A differential scanning calorimeter thermocouple temperature difference detection circuit

Abstract

The utility model provides a differential scanning calorimeter thermocouple temperature difference detection circuit belongs to calorimeter temperature difference detection circuit technical field, and the circuit specifically includes input filter module, first amplification module, second amplification module and output filter module, above -mentioned each module connects in proper order, input filter module is still connected with a connector DC2 for introducing the outside direct current signal into the circuit one side away from first amplification module, first amplification module main part includes parallel operational amplifier U2.1 and operational amplifier U2.2, the negative phase input of operational amplifier U2.1 is connected with the negative phase input of operational amplifier U2.2 through a resistance R18, and the combination forms differential amplifier circuit, this differential scanning calorimeter thermocouple temperature difference detection circuit can solve the current existing differential loss scanning calorimeter because the problem that the baseline of calorimeter is greater than 0 is caused to the direct transmission of the amplified misadjustment voltage and misadjustment current of amplifier to ADC collection after amplification.

Description

Technical Field

[0001] This utility model belongs to the technical field of calorimeter temperature difference detection circuit, specifically relating to a differential scanning calorimeter thermocouple temperature difference detection circuit. Background Technology

[0002] In differential scanning calorimeters, it is necessary to detect the temperature difference between the sample plate and the reference plate, and then convert it into a heat flux value. When measuring the temperature difference signal, it is easily affected by the operational amplifier input offset voltage and offset current, which leads to errors in the back-end measurement.

[0003] The existing solution uses an instrumentation amplifier for differential acquisition, and the offset voltage and offset current of the instrumentation amplifier are amplified and directly transmitted to the ADC for acquisition.

[0004] Existing technologies include an output voltage bias in ADC acquisition caused by the performance of the instrumentation amplifier itself. This bias affects the baseline of the differential scanning calorimeter, causing the baseline value to be greater than 0. Utility Model Content

[0005] In view of this, this utility model proposes a differential scanning calorimeter thermocouple temperature difference detection circuit, which can solve the problem that the baseline of the differential scanning calorimeter is not near 0 due to the output voltage bias.

[0006] This utility model is implemented as follows:

[0007] This utility model provides a differential scanning calorimeter thermocouple temperature difference detection circuit. The circuit specifically includes an input filtering module, a first amplification module, a second amplification module, and an output filtering module, which are connected in sequence. The input filtering module is also connected to a connector DC2 on the side away from the first amplification module.

[0008] The first amplification module includes operational amplifiers U2.1 and U2.2 connected in parallel; the negative phase input terminals of operational amplifiers U2.1 and U2.2 are connected through a resistor R18 to form a differential amplifier circuit.

[0009] The second amplification module includes operational amplifiers U14.1 and U14.2 connected in parallel. The non-inverting input terminals of operational amplifiers U14.1 and U14.2 are connected through a capacitor C2.

[0010] The output terminal of operational amplifier U2.1 is connected to the non-inverting input terminal of operational amplifier U14.1 through resistor R13; the output terminal of operational amplifier U2.2 is connected to the non-inverting input terminal of operational amplifier U14.2 through resistor R20.

[0011] The technical advantages of the differential scanning calorimeter thermocouple temperature difference detection circuit provided by this utility model are as follows: By setting connector DC2, external DC signals (S+ and S-) are introduced into the circuit to provide input signals for subsequent circuit processing; by setting operational amplifiers U2.1 and U2.2 to form a differential amplifier circuit, the input signal is initially amplified to increase the signal amplitude; by setting operational amplifier U14.1, the initially amplified input signal is further amplified; by setting operational amplifier U14.2, the preceding and following stage circuits are isolated, improving the circuit's load-carrying capacity.

[0012] Based on the above technical solution, the differential scanning calorimeter thermocouple temperature difference detection circuit of this utility model can be further improved as follows:

[0013] Furthermore, a capacitor C1 and a resistor R12 are connected in parallel between the negative input terminal and the output terminal of the operational amplifier U2.1, and the capacitor C1 and the resistor R12 form the feedback network of the operational amplifier U2.1; a capacitor C29 and a resistor R19 are connected in parallel between the negative input terminal and the output terminal of the operational amplifier U2.2, and the capacitor C29 and the resistor R19 form the feedback network of the operational amplifier U2.2.

[0014] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by setting resistors R12 and R19, the feedback strength of the differential amplifier circuit can be set, which determines the DC gain and low-frequency gain of the operational amplifier; by setting capacitors C1 and C29, high-frequency signals can be suppressed, the high-frequency gain of the circuit can be limited, and the circuit can be prevented from generating self-excited oscillations in the high-frequency range.

[0015] Furthermore, the input filtering module includes a common-mode inductor L2, the two inputs of which are connected to the connector DC2, and the two outputs are respectively connected to a protection resistor R1 and a resistor R2; capacitors C26 and C27 are connected in parallel between the two output lines of the common-mode inductor L2.

[0016] Furthermore, the resistance of resistors R1 and R2 is 0, and the capacitances of capacitors C26 and C27 are the same.

[0017] Furthermore, the operational amplifiers U2.1 and U2.2 share the same power supply pin, as do the operational amplifiers U14.1 and U14.2; all operational amplifiers are connected to a 2.5V power supply.

[0018] Furthermore, the output filtering module includes two resistors R53 and R54 connected in series, and two capacitors C91 and C92 connected in parallel; resistor R53 is connected to the output terminal of operational amplifier U14.1, and resistor R54 is connected to the output terminal of operational amplifier U14.2; the two ends of capacitors C91 and C92 are respectively connected to resistors R53 and R54.

[0019] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by setting resistors R53 and R54, impedance matching is achieved, signal reflection is reduced, and signal transmission efficiency is improved; by setting capacitors C91 and C92, high-frequency noise in the output signal is filtered out, ensuring the purity of the output signal.

[0020] Furthermore, both operational amplifier U2.1 and operational amplifier U2.2 are of model OPA2189IDR, and both operational amplifier U14.1 and operational amplifier U14.2 are of model TP5552-SR.

[0021] Furthermore, the connector DC2 is specifically a 2-pin connector with a pitch of 3.96mm.

[0022] Furthermore, the input filtering module also includes a capacitor C31, one end of which is connected to the resistor R2, and the other end is grounded.

[0023] Compared with existing technologies, the beneficial effects of the differential scanning calorimeter thermocouple temperature difference detection circuit provided by this utility model are as follows: When the input voltage is 0V, this solution can accurately detect that the differential voltage between the in-phase output and the negative-phase output is 0V. By setting dual operational amplifiers and ADC differential input, the influence of amplifier offset voltage and offset current on temperature difference signal acquisition is solved instead of instrumentation amplifier. This thermocouple temperature difference detection circuit can solve the problem in existing technologies where output voltage bias in ADC acquisition causes the differential scanning calorimeter baseline to be greater than 0. Attached Figure Description

[0024] Figure 1 The overall circuit diagram for the detection circuit;

[0025] Figure 2 This is the circuit diagram for the input filter module;

[0026] Figure 3 This is the circuit diagram of the first amplification module;

[0027] Figure 4 This is the circuit diagram of the second amplifier module;

[0028] Figure 5 This is the circuit diagram of the output filter module. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the scope of the present utility model.

[0030] like Figures 1-5 The diagram shows a differential scanning calorimeter thermocouple temperature difference detection circuit provided by this invention. This circuit includes an input filtering module, a first amplification module, a second amplification module, and an output filtering module, which are connected sequentially. A connector DC2 is also connected to the side of the input filtering module furthest from the first amplification module. Connector DC2 is mainly used to introduce external DC signals into the circuit provided in this application, providing input signals for subsequent circuit processing.

[0031] The input filtering module includes a common-mode inductor L2, three protection resistors R1, R2, and R26, two parallel capacitors C26 and C27, and a grounding capacitor C22. The common-mode inductor L2 is primarily used to suppress common-mode interference and improve the circuit's anti-interference capability. The protection resistors R1, R2, and R26 are all 0-ohm resistors, mainly used to prevent fires caused by circuit breaks. Capacitors C26, C27, and C22 are filter capacitors, mainly used to filter out noise on the power lines and improve the operational stability of subsequent operational amplifiers.

[0032] The forward output of inductor L2 is connected to resistor R1, and the reverse output is connected to resistor R2. One end of resistor R26 is connected to resistor R2, and the other end is grounded. One end of capacitor C22 is connected to resistor R1, and the other end is grounded. The two parallel capacitors C26 and C27 are connected to resistors R1 and R2 respectively.

[0033] The first amplification module mainly includes operational amplifier U2.1 and operational amplifier U2.2. The two operational amplifiers are combined to form a differential amplifier circuit, which initially amplifies the input temperature difference signal and increases the signal amplitude to facilitate subsequent processing.

[0034] The non-inverting input of operational amplifier U2.1 is connected to resistor R1, and the non-inverting input of operational amplifier U2.2 is connected to resistor R2; the negative input of operational amplifier U2.1 is connected to the negative input of operational amplifier U2.2 through resistor R18; the outputs of operational amplifiers U2.1 and U2.2 are independently connected to the second amplification module.

[0035] The positive power supply terminal of operational amplifier U2.1 is connected to the positive terminal of a 2.5V power supply and is also grounded through a capacitor C87; the negative power supply terminal of operational amplifier U2.1 is connected to the negative terminal of a 2.5V power supply and is also grounded through a capacitor C88. Both capacitors C87 and C88 are power supply filter capacitors, primarily used to filter out noise on the power lines and improve the operational amplifier's operational stability.

[0036] A resistor R12 and a capacitor C1 are connected in parallel between the negative input terminal and the output terminal of operational amplifier U2.1. Resistor R12 and capacitor C1 constitute the feedback circuit of operational amplifier U2.1. A resistor R19 and a capacitor C29 are connected in parallel between the negative input terminal and the output terminal of operational amplifier U2.2. Resistor R19 and capacitor C29 constitute the feedback circuit of operational amplifier U2.2.

[0037] The second amplification module includes operational amplifiers U14.1 and U14.2. Operational amplifier U14.1 serves as a secondary amplifier to further amplify the signal output from the first amplification module. Operational amplifier U14.2 serves as a buffer to isolate the preceding and following circuits and improve the circuit's load-carrying capacity.

[0038] Operational amplifier U14.1's non-inverting input is connected to the output of operational amplifier U2.1 via resistor R13, and is also grounded via capacitor C23. Operational amplifier U14.2's non-inverting input is connected to the output of operational amplifier U2.2 via resistor R20, and is also grounded via capacitor C30. The non-inverting inputs of operational amplifiers U14.1 and U14.2 are connected together via capacitor C2. The negative input of operational amplifier U14.1 is connected to its output, and the negative input of operational amplifier U14.2 is also connected to its output.

[0039] Resistors R13 and R20 are feedback resistors, mainly used to set the amplification factor; capacitors C23 and C30 are power supply filter capacitors, used to filter out noise on the power line.

[0040] The positive power supply terminal of operational amplifier U14.1 is connected to a 2.5V positive power supply, and is also grounded through capacitor C16; the negative power supply terminal of operational amplifier U14.1 is connected to a 2.5V negative power supply, and is also grounded through capacitor C15.

[0041] The output filtering module includes two resistors, R53 and R54, connected in series, and two capacitors, C91 and C92, connected in parallel. Resistor R53 is connected to the output of operational amplifier U14.1, and resistor R54 is connected to the output of operational amplifier U14.2. The two ends of the parallel capacitors C91 and C92 are connected to resistors R53 and R54, respectively. The end of resistor R53 furthest from operational amplifier U14.1 is denoted as IN-S+, and the end of resistor R54 furthest from operational amplifier U14.2 is denoted as IN-S-.

[0042] Resistors R53 and R54 are matching resistors used to achieve impedance matching, reduce signal reflection, and improve signal transmission efficiency; capacitors C91 and C92 are filter capacitors used to filter out high-frequency noise in the output signal and ensure the purity of the output signal.

[0043] Optionally, in the above scheme, the input filtering module also includes a capacitor C31. One end of capacitor C31 is connected to resistor R2, and the other end is grounded. Capacitor C31 is a reserved capacitor position for future circuit expansion.

[0044] Optionally, in the above scheme, operational amplifiers U2.1 and U2.2 are both of model OPA2189IDR, and operational amplifiers U14.1 and U14.2 are both of model TP5552-SR.

[0045] Optionally, in the above scheme, connector DC2 is specifically a 2-pin connector with a pitch of 3.96mm.

[0046] Optionally, in the above scheme, the capacitance values ​​of capacitors C26, C1, and C29 are all 1uF.

[0047] Optionally, in the above scheme, the capacitance values ​​of capacitors C22, C87, C88, C16, C15, and C91 are all 100nF.

[0048] Optionally, in the above scheme, the resistance values ​​of resistors R12 and R19 are equal; the resistance values ​​of resistors R13 and R20 are equal; and the resistance values ​​of resistors R53 and R54 are equal.

[0049] The specific principle of this utility model is as follows:

[0050] The preamplifier section of the instrumentation amplifier is constructed using dual operational amplifiers. The two differential signals are directly transmitted to the ADC with differential channel acquisition. The differential function of the ADC is used to solve the problem of non-zero baseline caused by offset voltage and offset current of the instrumentation amplifier.

[0051] First, the signal passes through a common-mode filter inductor to remove common-mode noise. Then, the positive and negative signals are amplified separately, passed through a low-pass filter, and then enter two followers. The outputs of the followers are then connected to the ADC. This means that the offset voltage and offset current of the amplifier connected to the positive terminal of the sensor will also appear at the negative terminal of the sensor. This is equivalent to converting the offset voltage and offset current of the amplifier into common-mode signals, which are then transmitted to the ADC in a differential form, thus eliminating their influence.

[0052] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A differential scanning calorimeter thermocouple temperature difference detection circuit, characterized in that, The circuit specifically includes an input filtering module, a first amplification module, a second amplification module, and an output filtering module, which are connected in sequence. The input filtering module is also connected to a connector DC2 on the side away from the first amplification module for introducing external DC signals into the circuit. The first amplification module includes operational amplifiers U2.1 and U2.2 connected in parallel; the negative phase input terminals of operational amplifiers U2.1 and U2.2 are connected through a resistor R18 to form a differential amplifier circuit. The second amplification module includes operational amplifiers U14.1 and U14.2 connected in parallel. The non-inverting input terminals of operational amplifiers U14.1 and U14.2 are connected through a capacitor C2. Operational amplifier U14.1 is used to amplify the signal amplified by the first amplification module, and operational amplifier U14.2 acts as a buffer to isolate the preceding and following circuits and improve the circuit's load capacity. The output terminal of operational amplifier U2.1 is connected to the non-inverting input terminal of operational amplifier U14.1 through resistor R13; the output terminal of operational amplifier U2.2 is connected to the non-inverting input terminal of operational amplifier U14.2 through resistor R20.

2. The differential scanning calorimeter thermocouple temperature difference detection circuit according to claim 1, characterized in that, A capacitor C1 and a resistor R12 are connected in parallel between the negative input terminal and the output terminal of operational amplifier U2.1, and the capacitor C1 and resistor R12 form the feedback network of operational amplifier U2.1; a capacitor C29 and a resistor R19 are connected in parallel between the negative input terminal and the output terminal of operational amplifier U2.2, and the capacitor C29 and resistor R19 form the feedback network of operational amplifier U2.2; The resistors R12 and R19 are used to set the feedback strength, which determines the DC gain and low-frequency gain of the operational amplifier; the capacitors C1 and C29 are used to suppress high-frequency signals, limit the high-frequency gain of the circuit, and prevent the circuit from generating self-oscillation in the high-frequency range.

3. The differential scanning calorimeter thermocouple temperature difference detection circuit according to claim 2, characterized in that, The input filtering module includes a common-mode inductor L2. The input terminal of the common-mode inductor L2 is connected to the connector DC2, and the two output terminals are respectively connected to a protection resistor R1 and a resistor R2. Capacitors C26 and C27 are connected in parallel between the two output lines of the common-mode inductor L2.

4. The differential scanning calorimeter thermocouple temperature difference detection circuit according to claim 2, characterized in that, The resistances of resistors R1 and R2 are 0, and the capacitances of capacitors C26 and C27 are the same.

5. The differential scanning calorimeter thermocouple temperature difference detection circuit according to claim 4, characterized in that, The operational amplifiers U2.1 and U2.2 share the same power supply pin, as do the operational amplifiers U14.1 and U14.2; all operational amplifiers are connected to a 2.5V power supply.

6. The differential scanning calorimeter thermocouple temperature difference detection circuit according to claim 5, characterized in that, The output filtering module includes two resistors R53 and R54 connected in series, and two capacitors C91 and C92 connected in parallel; resistor R53 is connected to the output terminal of operational amplifier U14.1, and resistor R54 is connected to the output terminal of operational amplifier U14.2; the two ends of capacitors C91 and C92 are respectively connected to resistors R53 and R54. The resistors R53 and R54 are matching resistors used to achieve impedance matching; the capacitors C91 and C92 are filter capacitors used to filter out high-frequency noise in the output signal.

7. The differential scanning calorimeter thermocouple temperature difference detection circuit according to claim 6, characterized in that, The operational amplifiers U2.1 and U2.2 are both of model OPA2189IDR, and the operational amplifiers U14.1 and U14.2 are both of model TP5552-SR.

8. The differential scanning calorimeter thermocouple temperature difference detection circuit according to claim 7, characterized in that, The connector DC2 is specifically a 2-pin connector with a pitch of 3.96mm.

9. A differential scanning calorimeter thermocouple temperature difference detection circuit according to claim 8, characterized in that, The input filtering module also includes a capacitor C31, one end of which is connected to the resistor R2, and the other end is grounded.

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