A device for measuring magnetic field induction. Induction converters for measuring magnetic field parameters
To measure the magnetic induction of an alternating magnetic field, converters with stationary (fixed) windings are used. The transform function of the converter corresponds to equation (4). The conversion coefficient connecting the effective value of the induced emf with the amplitude value of the induction of a periodically symmetrically varying magnetic field is determined by the expression
(9)
Where 
- curve shape coefficient;
- frequency of alternating magnetic field.
When the shape of the curve is distorted, the average value of the induced emf is usually measured 
.
To measure the induction of a constant magnetic field, both converters with a conditionally stationary winding and converters with forced movement of the winding can be used. In converters with a stationary winding, a change in the magnetic flux interlocking with the turns of the winding can occur as a result of a change in the field being measured, for example, when measuring the magnetic field caused by turning on some unit, or as a result of a one-time change in the position of the converter itself - removing the converter from the magnetic field or rotation in the field by 90 or 180°.
The output signal of such a converter is a current pulse or an EMF pulse, which occurs when the total magnetic flux changes. Changing the flow 
related to EMF and current as
;
(10)
Where 
-
total resistance of the measuring circuit taking into account the resistance of the converter;
Q - amount of electricity.
A ballistic galvanometer (when integrating current) or magnetoelectric, photogalvanometric and electronic webermeters with operational amplifiers used to integrate EMF are used as integrators.
Induction converters for measuring the parameters of magnetic fields in airspace are usually made in the form of measuring coils of various shapes, the beginning and end of the windings of which are located in one place, so that additional circuits are not created due to the supply wires.
V) 
a) 
b)
is taken to be equal to the field strength on the surface of the sample.
To measure magnetic induction and the intensity of inhomogeneous magnetic fields, it is advisable to use spherical induction transducers (Fig. 1, b). Magnetic
the flux coupled to such a coil is equal to
,
(11)
where B 0 is the induction at the center of the converter;
r - sphere radius;
w - number of turns per unit axis length zz", which must coincide with the vector IN 0 .
To measure MMF, inductive converters called magnetic potentialometers are used, usually made in the form of a uniform winding on a flexible insulating frame. The winding is made with an even number of layers so that the leads are in the middle of the winding (Fig. 1, c). The magnetic potentialometer is placed in a magnetic field so that its ends are at points A and B, between which the MMF is measured. The magnetic flux meshing with the turns of the potentialometer is equal to
(12)
The sensitivity threshold of measuring instruments with stationary induction transducers is determined mainly by mechanical interference (vibrations, seismic and acoustic influences), which lead to oscillations of the transducer and the induction of additional emf, as well as the drift of the integrating output transducer .
The most sensitive magnetoelectric webermeters have a division value of 5*10 
Wb, and photogalvanometric webermeters - 4*10 
Vb.
Induction transducers with rotating or vibrating sensing elements have conversion functions that correspond to equations (5 – 7).
On (Fig. 2, A)
diagram shown 
-converter (the so-called measuring generator), which consists of a frame 1 with the number of turns 
and rotates using a 2 c motor
angular frequency
;
(13)
Where 
- angle between the magnetic axis of the transducer andtransverse component
magnetic induction vector 
,
Where 
- angle between the axis of rotation of the transducer and the vector 
.
Fig.2.
At " = 1 from equation (5) we obtain
;
(14)
Considering that
we have
Converter conversion factor
(16)
Where E T - amplitude value of the generated EMF.
Rotating coil converters are highly sensitive (up to 300 V/T). The sensitivity threshold is limited by the noise level of the collector and interference from the electric motor and power circuit. To reduce the sensitivity threshold, brushless current collectors are used, and the generator is rotated through a gearbox so that the frequency of the output signal differs from the mains frequency and is not a multiple of the engine speed.
On (Fig. 2, b)
an even-harmonic converter is shown. A short-circuit ring 1 is used as a rotating element, which is rotated by a motor 2
in a stationary winding 3. Magnetic field created by a current induced in a short-circuited ring when it rotates in an external field with induction IN 0
,
changes with the same frequency both in magnitude and direction. As a result, the projection of the field magnetic induction vector onto the axis of the stationary winding, coinciding with the vector of the measured magnetic induction B, will change proportionally 
.
The total flux penetrating the stationary coil (we neglect the active resistance of the ring) is equal to
and EMF induced in a stationary winding,
;
(18)
The separation of the frequencies of the supply voltage and the useful signal allows you to filter
interference and create induction converters with a threshold on the considered principle
sensitivity 
Tl.
On (Fig. 2, c)
shows an S-transducer with radial oscillations excited by an electrostrictive vibrator. The vibrator is a thin-walled cylinder 1
made of ferroelectric ceramics PbZrO 3 with metallized internal 2
and external 3
surfaces where alternating control voltage is supplied U f .
The internal electrode has a longitudinal section 4 ,
and the outer one is a short-circuited turn on which the secondary multi-turn winding 5 is located. Due to radial electrostrictive oscillations, the cross-sectional area of the short-circuited turn periodically changes, and in the presence of a constant magnetic field, the magnetic induction vector of which is directed along the axis of the cylinder, an alternating current appears in the outer short-circuited turn , which causes an EMF in the secondary winding proportional to the induction 
.The frequency of electrostrictive oscillations and output EMF is equal to twice the frequency of the control voltage.
- Portable, self-powered device.
- Probe of special design for measurements on magnetic systems of separators (and on individual magnets).
- Easy setup for measurement.
- Wide measurement range.
- Fast and convenient reading of readings.
- High reliability in operation.
- Dust-proof design.
To measure the normal component of magnetic induction at the surface of the poles of permanent magnets, single or assembled magnetic separators. The range of measurement of magnetic induction of constant magnetic fields is from 0 to 500 mT. The error is no more than 2.5%.
Milliteslameter IMI-M designed for measuring the induction of magnetic and electromagnetic separators and columns.
The operating principle of the IMI-M meter is based on the Hall effect. The magnetic induction of the measured constant magnetic field in the Hall sensor is converted into an electrical signal, which causes the needle of the indicating device to move. The angle of deflection of the needle is directly proportional to the magnitude of the magnetic field induction.
Design of the IMI-M meter is a portable range device with a specially designed probe for measuring magnetic field induction. An indicating device is installed in the housing - a microammeter brand M 1690A. For protection from external influences and ease of measurements, the Hall transducer is placed inside a probe made of non-magnetic material. The Hall transducer plate is installed on the plane of the plate strictly in its center and covered with a glass. Inside the glass, the sensor leads are connected to the wires of the measuring cable, which transmits analog signals to the measuring circuit installed inside the device body. The distance between the Hall transducer plate and the magnet pole plane is equal to the thickness of the plate bottom - 0.6 mm. The plate is pressed to the probe handle using a nut. The measuring cable is fixed inside the probe with a fastening screw. The chamber for installing A332 batteries is located under the bottom cover of the meter.
Main technical characteristics of the IMI-M device:
1. Measuring ranges: 0…200 mT, 0…500 mT, 0…1000 mT.
2. Basic error in ranges:
· 0..200 mT, 0…500 mT - +2.5%
· 0…1000 mT - +4%
3. The settling time of the moving part of the device is no more than 4 seconds.
4. Instrument zero setting error +0.5%.
5. Weight of the device without packaging is 0.74 kg.
6. Overall dimensions of the device, no more:
Housings 150x150x80 mm,
Probe DN 18, length 80 mm.
7. Power source - four format A elements
Instruments for measuring magnetic induction and magnetic field strength (hereinafter - MP) are called Teslameters (Tm), by analogy with the measured value. The process of measuring magnetic quantities is more complex than determining electrical quantities; accordingly, instruments and circuits are also more complex.
The most common magnetic measuring instruments for determining induction and voltage are: Tm with a Hall transducer, ferromodulation and nuclear resonance teslameter.
TM with Hall transformer determine the parameters of medium (from 10-5 to 10-1 T) and strong (10-1 to 102 T) MP. The operating principle of such teslameters is based on the appearance of an emf in semiconductors placed in the influence zone MP.
In this case, the vector of magnetic induction of the desired MP must be perpendicular to the semiconductor wafer.
An electric current flows through the body of a semiconductor I. As a result, a potential difference is formed on the side faces of the plate, which is called the Hall EMF. EMF is determined by the compensation method or by a millivoltmeter, the scale of which is graduated in teslas. In practice, the Hall EMF depends on the following parameters:
Ex=C*I*B;
Where WITH– coefficient taking into account the design parameters of the semiconductor wafer;
I– current strength, A;
IN– magnetic induction, T.
Knowing the current strength I, coefficient WITH and meaning Ex, the device is calibrated in units of measurement MP, provided that the current strength is constant.
TM with a Hall transducer are easy to use, have small dimensions, which allows them to be used for measurements in small gaps. With their help, the parameters of constant, variable and pulsed fields are determined.
The measurement limits of a conventional device are from 2*10-3 to 2 T, with a relative error of ±1.5–2.5%.
The second type of devices for determining characteristics MP is ferromodulation teslameter (FMT). Use FMT to measure weak and medium, constant and variable (up to 1 kHz) MP.
The operation of FMT is based on the property of permalloy cores C to change their magnetic state when simultaneously exposed to constant and variable MP.
The most widely used in the measurement circuit of Fig. 2 are differential ferromodulation converters. Generator G is used to create a variable MP, which through coils ω affects the cores C.
Due to the fact that these coils are connected counter-currently, i.e. the end of one coincides with the other, there is no EMF in the circuit of the indicator coil ωi.
If we add cores C to the constant MP(measured field), so that the magnetic induction vector is parallel to the axis of the cores, an EMF will appear in the measuring winding. This phenomenon occurs due to the physical properties of permalloy, which changes its magnetic state under the influence of two dissimilar fields.
So, under the influence of the field B_, at the input of the selective amplifier of the DUT, along with odd harmonics, even harmonics will appear. In particular, the EMF of the second harmonic has a direct dependence on the voltage MP N and magnetic induction IN_.
E2 ≈ kH;
E2 ≈ k1B.
Where k And k1– coefficients taking into account the design features of the cores, frequency and excitation field strength ω;
N– measured voltage MP;
IN_- measured induction.
The synchronous rectifier receives an amplified EMF signal of the second harmonic from the output of the DUT, converts the EMF into one proportional to it (and therefore N And IN_) compensation current Ik.
Compensation current flowing through the compensating windings ωк, creates a compensating field VC, which tends to balance with B_, and has the opposite direction. Milliammeter, through which current also flows Ik, graduated in Tesla.
Ferromodulation teslameters have high sensitivity, accuracy, and can be used for continuous measurements of magnetic field parameters. FMT measurement limits are from 10-6 to 1 mT, with an error of 1 to 5%.
Teslameters with quantum magnetic measuring converters used to measure medium and weak MP, constant and variable fields with a frequency of up to 20 kHz. The principle of operation of quantum magnetic measuring converters is the interaction of the nuclei of molecules of a substance with MP.
Figure 3 shows a diagram of a common nuclear resonance converter. The flask contains the working substance. By means of a high-frequency generator and a coil encircling the flask, an alternating current is applied to the working substance. MP.
Interaction of nuclei with MP called precession. So, in the flask the particles precess around the magnetic induction vector of the alternating field.
At a right angle, on the flask with the working substance, the measured constant begins to act MP IN_. By smoothly changing the frequency of the alternating field, nuclear magnetic resonance is achieved - the coincidence of the precession frequency with the frequency of the alternating field. Resonance consists of an increase in the amplitude of precession.
This process is accompanied by the absorption of part of the energy of the alternating RF field, which leads to a change in the quality factor of the coil, and, accordingly, a change in the voltage at its ends.
The phenomenon of resonance can be observed on the screen of an electronic oscilloscope EO, the horizontal input of which is supplied with LFO voltage, and the vertical input is supplied with the rectified voltage of the working coil. The LFO supplies a low frequency current to the modulation coil KM, which serves to modulate the magnetic induction IN_.
Nuclear resonance teslameters are the most accurate, their relative error is 0.001–0.1%, in the range of 10-2–10 Tesla.
The magnetic induction meter ATT-8701 is intended for measuring the parameters of magnetic fields in industry, materials science, electrical engineering, as well as in laboratory research. ATT-8701 has the ability to measure constant and alternating (with a frequency of 40 Hz...10 kHz) magnetic fields. The device is equipped with an original single-axis sensor, which is more sensitive than traditional Hall effect sensors.
Main characteristics
- Microprocessor control
- Sensor - single channel
- Display 4-digit liquid crystal with backlight, size 58x34 mm
- Fixing current, maximum and maximum average value
- Relative dimension
- Power supply 9V (6 AAA batteries) or DC 9V AC adapter
- Overall dimensions: base unit 173x68x42 mm, sensor 177x29x17 mm
- Weight 428 g
- Overall dimensions in packaging 250x75x290, weight 1 kg.
This device, together with an interface converter and software either on a PC (Windows OS), or for tablets and mobile devices with Android OS, implements automated measurements of magnetic field parameters and a variety of mathematical processing and storage of measurement results.
Specifications
- Measuring range: -3000 mGs to 3000 mGs (-300...300 µT).
- Permission:
0.1 mG (-199.9...199.9 mG)/0.01 µT (-19.99...19.99 µT)
1 mG (>199.9 mG and<-199.9 мГс)/0.1 мкТл (>19.99 µT and< 19.99 мкТл) - Frequency of measured alternating magnetic field 40 Hz…10 kHz
- Measurement error ±(2%+2 mGs)
- Polling rate 1 time per second
- Units: mGs, mT
- RS232 serial interface with the ability to connect to a PC via USB using an interface converter and extensive software processing using programs and on a PC using Windows OS or for tablets and mobile devices with Android OS.
Standard equipment
- Device
- Sensor
- Carrying case
- User guide
- Software
To download the software, click the “Download” button or go to the “ ” -> section
Additional equipment
- USB-RS232 (TTL) interface converter Aktakom ACE-1025
- Aktakom Data Logger Kit AME-1025 (consists of Aktakom ACE-1025 interface converter and AKTAKOM Data Logger Monitor-W software)
- Software
The standard software does not have a physical medium and can be downloaded on the website in the “ ” section after purchasing and registering the device, indicating its serial number.
To download the software, click the “Download” button or go to the “ ” -> “ ” section, then log in by entering your username and password. If you have not previously registered on the site, follow the “Register” link and provide all the required information.
If the software is lost, downloading it will cost an additional fee. The software may be supplied on physical media (CD-ROM). Burning the software onto media (CD) and delivering it is available for an additional fee.
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Description of the controls of the magnetic induction meter ATT-8701
Articles about AKTAKOM products
Modern hand-held, inexpensive devices in many cases have interfaces for connecting to a personal computer (PC). The presence of such an interface makes it possible to use such a budget device as a universal recorder in a measurement laboratory. Most inexpensive devices use the long-established and well-known RS-232 protocol, and the offered software is very primitive. These two factors are limiting the full use of hand-held devices as mobile recorders. In modern computers, especially laptops, the RS-232 interface is becoming less and less common, and software limitations do not allow full use of measurement results. The AKTAKOM ATT series range of modern budget meters of non-electrical quantities has an RS-232 interface and can be used as a basis for building a multifunctional recording laboratory. Especially for this group of devices, a universal interface solution for communication with a PC is produced - interface modules from the ACE-1025, ACE-1026, ACE-1027 series, which provide connection of devices of this group via the USB interface. The proprietary software of “Your USB laboratory AKTAKOM” - AKTAKOM Data Logger Monitor allows you to effectively use the above devices as a multifunctional recording laboratory.
Questions and answers
What materials for this device are available on the AKTAKOM website? |
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For this device, after it is registered on the AKTAKOM website indicating the serial number, the following is available for download/read: Software
Documentation
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How to make measurements in constant and alternating magnetic fields using the magnetic induction meter ATT-8701? |
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Sensor placement in a constant magnetic field:
Sensor location in an alternating magnetic field:
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How to make relative measurements using the magnetic induction meter ATT-8701? |
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| Before starting measurements, press and hold the UNIT/ZERO button for about 2 seconds. The device will set the relative zero and the “0” symbol will light up in the upper left part of the display. To exit the relative measurement mode, press and hold again for 2 seconds. The device will exit the relative measurement mode and the “0” symbol will disappear from the display. An example of connection is shown in the illustration:
Android requirements for working with USB devices In order for your computer (tablet, smartphone) based on Android OS to work with devices connected to it with a USB interface, it must meet three requirements:  This utility can also, in some cases, set the necessary permissions on the system. Find "USB Host Diagnostics" in your installed applications and launch it. Diagnostics of USB Host functions using the “Start Diagnostics” button
At the end of the diagnostic process, the utility will display information about your mobile device.
Next, you need to install the AKTAKOM Smart Data Monitor (ASDM) software, which is free, and Aktakom Smart Data Logger (ASDL), which is paid. The software is available for installation on GooglePlay After connecting the device and allowing the application to interact with the tablet’s USB port
the application will begin to automatically process the data received from the device.
A “hot” connection of the channel when reading data has been implemented, but hot plugging of the device is not supported, for this reason all components must be connected to the Tablet PC before starting the software. 2. You can also read the instruction manual in reading mode before purchasing the device. To do this, you need a special identifier, which can be obtained by filling out an application on the AKTAKOM website or making a request in the online consultant of our website* indicating the device model that interests you. The ID for reading the instruction manual has a limited validity period, but can be extended upon your request. 3. If you have technical questions about the characteristics or the possibility of using this equipment before purchasing it, please contact our consultants. 4. A paper version of the operating manual (OM) is issued along with the purchased equipment. If you lose the paper version, you can read the operating manual for free on the website www.site (after registering the device indicating its serial number) or receive a paper copy for an additional fee. *during business hours on weekdays |
Measurement magnetic induction And magnetic field strength in constant and variable fields are performed using teslameters with Hall transformers. When such a converter is placed in a magnetic field, an emf is generated on its side faces.
Industrially produced teslameters of this type are designed for measuring magnetic induction in the range of 0.002...2 T, with a frequency range of up to 1 GHz. Their advantages include simplicity of design, ease of operation, and high metrological characteristics. Disadvantages: the device readings depend on temperature.
IN nuclear resonance teslameters As a converter, a type of quantum magnetic-measuring converter is used, the action of which is based on the interaction of atoms, atomic nuclei with a magnetic field. The measurement range of such devices reaches 10T with a measurement accuracy class within the range of 0.001...0.1.
Ferromodulation teslameters designed for small constant and variable low-frequency magnetic fields. The principle of their operation is based on the phenomenon of superconductivity and allows measurements of the magnetic field created by the biocurrents of the heart and human brain. The magnetic field strength in such devices is measured by an electrodynamic method based on the interaction of the current flowing through the frame with the measured magnetic field. The value of the field strength is judged by the angle of deflection of the frame placed in the measured magnetic field, with a constant value of the current in it.
Magnetic materials are divided into three groups: soft magnetic; hard magnetic; materials with special properties. Static and dynamic characteristics of magnetic materials and methods for their determination are regulated by relevant GOSTs and standards.
Equipment for determining the characteristics and parameters of magnetic materials consists of magnetizing and measuring windings, measuring instruments, registration, processing of the received information and various auxiliary devices. In industrial installations, to determine the static characteristics of magnetic materials, induction is determined using the induction-pulse method, and the field strength is determined indirectly by the current strength in the magnetizing coil and its parameters or using magnetic measuring instruments. In installations for determining the dynamic characteristics of magnetic materials, an induction magnetic measuring transducer and various methods for measuring its output signal are usually used.
Testing of magnetic materials tend to be carried out with uniform magnetization of the material, when the induction in different sections of the sample is the same. To test magnetic material in a closed magnetic circuit, samples in the form of a ring are used, which ensures the greatest measurement accuracy. But the production of such samples is a complex matter, so it is much easier to test material samples in the form of strips and rods using special devices - permeameters.
Basic static characteristics of materials are determined in constant magnetic fields and allow one material to be distinguished from another. These include: the main magnetization curve and the hysteresis cycle loop, the area of which is proportional to the energy spent on magnetization reversal, and the points of intersection with the coordinate axes make it possible to determine the main magnetic characteristics of materials. The most common way to determine static characteristics is the pulse induction method using a ballistic galvanometer and a webermeter.
Dynamic characteristics depend not only on the quality of the material itself, but also on the shape and size of the sample, the shape of the curve and the frequency of the magnetizing field. The dynamic hysteresis loop and its area determine the total energy dissipated during the magnetization reversal cycle, i.e. losses due to hysteresis phenomena, eddy currents, magnetic viscosity, etc. A family of dynamic loops characterizes a magnetic material for a given sample size, shape and frequency of the magnetic field. The geometric location of the top of the dynamic loops is the dynamic magnetization curve. Important parameters of magnetic materials in alternating magnetic fields are various types of magnetic permeability.