PASCO PS-2194 Ethanol Sensor - Manual (Page 2)

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E th a n o l S e n s o r PS- 2 1 94
2
Warm-up
The probe contains a heating element. After connecting the sen-
sor to a powered PASPORT interface, wait about 10 minutes for
the sensor’s temperature to stabilize.
If the temperature of the gas surrounding the probe changes, the
probe will need some time to stabilize again.
The sensitivity of probe changes with temperature. Make mea-
surements at a constant temperature after the probe temperature
has stabilized.
Collecting Data
1. Ensure that the membrane is installed and intact. There
should be no tears or discoloration.
2. Place the end of the probe just above a solution, or in a gas,
containing less than 3% ethanol.
3. Press or click the start button to begin recording data.
Calibration
For accurate measurements, first calibrate the sensor. You will
need a solution of 1% ethanol in water. The solution should be at
the same temperature as the solutions to be measured.
Calibration data is stored in the sensor’s memory and persists
until the sensor is calibrated again, even if the sensor is
unplugged from the interface.
1. Connect the sensor to an interface as described above.
2. Place the probe above the 1% ethanol solution.
3. Observe the ethanol concentration reading in software or on
the datalogger.
4. Wait until the reading stabilizes.
5. Press and hold the 1% CAL button on the sensor for 4 s.
Immediately after a successful calibration, the sensor’s output
reads 1%, and the button is illuminated.
About the Membrane
A roll of membrane material is included with the sensor. The
material is PTFE thread sealing tape, about 25 mm wide, typi-
cally used by plumbers. The membrane protects the sensing ele-
ment from liquid, but is permeable to ethanol gas.
Membrane Replacement
Change the membrane when it is torn or discolored.
1. Pull the retaining ring off the end of the probe.
2. Remove the and discard the old membrane.
3. Cut a 25 mm square of new membrane material.
4. Place the new membrane over the end of the probe.
5. Push the retaining ring onto the end of the probe over the
membrane.
6. Optionally, use a sharp knife to trim off excess membrane
from around the retaining ring.
Membrane replacement
Factors that Affect the
Measurement
Temperature and humidity: The sensor’s temperature is
determined by both its internal heater and the temperature of its
surroundings. Allow the probe time to reach a stable temperature
after you plug it in or after the temperature of its surroundings
changes. Keep temperature and humidity constant during calibra-
tion and measurement.
Air flow: Air flow around or into the probe affects its tempera-
ture. Minimize airflow during calibration and measurement.
Other gases: In addition to ethanol gas, the sensor responds
to hydrogen, isobutane, carbon monoxide, and methane.
old
membrane
new
membrane
excess
membrane
retaining
ring