# Building a Mass Balance to Measure Small Weights Using a Rotary Potentiometer

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Building a Mass Balance to Measure Small Weights Using a Rotary Potentiometer

Introduction:

Nowadays, we have mass balances, weighing scales etc to measure masses

but we hardly have devices that measure small masses. Sometimes, we

may have to measure objects with small masses say 10g to 100g and my

model is created backed up with this idea.

Components Used: Digital multi-meter, Meter rule, Retort Stand, Clamp,

Rotary potentiometer, Power supply (5V), Spring, Masses (in unit of

10g), 2k and 3k resistors, 1k variable resistor, amplifier.

Reason For Choice Of Components:

· Rotary Potentiometer: I used a rotary potentiometer so that when

masses are placed on the meter rule the change in voltage (output)

could be noted. The rotary potentiometer is of 5k Ohms but I connected

it to a 5V power supply as a more convenient way of measure. As the

potentiometer moves the resistance changes and also does the voltage.

· 2k, 3k Fixed Resistor and 1k Variable Resistor: I used these

resistors in order to make a Wheatstone Bridge so that there will be a

significant change in output when masses are added to the meter rule.

· Amplifier: I am using the amplifier in order to make my model more

sensitive and obtain a more accurate result.

· Spring: Without the spring, when masses a put on the meter rule, the

masses will pull the rule till the masses came to rest on a flat

surface. Therefore I am using a spring to stop this from happening

i.e. when masses are added the meter rule does not topple over and

reading could be efficiently and accurately taken.

Resources Used: I read up about the use of rotary potentiometer from

the AS Physics text book and also research about the significance of

the Wheatstone Bridge coupled with help from my Physics teacher.

[IMAGE]

SETUP DIAGRAM

[IMAGE]CIRCUIT DIAGRAM

PROCEDURE:

I connected one end of the rotary potentiometer to a 0V terminal of a

power supply and the other end to a 5V power supply.