|Calibration & Characterization||Test Services||Workshops & more|
Calibration & Characterization
Calibration & Characterization of magnetic and current measurement instruments
SENIS offers DC and AC calibration services for magnetic field measurement equipment in the field range of 1µT up to 9T! Senis offers Angular Calibration of the Probe.
Output vs Magnetic field (OB). The result of the DC calibration, called OB calibration, is a table which shows the actual values of the teslameter output reading, or the output voltage of the magnetic transducer, for a number of DC magnetic field intensities, at room temperature of the probe and electronic module. The standard OB calibration table includes 10 test points within the measurement range of the instrument. Different OB calibration tables are available upon request.
Output vs Magnetic field and Temperature (OBT). DC calibration may include temperature dependences of offset and transduction constant of a measurement instrument. The result of such DC calibration, called OBT calibration, is a table which shows the actual values of the teslameter output reading, or the output voltage of the magnetic transducer, for a number of DC magnetic field intensities and probe temperatures, at room temperature of the electronic module. The standard OBT calibration table includes data on 10 magnetic field values within the measurement range of the instrument and 3 temperatures (room temperature, a higher, and a lower temperature). Different OBT calibration tables are available upon request.
With the aid of an OBT calibration table, the accuracy of DC and low-frequency magnetic measurement can be increased up to the limit given by the resolution of the instrument.
Field Ranges and Equipment:
- Low magnetic fields: from 1µT to 45mT;
- Calibration equipment: calibrated Helmholtz coils, ammeter, Voltmeter
- Medium magnetic fields: from 43mT to 2.1T;
- Calibration equipment: iron-core electromagnet, NMR teslameter, Voltmeter
- Higher magnetic fields: from 2T to 9T;
- Calibration equipment: Calibrated superconducting magnet, ammeter, voltmeter
- When using a calibrated coil: up to 0.01% of the measured value, or up to offset fluctuation of the instrument under calibration (whatever is greater)
- When using the NMR Teslameter: 30ppm of the measured value, or up to offset fluctuation of the instrument under calibration (whatever is greater)
- Standard calibration temperature for OB calibration: 20°C ± 3°C (room temperature)
- Standard calibration temperatures for OBT calibration: 20°C ± 10°C
- Optionally, offset and low magnetic field calibration can be performed in the temperature range from -40°C to 160°C.
Analog Calibration Magnetic Field
AC calibration provides information about the actual small-signal frequency response of a magnetic measurement instrument. The calibration results are given as plots and tables, which show the actual values of the teslameter output reading, or the output voltage of the magnetic transducer, for a reference AC magnetic field with an amplitude of a few mT, at a number of frequencies, at room temperature of the probe and electronic module. The measurement results are presented as Complex Magnetic Sensitivity vs Frequency and as Bode plots of the tested instrument.
The standard AC calibration table includes 10 test frequencies within the frequency range of the instrument. Different AC calibration tables and analyses are available upon request.
Calibration Conditions and Equipment:
Max amplitude of the periodic magnetic field used for calibration: 10mT
Frequency range: DC to 1MHz
Calibration temperature: 20°C ±3°C
Optionally, AC calibration can be performed in the temperature range from -40°C to 160°C
Calibration equipment: see SENIS dedicated set-up
The result of the probe angular calibration is a set of three numbers for each sensing axis of the Hall probe, which provides the information about the exact orientation of the Hall elements in the probe with respect to the co-ordinate system of the probe package.
It is convenient to express the angular dependence of the Hall probe sensitivity by treating the sensitivity of a Hall element as a vector entity, S. Then the Hall voltage can be expressed as the scalar product of the vectors S and the vector of the magnetic field B:
Vh = S * B
In the case of a 3-axis Hall probe, this equation can be re-written the matrix form
[Vh] = [S] [B]
where [Vh] is a column matrix of the three Hall voltages of the three sensing axis X, Y, and Z, [S] is a 3 x 3 sensitivity matrix of the probe, and [B] is the column matrix of the three magnetic field components in the Cartesian coordinate system of the probe. The sensitivity matrix [S] can be determined by the angular calibration of the probe.
In the later applications of the calibrated teslameter, this matrix equation can be readily solved to find the unknown (measured) vector [B]:
[B] = [S]-1 [Vh]
where [S]-1 denotes the inverse matrix of the sensitivity matrix [S].
Accordingly, the result of the probe angle calibration is the sensitivity matrix [S] and its inverse matrix [S]-1.
Alternatively, the calibration result can be expressed as the angular errors of the magnetic sensing axes of a Hall device in the probe (tilt, roll and pitch angles) with reference to the probe coordinate system.