3B Scientific Pressure Balance User Manual

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3B SCIENTIFIC®

3B SCIENTIFIC3B SCIENTIFIC

U10355 Pressure balance

Instruction sheet

07/05 MH

PHYSICSPHYSICS

PHYSICS

PHYSICSPHYSICS

1 Tray

2 Carrier plate

3 Large cylinder

4 Stand rod

5 Base plate

6 Rod for weights

7 Air inlet

8 Connecting hose

9 Small cylinder

bl Safety cord

bm Weights

The pressure balance is for experiments that clearly illus-

trate key concepts of force and pressure.

. Safety instructions

• Risk of injury! The plungers and cylinders of the

pressure balance are made of glass. If the glass breaks the shards can cause cuts. Glass components should

be checked to make sure they are in a safe condition

before performing any experiment. The plastic buff-

ers inside the two glass syringes prevent the plungers

colliding heavily with the glass and may not be re-

moved.

• The tray 1 on the large plunger may not be loaded

with more than 500 g and that of the smaller cylinder

can take a maximum of 200 g.

• Risk of flying components! The small plunger 9 is

fastened by a safety cord bl to prevent it flying out

of the cylinder. You should check to see that the safety cord is tightly fastened.

• Appropriate usage: The pressure balance should only

be used for demonstration or student experiments

that are supervised by a teacher.

. Description, technical data

Two precision-made glass syringes [3, 9] of differing volume are attached to an acrylic carrier plate 2 on top

of an anodised aluminium stand rod 4. Each of the plungers has a tray 1 for holding weights bm. The sy-

ringes are linked by a connecting hose 8 so that they

form a closed system. An air inlet 7 allows air to be drawn into the system. A safety cord prevents the small plunger flying out of the cylinder. A rod 6 is included on

the base plate 5 upon which disc weights can be stacked

when not in use.

Volume of syringes: 10 ml and 50 ml Ratio of plunger

diameters: 10:3 (∅ 26.9 mm : 14.7 mm)

Ratio of plunger masses with tray: 10:3 Number of weights: 15

Mass of weights: 40 g each (approx.)

Base plate dimensions: 140 mm x 100 mm

Total weight: 1.2 kg

. Operation

• Preparation: open the air inlet, pull out the large cyl-

inder to about the 20-30 ml mark then close the inlet

again.

• Experiment procedure: first lay a weight onto the small plunger. Next lay weights one by one on top of the large plunger. When the fourth weight is laid on, the plunger starts to descend.

• Thus when the weight ratio is about 1 : 3.5 ± 0.5 weights, the system is in equilibrium. This ratio is

confirmed by placing weights in the ratio of 2 : 7 (if the plungers are very clean and weights precisely cen-

tered, the large plunger may start to descend). Equilibrium is also apparent for a weight ratio of 3 : 10.

• During the course of an experiment, air gradually

seeps out since syringes that were entirely airtight

would not move at all. It may be necessary to let in more air.

. Storage and cleaning

• For the equipment to function perfectly, it is essen-

tial that the plungers and cylinders are free of any

grease or dust. Even fingerprints can affect the functionality adversely. The equipment can be cleaned using methylated spirits (caution: flammable!). If the

safety cord is removed to facilitate cleaning, it can be

replaced by any suitable strong nylon cord (e.g. buttonhole thread).

• The equipment should be stored in a dry, dust-free location.

3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany • www.3bscientific.com • Technical amendments are possible