A Cathode Ray Oscilloscope (CRO) is a versatile electronic instrument used for visualizing and analyzing electrical signals. It can measure various signal characteristics, including voltage and time period. Here’s a detailed explanation of how these measurements can be made using a CRO:
### (I) Voltage Measurement
**1. Understanding Voltage Measurement:**
Voltage measurement on a CRO involves determining the amplitude of the signal displayed on the screen. The amplitude is the maximum value of the voltage wave.
**2. Procedure:**
- **Connect the Probe:**
Attach the CRO probe to the circuit or component where you want to measure the voltage. The probe is connected to the oscilloscope’s input channel (usually marked as CH1 or CH2).
- **Set the Vertical Scale:**
Adjust the vertical scale (volts/div) on the CRO. This setting determines how many volts each division on the screen represents. For example, if the vertical scale is set to 1 V/div, each vertical division on the screen corresponds to 1 volt.
- **Position the Trace:**
Adjust the vertical position control to center the waveform on the screen if needed. This ensures that you can easily measure the amplitude of the signal.
- **Measure the Peak-to-Peak Voltage:**
Identify the peak-to-peak voltage (the difference between the maximum and minimum values of the waveform). Count the number of vertical divisions between these points and multiply this by the vertical scale setting. For example, if the peak-to-peak voltage spans 4 divisions and the scale is set to 2 V/div, the peak-to-peak voltage is 4 divisions × 2 V/div = 8 volts.
- **Alternative: Measure RMS Voltage:**
Some oscilloscopes have built-in functions to measure RMS (Root Mean Square) voltage directly, which is particularly useful for AC signals. To use this feature, activate the RMS measurement mode from the oscilloscope’s menu.
### (II) Time Period Measurement
**1. Understanding Time Period Measurement:**
The time period measurement involves determining the duration of one complete cycle of the waveform. The time period (T) is the reciprocal of the frequency (f), given by T = 1/f.
**2. Procedure:**
- **Connect the Probe:**
As with voltage measurement, connect the oscilloscope probe to the point in the circuit where you want to measure the time period.
- **Set the Horizontal Scale:**
Adjust the horizontal scale (time/div) on the CRO. This setting determines how much time each division on the screen represents. For instance, if the time scale is set to 1 ms/div, each horizontal division represents 1 millisecond.
- **Position the Trace:**
Use the horizontal position control to center one complete cycle of the waveform on the screen. This will help you accurately measure the time period.
- **Measure the Time Period:**
Count the number of horizontal divisions that span one complete cycle of the waveform. Multiply this number by the time scale setting. For example, if one cycle spans 5 divisions and the time scale is 2 ms/div, the time period is 5 divisions × 2 ms/div = 10 milliseconds.
- **Alternative: Use the Time Measurement Feature:**
Many modern oscilloscopes offer automated time period measurements. Activate this function through the oscilloscope’s measurement menu to display the time period directly.
### Summary
In summary, a CRO measures voltage by analyzing the amplitude of the waveform on the vertical axis and measures the time period by analyzing the waveform’s duration on the horizontal axis. By properly setting the vertical and horizontal scales and utilizing the CRO’s measurement features, accurate readings of both voltage and time period can be obtained.