3B SCIENTIFIC PHYSICS 1017333 Mode D'emploi page 6

4. Technical data
Inputs
Connectors: 4-mm safety sockets
Internal resistance
Start input: 2.4 kΩ
Stop input: 5.6 kΩ
Switching edge
for both inputs: Rising edge
Trigger thresholds
Start input: Low 0...0.5 V, High 1...5 V
Stop input: Low 0...1 V, High 2...5 V
Display:
Display: 4-digit LED display
Measuring range: 1...9999 µs
Resolution: 1 µs
Precision: Quartz precision
General data:
Voltage supply: Plug-in power supply 12 V
AC, 500 mA
Dimensions: 100x75x35 mm³ approx
Weight: 400 g approx. incl. plug-in
power supply
5. Operation
Fig. 1 Schematic circuit diagram of inputs
•
Connect the power supply to the microsec-
ond counter.
•
Connect both inputs to normally closed
switches (see Fig. 1).
Measurement starts when the switch for the
Start input opens (disconnecting the input from
ground).
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2
Measurement stops when the switch for the
Stop input opens.
The display is reset to zero as soon as the Stop
and Start inputs are both reconnected to
Ground.
6. Example experiment
Determining the speed of sound in Kundt's
tube
Additionally required:
1 Microphone box (230 V, 50/60 Hz)
or
1 Microphone box (115 V, 50/60 Hz)
1 Kundt's tube E
1 Pulse box K
1 Microphone probe, long
1 Microphone probe, short
2 Adapter cable, BNC/4-mm plugs
•
Place the microphone probes in the Kundt's
tube and set up the apparatus. (see Fig. 2)
•
Connect the long microphone probe to the
Channel A input of the microphone box and
connect the short one to the input for Chan-
nel B.
•
Use a BNC/4-mm adapter cable to connect
the output of Channel A to the Start input of
the microsecond counter (plug red 4-mm
plug into green socket, black 4-mm plug into
black ground socket).
•
Connect the output of Channel B to the Stop
input of the microsecond counter (plug red
4-mm plug into red socket, black 4-mm plug
into black ground socket from the side).
•
Connect the pulse box to the speaker.
•
Set both outputs to trigger mode and set the
gain for both channels to a medium value.
•
Connect the microsecond counter and mi-
crophone box to their power supplies and
plug them into the mains.
•
Trigger a click pulse from the pulse box and
read off from the counter the time it takes for
the sound to propagate from the long micro-
phone probe to the short one.
Use the distance between the two microphones
and the time measured to calculate the speed of
sound in the tube at room temperature.
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