Do you have a digital multimeter?
If not this is the right time to buy one.
If you are low on money any $15 digital multimeter will do
If you can afford to spend a little bit more money I recommend a digital multimeter that can measure
- voltage
- current (from Microampere up to 10 A)
- resistance
- diode-forward-voltage
- frequency (which not all digital multimeters can measure)
- duty-cycle (which not all digital multimeters can measure)
- capacity (which not all digital multimeters can measure)
- transistor amplifying factor "beta"
Something like this
