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VOLTAGE SENSOR ML17F
USER’S GUIDE
CENTRE FOR MICROCOMPUTER APPLICATIONS
http://www.cma-science.nl
Short description
The Voltage sensor ML17f is designed for exploring the basic principles of electricity.
With a wide input voltage range of – 15 to +15 V this sensor can be used to measure
voltages in AC and DC circuits. The sensor is equipped with two 4-mm banana plugs
and two additional alligator clips are delivered with the sensor. The sensor has
differential inputs, which means that measurements can be done directly across
circuit elements without the constraints of common grounding. It can be used to
measure positive potentials, as well as negative potentials. The sensor should be
connected parallel to a circuit element to measure the potential difference across
the element. The sensor is provided with over-voltage protection and voltages up to
± 30 V (related to ground) will not damage the sensor. It never can be used for
higher voltages or 220 V.
The Voltage sensor is an I2C digital sensor, which gives calibrated values of the
measured quantity. This sensor can only be connected to special interfaces that
support I2C digital sensors like the CMA MoLab interface. The sensor cable needed
to connect the sensor to an interface is not supplied with the sensor (sensor cables
are supplied with interfaces).
Sensor specifications
For sampling rates up 1 kHz (1000 samples per second) the Voltage sensor works as a
digital sensor and converts the measured voltage to a digital value via 14-bit analogto-digital conversion. For sampling rates above 1 kHz the sensor works as an analog
sensor. The analog signal generated by the sensor (on its ADC pin) is read by the
connected interface and is converted to a digital value by the 12-bit AD converter on
the interface. The maximum sampling rate of the sensor is 100 kHz (samples per
second).
Practical information
CAUTION: NEVER use high voltages or household AC.
 The Voltage sensor is used to measure the potential difference between the ends
of an electrical component and is therefore connected across (i.e. in parallel) the
component.
 Make sure you observe the correct polarity i.e. connect the black lead from the
Voltage Sensor to the negative terminal of the cells, otherwise the sensor will give
readings with the wrong sign.
 The Voltage Sensor(s) can be used in conjunction with a Current sensor(s)
anywhere in a circuit.
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 For reasons of accuracy, if more than one Voltage sensor is being used in a circuit,
ensure they share a common earth (connect their black leads to each other).
Collecting data
The Voltage sensor works only with specific interfaces. The sensor will be
automatically detected when connected to such an interface. For detailed
information about measurements with sensors consult the User Manuals of the
interface and the Coach 6 software.
Calibration
The Voltage sensor is supplied with a factory calibration in volt (V). The Coach 6
program allows shifting the pre-defined calibration or creating a new two-point
linear calibration if needed. The user calibration is stored in non-volatile user sensor
memory.
Suggested experiments
The Voltage sensor can be used in various experiments such as:
 Charging and discharging capacitors.
 Characteristics of a light bulb and a diode.
 Measurements of internal resistance and EMF.
 Measurements in series and parallel electrical circuits.
 Together with a Current Sensor it can be used to explore the relationship
between the current and the voltage in electrical circuits.
Figure 2. Measuring a battery
voltage.
Figure 2. Measuring the voltage during
charging and discharging a capacitor.
ML17f Voltage Sensor User’s Guide | 3
Technical Specifications
Sensor kind
Up to 1000 Hz - digital
(on-sensor analog to digital conversion)
(14-bits resolution, communication via I2C)
Above 1000 Hz - analog
(on-interface analog to digital conversion)
Measuring range
Differential -15 .. +15 V
Resolution
Typical ± 2 mV, Maximal ± 3 mV
Accuracy
Typical ± 0.3 % and Maximal ± 1 % at full range
Max. over voltage protection
± 30 V
Input impedance
5.3 ± 1.5% MΩ at 25°C
Zero offset
Zero-voltage offset drift: typical ± 1 mV at 25°C
Maximal sampling rate
100 kHz
Sensor dimensions
Housing: 42 x 18 x 16 mm
Electric cords: length 35 cm; diameter 3 mm
Connection
5-pins mini jack plug
Warranty:
The Voltage sensor ML17f 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. 15/05/2013
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