A temperature control method for an electric heater and an electric heater using the same

Abstract

The application discloses a temperature control method for an electric heater and an electric heater applying the temperature control method, and relates to the technical field of electric heaters. The method comprises the following steps: acquiring the real-time distance between a human body and the electric heater through a radar distance measuring module, and collecting the ambient temperature; inputting the distance and the ambient temperature into a human body sensible temperature calculation model containing a distance attenuation compensation factor, and outputting the actual sensible temperature of the human body; comparing the temperature difference between the actual sensible temperature and the user set temperature, and judging whether the absolute value of the temperature difference is smaller than a preset dead zone threshold value; if the absolute value of the temperature difference is smaller than the preset dead zone threshold value, the current heating power is maintained; if the absolute value of the temperature difference is greater than or equal to the preset dead zone threshold value, the heating power is adjusted through a PID controller, so that the sensible temperature is maintained within the set range. The actual sensible temperature of the human body is taken as the control target, the distance loss is dynamically compensated through the radar distance measurement, the dead zone is introduced to avoid frequent power jumps, and the temperature control stability and the energy saving effect are considered.

Description

Technical Field

[0001] This invention relates to the field of electric heater technology, and more specifically to a temperature control method for electric heaters and an electric heater using the temperature control method. Background Technology

[0002] As an indoor heating device, electric heaters have evolved through two main stages in temperature control: mechanical thermostat control and electronic temperature sensor control. Mechanical thermostats use bimetallic strips or capillary thermostats to detect the ambient air temperature and switch the heating power on / off when a set threshold is reached, resulting in relatively low temperature control accuracy. Electronic thermostats employ temperature sensors such as NTC thermistors in conjunction with a microcontroller to achieve digital temperature acquisition and PID closed-loop control, significantly improving the accuracy of air temperature control. In recent years, some smart electric heaters have also incorporated WiFi or Bluetooth communication modules for remote control, and a few products use pyroelectric infrared sensors to detect human presence for automatic standby when unattended.

[0003] The existing solutions described above all control the ambient air temperature around the electric heater, indirectly providing heating by maintaining a constant air temperature. However, the temperature actually felt by the human body is the result of a combination of factors, including ambient temperature, heat radiation intensity, and the distance between the human body and the heat source. When a user is active indoors, the distance between the human body and the electric heater changes, and the intensity of heat radiation reaching the body changes accordingly. This causes fluctuations in the perceived temperature even if the air temperature remains constant. Therefore, existing temperature control methods that control only air temperature are insufficient to maintain a stable perceived temperature for the human body.

[0004] To address the aforementioned issues, this invention obtains the distance to the human body by incorporating a radar ranging module into the electric heater, and constructs a calculation model for the perceived human body temperature that includes a distance attenuation compensation factor in conjunction with the ambient temperature. The actual perceived human body temperature is used as the control target for dynamic power adjustment, thereby overcoming the technical defect of misaligned control targets in existing solutions. Summary of the Invention

[0005] To overcome the technical problem that existing electric heaters, which use ambient air temperature as the control target, cannot maintain a constant human body temperature, this invention provides a temperature control method for electric heaters and an electric heater using this temperature control method.

[0006] The temperature control method for electric heaters provided by the present invention includes the following steps.

[0007] The real-time distance between the human body and the electric heater is obtained through a radar ranging module.

[0008] The ambient temperature is collected using a temperature acquisition module.

[0009] The real-time distance and the ambient temperature are input into the human body temperature calculation model, which includes a distance attenuation compensation factor, and the model outputs the actual human body temperature.

[0010] The actual perceived temperature of the human body is compared with the temperature set by the user to obtain the temperature difference value.

[0011] Determine whether the absolute value of the temperature difference is less than a preset dead zone threshold.

[0012] When the absolute value of the temperature difference is less than the preset dead zone threshold, the current heating power is maintained.

[0013] When the absolute value of the temperature difference is greater than or equal to the preset dead zone threshold, the heating power of the electric heater is adjusted by the PID controller according to the temperature difference value, so that the actual body temperature is maintained within the preset range of the user-set temperature.

[0014] The human body's perceived temperature calculation model calculates the actual perceived temperature of the human body according to the following formula.

[0015] T_sense = T_env + ΔT_rad - k × d; where T_sense is the actual perceived temperature of the human body, T_env is the ambient temperature, ΔT_rad is the equivalent temperature rise of the electric heater under the current power, d is the real-time distance, and k is the distance attenuation coefficient of the electric heater, which is obtained through a pre-calibration experiment.

[0016] The step of adjusting the heating power of the electric heater according to the temperature difference value via a PID controller further includes: using the temperature difference value as the input of the PID controller, performing proportional, integral, and derivative operations to output a power control signal, and adjusting the heating power or operating level of the electric heater via the power control signal.

[0017] When the real-time distance increases, the PID controller increases the heating power to compensate for the distance loss; when the real-time distance decreases, the PID controller decreases the heating power.

[0018] The step of obtaining the real-time distance between the human body and the electric heater through the radar ranging module further includes the following.

[0019] The real-time distance is detected by a millimeter-wave radar sensor located on the front of the electric heater, and the detection accuracy of the millimeter-wave radar sensor is ±1cm.

[0020] When the radar sensor detects multiple human targets, it prioritizes locking the closest human target as the temperature control benchmark; after the closest human target leaves the detection range, it locks the human target with the longest dwell time as the temperature control benchmark.

[0021] The step of acquiring ambient temperature through the temperature acquisition module further includes the following.

[0022] The air inlet temperature is obtained by a first temperature sensor located at the air inlet of the electric heater.

[0023] The air outlet temperature is obtained by a second temperature sensor located at the air outlet of the electric heater.

[0024] The ambient reference temperature is obtained by a third temperature sensor located on the outer casing of the electric heater.

[0025] The ambient temperature is obtained by using the ambient reference temperature as the primary factor and the inlet and outlet temperatures as secondary factors for compensation and correction.

[0026] As a further improvement, the temperature control method also includes a standby detection and wake-up step.

[0027] When the radar ranging module continuously detects that the duration of no human activity exceeds a preset time threshold, the main control chip outputs a standby control signal, and the electric heater responds to the standby control signal to enter standby mode or low-temperature antifreeze mode, and the heating power is reduced.

[0028] When the radar ranging module detects human activity again, the main control chip outputs a recovery control signal, and the electric heater responds to the recovery control signal to exit the standby mode or the low temperature antifreeze mode and return to the original temperature control state.

[0029] The preset range is ±0.5℃.

[0030] The electric heater using the above-mentioned temperature control method provided by the present invention includes the following.

[0031] A radar ranging module is installed on the front of the electric heater, and the radar ranging module outputs the real-time distance between the human body and the electric heater.

[0032] The temperature acquisition module includes a first temperature sensor located at the air inlet of the electric heater, a second temperature sensor located at the air outlet of the electric heater, and a third temperature sensor located on the outer casing of the electric heater. The temperature acquisition module outputs the ambient temperature.

[0033] The main control chip is communicatively connected to the radar ranging module and the temperature acquisition module. The main control chip integrates a human body temperature calculation module, a comparison control module, and a dead zone detection module. The human body temperature calculation module receives the real-time distance and the ambient temperature, and includes a human body temperature calculation model with a distance attenuation compensation factor. The human body temperature calculation module outputs the actual human body temperature. The comparison control module receives the actual human body temperature and the user-set temperature, and outputs the temperature difference value. The dead zone detection module determines whether the absolute value of the temperature difference is less than a preset dead zone threshold. When the absolute value of the temperature difference is less than the preset dead zone threshold, the main control chip maintains the current heating power; when the absolute value of the temperature difference is greater than or equal to the preset dead zone threshold, it outputs a power control signal.

[0034] A heating element is electrically connected to the main control chip. The heating element adjusts the heating power in response to the power control signal so that the actual body temperature is maintained within the preset range of the user-set temperature.

[0035] The radar ranging module is a millimeter-wave radar sensor, and the detection accuracy of the millimeter-wave radar sensor is ±1cm. The millimeter-wave radar sensor identifies multiple human targets, prioritizes locking the closest human target as the temperature control benchmark, and locks the human target with the longest dwell time as the temperature control benchmark after the closest human target leaves the detection range.

[0036] The first temperature sensing probe, the second temperature sensing probe, and the third temperature sensing probe are all NTC thermistors.

[0037] The electric heater also includes a remote wireless temperature patch, which is placed in the user's activity area and wirelessly connected to the main control chip. The remote wireless temperature patch sends temperature data of the user's activity area to the main control chip, and the temperature data is used to calibrate the ambient temperature.

[0038] Compared with the prior art, the present invention has the following beneficial effects.

[0039] First, the present invention uses a radar ranging module to sense the distance between the human body and the electric heater in real time, and combines it with a human body temperature calculation model that includes a distance attenuation compensation factor. The actual human body temperature is used instead of the ambient air temperature as the control target to dynamically adjust the power, so that the human body temperature is maintained within ±0.5℃ of the set value, avoiding fluctuations in body temperature caused by user movement.

[0040] Secondly, this invention reduces ineffective energy consumption by using unmanned automatic standby logic and adjusting power output in real time based on human distance. It actively compensates when the user is far away, actively reduces power when the user is close, and enters low-power standby when no one is around.

[0041] Third, by setting a dead zone judgment step before PID regulation, the present invention maintains the current heating power when the absolute value of the temperature difference is less than the preset dead zone threshold, avoiding frequent power jumps caused by small temperature differences, extending the service life of heating elements and relays, and further improving temperature control stability. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure and sensor layout of the electric heater of the present invention.

[0043] Figure 2 This is a flowchart of the temperature control method of the present invention.

[0044] Figure 3 This is a schematic block diagram illustrating the working principle of the electric heater of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0046] In the description of this invention, the terms "installation," "setting," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a signal connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] Example 1: This example provides a temperature control method for electric heaters.

[0048] like Figure 2 As shown, after the electric heater is turned on, the system first performs initialization, including self-testing of each sensor and loading of parameters. The user sets the desired body temperature T_set (e.g., 22℃) through the electric heater control panel or remote control.

[0049] The system continuously executes the following control loop at a sampling frequency of 1Hz: Step S1, acquire the real-time distance between the human body and the electric heater. Specifically, the real-time distance d between the human body and the electric heater is detected by a millimeter-wave radar sensor located on the front of the electric heater. In this embodiment, the millimeter-wave radar sensor operates at a frequency of 60GHz, has a detection accuracy of ±1cm, and a detection range of 0.5m to 8m. When the radar detects multiple human targets, it prioritizes locking onto the closest human target as the temperature control reference; after the closest human target leaves the detection range, it locks onto the human target with the longest dwell time as the temperature control reference.

[0050] Step S2: Collect ambient temperature. Specifically, the inlet temperature is detected by a first temperature probe T1 located at the air inlet of the heater, the outlet temperature is detected by a second temperature probe T2 located at the air outlet, and the ambient reference temperature is detected by a third temperature probe T3 located on the heater's outer casing. Each temperature probe uses an NTC thermistor; the resistance changes with temperature and is converted into a digital temperature value by the ADC (Analog-to-Digital Converter) module built into the main control chip. The ambient temperature T_env is primarily based on the outer casing ambient reference temperature measured by T3, with compensation and correction based on the temperatures of T1 and T2 to eliminate interference from the heater's own heating.

[0051] Step S3: Calculate the actual perceived temperature of the human body. Based on the real-time distance d obtained in step S1 and the ambient temperature T_env obtained in step S2, the main control chip calculates the actual perceived temperature T_sense of the human body using the human perceived temperature calculation model. In this embodiment, the human perceived temperature calculation model uses the following formula: T_sense = T_env + ΔT_rad - k × d; where ΔT_rad is the equivalent temperature rise of the electric heater under the current power, which is related to the heating power and heating element characteristics of the electric heater; d is the real-time distance measured by radar; and k is the distance attenuation coefficient. The value of coefficient k is obtained through calibration experiments before the electric heater leaves the factory. The calibration method is as follows: in a dark room environment, a black ball thermometer is placed at different distances directly in front of the electric heater, and the ambient temperature, the power of the electric heater, and the reading of the black ball thermometer are recorded simultaneously. The value of k is obtained through curve fitting. In the convection electric heater of this embodiment, the typical range of k is 0.3~0.8℃ / m.

[0052] Step S4, Dead Zone Determination. The main control chip compares the actual perceived human body temperature T_sense calculated in step S3 with the user-set temperature T_set, calculating the temperature difference ΔT = T_set - T_sense. The main control chip determines whether the absolute value of the temperature difference ΔT is less than a preset dead zone threshold (in this embodiment, the dead zone threshold is set to 0.3℃). When |ΔT| is less than 0.3℃, the main control chip maintains the current heating power and does not perform PID adjustment; when |ΔT| is greater than or equal to 0.3℃, the main control chip starts the PID adjustment step.

[0053] Step S5, PID Adjustment. A PID control strategy is adopted, using ΔT as the input. After proportional, integral, and derivative calculations, a power control signal P_out is output to dynamically adjust the heating power or setting of the electric heater. When T_sense is lower than T_set, the heating power is increased; when T_sense is higher than T_set, the heating power is decreased. Specifically, when the radar detects an increase in the real-time distance d, the ΔT_rad term decreases, the calculated T_sense value decreases, and the PID controller increases the heating power to compensate for the distance loss; when the real-time distance d decreases, the PID controller decreases the heating power. Through this closed-loop control, the actual perceived human body temperature T_sense is maintained within ±0.5℃ of the user-set temperature T_set.

[0054] Step S6, Standby Determination. When the radar continuously detects no human activity for more than a preset time (30 minutes in this embodiment), the main control chip controls the electric heater to enter standby mode or low-temperature anti-freeze mode, reducing power output; when the radar detects human activity again, the main control chip controls the electric heater to return to the original set temperature control state.

[0055] Example 2: This example provides an electric heater that implements the temperature control method described in Example 1.

[0056] like Figure 1 and Figure 3 As shown, the electric heater includes: a radar ranging module 1, a temperature acquisition module, a main control chip MCU, and a heating element HEATER.

[0057] The radar ranging module 1 is located on the front of the electric heater and outputs the real-time distance d between the human body and the electric heater. In this embodiment, the radar ranging module 1 uses a millimeter-wave radar sensor with a working frequency of 60GHz, a detection accuracy of ±1cm, and a detection range of 0.5m to 8m. It can simultaneously identify multiple human targets, prioritize locking the closest human target as the temperature control reference, and lock the human target with the longest dwell time as the temperature control reference after the closest human target leaves the detection range.

[0058] The temperature acquisition module includes a first temperature probe T1 located at the air inlet of the electric heater, a second temperature probe T2 located at the air outlet of the electric heater, and a third temperature probe T3 located on the outer casing of the electric heater. Each temperature probe uses an NTC thermistor to detect the air inlet temperature, air outlet temperature, and ambient reference temperature, respectively. The main control chip uses the temperature measured by the third temperature probe T3 as the primary value and compensates for the temperatures measured by the first and second temperature probes T1 and T2 to obtain the ambient temperature T_env. As a further preferred embodiment, the electric heater in this embodiment also includes a remote wireless temperature patch (not shown in the figure). This remote wireless temperature patch is placed in the user's activity area (such as next to a sofa or on a bedside table) and connects to the main control chip via Bluetooth or 2.4G wireless communication to send temperature data of the user's activity area to the main control chip for calibrating the ambient temperature T_env.

[0059] The main control chip (MCU) is communicatively connected to the radar ranging module 1 and the temperature acquisition module, receiving the distance signal output by the radar ranging module 1 and the temperature signal output by the temperature acquisition module. The main control chip has a built-in human body temperature calculation module, a comparison control module, and a dead zone judgment module. The human body temperature calculation module calculates the actual human body temperature T_sense based on the real-time distance d and the ambient temperature T_env using a human body temperature calculation model that includes a distance attenuation compensation factor. The comparison control module compares the actual human body temperature T_sense with the user-set temperature T_set and outputs the temperature difference value ΔT. The dead zone judgment module determines whether the absolute value of the temperature difference value ΔT is less than a preset dead zone threshold (in this embodiment, the dead zone threshold is set to 0.3℃). When |ΔT| is less than the dead zone threshold, the main control chip maintains the current heating power; when |ΔT| is greater than or equal to the dead zone threshold, the main control chip starts PID control and outputs a power control signal to the heating element. Specifically, the comparison control module adopts a PID control strategy, taking the difference between T_sense and T_set as input, and outputting a PWM power control signal after proportional, integral, and derivative operations to adjust the duty cycle of the heating element.

[0060] The heating element (HEATER) is electrically connected to the main control chip, and adjusts the heating power according to the power control signal output by the main control chip. In this embodiment, the heating element is a PTC ceramic heating element or a nickel-chromium alloy heating wire, which works with a fan (FAN) to blow heat out. When the heating power increases, the outlet temperature rises, and the thermal radiation equivalent temperature rise ΔT_rad increases; when the heating power decreases, the outlet temperature decreases.

[0061] As a preferred embodiment, the electric heater also integrates a tilt-off power-off protection unit and an overheat protection unit (not shown in the figure). The tilt-off power-off protection unit includes a gravity switch or tilt sensor, which cuts off the heating power when the electric heater tilts beyond a set threshold. The overheat protection unit includes a temperature fuse or bimetallic thermostat located near the heating element, which cuts off the power when the heating element temperature exceeds a safety threshold. All of the above safety protection units are electrically connected to the main control chip, which records and reports the protection status.

[0062] The working process of the electric heater in this embodiment is as follows.

[0063] After powering on, the user sets their desired perceived temperature T_set to 22℃ via the control panel. Radar ranging module 1 detects an initial distance of 2m from the user, and the temperature acquisition module collects the current ambient temperature T_env as 18℃. The main control chip calculates the current perceived temperature T_sense as 19.5℃ based on the perceived temperature calculation model, with a temperature difference ΔT = 2.5℃, exceeding the dead zone threshold of 0.3℃. The comparison control module outputs a power control signal, and the heating element starts heating at a higher power.

[0064] As heating progresses, the ambient temperature gradually increases, and the equivalent temperature rise ΔT_rad from thermal radiation increases, causing T_sense to gradually approach T_set. When T_sense rises to 21.8℃, ΔT = 0.2℃, which is less than the dead zone threshold of 0.3℃. The dead zone detection module controls the main control chip to maintain the current heating power, and the PID controller does not operate to avoid minor power fluctuations.

[0065] When the user moves from 2m to 4m, the radar ranging module 1 detects the distance change. The body temperature calculation model of the main control chip reduces the calculated value of T_sense according to the increased distance (the distance attenuation term k×d increases), and T_sense drops to 21.2℃. The temperature difference ΔT = 0.8℃, which is greater than the dead zone threshold. The comparison control module then increases the heating power to compensate. Conversely, when the user returns from 4m to 2m, the system reduces the heating power.

[0066] When the user leaves the room and the radar does not detect human activity for 30 consecutive minutes, the main control chip puts the heater into standby mode, reducing heating power and retaining only the low-power detection function of the radar module. When the user returns to the room and the radar detects human activity again, the main control chip restores the heater to the original temperature setting and restarts the closed-loop control.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A temperature control method for an electric heater, characterized in that, Includes the following steps: The real-time distance d between the human body and the electric heater is obtained through the radar ranging module (1); The ambient temperature T_env is collected via the temperature acquisition module; The real-time distance d and the ambient temperature T_env are input into the human body perceived temperature calculation model, which includes a distance attenuation compensation factor, and outputs the actual human body perceived temperature T_sense. Compare the actual perceived human body temperature T_sense with the user-set temperature T_set to obtain the temperature difference value e; Determine whether the absolute value of the temperature difference e is less than a preset dead zone threshold; When the absolute value of the temperature difference e is less than the preset dead zone threshold, the current heating power is maintained; When the absolute value of the temperature difference e is greater than or equal to the preset dead zone threshold, the heating power of the electric heater is adjusted by the PID controller according to the temperature difference e, so that the actual body temperature is maintained within the preset range of the user-set temperature.

2. The temperature control method according to claim 1, characterized in that, The human body's perceived temperature calculation model calculates the actual perceived temperature of the human body according to the following formula: T_sense = T_env + ΔT_rad - k × d; where T_sense is the actual perceived temperature of the human body, T_env is the ambient temperature, ΔT_rad is the equivalent temperature rise of the electric heater under the current power, d is the real-time distance, and k is the distance attenuation coefficient of the electric heater, which is obtained through a pre-calibration experiment.

3. The temperature control method according to claim 1, characterized in that, The step of adjusting the heating power of the electric heater using a PID controller based on the temperature difference value e further includes: The temperature difference value e is used as the input of the PID controller. After proportional, integral and derivative operations, a power control signal is output. The power control signal adjusts the heating power or working level of the electric heater. When the real-time distance d increases, the PID controller increases the heating power to compensate for the distance loss; when the real-time distance d decreases, the PID controller decreases the heating power.

4. The temperature control method according to claim 1, characterized in that, The step of obtaining the real-time distance between the human body and the electric heater through the radar ranging module (1) further includes: detecting the real-time distance by a millimeter-wave radar sensor set on the front of the electric heater, wherein the detection accuracy of the millimeter-wave radar sensor is ±1cm; when the radar sensor detects multiple human targets, the closest human target is prioritized as the temperature control reference; after the closest human target leaves the detection range, the human target with the longest dwell time is locked as the temperature control reference.

5. The temperature control method according to claim 1, characterized in that, The step of acquiring ambient temperature through the temperature acquisition module further includes: The air inlet temperature is obtained by the first temperature sensor (2) located at the air inlet of the electric heater; The air outlet temperature is obtained by a second temperature sensor (3) located at the air outlet of the electric heater. The ambient reference temperature is obtained by a third temperature sensor (4) installed on the outer shell of the electric heater; The ambient temperature T_env is obtained by using the ambient reference temperature as the primary factor and the inlet and outlet temperatures as secondary factors for compensation and correction.

6. The temperature control method according to claim 1, characterized in that, It also includes the steps for determining whether the device is in standby mode and waking it up: When the radar ranging module (1) continuously detects that the duration of no human activity exceeds a preset time threshold, the main control chip outputs a standby control signal, and the electric heater responds to the standby control signal to enter standby mode or low temperature antifreeze mode, and the heating power is reduced. When the radar ranging module (1) detects human activity again, the main control chip outputs a recovery control signal, and the electric heater responds to the recovery control signal to exit the standby mode or the low temperature antifreeze mode and return to the original temperature control state.

7. The temperature control method according to claim 1, characterized in that, The preset range is ±0.5℃.

8. An electric heater, characterized in that, include: A radar ranging module (1) is installed on the front of the electric heater and outputs the real-time distance between the human body and the electric heater. The temperature acquisition module includes a first temperature sensor (2) located at the air inlet of the electric heater, a second temperature sensor (3) located at the air outlet of the electric heater, and a third temperature sensor (4) located on the outer shell of the electric heater. The temperature acquisition module outputs the ambient temperature. The main control chip is connected to the radar ranging module (1) and the temperature acquisition module. The main control chip has a built-in human body temperature calculation module, a comparison control module and a dead zone judgment module. The human body temperature calculation module receives the real-time distance and the ambient temperature, and has a built-in human body temperature calculation model containing a distance attenuation compensation factor, and outputs the actual human body temperature. The comparison control module receives the actual perceived temperature of the human body and the temperature set by the user, and outputs the temperature difference value. The dead zone determination module is used to determine whether the absolute value of the temperature difference is less than a preset dead zone threshold; the main control chip maintains the current heating power when the absolute value of the temperature difference is less than the preset dead zone threshold, and outputs a power control signal when the absolute value of the temperature difference is greater than or equal to the preset dead zone threshold. A heating element is electrically connected to the main control chip. The heating element adjusts the heating power in response to the power control signal so that the actual body temperature is maintained within the preset range of the user-set temperature.

9. The electric heater according to claim 8, characterized in that, The radar ranging module (1) is a millimeter-wave radar sensor, and the detection accuracy of the millimeter-wave radar sensor is ±1cm. The millimeter-wave radar sensor identifies multiple human targets, prioritizes locking the closest human target as the temperature control reference, and locks the human target with the longest dwell time as the temperature control reference after the closest human target leaves the detection range. The first temperature probe (2), the second temperature probe (3) and the third temperature probe (4) are all NTC thermistors.

10. The electric heater according to claim 8, characterized in that, It also includes a remote wireless temperature patch, which is placed in the user's activity area and is wirelessly connected to the main control chip. The remote wireless temperature patch sends temperature data of the user's activity area to the main control chip, and the temperature data is used to calibrate the ambient temperature.

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