What Is an Induction Test Pencil?
An induction test pencil is a device that checks voltage. Unlike a tester, it cannot check the voltage value.
Induction test pencils can be used to check the voltage by simply placing them on the charging path to be investigated. Induction Test Pencils are available for low voltage, high voltage, alternating current, and both AC and AC-DC, so it is necessary to distinguish between these types. It is also necessary to know whether the charging circuit is AC or DC.
Induction Test Pencil Usage
Induction test pencils are used to check for no-voltage in the charging path.
In the case of low-voltage electrical work, it is used to verify that there is no voltage at the relevant terminal block immediately before any work is done. In the case of high-voltage, after opening the power supply with a circuit breaker or disconnecting device, the electric inspection is carried out at the lower charging section of the circuit.
Induction test pencils for both AC and DC are required to check for residual charge after the circuit breaker is opened.
Induction Test Pencil Principle
Induction test pencils these days are often equipped with a lamp that glows or emits a sound when a voltage is detected.
These mechanisms use an internal amplifier to amplify the minute electrical signals detected and emit a sound or light through a built-in battery. To detect an electric current, it is necessary to create an electric circuit, which is a closed loop, because electricity must flow. Induction test pencils detect the electricity in the charging section and create an electric circuit using the ground capacitance between the Induction Test Pencil and the detector (human).
Ground capacitance is the capacitor component between an object and the ground. In a DC circuit, once a capacitor is charged, it stops conducting electricity and becomes an insulator. For this reason, when conducting current detection in a DC circuit, voltage detection is no longer possible after a certain period.
In the case of AC circuits, however, the capacitor repeatedly charges and discharges, so it does not become an insulator and can continue to detect voltage.