Download Sensor specifications - CMA

MAGNETIC FIELD SENSOR 024I
User’s Guide
Figure 1. Magnetic field sensor 024i
CENTRE FOR MICROCOMPUTER APPLICATIONS
http://www.cma-science.nl
Description
The Magnetic field sensor 024i contains a Hall-element, which is sensitive magnetic
field strength. The element is mounted at the end of a narrow tube at the position 0
cm indicated by the marks on the tube.
The sensor has two ranges: from -100 to + 500 mT and from -10 to 50 mT.
The Hall-element is mounted perpendicular to the direction of the narrow end (tube)
of the sensor. If the field lines are longitudinal to the tube, the output voltage of the
sensor has the highest value. The sensor is therefore very suitable for measuring the
magnetic field inside coils, or near (very strong) permanent magnets. The sensor is
less suited to measure the field in slit-shaped cavities.
A push button switches between the two ranges of the sensor. When the push button
is pressed down, the range -10 .. 50 mT is selected, when the push button is in the
upper position, the -100 .. 500 mT range is selected.
Because the output signal of a Hall-element is very small, the Hall-element is
contained in an integrated circuit with a differential amplifier with temperature
compensation in order to get a good quality output signal.
The Magnetic field sensor is equipped with an analog BT plug and can be
connected to the interfaces CMA: €Lab, CoachLab II/II+ and ULAB. Furthermore
the sensor can be used with Texas Instruments CBL, CBL2 and Vernier LabPro.
Sensor specifications
The Magnetic field sensor has a memory chip (EEPROM) with information about
the sensor. Through a simple protocol (I2C) the sensor transfers its data: name,
quantity, unit and calibration to the interface1.
Examples of experiments
Magnetic field sensor 024i can be used for:
- Measurements of the magnetic field near a (strong) permanent magnet;
- Measurements of the magnetic field near a current-carrying wire;
- Measurements of the magnetic field near or inside a coil or solenoid.
Calibration
The output of the Magnetic field sensor is linear with respect to magnetic field. To
collect data you can:
1. Use the calibrations supplied by the sensor’s EEPROM memory. The sensor
contains two calibrations, one for each range. When switching to another range,
disconnect and reconnect the sensor to make sure Coach detects the changed
calibration information.
1
This is valid for the following interfaces: CMA €Lab, BT inputs of CoachLab II/II+ and ULAB,
TI CBLand CBL2, and Vernier LabPro.
2
2. Use the calibrations supplied in the standard sensor library of the Coach
program. There are two calibrations available in the sensor library in Coach 2:
 Magnetic field sensor (024i) (CMA) (-10 .. 50 mT)
 Magnetic field sensor (024i) (CMA) (-100 .. 500 mT).
Figure 2.
Default calibration graphs of the two ranges of the Magnetic field sensor
(used in the standard Coach sensor library and in the sensor’s memory).
Magnetic field (mT) = 50 * Vout (V) - 10
Magnetic field (mT) = 500 * Vout (V) - 100
(-10 .. 50 mT range)
(-100 .. 500 mT range)
Coefficients of the calibration functions:
a= 50; b= -10
(-10 .. 50 mT range)
a= 500; b= -100
(-100 .. 500 mT range)
2
This sensor definition is present in the standard sensor library of Coach 6.25 and later.
3
Technical data
Measurement ranges
-10 .. 50 mT
-100 .. 500 mT
Accuracy
±5%
Voltage output range
0 .. 3 V
Voltage offset
0.5 V ± 3%
Resolution using 12 bit 5V AD
converter
0.024 mT (-10 .. 50 mT range)
0.24 mT (-100 .. 500 mT range)
Calibration functions
Magnetic field (mT) = 50 * Vout (V) – 10
Magnetic field (mT) = 500 * Vout (V) – 100
Dimensions
Complete sensor: 275 x 34 x 24 mm3
Length tube: 130 mm
Diameter tube: 7 mm
Current requirement
Max. 60 mA
Operating temperature range
0 .. 50 °C
Connection
Right-hand BT (British Telecom) connector
Warranty:
The 024i Magnetic field sensor is warranted to be free from defects in materials and
workmanship for a period of 12 months from the date of purchase provided that it
has been used under normal laboratory conditions. This warranty does not apply if
the sensor has been damaged by accident or misuse.
Note: This product is to be used for educational purposes only. It is not appropriate
for industrial, medical, research, or commercial applications.
Rev. 1/11/12
4