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Sahithyan's S1
Sahithyan's S1 -- Electrical Fundamentals

Lab Apparatus

Multimeter

Measures voltage, current, frequency.

There are 3 variants:

  • Moving coil meter
  • Moving iron meter
  • Moving rectifier meter

Oscilloscope

Aka O’scope. Graphically displays electrical signals and how they vary with time. Used when designing, manufacturing, and repairing electrical equipment. Comes in either 1 or 2 or 4 channels. Each channel is used to connect a probe using BNC connector. Vertical section controls the voltage or current scale for each channel. Horizontal section controls the time scale.

Passive Voltage Probes

Measures voltage difference between ground clip and hook clip. Hook is covered with a retractable cover. The BNC connector includes a capacitor compensation trimmer.

Each channel inside the oscilloscope includes a resistor and capactior. Works for low frequencies. Picks up noises for higher frequencies. To mitigate this, a coax cable is included in the probe.

Most probes include a switch between 1x and 10x, which refers to how much the amplitude of the signal is attenuated (reduced). The 10x setting has an additional resistor and a compensation capacitor.

Calibration

  • Set 10x on the probe
  • Connect it to the oscilloscope
  • Make sure only the appropriate channel is turned on
  • Make sure DC option is selected in Coupling setting
    To see all parts of the signal
  • Select 10x option in Probe setting
  • Make sure Type setting is selected to Edge
  • Make sure Source setting is selected to the appropriate channel
  • Attach ground clip to the ground tab
  • Hook the probe around the signal tab
  • Adjust the vertical and horizontal scale knobs
    To clearly see the waveform. Turning the knobs clockwise decreases the time or voltage scale (like zooming in).
  • Adjust the smaller knob of channel 1 To center the waveform vertically
  • Use the knob in the Trigger section To raise the level somewhere between the min and max of the waveform
  • Adjust the capacitor compensation trimmer
    Until the square wave has straight edges

While visualizing 2 voltages of a circuit, the ground clip is connected to the reference point. Only 1 ground clip of the multiple probes must be connected to prevent short circuits inside the oscilloscope.

Current Probe

Operation is similar to current transformer. Steps down the current, converts to a voltage signal, and renders it in the oscilloscope. Has a sensor head, which can be opened by the opening lever. Powered through power supply cable.

Calibration

  • Connect the BNC connector to a channel
  • Connect power supply cable into a power supply port in the rear side of the oscilloscope
  • Connect the sensor head to the circuit
  • Turn on the channel

Variac

A variable AC power supply. Input is connected to AC power supply.

Rheostat

A variable resistor. Used to control the current in a circuit.