Design method of thermostatic bath

Abstract

The invention provides a design method of a thermostatic bath. The method belongs to the technical field of oscillators, and comprises the following steps: when an external temperature is changed from a first external temperature to a second external temperature, testing a temperature change corresponding to a crystal resonator; based on the temperature change, determining a current temperature coefficient corresponding to the to-be-designed thermostatic bath; determining the position of a temperature sensor based on the current temperature coefficient corresponding to the to-be-designed thermostatic bath; and based on the temperature change corresponding to the crystal resonator, adjusting the gain of a temperature control circuit in the to-be-designed thermostatic bath to obtain the designed to-be-designed thermostatic bath. According to the method provided by the embodiment of the invention, blindness caused by a trial and error method in traditional thermostatic bath design can be overcome, and the design efficiency of the thermostatic bath is greatly improved; and meanwhile, by finely adjusting the gain on the circuit, the temperature control precision higher than that of the traditional design can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of oscillators, and in particular to a design method for a thermostatic bath. Background Art

[0002] In order to ensure that the oven-controlled crystal oscillator achieves high frequency temperature stability, the temperature of its core component, the crystal resonator, needs to remain constant when the ambient temperature fluctuates. To ensure this, a constant temperature bath is usually used at this stage.

[0003] The current design idea of ​​thermostat is "stabilize the temperature sensor first, then stabilize the crystal resonator", that is, firstly, through a high-gain temperature control circuit, the temperature of the temperature sensor is almost unchanged when the ambient temperature changes; then, by repeatedly adjusting the thermal layout of the heating element, temperature sensor and crystal resonator, the crystal resonator is placed on the same isotherm as the temperature sensor as much as possible. Obviously, this method requires multiple rounds of iterations, a long design cycle, low efficiency, and the final temperature control accuracy of the quartz crystal resonator is usually not ideal. Therefore, a high-efficiency and high-precision thermostat design method is very meaningful. Summary of the invention

[0004] The embodiment of the present invention provides a design method of a thermostatic bath, so as to solve the problems of low efficiency in the current thermostatic bath design process and low precision of the thermostatic bath finally obtained.

[0005] In a first aspect, an embodiment of the present invention provides a method for designing a thermostatic bath, comprising: When the outside temperature changes from the first outside temperature to the second outside temperature, testing the temperature change corresponding to the crystal resonator in the thermostatic bath to be designed; Based on the temperature change, determine the current temperature coefficient corresponding to the thermostatic bath to be designed; wherein the temperature coefficient includes a negative temperature coefficient, a zero temperature coefficient and a positive temperature coefficient; Based on the current temperature coefficient corresponding to the thermostatic bath to be designed, determining the position of the temperature sensor in the thermostatic bath to be designed; Based on the temperature change corresponding to the crystal resonator, the gain of the temperature control circuit in the thermostatic bath to be designed is adjusted to obtain the designed thermostatic bath to be designed.

[0006] In a possible implementation, the thermostatic bath to be designed further includes a heating element; The temperature coefficient corresponding to the thermostatic bath to be designed is defined as: When the thermal resistance between the temperature sensor and the crystal resonator is greater than the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient; When the thermal resistance between the temperature sensor and the crystal resonator is equal to the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient; When the thermal resistance between the temperature sensor and the crystal resonator is less than the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient.

[0007] In a possible implementation, determining a current temperature coefficient corresponding to the thermostatic bath to be designed based on the temperature change includes: If the outside temperature rises and the temperature of the crystal resonator drops, it is determined that the current temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient; If the external temperature rises and the temperature change degree of the crystal resonator is less than the preset temperature change threshold, it is determined that the current temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient.

[0008] If the outside temperature rises, the temperature of the crystal resonator rises, and it is determined that the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient.

[0009] In a possible implementation, determining the position of a temperature sensor in the thermostatic bath to be designed based on a current temperature coefficient corresponding to the thermostatic bath to be designed includes: If the current temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient or a zero temperature coefficient, there is no need to adjust the position of the temperature sensor in the thermostatic bath to be designed; If the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient, the temperature sensor in the thermostatic bath to be designed is moved in a target direction away from the heating element.

[0010] In a possible implementation, if the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient, the temperature sensor in the thermostatic bath to be designed is moved in a target direction away from the heating element, including: If the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient, the temperature sensor in the thermostatic bath to be designed is moved in the target direction away from the heating element, and the step of testing the temperature change corresponding to the crystal resonator in the thermostatic bath to be designed when the outside temperature changes from the first outside temperature to the second outside temperature is returned until the current temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient or a negative temperature coefficient.

[0011] In a possible implementation, based on the temperature change corresponding to the crystal resonator, the gain of the temperature control circuit in the thermostatic bath to be designed is adjusted to obtain a designed thermostatic bath to be designed, including: Determine a temperature change difference corresponding to the crystal resonator in the thermostatic bath to be designed when the external temperature changes from a first external temperature to a second external temperature; The gain of the temperature control circuit in the thermostatic bath to be designed is reduced to a first gain value, and a first temperature change value corresponding to the crystal resonator in the thermostatic bath to be designed is determined when the outside temperature changes from the first outside temperature to the second outside temperature when the gain of the temperature control circuit is the first gain value; According to the temperature change difference, the first gain value and the first temperature change value, a first target gain value of the temperature control circuit is determined; and the gain of the temperature control circuit is adjusted based on the first target gain value to obtain a designed constant temperature bath to be designed.

[0012] In a possible implementation, the ambient temperature change value, the first gain value, the first temperature change value, and the first target gain value satisfy the following relationship: K x1 =-K1*ΔT1 / ΔT0 Among them, K x1 is the first target gain value; K1 is the first gain value; ΔT1 is the first temperature change value; ΔT0 is the temperature change difference.

[0013] In a possible implementation, based on the temperature change corresponding to the crystal resonator, the gain of the temperature control circuit in the thermostatic bath to be designed is adjusted to obtain a designed thermostatic bath to be designed, including: Determine a temperature change difference corresponding to the crystal resonator in the thermostatic bath to be designed when the external temperature changes from a first external temperature to a second external temperature; The gain of the temperature control circuit in the thermostatic bath to be designed is reduced to a first gain value, and a first temperature change value corresponding to the crystal resonator in the thermostatic bath to be designed is determined when the outside temperature changes from the first outside temperature to the second outside temperature when the gain of the temperature control circuit is the first gain value; The gain of the temperature control circuit in the thermostatic bath to be designed is reduced to a second gain value, and a second temperature change value of the crystal resonator in the thermostatic bath to be designed corresponding to the change of the ambient temperature from the first ambient temperature to the second ambient temperature is determined when the gain of the temperature control circuit is the second gain value; According to the temperature change difference, the first gain value, the first temperature change value, the second gain value and the second temperature change value, the second target gain value of the temperature control circuit is determined; the gain of the temperature control circuit is adjusted based on the second target gain value to obtain the designed constant temperature bath to be designed.

[0014] In a possible implementation, the ambient temperature change value, the first gain value, the first temperature change value, the second gain value, the second temperature change value, and the second target gain value satisfy the following relationship: K x2 =-(ΔT2-ΔT1) / (1 / K2-1 / K1) / ΔT0 Among them, K x2 is the second target gain value; ΔT2 is the second temperature change value; ΔT1 is the first temperature change value; K2 is the second gain value; K1 is the first gain value; ΔT0 is the temperature change difference.

[0015] In a possible implementation, the heating element is a heating transistor; The temperature control circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first operational amplifier and a second operational amplifier; A first end of the first resistor is connected to a power supply, a second end of the first resistor is connected to a first end of the temperature sensor and a non-inverting input end of the first operational amplifier through a fourth resistor, and a second end of the temperature sensor is grounded; The first end of the second resistor is connected to the power supply, and the second end is connected to the first end of the third resistor and the out-of-phase input end of the first operational amplifier; the second end of the third resistor is grounded; A first end of the eighth resistor is connected to the out-of-phase input terminal of the first operational amplifier, and a second end of the eighth resistor is connected to the output terminal of the first operational amplifier; A first end of the sixth resistor is connected to the power supply, a second end is connected to the first end of the fifth resistor and the non-inverting input end of the second operational amplifier, and a second end of the fifth resistor is connected to the output end of the first operational amplifier; The first end of the seventh resistor is connected to the power supply, and the second end is respectively connected to the out-of-phase input terminal of the second operational amplifier and the emitter of the heating transistor; the collector of the heating transistor is grounded, and the base is connected to the output terminal of the second operational amplifier.

[0016] The embodiment of the present invention provides a design method for a thermostatic bath. Compared with the problem of low precision in the traditional method, the embodiment of the present invention divides the design process of the thermostatic bath into the position adjustment link of the temperature sensor and the gain coefficient control link of the temperature control circuit. In general, the general structure of the thermostatic bath is determined by adjusting the position of the temperature sensor. In detail, the accuracy of the thermostatic bath can be improved by controlling the gain coefficient of the temperature control circuit. Since the traditional thermostatic bath design method mostly uses the trial and error method to adjust the position of the temperature sensor, the efficiency is low. In this embodiment, the temperature coefficient of the thermostatic bath is divided into a negative temperature coefficient, a zero temperature coefficient and a positive temperature coefficient. In this case, the negative temperature coefficient and the zero temperature coefficient are assumed to be normal. When adjusting, only the thermostatic bath under the positive temperature coefficient is adjusted. Moreover, the temperature coefficient is used as an adjustment index, which can greatly reduce the number of iterations during design, reduce costs, and also improve efficiency. In summary, it can be seen that the method provided by the embodiment of the present invention can overcome the blindness caused by the trial and error method in the design of the traditional thermostatic bath, and greatly improve the design efficiency of the thermostatic bath; at the same time, by finely adjusting the gain on the circuit, a higher temperature control accuracy can be obtained than the traditional design. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 is a flow chart of the implementation of the design method of the thermostatic bath provided by the embodiment of the present invention; Figure 2 This is a thermal distribution diagram of the main components in the negative temperature coefficient thermostatic bath provided by an embodiment of the present invention; Figure 3 It is a thermal distribution diagram of the main components in the zero temperature coefficient thermostatic bath provided by an embodiment of the present invention; Figure 4 This is a thermal distribution diagram of the main components in the positive temperature coefficient thermostatic bath provided by an embodiment of the present invention; Figure 5 4 is a schematic diagram of a heating circuit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0021] Figure 1 : is a flow chart of a method for designing a thermostatic bath provided by an embodiment of the present invention, and the method may include: Step 110: When the external temperature changes from the first external temperature to the second external temperature, the temperature change corresponding to the crystal resonator in the thermostatic bath to be designed is tested.

[0022] In this embodiment, the thermostatic bath to be designed may include a heating element, a temperature sensor, a crystal resonator, a temperature control circuit and other parts. The heating element is the position with the highest temperature in the thermostatic bath to be designed, and is used to generate heat to maintain the temperature in the thermostatic bath to be designed so that the temperature of the crystal resonator is constant; the temperature sensor is used to measure the temperature in the thermostatic bath to be designed, and transmit the detected temperature to the temperature control circuit through an electrical signal; the temperature control circuit is used to control the temperature generated by the heating element through positive and negative feedback according to the received temperature signal, so as to adjust the temperature in the thermostatic bath.

[0023] In this embodiment, when testing, the temperature change or B-mode frequency change corresponding to the crystal resonator in the thermostatic bath to be designed can be recorded when the external temperature rises from the first external temperature to the second external temperature. The temperature change or B-mode frequency change corresponding to the crystal resonator in the thermostatic bath to be designed can also be recorded when the external temperature drops from the first external temperature to the second external temperature. The specific external temperature change can be set as needed. For the sake of convenience, each embodiment in this embodiment takes the parameter change corresponding to the thermostatic bath to be designed when the external temperature rises as an example.

[0024] Step 120: Based on the temperature change, determine the current temperature coefficient corresponding to the thermostatic bath to be designed; wherein the temperature coefficient includes a negative temperature coefficient, a zero temperature coefficient, and a positive temperature coefficient.

[0025] In this embodiment, according to the thermal resistance between the temperature sensor and the crystal resonator, and the thermal resistance between the crystal resonator and the heating element, the thermostatic bath to be designed can be divided into a negative temperature coefficient thermostatic bath, a zero temperature thermostatic bath, and a positive temperature coefficient thermostatic bath. The classification criteria are as follows: When the thermal resistance between the temperature sensor and the crystal resonator is greater than the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient.

[0026] When the thermal resistance between the temperature sensor and the crystal resonator is equal to the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient.

[0027] When the thermal resistance between the temperature sensor and the crystal resonator is less than the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient.

[0028] Considering that it is difficult to obtain accurate thermal resistance, in order to improve accuracy and reduce the amount of calculation, this embodiment takes into account the different characteristics of the thermostatic bath to be designed under different temperature coefficients, namely: If the thermostatic bath to be designed is a negative temperature coefficient thermostatic bath, when the outside temperature rises from low temperature to high temperature, the temperature of the crystal resonator therein will decrease; If the thermostatic bath to be designed is a zero temperature coefficient thermostatic bath, then when the outside temperature rises from low temperature to high temperature, the temperature of the crystal resonator therein remains basically unchanged; If the thermostatic bath to be designed is a positive temperature coefficient thermostatic bath, when the outside temperature rises from low temperature to high temperature, the temperature of the crystal resonator therein will increase.

[0029] Accordingly, the current temperature coefficient corresponding to the thermostatic bath to be designed can be determined in the following way: If the outside temperature gradually increases, the temperature of the crystal resonator gradually decreases, and the decrease is greater than the preset temperature change threshold, it can be determined that the current temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient.

[0030] If the outside temperature gradually increases and the temperature of the crystal resonator remains substantially unchanged, that is, the degree of change is less than a preset temperature change threshold, it can be determined that the current temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient.

[0031] If the outside temperature gradually increases, the temperature of the crystal resonator also gradually increases, which means that the current temperature coefficient corresponding to the constant temperature bath to be designed is a positive temperature coefficient.

[0032] In another optional embodiment, considering that when the temperature of the crystal resonator changes, its corresponding B-mode frequency will also change accordingly, accordingly, in another optional embodiment, the B-mode frequency change corresponding to the crystal resonator in the thermostatic bath to be designed can also be recorded when the external temperature rises, so as to determine the current temperature coefficient corresponding to the thermostatic bath to be designed according to the B-mode frequency change. That is: If the outside temperature gradually increases, the B mode frequency also gradually increases, that is, the frequency increase is greater than the preset frequency change threshold, then it is determined that the current temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient.

[0033] If the outside temperature gradually increases and the B-mode frequency remains substantially unchanged, that is, the degree of change in the B-mode frequency is less than a preset frequency change threshold, then the current temperature coefficient corresponding to the thermostatic bath to be designed is determined to be a zero temperature coefficient.

[0034] If the outside temperature gradually increases and the B mode frequency gradually decreases, it is determined that the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient.

[0035] Step 130: Determine the position of the temperature sensor in the thermostatic bath to be designed based on the current temperature coefficient corresponding to the thermostatic bath to be designed.

[0036] In this embodiment, the current temperature coefficient corresponding to the thermostatic bath to be designed is used as a reference for adjusting the position of the temperature sensor. Considering that a thermostatic bath with a zero temperature coefficient is difficult to obtain, but a thermostatic bath with a negative temperature coefficient is easy to obtain, if the current temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient or a zero temperature coefficient, the thermostatic bath to be designed is considered to be standard at this time, and the position of the temperature sensor therein does not need to be adjusted.

[0037] If the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient, it is necessary to increase the thermal resistance between the heating elements in the sensor industry, that is, to move the temperature sensor in the thermostatic bath to be designed in the target direction away from the heating elements.

[0038] Figure 2-Figure 4 They are the thermal distribution diagrams of the main components in the negative temperature coefficient thermostat, the zero temperature coefficient thermostat and the positive temperature coefficient thermostat provided by the embodiments of the present invention. Figure 2-Figure 4 This embodiment is described.

[0039] exist Figure 2-Figure 4 The device includes a heating element 1, a temperature sensor 2 and a crystal resonator 3. The curve is an isotherm. The location of the heating element 1 is the location with the highest temperature in the thermostatic bath to be designed. With the heating element 1 as the origin, heat flows outward along the direction of the marked arrow.

[0040] exist Figure 2 The thermal resistance R between the heating element 1 and the temperature sensor 2 is 12 Greater than the thermal resistance R between the heating element 1 and the crystal resonator 3 13 The heat P at the isothermal line where the crystal resonator 3 is located flows to the isothermal line where the temperature sensor 2 is located. The thermal resistance R between the temperature sensor 2 and the crystal resonator 3 23When the gain of the temperature control circuit is very high, the temperature T2 detected by the temperature sensor 2 does not change when the external temperature changes, and the temperature of the crystal resonator 3 is: T3=T2+P*R 23 In this case, when the outside temperature changes from low temperature to high temperature, T2 remains unchanged. In order to prevent the temperature of the crystal resonator 3 from rising, the heating element 1 reduces the heat generation, so that the heat P decreases linearly with the outside temperature, and then the temperature T3 of the crystal resonator 3 decreases linearly with the outside temperature. This is the characteristic and principle of the negative temperature coefficient thermostat.

[0041] exist Figure 3 In the example, since the gain of the temperature control circuit is very high, when the external temperature changes, it can be considered that the temperature of the temperature sensor 2 will not change. Correspondingly, since the temperature sensor 2 and the crystal resonator 3 are on the same isotherm, it can also be considered that the temperature of the crystal resonator 3 will not change. This is the characteristic and principle of the zero temperature coefficient thermostat.

[0042] exist Figure 4 The thermal resistance R between the heating element 1 and the temperature sensor 2 is 12 Smaller than the thermal resistance R between the heating element 1 and the crystal resonator 3 13 , the heat P at the isotherm where the temperature sensor 2 is located flows to the isotherm where the crystal resonator 3 is located, and the thermal resistance R between the temperature sensor 2 and the crystal resonator 3 23 When the gain of the temperature control circuit is very high, the temperature T2 detected by the temperature sensor 2 does not change when the external temperature changes, and the temperature of the crystal resonator 3 is: T3=T2-P*R 23 In this case, when the outside temperature changes from low temperature to high temperature, T2 remains unchanged. In order to prevent the temperature of the crystal resonator 3 from rising, the heating element 1 reduces the heat generation, so that the heat P decreases linearly with the outside temperature, and then the temperature T3 of the crystal resonator 3 increases linearly with the outside temperature. This is the characteristic and principle of the positive temperature coefficient thermostat.

[0043] against Figure 4 Given the situation in the positive temperature coefficient thermostatic bath, it is necessary to adjust the position of the temperature sensor 2. The following describes how to adjust the position of the temperature sensor 2 in the positive temperature coefficient thermostatic bath through an optional embodiment.

[0044] If the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient, the temperature sensor 2 in the thermostatic bath to be designed is moved in the target direction away from the heating element 1, and returns to the step of testing the temperature change corresponding to the crystal resonator 3 in the thermostatic bath to be designed when the external temperature changes from the first external temperature to the second external temperature, until the current temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient or a negative temperature coefficient.

[0045] In this embodiment, if Figure 4 As shown, the dotted line is the target direction, and "★" is the final position of the temperature sensor 2. The purpose of adjusting the position of the temperature sensor 2 is to increase the thermal resistance between the temperature sensor 2 and the heating element 1. After each adjustment, it is necessary to retest the temperature change and B-mode frequency change of the crystal resonator 3 in the thermostatic bath to be designed when the external temperature changes, and determine the current temperature coefficient corresponding to the thermostatic bath to be designed based on the obtained data. Stop adjusting the position of the temperature sensor 2 until the current temperature coefficient corresponding to the thermostatic bath to be designed is converted to a zero temperature coefficient or a negative temperature coefficient.

[0046] In this embodiment, the target direction is determined based on the isotherm, and after each position adjustment, the current position of the temperature sensor 2 is not on the same isotherm as the previous position.

[0047] Step 140: Based on the temperature change corresponding to the crystal resonator, the gain of the temperature control circuit in the thermostatic bath to be designed is adjusted to obtain a designed thermostatic bath to be designed.

[0048] In this embodiment, for the zero temperature coefficient thermostat to be designed and the negative temperature coefficient thermostat to be designed. Theoretically, there is no need to adjust the gain of the temperature control circuit in these two cases. Therefore, this embodiment mainly adjusts the gain of the temperature control circuit of the positive temperature coefficient thermostat to be designed. Of course, in actual use, in order to improve the accuracy, the gain of the temperature control circuit of the zero temperature coefficient thermostat to be designed and the negative temperature coefficient thermostat to be designed can also be adjusted according to this embodiment.

[0049] In this embodiment, in order to determine the target gain value to be adjusted by the temperature control circuit, this embodiment provides two different methods, and the first method is described below: Determine the temperature change difference corresponding to the crystal resonator in the designed constant temperature bath when the external temperature changes from the first external temperature to the second external temperature.

[0050] The gain of the temperature control circuit in the thermostatic bath to be designed is reduced to a first gain value, and a first temperature change value corresponding to the crystal resonator in the thermostatic bath to be designed is determined when the gain of the temperature control circuit is the first gain value and the external temperature changes from the first external temperature to the second external temperature.

[0051] According to the external temperature change value, the first gain value and the first temperature change value, a first target gain value of the temperature control circuit is determined; and the gain of the temperature control circuit is adjusted based on the first target gain value to obtain a designed constant temperature bath to be designed.

[0052] In this embodiment, the temperature change difference is determined according to the temperature change corresponding to the crystal resonator in the thermostatic bath to be designed when the outside temperature changes from the first outside temperature to the second outside temperature recorded in step 110. In particular, since the temperature change value of the crystal resonator is 0 only when the thermostatic bath to be designed has a zero temperature coefficient, but since it is difficult for the thermostatic bath to be designed to reach a zero temperature coefficient in actual operation, the temperature change difference is less than 0 in actual applications.

[0053] The current gain of the temperature control circuit in the thermostatic bath to be designed is reduced to the first gain value. In this case, the first temperature change value corresponding to the crystal resonator in the thermostatic bath to be designed is determined when the ambient temperature changes from the first ambient temperature to the second ambient temperature.

[0054] For example, suppose that when determining the temperature change difference, the outside temperature is adjusted from 20°C to 40°C, and the preset temperature change amount is 20°C. Accordingly, to determine the first temperature change value, the outside temperature at this time can also be adjusted from 20°C to 40°C, or the preset temperature change amount can be increased based on the current outside temperature to test the temperature change of the crystal resonator in this process to determine the first temperature change value.

[0055] Afterwards, suppose: β=ΔT1*K1 Wherein, β is the product coefficient, ΔT1 is the first temperature change value; and K1 is the first gain value.

[0056] To make the temperature change of the crystal resonator zero when the external temperature changes, we have: ΔT=ΔT0+β / K x1 =0 Among them, ΔT is the target temperature change; ΔT0 is the temperature change difference; K x1 is the first target gain value.

[0057] Substituting the above formula into the solution, we get: K x1 =-K1*ΔT1 / ΔT0 That is, in actual use, the first target gain value can be directly calculated based on the above formula, the first gain value, the first temperature change value and the temperature change difference value measured by the temperature sensor, and the gain of the temperature control circuit is adjusted to the first target gain value to obtain a designed constant temperature bath.

[0058] The second method for calculating the target gain value is described below: Determine the temperature change difference corresponding to the crystal resonator in the designed constant temperature bath when the external temperature changes from the first external temperature to the second external temperature.

[0059] The gain of the temperature control circuit in the thermostatic bath to be designed is reduced to a first gain value, and a first temperature change value corresponding to the crystal resonator in the thermostatic bath to be designed is determined when the gain of the temperature control circuit is the first gain value and the external temperature changes from the first external temperature to the second external temperature.

[0060] The gain of the temperature control circuit in the thermostatic bath to be designed is reduced to a second gain value, and a second temperature change value corresponding to the crystal resonator in the thermostatic bath to be designed is determined when the gain of the temperature control circuit is the second gain value and the external temperature changes from the first external temperature to the second external temperature.

[0061] According to the external temperature change value, the first gain value, the first temperature change value, the second gain value and the second temperature change value, the second target gain value of the temperature control circuit is determined; the gain of the temperature control circuit is adjusted based on the second target gain value to obtain the designed constant temperature bath to be designed.

[0062] In this embodiment, when the current temperature coefficient of the thermostatic bath to be designed is a negative temperature coefficient or a zero temperature coefficient, when the external temperature changes, the temperature change of the crystal resonator measured by the temperature sensor may not be very obvious. Therefore, the first method may have errors under certain circumstances. Therefore, this embodiment provides a second method for calculating the target gain value of the temperature control circuit.

[0063] In the second method, the corresponding temperature change value can be determined based on the change in the B-mode frequency of the crystal resonator. Specifically: In this embodiment, similar to the first method, the temperature change difference corresponding to the crystal resonator in the thermostatic bath to be designed when the external temperature changes from the first external temperature to the second external temperature is first determined. The temperature change difference in this embodiment can be determined by data measured by a temperature sensor.

[0064] The gain of the temperature control circuit in the thermostatic bath to be designed is reduced to a first gain value, and when the external temperature changes from the first external temperature to the second external temperature, the change in the first B mode frequency corresponding to the crystal resonator in the thermostatic bath to be designed is measured when the gain of the temperature control circuit is the first gain value, and the first temperature change value is determined based on the change in the first B mode frequency.

[0065] At this time, there is the following relationship between the first temperature change value and the temperature change difference: ΔT0+β / K1=ΔT1 The gain of the temperature control circuit in the thermostatic bath to be designed is reduced to a second gain value, and the change in the second B-mode frequency corresponding to the crystal resonator in the thermostatic bath to be designed is measured when the gain of the temperature control circuit is the second gain value and the external temperature changes from the first external temperature to the second external temperature, and the second temperature change value is determined based on the change in the second B-mode frequency, wherein the first gain value is greater than the second gain value.

[0066] At this time, there is the following relationship between the second temperature change value and the temperature change difference: ΔT0+β / K2=ΔT2 Wherein, K2 is the second gain value.

[0067] Based on these two formulas: β=(ΔT2-ΔT1) / (1 / K2-1 / K1) To make the temperature change of the crystal resonator zero when the external temperature changes, we have: ΔT=ΔT0+β / K x2 =0 Among them, ΔT is the target temperature change; ΔT0 is the temperature change difference; K x2 is the second target gain value.

[0068] Substituting the above formula into the solution, we get: K x2 =-(ΔT2-ΔT1) / (1 / K2-1 / K1) / ΔT0 That is, in actual use, the second target gain value can be directly calculated based on the above formula, the first gain value, the second gain value, the temperature change difference measured by the temperature sensor, the first temperature change value and the second temperature change value obtained by the B mode frequency. And the gain of the temperature control circuit is adjusted to the second target gain value to obtain the designed constant temperature bath.

[0069] Optionally, in some embodiments, see Figure 5The heating element may be a heating transistor T1; since the thermistor RT has a negative temperature coefficient, the thermistor RT may be used as a temperature sensor.

[0070] Accordingly, the temperature control circuit may include the following elements: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor RK, a first operational amplifier OP1 and a second operational amplifier OP2.

[0071] The connection relationship of each component is as follows: the first end of the first resistor R1 is connected to the power supply Vcc, the second end and the first end of the temperature sensor RT are connected to the in-phase input terminal of the first operational amplifier OP1 through the fourth resistor R4, and the second end of the temperature sensor RT is grounded.

[0072] The first end of the second resistor R2 is connected to the power supply Vcc, and the second end is connected to the first end of the third resistor R3 and the out-of-phase input end of the first operational amplifier OP1; the second end of the third resistor R3 is grounded; A first end of the eighth resistor RK is connected to the out-of-phase input terminal of the first operational amplifier OP1, and a second end of the eighth resistor RK is connected to the output terminal of the first operational amplifier OP1.

[0073] The first end of the sixth resistor R6 is connected to the power supply Vcc, the second end is connected to the first end of the fifth resistor R5 and the non-inverting input end of the second operational amplifier OP2, and the second end of the fifth resistor R5 is connected to the output end of the first operational amplifier OP1.

[0074] The first end of the seventh resistor R7 is connected to the power supply Vcc, and the second end is respectively connected to the out-of-phase input terminal of the second operational amplifier OP2 and the emitter of the heating transistor T1; the collector of the heating transistor T1 is grounded, and the base is connected to the output terminal of the second operational amplifier OP2.

[0075] In this embodiment, the first resistor R1, the temperature sensor RT, the fourth resistor R4, the second resistor R2 and the third resistor R3 respectively constitute the positive and negative bridges of the first operational amplifier OP1. The first operational amplifier OP1 linearly amplifies and outputs the smile voltage change caused by the temperature change of the temperature sensor RT, and the amplification factor is determined by the ratio of the eighth resistor RK and the fourth resistor R4.

[0076] The second operational amplifier OP2 samples the output voltage of the first operational amplifier OP1. The sampling ratio is determined by the fifth resistor R5 and the sixth resistor R6, and the voltage of the seventh resistor R7 is embedded to achieve linear VI conversion. By heating the heating transistor T1, the current changes linearly with the external temperature. When the external temperature rises from low temperature to high temperature, the temperature of the temperature sensor RT increases linearly. The temperature change ΔT of the temperature sensor RT is inversely proportional to the gain K of the temperature control circuit, that is: ΔT*K=β Therefore, in the traditional thermostatic bath design, when the gain of the temperature control circuit is very high, the temperature of the thermistor RT can be considered constant.

[0077] In addition, in this embodiment, the gain of the temperature control circuit can be changed according to the adjustment of the ratio of the eighth resistor RK to the fifth resistor R5. Therefore, the gain adjustment of the temperature control circuit is essentially to adjust the ratio of the eighth resistor RK to the fifth resistor R5.

[0078] In summary, the embodiment of the present invention realizes a high-efficiency design of a thermostatic bath. Considering that a zero temperature coefficient thermostatic bath is difficult to obtain, but a negative temperature coefficient thermostatic bath is easy to realize, only the positive temperature coefficient thermostatic bath is adjusted, and the negative temperature and the zero temperature coefficient are used as adjustment references, which greatly improves the design efficiency of the thermostatic bath, reduces design iterations, and reduces costs. In addition, a high-precision design of the thermostatic bath is realized, and the temperature change of the crystal resonator can be close to zero when the external temperature changes by finely adjusting the gain of the temperature control circuit.

[0079] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0080] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0081] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0082] In the embodiments provided by the present invention, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0083] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0084] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0085] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various constant temperature bath design method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium.

[0086] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A design method for a thermostatic bath, characterized in that: include: When the external temperature changes from the first external temperature to the second external temperature, testing the temperature change corresponding to the crystal resonator in the thermostatic bath to be designed; Based on the temperature change, determining a current temperature coefficient corresponding to the thermostatic bath to be designed; wherein the temperature coefficient includes a negative temperature coefficient, a zero temperature coefficient, and a positive temperature coefficient; Determining the position of a temperature sensor in the thermostatic bath to be designed based on a current temperature coefficient corresponding to the thermostatic bath to be designed; Based on the temperature change corresponding to the crystal resonator, the gain of the temperature control circuit in the thermostatic bath to be designed is adjusted to obtain the designed thermostatic bath to be designed.

2. The design method of a thermostatic bath according to claim 1, characterized in that: The thermostatic bath to be designed further comprises a heating element; The temperature coefficient corresponding to the thermostatic bath to be designed is defined as: When the thermal resistance between the temperature sensor and the crystal resonator is greater than the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient; When the thermal resistance between the temperature sensor and the crystal resonator is equal to the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient; When the thermal resistance between the temperature sensor and the crystal resonator is smaller than the thermal resistance between the crystal resonator and the heating element, the temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient.

3. The design method of a thermostatic bath according to claim 2, characterized in that: The determining, based on the temperature change, a current temperature coefficient corresponding to the thermostatic bath to be designed includes: If the external temperature rises and the temperature of the crystal resonator drops, determining that the current temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient; If the external temperature rises and the temperature change degree of the crystal resonator is less than the preset temperature change threshold, determining that the current temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient; If the external temperature increases, the temperature of the crystal resonator increases, and then it is determined that the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient.

4. The design method of a thermostatic bath according to claim 3, characterized in that: The determining, based on a current temperature coefficient corresponding to the thermostatic bath to be designed, a position of a temperature sensor in the thermostatic bath to be designed, includes: If the current temperature coefficient corresponding to the thermostatic bath to be designed is a negative temperature coefficient or a zero temperature coefficient, there is no need to adjust the position of the temperature sensor in the thermostatic bath to be designed; If the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient, the temperature sensor in the thermostatic bath to be designed is moved in a target direction away from the heating element.

5. The design method of a thermostatic bath according to claim 4, characterized in that: If the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient, moving the temperature sensor in the thermostatic bath to be designed in a target direction away from the heating element includes: If the current temperature coefficient corresponding to the thermostatic bath to be designed is a positive temperature coefficient, the temperature sensor in the thermostatic bath to be designed is moved in a target direction away from the heating element, and the step of testing the temperature change corresponding to the crystal resonator in the thermostatic bath to be designed when the external temperature changes from the first external temperature to the second external temperature is returned to, until the current temperature coefficient corresponding to the thermostatic bath to be designed is a zero temperature coefficient or a negative temperature coefficient.

6. The design method of a thermostatic bath according to claim 1, characterized in that: The step of adjusting the gain of the temperature control circuit in the thermostatic bath to be designed based on the temperature change corresponding to the crystal resonator to obtain the designed thermostatic bath to be designed includes: Determine a temperature change difference corresponding to the crystal resonator in the designed constant temperature bath when the external temperature changes from a first external temperature to a second external temperature; reducing the gain of the temperature control circuit in the thermostatic bath to be designed to a first gain value, and determining a first temperature change value of the crystal resonator in the thermostatic bath to be designed corresponding to when the external temperature changes from the first external temperature to the second external temperature, when the gain of the temperature control circuit is at the first gain value; Determine a first target gain value of the temperature control circuit according to the temperature change difference, the first gain value, and the first temperature change value; and adjust the gain of the temperature control circuit based on the first target gain value to obtain the designed constant temperature bath.

7. The design method of a thermostatic bath according to claim 6, wherein: The external temperature change value, the first gain value, the first temperature change value, and the first target gain value satisfy the following relationship: K x1 =-K1*ΔT1 / ΔT0 Among them, K x1 is the first target gain value; K1 is the first gain value; ΔT1 is the first temperature change value; ΔT0 is the temperature change difference.

8. The design method of a thermostatic bath according to claim 1, characterized in that: The step of adjusting the gain of the temperature control circuit in the thermostatic bath to be designed based on the temperature change corresponding to the crystal resonator to obtain the designed thermostatic bath to be designed includes: Determine a temperature change difference corresponding to the crystal resonator in the designed constant temperature bath when the external temperature changes from a first external temperature to a second external temperature; reducing the gain of the temperature control circuit in the thermostatic bath to be designed to a first gain value, and determining a first temperature change value of the crystal resonator in the thermostatic bath to be designed corresponding to when the external temperature changes from the first external temperature to the second external temperature when the gain of the temperature control circuit is at the first gain value; reducing the gain of the temperature control circuit in the thermostatic bath to be designed to a second gain value, and determining a second temperature change value of the crystal resonator in the thermostatic bath to be designed corresponding to when the external temperature changes from the first external temperature to the second external temperature, when the gain of the temperature control circuit is at the second gain value; Determine a second target gain value of the temperature control circuit based on the temperature change difference, the first gain value, the first temperature change value, the second gain value, and the second temperature change value; and adjust the gain of the temperature control circuit based on the second target gain value to obtain the designed constant temperature bath.

9. The design method of a thermostatic bath according to claim 8, wherein: The external temperature change value, the first gain value, the first temperature change value, the second gain value, the second temperature change value, and the second target gain value satisfy the following relationship: K x2 =-(ΔT2-ΔT1) / (1 / K2-1 / K1) / ΔT0 Among them, K x2 is the second target gain value; ΔT2 is the second temperature change value; ΔT1 is the first temperature change value; K2 is the second gain value; K1 is the first gain value; ΔT0 is the temperature change difference.

10. The design method of a thermostatic bath according to claim 2, characterized in that: The heating element is a heating transistor; The temperature control circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first operational amplifier and a second operational amplifier; The first end of the first resistor is connected to the power supply, the second end and the first end of the temperature sensor are connected to the non-inverting input end of the first operational amplifier through the fourth resistor, and the second end of the temperature sensor is grounded; The first end of the second resistor is connected to the power supply, and the second end is connected to the first end of the third resistor and the out-of-phase input terminal of the first operational amplifier; the second end of the third resistor is grounded; A first end of the eighth resistor is connected to the out-of-phase input terminal of the first operational amplifier, and a second end of the eighth resistor is connected to the output terminal of the first operational amplifier; The first end of the sixth resistor is connected to the power supply, the second end is connected to the first end of the fifth resistor and the non-inverting input terminal of the second operational amplifier, and the second end of the fifth resistor is connected to the output terminal of the first operational amplifier; The first end of the seventh resistor is connected to the power supply, and the second end is respectively connected to the out-of-phase input terminal of the second operational amplifier and the emitter of the heating transistor; the collector of the heating transistor is grounded, and the base is connected to the output terminal of the second operational amplifier.

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