A biomagnetic imaging system with adjustable spatial resolution

Abstract

The application discloses a kind of biological magnetic imaging systems with adjustable spatial resolution, including detection unit, stimulation unit, optical pumping atomic magnetic field measurement unit and data acquisition processing device;Optical pumping atomic magnetic field measurement unit is set in magnetic shield room;Optical pumping atomic magnetic field measurement unit includes atomic gas chamber;Detection unit includes laser, diffractive optical element, collimating lens, imaging zoom lens group and multiple fixed pitch photodetector;Diffractive optical element and collimating lens are set along laser exit light path;Imaging zoom lens group is set behind the exit light path of atomic gas chamber;Photodetector receives signal light emitted by imaging zoom lens group;Data acquisition processing device is electrically connected with each photodetector.The application can save time and cost under the premise, adjust the spatial resolution of system conveniently and quickly, has wide application scene, can adapt to magnetocardiography, magnetoencephalography, muscle magnetism and different application needs, and is suitable for constructing atomic magnetometer array with adjustable pitch.

Description

Technical Field

[0001] This invention belongs to the field of magnetic imaging, specifically relating to a biomagnetic imaging system with adjustable spatial resolution. Background Technology

[0002] Magnetic imaging technology plays an important role in disease diagnosis. For example, magnetocardiography (MCG) has been widely used for screening and predicting cardiovascular diseases; magnetoencephalography (MEG) has been used to predict neurological diseases such as epilepsy and Alzheimer's disease; and muscle magnetic signal detection is of great significance in assessing whether neuromuscular function is normal, showing great potential application value.

[0003] Currently, there are two main types of high-sensitivity magnetic field sensors used for magnetic imaging: superconducting magnetometers and optically pumped atomic magnetometers. Superconducting magnetometers require cryogenic environments, resulting in large device size, difficulty in miniaturization, and high maintenance costs. In contrast, optically pumped atomic magnetometers do not require cryogenic environments, offer better portability and lower costs, and therefore show greater potential and broader application prospects in clinical applications such as disease diagnosis.

[0004] Highly sensitive optically pumped atomic magnetometers utilize the interaction between resonant lasers and spin-polarized, magnetically sensitive atomic vapors to achieve extremely sensitive detection of magnetic fields. Advances in optical pumping technology help atoms maintain persistent spin polarization at their ground-state magneton levels. These coherent spins undergo Larmor precession under the influence of the external magnetic field being measured, and the Larmor precession frequency quantifies the response of the atomic medium to the external magnetic field. In experiments, the intensity of the external magnetic field can be precisely measured by detecting the Larmor precession frequency of the atoms.

[0005] Magnetic fields exhibit specific spatial distribution characteristics. Constructing an optically pumped atomic magnetometer array (OPAMA) not only allows for the measurement of the spatial distribution of magnetic field strength but also enables gradient differential analysis of the spatial magnetic field to suppress environmental noise, thereby improving the magnetometer's detection sensitivity. However, the required spatial resolution (i.e., the spacing between adjacent OPAMAs) varies depending on the magnetic field distribution generated by different signal sources. For example, compared to measuring adult magnetocardiogram (MCC) signals, fetal MCC signals require a higher spatial resolution for the OPAMA array.

[0006] In practical applications, the spatial resolution of a magnetic imaging system based on an optically pumped atomic magnetometer array depends on the spacing between adjacent magnetic sensors. Depending on whether the measurement environment requires magnetic shielding, optically pumped atomic magnetometers can be categorized into zero-field magnetometers (requiring magnetic shielding) and full-field magnetometers (not requiring magnetic shielding). Regardless of whether it's a zero-field or full-field type, the area where the sensor measures the magnetic field is the area covered by the probe beam. For discrete atomic magnetometer arrays, the spacing between the detector units is difficult to adjust; while for integrated atomic magnetometer arrays, once the baseline is determined, adjustments require replacing optical components, making the process complex and costly. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a spatially adjustable biomagnetic imaging system that can adapt to the different biomagnetic imaging application requirements such as magnetocardiography, magnetoencephalography, and magnetomyography, in order to address the shortcomings of the prior art.

[0008] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a biomagnetic imaging system with adjustable spatial resolution, comprising a detection unit, a stimulation unit, an optically pumped atomic magnetic field measurement unit, and a data acquisition and processing device; the optically pumped atomic magnetic field measurement unit is disposed in a magnetically shielded chamber, and the stimulation unit is used to apply electrical stimulation to the object to be measured in the magnetically shielded chamber; the optically pumped atomic magnetic field measurement unit includes an atomic gas chamber; the detection unit includes a laser, a diffractive optical element, a collimating lens, an imaging zoom lens group, and multiple photodetectors with fixed spacing; the diffractive optical element and the collimating lens are disposed along the laser emission path to form a detection light spot array on the atomic gas chamber; the imaging zoom lens group is disposed behind the emission path of the atomic gas chamber to adjust the detection beam spacing to match the fixed spacing of the photodetectors; the photodetectors receive the signal light emitted through the imaging zoom lens group; the data acquisition and processing device is electrically connected to each photodetector.

[0009] Preferably, the stimulation unit includes a stimulation current driver and a stimulation electrode pad, the output terminal of which is electrically connected to the stimulation electrode pad, and the stimulation electrode pad is used to fix the object to be tested to apply electrical stimulation.

[0010] Preferably, the diffractive optical element is used to split the laser beam emitted by the laser into a probe beam array, and the collimating lens is used to collimate the probe beam array. The focal length combination of the diffractive optical element and the collimating lens together determines the initial spacing of the probe beam spot array projected onto the atomic gas cell.

[0011] Preferably, the imaging zoom lens group is a switchable imaging zoom lens group, which consists of a convex lens and a concave lens mounted on a lens flipping frame. By switching imaging zoom lens groups with different focal length combinations, the spacing of the probe beam penetrating the atomic gas cell can be scaled and adjusted according to a specific ratio, thereby accurately matching the probe light spot array with different initial spacings to the multiple photodetectors, and realizing the adjustment of the spatial resolution of the biomagnetic imaging system.

[0012] Preferably, a fixed support is provided inside the magnetic shielding chamber to support the object to be tested, and the fixed support is driven by a non-magnetic two-dimensional mobile platform located outside the magnetic shielding chamber.

[0013] Preferably, the optically pumped atomic magnetic field measurement unit is disposed on the upper or lower side of the fixed bracket; rubidium vapor is encapsulated in the atomic gas chamber, and a non-magnetic heating element and a non-magnetic temperature sensor are mounted on the outer wall of the atomic gas chamber. The non-magnetic temperature sensor is electrically connected to the temperature control unit. Each beam of probe light interacts with the rubidium vapor in the atomic gas chamber to form a magnetic sensing area. The signal light emitted from the magnetic sensing area is received by the corresponding photodetector. The data acquisition and processing device is used to collect the electrical signals emitted by each photodetector and process the data to obtain a biomagnetic imaging map of the object under test.

[0014] Preferably, the system also includes a calibration unit, which includes a magnetic field compensation coil disposed in the magnetic shielding chamber. The magnetic field compensation coil is used to generate a gradient magnetic field to compensate for the non-uniformity of the ambient magnetic field, thereby forming a uniform magnetic field environment in the region where the atomic gas chamber is located. The data acquisition and processing device acquires the signals of each magnetic sensing region under this uniform magnetic field environment and calculates a calibration factor to achieve consistent calibration of the signals of each magnetic sensing region.

[0015] Preferably, the magnetic field compensation coil is a triaxial square Helmholtz coil.

[0016] Preferably, the non-magnetic heating element is driven by a signal with a frequency of 20 kHz-200 kHz, which is output by a high-voltage power amplifier. This frequency far exceeds the bandwidth range of the optically pumped atomic magnetic field measurement unit, thus avoiding the influence of the heating magnetic field frequency on the signal under test and improving the sensitivity of the optically pumped atomic magnetic field measurement unit.

[0017] Preferably, the non-magnetic temperature sensor is a PT1000 non-magnetic temperature sensor.

[0018] Spatial resolution is crucial for biomagnetic imaging. In magnetoencephalography (MEG), spatial resolution determines the accuracy of diagnosis regarding the normality of muscle nerve fiber conduction function; in magnetoencephalography (MEG), spatial resolution determines the accuracy of localizing abnormal brain activity. Furthermore, different magnetic imaging scenarios have varying requirements for magnetic field spatial resolution. This invention's spatially adjustable biomagnetic imaging system allows for convenient and rapid adjustment of the system's spatial resolution while saving time and costs. It has a wide range of applications, adapting to the needs of different biomagnetic imaging applications such as magnetocardiography (MCG), magnetoencephalography (MEG), and magnetoencephalography (MEG), and is also suitable for constructing atomic magnetometer arrays with adjustable spacing.

[0019] This invention is based on optical path design and magnetic imaging design, and specifically includes the following two aspects.

[0020] 1) Adjustable optical path design for the spacing of the probe beam:

[0021] This invention selects a diffractive optical element (DOE) to split the laser beam emitted by a laser into an array of probe beams. A DOE is an optical element that modulates the amplitude and phase of light by etching specific microstructure patterns on its surface. Array beams generated by DOEs are highly efficient, have good uniformity in intensity distribution, and offer good flexibility; different beam configurations can be generated by selecting different types of DOEs. In the optical path design, the spacing of the probe beams can be adjusted by selecting DOEs with different diffraction angles or changing the focal length of the collimating lens, thus achieving spatial resolution adjustment in the magnetic imaging system or optically pumped atomic magnetic field measurement unit. The spacing of the probe beams is adjusted by using DOEs with collimating lenses of different focal lengths (f1, f2). The number of probe beams in the probe beam array is achieved by selecting different types of DOEs. In the biomagnetic imaging system of this invention, the focal length combination of the diffractive optical element and the collimating lens jointly determines the initial spacing of the probe beam spot array projected onto the atomic gas cell.

[0022] The spatial resolution of a magnetic imaging system depends not only on the spacing between the magnetic sensing regions but also on the spacing between the probe beams and the probe beam spot size. Furthermore, resolution and magnetic sensing sensitivity are mutually restrictive. When the spacing between the magnetic sensing regions in a magnetic imaging system is large and greater than or equal to the probe beam spot size, the spatial resolution of the imaging system is equal to the spacing between the probe beams. When the spacing between the magnetic sensing regions is smaller than the probe beam spot size, crosstalk occurs between the signals from each magnetic sensing region. To improve spatial resolution, the size of the probe beam should be minimized. However, when the probe beam is small, the number of effective atoms participating in the magnetic field measurement decreases, which reduces the sensitivity of the magnetic sensor. Different magnetic imaging systems have different sensitivity requirements for the magnetic sensor; therefore, the minimum spatial resolution (probe beam spot diameter) will also vary.

[0023] 2) Magnetic imaging design:

[0024] In addition to generating adjustable-spacing probe beams, the detection scheme for these adjustable probe beams also needs to be considered. The optically pumped atomic magnetic field measurement unit transmits the signal light collected by the probe light passing through the atomic gas cell to the photodetector. The photodetector receives the signal light, extracts the magnetic field signal, and emits an electrical signal. Once the spacing of the probe beams changes within the atomic gas cell, the most direct approach using current technology is to change the spacing between the photodetectors. However, this is experimentally complex and costly. Therefore, before the probe beams reach the photodetectors after passing through the atomic gas cell, we use an imaging scaling lens group with different focal length combinations to scale and adjust the spacing of the probe beams penetrating the atomic gas cell according to a specific ratio to match the spacing between the photodetectors. To achieve the above-mentioned adjustable-spacing probe beam collection scheme, we designed an optical path. It is particularly important that the centers of the convex and concave lenses with different focal lengths be aligned with the optical axis of the optical path, and that these convex and concave lenses with different focal lengths can be easily switched to adjust the spatial resolution of the magnetic imaging system.

[0025] Compared with the prior art, the present invention has the following advantages: the spatial resolution adjustable biomagnetic imaging system of the present invention can conveniently and quickly adjust the spatial resolution of the magnetic imaging system while saving time and cost, has a wide range of application scenarios, can adapt to different biomagnetic imaging application needs such as cardiac magnetoencephalography, brain magnetoencephalography, and myoencephalography, and is also suitable for constructing atomic magnetometer arrays with adjustable spacing. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the optical path design principle in the embodiment;

[0027] Figure 2 This is a schematic diagram of the structure of the spatially adjustable biomagnetic imaging system built in the embodiment;

[0028] Figure 3 Optical path diagram for adjusting the probe beam spacing to match collimating lenses with different focal lengths for DOE;

[0029] Figure 4 A schematic diagram of the optical path for collecting probe beams at different spacings;

[0030] Figure 5 Six uniform diffraction spots generated by the DOE as measured in the laboratory;

[0031] The specific reference numerals in the figure are as follows:

[0032] 11-Laser, 12-Diffractive optical element, 13-Collimating lens, 14-Convex lens, 15-Concave lens, 16-Photodetector, 21-Stimulation current driver, 22-Stimulation electrode, 23-Wire, 3-Atomic gas chamber, 31-Non-magnetic heating element, 32-Non-magnetic temperature sensor, 33-Magnetic sensing area, 34-Data transmission cable, 4-Magnetic shielding chamber, 41-Fixed bracket, 42-Non-magnetic two-dimensional moving platform, 43-Magnetic field compensation coil, 5-Data acquisition and processing device, 6-Mouse. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Devices or structures not limited thereto in this invention employ conventional techniques in the art.

[0034] The spatial resolution adjustable biomagnetic imaging system of the embodiment, such as Figure 1 and Figure 2 As shown, the system includes a detection unit, a stimulation unit, an optically pumped atomic magnetic field measurement unit, a data acquisition and processing device 5, and a calibration unit. The optically pumped atomic magnetic field measurement unit and a fixing bracket 41 are housed within a magnetically shielded chamber 4. The fixing bracket 41 supports the object under test and is driven by a non-magnetic two-dimensional moving platform 42 located outside the magnetically shielded chamber 4. The optically pumped atomic magnetic field measurement unit is positioned below the fixing bracket 41. The stimulation unit applies electrical stimulation to the object under test within the magnetically shielded chamber 4. The stimulation unit includes a stimulation current driver 21 and stimulation electrode pads 22. The output terminal of the stimulation current driver 21 is electrically connected to the stimulation electrode pads 22, which are fixed to the object under test to apply electrical stimulation.

[0035] The optically pumped atomic magnetic field measurement unit includes a rubidium vapor encapsulation ( Figure 1 The atomic gas chamber 3 (illustrated by multiple small spheres) has a non-magnetic heating element 31 and a non-magnetic temperature sensor 32 mounted on its outer wall. The non-magnetic temperature sensor 32 is electrically connected to the temperature control unit. In this embodiment, the non-magnetic heating element 31 is driven by a signal with a frequency of 20 kHz-200 kHz, which is output by a high-voltage power amplifier. The non-magnetic temperature sensor 32 is a PT1000 non-magnetic temperature sensor.

[0036] The calibration unit includes a magnetic field compensation coil 43 installed in the magnetic shielding chamber 4. The magnetic field compensation coil 43 is used to generate a gradient magnetic field to compensate for the non-uniformity of the ambient magnetic field, thereby forming a uniform magnetic field environment in the region where the atomic gas chamber 3 is located. In this embodiment, the magnetic field compensation coil 43 adopts a triaxial square Helmholtz coil. The data acquisition and processing device 5 acquires the signals of each magnetic sensing region 33 in this uniform magnetic field environment and calculates the calibration factor to achieve consistent calibration of the signals of each magnetic sensing region 33.

[0037] The detection unit includes a laser 11, a diffractive optical element (DOE) 12, a collimating lens 13, a switchable imaging zoom lens group, and multiple photodetectors 16 with fixed spacing. The data acquisition and processing device 5 is electrically connected to each photodetector 16. The diffractive optical element 12 and the collimating lens 13 are arranged along the laser emission path to form a probe beam array on the atomic gas cell 3. In this embodiment, a diffractive optical element (DOE) 12 with a fixed diffraction angle is selected, and it is combined with collimating lenses 13 with different focal lengths to achieve spatial resolution adjustment of the magnetic imaging system. The DOE is used to split the laser beam emitted by the laser 11 into a probe beam array, and the collimating lens 13 is used to collimate the probe beam array. The focal length combination of the DOE and the collimating lens 13 jointly determines the initial spacing of the probe beam array projected onto the atomic gas cell 3. The optical path diagram of the DOE and collimating lenses 13 with different focal lengths (f1, f2) adjusting the probe beam spacing is shown below. Figure 3 As shown. We measured it in the laboratory. Figure 5 The six uniform diffraction spots produced by the DOE shown can be used to construct an atomic magnetometer array. Figure 5 As shown, the diffraction spot generated by DOE is uniformly distributed, thus enabling multiple magnetic sensing regions 33 to be realized in the same optically pumped atomic magnetic field measurement unit (atomic gas cell 3). Compared with optical fiber splitting and polarization splitting prisms, the DOE splitting scheme adopted in this invention has low complexity, high integration and high stability, and is easy to construct a compact integrated atomic magnetometer array with adjustable spacing.

[0038] After selecting the DOE and collimating lens 13 with determined parameters, it is necessary to design detection schemes for different spatial resolutions. We use a photodetector 16 with a fixed spacing to receive the signal light emitted through the imaging scaling lens group. Therefore, for magnetic imaging systems with different spatial resolutions, the spacing needs to be adjusted before the probe light passes through the atomic gas cell 3 and reaches the photodetector 16. Here, the imaging scaling lens group is selected to adjust the beam spacing. In order to shorten the optical path as much as possible, a combination of convex lens 14 and concave lens 15 is used to adjust the beam spacing. The combination of convex lens 14 and concave lens 15 with different focal lengths can achieve different proportions of spacing adjustment, thereby realizing the collection of probe beams with different spacings. A schematic diagram of the collection optical path for probe beams with different spacings is shown below. Figure 4For the assembly and selection of convex lenses 14 and concave lenses 15 with different focal lengths, we use a lens flipping frame. Before setting up the optical path, all convex lenses 14 and concave lenses 15 involved in the experiment are installed into the optical path system using the lens flipping frame, and the focal length parameters of each lens are clearly marked. When the system is used for magnetic imaging later, lenses with different focal lengths and lens groups with different scaling ratios are selected according to specific needs. In this embodiment, the imaging scaling lens group consists of convex lenses 14 and concave lenses 15 installed on the lens flipping frame. The imaging scaling lens group is located behind the outgoing optical path of the atomic gas cell 3 and is used to adjust the spacing of the detection beam to match the fixed spacing of the photodetector 16. By switching imaging scaling lens groups with different focal length combinations, the spacing of the detection beam penetrating the atomic gas cell 3 is scaled and adjusted according to a specific ratio, thereby accurately matching the detection light spot arrays with different initial spacings onto multiple photodetectors 16, realizing the adjustment of the spatial resolution of the biomagnetic imaging system.

[0039] Each probe beam interacts with rubidium vapor in the atomic gas chamber 3 to form a magnetic sensing region 33. The signal light emitted from the magnetic sensing region 33 is received by the corresponding photodetector 16 and then transmitted to the data acquisition and processing device 5 via the corresponding data transmission cable 34. The data acquisition and processing device 5 collects the electrical signals emitted by each photodetector 16 and processes the data to obtain a biomagnetic imaging image of the object under test.

[0040] Taking mouse magnetic resonance imaging (MRMI) as an example, the aforementioned biomagnetic imaging system was used to obtain MRMI images. Before the experiment, the mice to be tested (6) were first anesthetized to a resting state. Then, the limbs of the mice (6) were fixed to the support frame (41), and the position of the stimulating electrode pads (22) was determined. Subsequently, the amplitude, period, and duration of the stimulating current from the stimulating current driver (21) were determined. Finally, a non-magnetic two-dimensional translation stage was used to move the stimulation site of the mouse (6) to the upper side of the optically pumped atomic magnetic field measurement unit. The support frame (41) was moved instead of the optically pumped atomic magnetic field measurement unit because the stability and performance of the optically pumped atomic magnetic field measurement unit are affected by the minute vibrations of the two-dimensional translation stage. After connecting and placing the stimulating electrode pads (22), data was collected using the data acquisition and processing device (5). Then, the two-dimensional translation stage was moved to move the position of the mouse (6) relative to the optically pumped atomic magnetic field measurement unit, thus recording the distribution of MRMI intensity at different spatial positions of the mouse (6). Finally, the data was processed by the data acquisition and processing device (5) to obtain a visualized two-dimensional MRMI distribution map of the mouse (6).

Claims

1. A biomagnetic imaging system with adjustable spatial resolution, characterized in that The biological magnetic imaging system comprises a detection unit, a stimulation unit, a light-pumped atomic magnetic field measurement unit and a data acquisition and processing device; the light-pumped atomic magnetic field measurement unit is arranged in a magnetic shielding chamber; the stimulation unit is used for applying electric stimulation to a to-be-detected object in the magnetic shielding chamber; the light-pumped atomic magnetic field measurement unit comprises an atomic gas chamber; the detection unit comprises a laser, a diffractive optical element, a collimating lens, an imaging zoom lens group and a plurality of photoelectric detectors with fixed intervals; The diffractive optical element and the collimating lens are arranged along a laser light exit path, and are used for forming a detection light spot array on the atomic gas chamber; the imaging zoom lens group is arranged behind an exit path of the atomic gas chamber, and is used for adjusting the interval of the detection light beams to match the fixed intervals of the photoelectric detectors; the photoelectric detectors receive signal light emitted by the imaging zoom lens group; the data acquisition and processing device is electrically connected with each photoelectric detector; the diffractive optical element is used for splitting the laser emitted by the laser into a detection light beam array; the collimating lens is used for collimating the detection light beam array; the focal length combination of the diffractive optical element and the collimating lens jointly determines the initial interval of the detection light spot array projected onto the atomic gas chamber; the imaging zoom lens group is a switchable imaging zoom lens group, which is composed of a convex lens and a concave lens mounted on a lens flipping frame; by switching the imaging zoom lens group with different focal length combinations, the interval of the detection light beams penetrating through the atomic gas chamber is scaled and adjusted according to a specific ratio, so that the detection light spot arrays with different initial intervals are accurately matched to the plurality of photoelectric detectors, and the spatial resolution of the biological magnetic imaging system is adjusted.

2. The spatially resolved biomagnetic imaging system of claim 1, wherein The stimulation unit comprises a stimulation current driver and a stimulation electrode sheet, the output end of the stimulation current driver is electrically connected with the stimulation electrode sheet, and the stimulation electrode sheet is used for being fixed to the to-be-detected object to apply electric stimulation.

3. The spatially resolved biomagnetic imaging system according to any one of claims 1-2, characterized in that, A fixing support is arranged in the magnetic shielding chamber, and the fixing support is used for supporting the to-be-detected object; the fixing support is driven by a non-magnetic two-dimensional moving platform arranged outside the magnetic shielding chamber.

4. The spatially resolved biomagnetic imaging system of claim 3, wherein, The light-pumped atomic magnetic field measurement unit is arranged on the upper side or the lower side of the fixing support; a rubidium vapor is encapsulated in the atomic gas chamber, a non-magnetic heating sheet and a non-magnetic temperature sensor are arranged on the outer wall of the atomic gas chamber, the non-magnetic temperature sensor is electrically connected with a temperature control unit, each detection light beam interacts with the rubidium vapor in the atomic gas chamber to form a magnetic sensing area, and signal light emitted from the magnetic sensing area is received by a corresponding photoelectric detector; the data acquisition and processing device is used for collecting electric signals emitted by the photoelectric detectors and processing data to obtain a biological magnetic imaging diagram of the to-be-detected object.

5. The spatially resolved biomagnetic imaging system of claim 4, wherein, A calibration unit is further included, the calibration unit comprises a magnetic field compensation coil arranged in the magnetic shielding chamber, the magnetic field compensation coil is used for generating a gradient magnetic field to compensate for the non-uniformity of the environmental magnetic field, so as to form a uniform magnetic field environment in the area where the atomic gas chamber is located; the data acquisition and processing device acquires signals of each magnetic sensing area in the uniform magnetic field environment, and calculates a calibration factor to realize consistency calibration of signals of each magnetic sensing area.

6. The spatially resolved biomagnetic imaging system of claim 5, wherein, The magnetic field compensation coil is a three-axis square Helmholtz coil.

7. The spatially resolved biomagnetic imaging system of claim 4, wherein, The non-magnetic heating sheet is driven by a signal with a frequency of 20 kHz-200 kHz, which is output by a high-voltage power amplifier.

8. The spatially resolved biomagnetic imaging system of claim 4, wherein, The non-magnetic temperature sensor is a PT1000 non-magnetic temperature sensor.

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