Measurement of Voltage Current and Frequency by Oscilloscope

Normally, an oscilloscope is an important tool in an electrical field which is used to display the graph of an electrical signal as it varies with respect to time. But some of the scopes have additional features apart from their fundamental use. Many oscilloscopes have the measurement tool that help us to measure waveform characteristics like frequency, voltage, amplitude, and many more features with accuracy. Generally, a scope can measure time-based as well as voltage-based characteristics.

Voltage Measurement

The oscilloscope is mainly voltage oriented device or we can say that it is a voltage measuring device. Voltage, current and resistance all are internally related to each other.

Just measure the voltage, rest of the values is obtained by calculation. Voltage is the electric potential difference between two points in a circuit. It is measured from peak-to-peak, showing the difference between the maximum and minimum points. The oscilloscope displays these maximum and minimum voltages and calculates their average. You should specify which voltage you are referring to. Typically, an oscilloscope has a fixed input range, but this can be increased using a potential divider circuit.

Method to Measure Voltage

1. The simplest way to measure signal is to set the trigger button to auto that means oscilloscope start to measure the voltage signal by identifying the zero voltage point or peak voltage by itself. As any of these two points identified the oscilloscope triggers and measure the range of the voltage signal.
2. Vertical and horizontal controls are adjusted so that the displayed image of the sine wave is clear and stable. Now take measurements along the center vertical line which has the smallest divisions. Reading of the voltage signal will be given by vertical control.

Current Measurement

An oscilloscope cannot measure electrical current directly. Instead, it measures current indirectly by using probes or resistors. The resistor measures voltage across two points, and Ohm’s Law is used to calculate the current. Alternatively, a clamp-on current probe can be used with the oscilloscope.

Method to Measure Current

1. Attach a probe with the resistor to an electrical circuit. Make sure that resistor’s power rating should be equal or greater than the power output of the system.
2. Now take the value of resistance and plug into Ohm’s Law to calculate the current.

According to Ohm’s Law,

Frequency Measurement

Frequency is measured on an oscilloscope by analyzing the signal’s frequency spectrum on the screen and making a simple calculation. Frequency is defined as the number of cycles a wave completes in one second. The oscilloscope can measure frequencies in the hundreds of MHz range. It checks signal performance by measuring the wave’s rise and fall times.

Method to Measure Frequency

1. Increase the vertical sensitivity to get the clear picture of the wave on the screen without chopping any of its amplitude off.
2. Now adjust the sweep rate in such a way that screen displays a more than one but less than two complete cycles of the wave.
3. Now count the number of divisions of one complete cycle on the graticule from start to end.
4. Now take horizontal sweep rate and multiply it with the number of units that you counted for a cycle. It will give you the period of the wave. The period is the number of seconds each repeating waveform takes. With the help of period, you can simply calculate the frequency in cycles per second (Hertz).