Drop / Bubble Counter
8
Clamp the reservoir and position in the gap
between the receiver and emitter so that
the reservoir is touching the emitter’s
moulding.
Adjust the Counter or reservoir vertically so
the moulding ring at the bottom of the
reservoir barrel is level with the lower edge
of the emitter moulding.
Adjust the reservoir laterally so the
reservoir is just touching the moulding of
the large hole in the alignment plate. In this
position bubbles rising should pass through
the light path between the receiver and
emitter.
Note: You may need to make fine lateral
adjustments of the reservoir.
Check the reservoir is vertical and parallel to
the Counter.
Note: Try to keep the experimental apparatus higher than
the water level in the reagent reservoir to prevent backflow
of water into the experimental apparatus.
Pour approximately 10 cm
3
of water into the reservoir.
Test to make sure the bubbles cause the red LED
indicator on the Counter to blink as they rise through
the water
Press the zero reset button on the Counter. Run the
experiment (remember to turn the stopcock to an
open position).
Practical information
The fastest speed that data can be captured is 50 Hz (20 ms). If an intersample time of
less than 20 milliseconds is selected, then the values obtained will either default to the
lowest reading or the set up will be rejected by the logger/software.
A replacement parts pack for the Counter reservoir is available from Data Harvest, which
contains 2 x 3-way stopcocks and 5 plastic tips - use Product No. 3271.
The
Smart Q
Drop / Bubble Counter works by recording interruptions of a beam of
infrared energy. The receiver can be sensitive to high levels of ambient infrared light or
heat. Shield the Counter from bright light e.g. sunlight, which can produce a false OFF
result. Work in an area away from direct light, or rotate through 180˚ so the external light
source is directed towards the emitter.
Any calculations for drops per cm
3
will only be valid for the same dropper with the same
type of solution and flow rate.
If the flow rate is too fast the drops will merge to form a continuous stream. The flow rate
should be set so that each drop passes thorough the Counter before the succeeding drop.
With a titration use a very slow drop rate (e.g. with a maximum speed of 1.5 drops a
second) so the drops can add too and mix thoroughly with the reactant, allowing the
electrode time to respond.
If you use a burette as a reservoir you will need to devise a method of stopping the flow
from the burette without altering the drop rate. If the burette has a replaceable tip, use a
length of plastic tubing to link the tip to the burette. A tube clamp can be used to crimp the
plastic tubing and shut off the flow. A bung inserted into the top of a burette will also
Reagent
reservoir
Drop/Bubble
Counter
Counter must be
at 90º, use the
moulding line to
get a vertical
Alignment
Adapter
Reservoir just
touching the
moulding of the
large hole in
the adapter