PASCO PASPort PS-2117 User manual

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Instruction Sheet
012-08470D
Drop Counter
PS-2117
Included Parts
Additional Parts Required
• PASPORT compatible PASCO interface or datalogger
• Three-finger Clamp (SE-9445)
• Support Rod and Stand (SE-9451)
• Multi Clamp (ME-9507)
• Magnetic Stir Plate (SE-7700)
• Beaker, 150 mL
Additional Parts Recommended
• Buret, 50 mL (SE-7703)
• Chemistry Sensor (PS-2170)
• pH Sensor (PS-2102)
• Temperature Sensor (PS-2125)
• Other sensors for measuring conductivity or
oxygen-reduction potential (ORP)
• Micro Stir Bars, set of 5 (PS-2565)
Quick Start
1. Connect the Drop Counter to your PASPORT compatible
PASCO interface.
2. If you are using a computer, connect the interface to it and
start the data acquisition software.
3. Press or click the start button to begin recording data.
4. Allow drops of liquid to fall through the rectangular open-
ing.
Introduction
The Drop Counter measures the number of drops of fluid that fall
through the rectangular opening of the sensor. It is typically used
in conjunction with a pH sensor and other equipment to perform
Micro Stir
Bar
Syringe
Support Rod
Stopcock (2)
Drop Tip
PS-2117 Drop Counter
• Drop Counter • Stopcock (2)
• Micro Stir Bar • Drop Tip
• Syringe (60 mL) • Support Rod

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Drop Counter PS-2117
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a titration. Data from the Drop Counter and other sensors are
recorded and displayed in software such as PASCO Capstone, or
on a datalogging interface such as an Xplorer GLX.
The Drop Counter can be mounted on a support rod and the sup-
port rod can be clamped to a rod stand. The counter is equipped
with three integrated probe holders. The included Micro Stir Bar
fits onto the end of a pH probe or probe of the same diameter.
Acid-base Titration
These steps explain a typical use of the Drop Counter.
Procedure
1. Set up the equipment and consumables as illustrated in Fig-
ure 1. Attach both stopcocks to the syringe, and attach the
drop tip to the bottom stopcock. Line up the drop tip with the
rectangular opening in the Drop Counter.
2. Start with the valves of the stopcocks turned parallel to the
table top. Add the solutions to the syringe and beaker.
3. Write down the initial volumes of both solutions (in the
syringe and in the beaker), and the molarity of the titrant (in
the syringe).
4. Connect the Drop Counter and pH sensor to your PASPORT
compatible PASCO interface (or interfaces).
5. If you are using a computer, connect the interface to it and
start the data acquisition software.
6. Start the stir plate.
7. Click or press the start button to begin recording data.
8. Open the top stopcock. Slowly adjust the bottom stopcock to
start delivering titrant at about 2 drops per second.
9. Observe the data appearing on the pH versus drop count
graph (Figure 2). After the equivalence point is reached, wait
until the pH curve flattens.
Figure 2: Graph of pH versus drop count
10. Close the stopcocks.
11. Stop data recording.
12. Read the final volume of fluid in the syringe and calculate
the net volume of titrant that was dispensed.
13. Read the final drop count on the graph.
14. In the calculator window of the software or datalogger, enter
a calculation as shown below, but using your own values of
total volume dispensed and final drop count. The calculation
gives the volume of titrant dispensed over time based on the
number of drops and the average volume per drop.
volume = [Drop Count (drops)] * 100/3050
In this example, “100” is the total volume dispensed (in mL)
and “3050” is the final drop count.
15. In the graph, change the horizontal axis to the calculated
“volume” (Figure 3).
150 mL
beaker with
100 mL of
0.005 M HCl
Stir Plate
pH
Probe
Drop
Counter
Figure 1: Titration set-up
Micro
Stir Bar
60mLsyringe
with 50 mL of
0.1 M NaOH
Stopcock
Stopcock
Drop
Counter
Drop Tip
Three-finger
Clamp
Multi Clamp
equivalence point
final drop count

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Drop Counter PS-2117
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Figure 3: Graph of pH versus volume
Tips
• Except for opening and closing the stopcocks, do not touch
the syringe during the titration; otherwise, the drop size may
change significantly.
• The drop rate must remain approximately constant (about 2
drops per second) in order for the drop size to remain con-
stant.
• Drop size depends on the exact position of the bottom stop-
cock. Therefore, the average drop size will be different for
every titration. For each titration, re-enter the volume used
and drop count values in the calculation.
Other Titrations
Titrations with different solutions can be performed using the
same equipment and procedure. Other probes (such as conductiv-
ity or ORP) can be used in place of the pH probe.
Theory of Operation
The Drop Counter uses an
infrared light source and a
photodetector. Lenses
spread the light into a
“sheet” and refocus it
onto the photodetector.
When a drop of fluid
passes through the Drop
Counter, it partially
blocks this sheet of light, and the photodetector registers a
momentary decrease in light intensity.
The Drop Counter uses infrared light and ignores visible light.
On power up, it automatically adjusts the light level for the best
sensitivity. Use the Drop Counter away from direct sunlight or
other sources of infrared that may interfere with it.
When the Drop Counter detects a falling drop, the green indicator
light emitting diode (LED) flashes. If something stationary is
blocking the photodetector, the indicator LED remains on.
Troubleshooting
Specifications
Technical Support
For assistance with any PASCO product, contact PASCO at:
For more information about the Drop Counter and the latest revi-
sion of this Instruction Sheet, visit the PASCO web site and enter
PS-2117 in the Search window.
Limited Warranty For a description of the product warranty, see the
PASCO catalog. Copyright The PASCO scientific 012-08470D Drop
Counter Instruction Sheet is copyrighted with all rights reserved. Permis-
sion is granted to non-profit educational institutions for reproduction of any
part of this manual, providing the reproductions are used only in their labo-
ratories and classrooms, and are not sold for profit. Reproduction under
Select volume calculation
for horizontal axis
detector
collimating
lens focusing
lens
sheet of light
dropinfrared light
source
Figure 4: Diagram of Drop Counter
Problem Cause Solution
Indicator light flashes
twice for a single drop.
Drop Counter registers
more drops than
actually dispensed.
Fluid is splashing
back into the drop
window.
Adjust the position
of the beaker, Drop
Counter, or syringe
to eliminate splash
back
Indicator LED remains
on constantly. Drop
Counter does not
register drops.
Lenses in drop
window are dirty or
wet.
Clean lenses with
water and dry with a
cotton swab or
tissue.
Maximum drop rate 40 drops per second
Default sample rate 5 samples per second
Maximum sample rate 10 samples per second
Minimum object detection size 0.64 mm diameter
Enclosure Polypropylene, water resistant,
chemically resistant to mild acids
and bases
Detector type Infrared photodetector with
collimating lens
Address: PASCO scientific
10101 Foothills Blvd.
Roseville, CA 95747-7100
Phone: [phone] (worldwide)
800-772-8700 (U.S.)
Web: www.pasco.com
Email: [email protected]

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Drop Counter PS-2117
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any other circumstances, without the written consent of PASCO scientific,
is prohibited. Trademarks PASCO, PASCO scientific, PASCO Cap-
stone, PASPORT, and Xplorer GLX are trademarks or registered trade-
marks of PASCO scientific, in the United States and/or in other countries.
All other brands, products, or service names are or may be trademarks or
service marks of, and are used to identify, products or services of, their
respective owners. For more information visit www.pasco.com/legal.
Product End of Life Disposal Instructions:
This electronic product is subject to disposal and recycling regu-
lations that vary by country and region. It is your responsibility to
recycle your electronic equipment per your local environmental
laws and regulations to ensure that it will be recycled in a manner
that protects human health and the environment. To find out
where you can drop off your waste equipment for recycling,
please contact your local waste recycle/disposal service, or the
place where you purchased the product.
The European Union WEEE (Waste Electronic
and Electrical Equipment) symbol (to the right)
and on the product or its packaging indicates
that this product must not be disposed of in a
standard waste container.