CMA ML39m Gas Pressure Sensor User’s Guide

GAS PRESSURE SENSOR ML39M
USER’S GUIDE
CENTRE FOR MICROCOMPUTER APPLICATIONS
http://www.cma-science.nl
Short description
The Gas Pressure sensor ML39m is designed to measure relative gas pressure in the
range between ‐100 to 300 kPa (positive or negative differential changes in
pressure). The pressure is measured via a pressure port located on the side of the
sensor box. The end of the white pressure port has a small threaded end called a
Luer‐lock. With a gentle half turn, you may directly attach the plastic Luer‐lock
connector or the 20 mL plastic syringe (included with the sensor).
The pressure sensor is a very precise piezoresistive pressure sensor. It consists of a
silicon diaphragm with piezoresistive strain gauges diffused into it, fused to a glass
backplate. Applied pressure causes mechanical stress of the diaphragm, which is
transduced into a resistance change by means of the piezoresistive effect.
The Gas Pressure sensor is fairly durable, but it is designed only for use with non‐
corrosive, non‐ionic working gasses such as air, dry gases and the like. Do not get it
wet.
The sensor is delivered with the following accessories:
 one plastic 20‐ml syringe with Luer‐lock,
 one plastic Luer‐lock connector, and
 one plastic tube with an inside diameter of circa 6 mm. This tube can be attached
to the other end of the Luer‐lock connector.
The Gas Pressure 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
The Gas Pressure sensor ML39m is a digital sensor that converts the measured gas
pressure value to a digital value via 14‐bit analog‐to‐digital conversion. The
resolution of the sensor is typical 0.0244 kPa. The maximal sampling rate of the
sensor is 1000 Hz.
Collecting data
This Gas Pressure 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.
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Calibration
The Gas Pressure sensor is supplied with a factory calibration in kPa. 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
This Gas Pressure sensor can be used in various experiments such as:
 Investigate the relationship between pressure and volume, Boyle’s law.
 Study the effect of temperature on gas pressure, Gay‐Lussac’s law.
 Measure vapor pressure of liquids.
 Measurements of reaction rates as a gas is produced in a chemical reaction.
Figure 1. Using the pressure sensor and the plastic syringe in an experiment to verify Boyle’s law.
Pressure Units
Pressure can be measured in many different units. Some equivalent values for 1
atmosphere are:
1 atmosphere = 101.325 kPa
1 atmosphere = 760 mm Hg
1 atmosphere = 29.92 in. of Hg (at 0°C)
1 atmosphere = 14.70 psi
1 atmosphere = 1013 millibar
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Technical Specifications
Sensor kind
Digital: on‐sensor analog to digital conversion
(14‐bits resolution, communication via I2C)
Measuring range
‐ 100 .. 300 kPa (‐1000 .. 3000 hPa)
Resolution
Typical 0.0244 kPa (0.244 hPa)
Linearity sensitivity error: Typical ± 0.3 % of full range
Sensitivity‐temperature characteristics: ± 1.0% of full
range at temperature (compensation) range 15 to 45°C,
where zero at 30°C
Accuracy: Typical ± 1.0 % of full range
Pressure port female Luer‐lock
Only for non‐corrosive gasses, non‐ionic working gasses
such as air, dry gases and the like
90% of applied pressure value: typical, 0.2 ms
(before digital condition and conversion)
1000 Hz
Uncertainty
Connection
Usage
Respond time
Maximal sampling rate
Sensor dimensions
Connection
Housing: 68 x 18 x 16 mm (W x D x H)
Length of female Luer‐lock connector: 6.2 mm
5‐pins mini jack plug
Warranty:
The Relative Pressure sensor ML39m 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. 17/11/2011
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