Drop Counter (High Accuracy)
(PS-2117)
Stainless steel rod
Drop detection opening
1/2 inch electrode
holder
1/4 inch probe
holder
Screw
The PASPORT Drop Counter measures fluid volume and counts drops as liquid is passed through the
opening. To accurately measure volume, carefully set the drop size before conducting experiments. While
the drop counter will work with burets and pipets, it comes with a plastic syringe with two valves at the base
of the syringe. One controls drop size and the other controls rate of flow.
The Drop Counter does not operate in Manual Sampling mode. In order for the Drop Counter to function
properly, all manual sampling settings must be cleared by unchecking any boxes in the Sampling Options
Window.
Specifications
Measurements
Range
Default Sample Rate
Maximum Sample Rate
Object Detection Size
Fluid Volume, Drops
0 to 40 drops per second
5 samples per second
10 samples per second
0.64mm diameter (liquid drop or
fine particle)
Equipment Setup
Use a right angle clamp to horizontally mount the drop counter to a rod stand.
Use a three-fingered clamp to mount an empty buret or the syringe that accompanies the PASPORT Drop
Counter above the drop detection opening of the Drop Counter.
1. Connect the Drop Counter to a PASPORT Interface.
2. Place a beaker beneath the Drop Counter, under the drop detection opening.
3. If desired, an electrode can be mounted in the 1/4-inch or 1/2-inch electrode openings using the
mounting screws.
Calibration
Calibrating the drop counter entails ensuring that the instrument is measuring the volume properly. To do
this, either a glass buret or the plastic syringe and valves that come with the Drop Counter may be used. For
a glass buret, the volumetric comparison is used. For the plastic syringe, we recommend using a
gravimetric comparison, if the density of the liquid is known or near that of water (1g/ml).
Glass Buret Calibration
Open the Setup window in DataStudio and select the Drop Counter from the sensor list. Make sure no
manual sampling options are selected.
1. Click the Calibrate Sensors tab. The DataStudio Calibration Window will open. Select Drop Counter
from the drop-down list.
2. DataStudio will measure drops per milliliter and the total volume dropped through the Drop Counter.
3. Allow about 10 mL of fluid to drop through the counter at about 3-4 drops per second and measure the
actual volume of the liquid released.
4. Compare this with the reading showing in the calibration window.
5. Click Read from Sensor. This will automatically transfer the reading from the Present Sensor
Measurement to the Sensor Value (drops) box for Calibration Point 2.
6. Change the value in the Standard Value (ml) box to match the known value of the volume released.
Click OK.
Note: Glass burets will not deliver the same rate or drop size for the total volume of the buret. If the drop
rate slows, take a volume reading and refill the buret before resuming operation.
Plastic Syringe Calibration
Open the Setup window in DataStudio and select the DropCounter from the sensor list. Make sure no
manual sampling options are selected.
1. Click the Calibrate Sensors tab. The DataStudio Calibration Window will open. Delect Drop Counter
from the drop-down list.
2. Measure the mass of an empty, light cup. Record the mass to 0.01 precision.
3. Place the cup below the drop counter. Release about 10 mL of liquid into the cup.
4. Click Read from Sensor to transfer the drop count to the Sensor Value (drops) box.
5. Measure the mass of the cup + liquid.
6. Determine the mass of the liquid and convert to milliliters, using the density of water (1 g/mL), or the
density of the liquid being measured, if it differs from water.
7. Enter this amount into the Standard Value (ml) box and click OK.
Drop Count Rate and Drop Size Calibration
In order to avoid the risk of inaccurate volume measurements, do not allow the drop rate to fall below 1 drop
per second. If this occurs, stop and add more liquid to the buret.
For best results, the syringe included with the Drop Counter is recommended.
Use the top valve to control the flow rate. Use the bottom valve to start and stop the flow of liquid.
Set up the Drop Counter Syringe or a buret as before.
1. Open the Setup Window in DataStudio and select Count. Create a digits display to display Drops. To
verify a consistent drops/ml rate, create a Graph display of Drops versus Fluid Volume (ml).
2. Fill the syringe or buret with the liquid to be measured.
3. Place a beaker below the drop detection opening.
4. Open the top valve of the syringe or buret. Slowly open the bottom valve, to allow a small amount of the
fluid through the tip of the syringe.
5. Close both valves by turning them to the horizontal position.
6. Open the bottom valve completely.
7. Slowly turn the top valve until drops begin to fall from the tip of the syringe. Once you have adjusted the
top valve to the appropriate drop size and rate, close the bottom valve once more.
8. Remove the beaker and place a graduated cylinder below the drop detection opening.
9. Open the Calibration dialog by clicking the Calibrate Sensors tab in the Setup menu.
10. Open the bottom valve and allow 10 mL of solution to fall into the graduated cylinder. Close the valve
and read the amount in the cylinder. Enter this value into the calibration menu, click OK.
Typical Applications
Titrations