Measuring the time constant of an RC circuit using a digital Oscilloscope:
Objective:
The main objective of this lab is to understand the basic characteristics of an RC circuit and
measure the time constant of an RC circuit.
Theory:
Time constant of an RC circuit can be measured in two different ways using a digital oscilloscope.
The charging and the discharging curves of an RC circuit are shown is shown in the following
figure. The time constant theoretically given by τ = RC, is the time taken by the circuit to charge
the capacitor from 0 to 0.632 times of the maximum voltage. This can be derived from the
charging equation of an RC circuit given in equation 1.
In case of discharging, the time constant is the amount of time required to reduce the voltage
across the capacitor from the maximum value to 0.368 of the maximum value. This relation can
be derived from equation 2 by replacing t by τ.
Apparatus:
Resistor close to 500 Ω, capacitor close to 30 μF, digital oscilloscope, circuit board, function
generator, connecting wires and oscilloscope probes.
