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Water Resistance
Go Direct Drop Counter is not water resistant and should never be immersed in
water.
If water gets into the device, immediately power the unit down (press and hold
the power button for more than three seconds). Disconnect the sensor and
charging cable, and remove the battery. Allow the device to dry thoroughly
before attempting to use the device again. Do not attempt to dry using an
external heat source.
How the Sensor Works
The sensor has an infrared LED emitter on one end of the area through which
the drop falls (1.3 × 3.7 cm) and a detector on the other end. When the infrared
beam (centered at 890 nm) between the source and detector is blocked by a drop
of titrant, a digital signal is sent to the data-collection software. The drops are
then converted to volume units (e.g., milliliters) in the data-collection program.
A red LED indicator light flashes each time a drop of liquid passes through the
Drop Counter.
Use Go Direct Drop Counter with other Vernier sensors such as our
Ion-Selective Electrodes, Conductivity Probe, or other Vernier pH Sensors. The
Vernier Drop Counter can accommodate many third-party electrodes when used
in conjunction with the Electrode Amplifier.
Troubleshooting
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Set a slow drop rate. For the best, most accurate data, we recommend setting
the rate at 2 seconds/drop or slower. A slow rate provides enough time for
each drop of titrant to be thoroughly mixed in the solution and the pH
sensor (or other sensor) to respond.
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Minimize the volume of solution to be titrated. We recommend 5–10 mL of
test solution. Larger volumes will take longer to mix and may require a very
slow drop rate for best results.
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Use the Vernier Microstirrer. It helps deliver solution directly to the pH
bulb, minimizing the response time. Also, you can run a magnetic stirrer at a
very high speed and the Microstirrer will not form a visible vortex, which
prevents splashing.
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Add only as much distilled water to the titrated solution as is necessary to
cover the bulb of the pH Sensor (or other sensor).
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Use the plastic reagent reservoir that is supplied with the Drop Counter. The
reagent reservoir provides a wider diameter and less change in the
hydrostatic pressure per unit volume of titrant above the 2-way valve.
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Use the pair of 2-way valves; one for drop rate adjustment and the other as
an on-off valve. This eliminates the need to do a fine adjust during the
initial readings and also allows for a consistent rate to be set.
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Manually release drops at a slower rate to allow for more thorough mixing
when near the equivalence point.
For additional troubleshooting and FAQs, see
When you are satisfied that the titration has proceeded past the equivalence
point, shut off the lower 2-way valve of the reagent reservoir and stop the
data collection.
Videos
View videos related to this product at
Calibrating the Sensor
There are three different ways to handle the reporting of volume:
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Use the stored calibration.
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Manually enter a drops/mL ratio value. If you have done a previous
calibration with a particular apparatus, you can enter the drops/mL ratio.
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Perform an Automatic drops/mL calibration. You can calibrate the reagent
reservoir or a buret. To perform your own drops-per-mL calibration, follow
these steps:
1. Place a 10 mL graduated cylinder below the slot of the Drop Counter.
2. Fill the reagent reservoir about 3/4 full with the titrant solution.
3. Choose to calibrate the Drop Counter in your data-collection program.
4. Open the bottom 2-way (on-off) valve to begin releasing drops through the
Drop Counter.
5. Release drops until there is 9–10 mL of liquid in the graduated cylinder.
6. Close the bottom valve to stop the drops.
7. Type the exact volume, to the nearest 0.1 mL, of liquid in the graduated
cylinder in the Volume (mL) box of the Calibrate drops dialog box.
8. Choose to stop the calibration routine of your program.
9. The number of drops/mL will be displayed.
10. You can now continue with the titration.
Care and Maintenance
Battery Information
Go Direct Drop Counter contains a small lithium-ion battery. The system is
designed to consume very little power and not put heavy demands on the
battery. Although the battery is warranted for one year, the expected batter life
should be several years. Replacement batteries are available from Vernier (order
code: GDX-BAT-300).
Storage and Maintenance
To store Go Direct Drop Counter for extended periods of time, put the device in
sleep mode by holding the button down for at least three seconds. The red LED
will stop flashing to show that the unit is in sleep mode. Over several months,
the battery will discharge but will not be damaged. After such storage, charge
the device for a few hours, and the unit will be ready to go.
Exposing the battery to temperatures over 35°C (95°F) will reduce its lifespan. If
possible, store the device in an area that is not exposed to temperature extremes.
