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 Instrumentation
 FLUXMETERS and ACCESSORIES
DIGITAL FLUXMETER 
The most advanced Fluxmeter available in the market for measurements of magnetic materials and circuits Calibration Certification Service, available from stock, high accuracy, RS 232 interface, digital display.
The most common magnetic field measurements to perform
using the fluxmeter are:
· Magnet working point measurement ·
· Residual induction measurement ·
· Magnet quality control ·
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FLUXMETER WORKING PRINCIPLE
The fluxmeter is a dynamic meter of the magnetic flux.
The fluxmeter is based on the electromagnetic induction principle: the magnetic flux variation during the time in a circuit produces a voltage V (induced):
Therefore it is possible to determine easily that the flux is equal to the integral of the voltage during the time:
Using the voltage generated to the terminals of a coil to supply an electronic integrator it is obtained a reading directly proportional to the linked flux.
From the induction law we see that is the variation of a magnetic flux that produces a voltage therefore the flux measurement using the fluxmeter must be performed in dynamic conditions either moving the measuring coil or varying and/or moving the field source.
Here below it is reported how to perform the most common measurements using the fluxmeter.
DATA SHEET
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Applications
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flux measurements in static or transient events
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permanent magnets in open circuit: measurement of intrinsic induction on working point (Jw ~= Br )
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soft magnetic materials: residual field testing
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BH curves measurement
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measurement of magnetic moment of permanent magnetism in open circuit
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strength field measurement (H) , also for fast transient events
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measurement of the flux generated by motors or other electromagnetic devices
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uniform and easily accessible magnetic field generator
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Controlling the quality of permanent magnets 
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STANDARD HELMHOLTZ COILS
| HELMHOLTZ COIL |
HM/R15 |
| Kh constant |
4.5 • 10-6 m |
| measurement area |
dia. 12 mm (0.472") H 9 mm (0.354") |
| weight |
1,2 kg. |
| HELMHOLTZ COIL |
HM/R32 |
| Kh constant |
1.1 • 10-4 m |
| measurement area |
dia. 29 mm (1.141") H 19 mm (0.748") |
| weight |
4 kg. |
| HELMHOLTZ COIL |
HM/R58 |
| Kh constant |
4.5 • 10-4 m |
| measurement area |
dia. 53 mm (2.086") H 34 mm (1.338") |
| weight |
6 kg. |
| HELMHOLTZ COIL |
HM/R100 |
| Kh constant |
2.8 • 10-3 m |
| measurement area |
dia. 90 mm (3.543") H 60 mm (2.362") |
| weight |
10 kg. |
| HELMHOLTZ COIL |
HM/R150 |
| Kh constant |
7.3 • 10-3 m |
| measurement area |
dia. 135 mm (5.314") H 90 mm (3.543") |
| weight |
12 kg. |
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Customized Helmholtz Coils available on demand, 2 and 3 axis
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working points
Controlling the quality of permanent magnets
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MTC-1 Precision Volt-Second Generator
When the optimum performance of a measurement instrument is required, that instrument must be periodically calibrated to a traceable standard. This standard must provide a calibration accuracy which exceeds the intrinsic accuracy of the measurement instrument by a comfortable margin. A margin broad enough so as not to unduly influence the overall calibrated accuracy of that instrument.
The MTC-1 Volt-Second Generator is a precision traceable standard with 11 impulse outputs from 0.0001 V-S to 10 V-S, which corresponds to a range of 104 to 109 maxwell-turns, and has an overall instrument accuracy which is better than ±0.05%.
Used as a primary standard to calibrate fluxmeters, electronic integrators and ballistic galvonometers without recourse to standard search coils or reference magnets, the MTC-1 will calibrate a quality fluxmeter precisely enough to allow the fluxmeter to be used as a secondary standard for calibration of search coils, reference magnets, Hall probes and gaussmeters.
Features
- Trackable Accuracy: ±0.05%, NIST Traceability
- Broad Range: 0.0001 to 10 Volt-Seconds; 104 to 109 Maxwell-Turns
- Stand Alone Calibration: Without recourse to search coils or reference magnets
- Direct Calibration: Fluxmeters, Electronic Integrators, Ballistic Galvanometers
- Indirect Calibration: Gaussmeters, Hall-probes, Search Coils, Reference Magnets
- Convenient Scaling: Scaled to read Volt-Seconds and Kilomaxwell-Turns
Principles of Operation
Most fluxmeters measure the total change in flux of a changing magnetic field by integrating the voltage induced in a sensing coil. Each magnetic line, maxwell, in linking a conductor induces in it a 10-8 volt-second impulse.
From the physical relationship, 1 volt = 1 weber/second and 1 weber = 108 maxwell-turns, the MTC-1 volt-second generator becomes a standard by simulating maxwell-turns from the derived relationship 1 volt-second = 108 maxwell-turns.
The MTC-1 produces an output pulse with a calibrated height (voltage) and calibrated width (time), the integral of which is height x width or volt-seconds. This volt-second pulse becomes the source by which the fluxmeter is calibrated.
Two output voltages and seven time intervals are provided which produce 14 different volt-second combinations for 11 different maxwell outputs from 104 to 109 maxwell-turns.
A 1 volt base is regulated by a precision voltage regulator IC operating with a precision divider network to produce simultaneous 1 volt and 0.01 volt output pulses.
The time base for the MTC-1 is a 3.276 MHz crystal-controlled oscillator which is divided down and buffered to provide a 100 Hz TTL compatable clock signal to the output circuit. The overall accuracy of the time base is ±0.005%.
The timer turns on the output for 1 to 1000 clock pulses producing 104 to 107 maxwell-turns at the 0.01 Volt output or 106 to 109 maxwell-turns at the 1 volt output.
Specifications
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Range
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2 Voltage Ranges 0.01V, 1V ±0.01%
7 time intervals: 0.01, 0.05, 0.1, 0.5, 1, 5, 10 seconds ±0.005%
14 Volt-Second output pulses corresponding to 11 Maxwell-Turn ranges. From 0.0001 to 10 Volt-Seconds; 104 to 109 Maxwell-Turns
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Stability
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Voltage Base: ±0.004%/°C; ±0.01% @ 25 ±10°C
Time Base: ±0.005%; -25°C to 75°C
Divider Network: ±0.0002%/°C; ±0.002% @ 25 ±10°C
Volt-Second Product: ±0.0042%/°C, ±0.005%; ±0.047% @ 25 ±10°C
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Accuracy
(Factory Set)
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Calibration (set voltage): ±0.01%*
Volt-Second Product: ±0.03% @ 25°C
*Depends on voltage standard used
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Source
Resistance
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0.01V Range 0.2 ohm
1V Range 20.0 ohm
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Power
Input
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105 V - 125 V 50 Hz/60 Hz Std.
210 V - 250 V 50 Hz/60 Hz Opt.
Approx. 14 VA
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FLUX MEASURING SENSOR mod.LPH-P...
Custom measuring coils designed and built to measure magnetic flux with the Digital Flux instrument in any magnetic circuit.
| Customer dwg |
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| outside diameter |
50,5 mm |
| max. useful length |
60 mm |
| magnetic material |
ferrite |
| magnetic orientation |
radial |
| number of poles |
6 |
| magnet length |
54 mm |
This tensiometer match with the DIGITAL FLUXmeter. 
Controlling the quality of permanent magnets
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FLUX MEASURING SENSOR mod.LPH-200
Tensiometer for "H" measurements to be connected to the Digital Flux.
| magnetic area |
7.000 mm2 |
| dimensions |
L 80, W 8, H 2,5 mm |
| non-magnetic support |
LPS-200 (optional) |
This tensiometer match with the DIGITAL FLUXmeter.
Controlling the quality of permanent magnets
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Controlling the quality of permanent magnets
The fluxmeter is often used to control the quality of permanent magnets. The main reason is its versatility: it is possible to build wound fluxmetric coils that match perfectly any magnetic item to be measured. The same fluxmeter can measure a big variety of devices using the proper measuring coils.
Although there are devices than need an ‘ad hoc’ coil, there are some ‘universal’ coils suitable for wide ranges of shapes, dimensions, materials: it is the case of Helmholtz coils and potential coils.
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Helmholtz coils
Helmholtz coils are probably the most easy, fast and cheap way to control the quality of permanent magnets. They are made by two identical coaxial coils fixed at a distance equal to their radius. This configuration permits a wide uniformity volume inside the coil, guaranteeing a measure independent from positioning errors. The picture below shows the uniformity volume in a Helmholtz coil.
The measure with Helmholtz coils is described in the International Standard IEC 60404-14. |
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| The Helmholtz coil’s reading is proportional to the residual induction Br of the material (more precisely, to the magnetic polarisation of the working point Jd, see picture above). The measuring procedure, very simple, is quickly described below. |
| Jd is calculated by the read flux and the coil’s constant KH (that is given in the coil’s certificate) using the formula: |
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Potential coils
If H is a constant magnetic field between two points at a distance d, the difference of magnetic potential .gif) P between the two points is given by P = H•d.
The potential coils permit to measure easily the demagnetization field Hd of a permanent magnet through the measure of the magnetic potential. It is sufficient to know the thickness d of the magnet and make a measure of flux .gif) in its surface with the potential coil to calculate Hd: Hd = 2Kp•/d where Kp is the constant (certificate) of the potential coils. |
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