transistor is turned on, the corresponding gain selection channel is turned on.

[0042] In one implementation, the gain selection channel of the first gain selection unit further includes:

[0043] The base of the second transistor is connected to the emitter of the first transistor, the collector of the second transistor is connected to the second voltage, and the emitter of the second transistor is connected to the reverse input terminal of the operational amplifier via a resistor.

[0044] It should be noted that the first transistor is an NPN transistor, and the second transistor is a PNP transistor.

[0045] like Figure 3As shown, the gain selection channel is explained by taking transistor Q80 and transistor Q81 as examples. Transistor Q80 is used as the first transistor, and resistor R271 is connected in parallel between its collector and base, its emitter is connected to the second voltage through resistor R245, and its collector is connected to the first voltage; transistor Q81 is used as the second transistor, and its base is connected to the emitter of transistor Q80, its collector is connected to the second voltage, and its emitter is connected to the reverse input terminal of the operational amplifier through resistor R276. Figure 3 There are four gain selection channels in total, and the composition of each gain selection channel is the same.

[0046] exist Figure 3 In the embodiment, transistor Q80 and transistor Q81 serve as a gain selection channel, transistor Q82 and transistor Q83 serve as a gain selection channel, transistor Q84 and transistor Q85 serve as a gain selection channel, and transistor Q86 and transistor Q87 serve as a gain selection channel.

[0047] According to the signal collected by the sensor, one or more of the first gain selection channels are selected as the target gain selection channel.

[0048] It should be noted that the first voltage can provide a bias voltage for the transistor, and the second voltage is a “0” voltage.

[0049] In one embodiment, the gain selection channel of the second gain selection unit includes:

[0050] The third transistor has an emitter connected to the third voltage via a resistor, a collector connected to the fourth voltage, and a base connected to the second bias voltage.

[0051] In one embodiment, the gain selection channel of the second gain selection unit further includes:

[0052] The fourth transistor has a base connected to the emitter of the third transistor, a collector connected to the third voltage, and an emitter connected to the inverting input terminal of the operational amplifier via a resistor.

[0053] It should be noted that the third transistor is a PNP transistor, and the fourth transistor is an NPN transistor.

[0054] like Figure 3 As shown, the second gain selection channel is explained by taking transistor Q94 and transistor Q95 as examples. Transistor Q94 is used as the third transistor, and resistor R259 is connected in parallel between its collector and base, its emitter is connected to the third voltage through resistor R252, and its collector is connected to the fourth voltage; transistor Q95 is used as the fourth transistor, and its base is connected to the emitter of transistor Q95, its collector is connected to the third voltage, and its emitter is connected to the reverse input terminal of the operational amplifier through the second gain resistor (resistor R272). Figure 3 There are four gain selection channels in total, and the composition of each gain selection channel is the same.

[0055] Transistor Q94 and transistor Q95 serve as a gain selection channel, transistor Q92 and transistor Q93 serve as a gain selection channel, transistor Q91 and transistor Q90 serve as a gain selection channel, and transistor Q89 and transistor Q88 serve as a gain selection channel.

[0056] According to the signal collected by the sensor, one or more gain selection channels are selected from the above-mentioned gain selection channels as the target gain selection channel.

[0057] It should also be noted that the third voltage can provide a bias voltage for the transistor, and the bias voltage can be the same as the first voltage or different from the first voltage, while the second voltage is a "0" voltage.

[0058] It should also be noted that the first transistor, the second transistor, the third transistor and the fourth transistor are all triodes.

[0059] It should be noted that the first transistor and the third transistor can be used as gain switching transistors, and the second transistor and the fourth transistor can be used as temperature compensation transistors. The temperature compensation transistor uses the negative temperature characteristics of the PN junction to compensate for temperature. When the temperature changes, the Vbe junction voltage of the gain switching transistor will change, and the Vbe of the temperature compensation transistor will also change accordingly with the temperature. The temperature changes of the two transistors are combined together to offset each other, thereby achieving segmented linear compensation at different temperatures.

[0060] It should be noted that the overall slope of the sensor's input signal first increases from small to large, the linearity remains approximately unchanged in the middle section, and then decreases from large to small. In order to linearize the overall signal, the nonlinear parts on both sides can be linearized based on the middle section. According to the sensor characteristics, it is necessary to provide a larger gain at the beginning of the first half and then gradually reduce it. As the signal reaches the linear region, the gain remains unchanged, and the gain in the second half increases from small to large. Therefore, it is necessary to use multiple first transistors to compensate for the first half of the sensor signal, and multiple third transistors to compensate for the second half of the sensor signal.

[0061] In one embodiment, the correction circuit further includes:

[0062] The correction circuit also includes:

[0063] The gain resistor is connected in parallel between the output terminal and the inverting input terminal of the operational amplifier.

[0064] It should also be noted that in Figure 3In the circuit, resistors R272, R257, R255, R253, R273, R274, R275, and R276 are used to set the signal gain of different intervals;

[0065] U34 uses different voltage gains according to the input signal voltage range to correct the nonlinear signal;

[0066] Transistors Q81, Q83, Q85, Q87, Q88, Q90, Q92, and Q94 are transistors for gain switching. They start to conduct after reaching the segmented voltage interval. After conduction, the output gain of the operational amplifier can be changed.

[0067] Transistors Q80, Q82, Q84, Q86, Q89, Q91, Q93, and Q95 are temperature compensation transistors. The negative temperature characteristic of the PN junction is used to compensate for temperature. When the temperature changes, the Vbe junction voltage of the gain switching transistor will change, and the Vbe of the temperature compensation transistor will also change accordingly with the temperature. The temperature changes of the two transistors are combined to offset each other, so segmented linear compensation can be achieved at different temperatures.

[0068] When the sensor signal voltage is in the middle section, the gain switching transistors are not turned on, and the operational amplifier gain is 1; when the voltage gradually decreases from the middle section, the gain switching transistors Q88, Q90, Q92, and Q94 are turned on in sequence, and the signal gain increases accordingly; when the voltage gradually increases from the middle section, the gain switching transistors Q87, Q85, Q83, and Q81 are turned on in sequence, and the signal gain increases accordingly. The gain of the input signal in different intervals is shown in Table 1.

[0069] Table 1 Input signal gain comparison table

[0070]

[0071] According to the circuit simulation, the segmented linearization circuit is verified under the temperature change of -40 ~ 85℃. The simulation results are as follows Figure 4 As shown in the figure, it can be seen that under temperature changes, the output of the piecewise linearization correction circuit with temperature compensation function basically does not change with temperature. The nonlinear error at the lowest and highest points mainly comes from the insufficient number of segments, which can be solved by increasing the number of segments.

[0072] The above embodiments are merely illustrative of the principles and effects of the present application, and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A piecewise linearization correction circuit with temperature compensation function, characterized in that: The correction circuit comprises: a gain selection circuit and an operational amplifier; The gain selection circuit includes a plurality of gain selection channels, each of which corresponds to a gain multiple; The positive input terminal of the operational amplifier is connected to the output terminal of the sensor, and is used to receive the sensing signal collected by the sensor; the reverse input terminal of the operational amplifier is connected to the output terminal of the gain selection circuit, and the gain of the operational amplifier is determined based on the conduction conditions of the multiple gain selection channels, and the conduction conditions of the gain selection channels are determined based on the size of the sensing signal; The sensing signal includes a front-end signal, a middle-end signal, and a final-end signal, wherein the slope of the front-end signal gradually increases, and the slope of the final-end signal gradually decreases; the multiple gain selection channels include a first gain selection unit and a second gain selection unit; when the sensor collects the front-end signal, one or more gain selection channels in the first gain selection unit are turned on; when the sensor collects the final-end signal, one or more gain selection channels in the second gain selection unit are turned on; The gain selection channel of the first gain selection unit comprises: a first transistor, whose collector is connected to a first voltage, whose emitter is connected to a second voltage via a resistor, and whose base is connected to a first bias voltage; The gain selection channel of the second gain selection unit includes: a third transistor, an emitter of which is connected to a third voltage via a resistor, a collector of which is connected to a fourth voltage, and a base of which is connected to a second bias voltage.

2. The piecewise linearization correction circuit with temperature compensation function according to claim 1, characterized in that: The gain selection channel of the first gain selection unit also includes: The base of the second transistor is connected to the emitter of the first transistor, the collector of the second transistor is connected to the second voltage, and the emitter of the second transistor is connected to the reverse input terminal of the operational amplifier via a resistor.

3. The piecewise linearization correction circuit with temperature compensation function according to claim 2, characterized in that: The first transistor is an NPN transistor, and the second transistor is a PNP transistor.

4. The piecewise linearization correction circuit with temperature compensation function according to claim 1, characterized in that: The gain selection channel of the second gain selection unit also includes: The fourth transistor has a base connected to the emitter of the third transistor, a collector connected to the third voltage, and an emitter connected to the inverting input terminal of the operational amplifier via a resistor.

5. The piecewise linearization correction circuit with temperature compensation function according to claim 4, characterized in that: The third transistor is a PNP transistor, and the fourth transistor is an NPN transistor.

6. The piecewise linearization correction circuit with temperature compensation function according to claim 1, characterized in that: The correction circuit also includes: a plurality of voltage-dividing resistors and a reference voltage source, wherein the plurality of voltage-dividing resistors are connected in series and then connected in parallel with the reference voltage source; and one or more of the voltage-dividing resistors provide a conduction voltage for the plurality of gain selection channels.

7. The piecewise linearization correction circuit with temperature compensation function according to claim 1, characterized in that: The correction circuit also includes: The gain resistor is connected in parallel between the output terminal and the inverting input terminal of the operational amplifier.

Images