Voltage divider
From HvWiki
In electronics, the voltage divider is a circuit used to create a voltage (Vout) which is proportional to another voltage (Vin).
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Use for measuring direct current and low frequency voltages
In the high voltage arena, this can be used to measure high voltages using a standard voltmeter. This is typically accomplished by creating a voltage divider with a ratio for R1/R2 of 999/1, thus converting an input voltage in the kilovolts range into an output voltage in volts.
When selecting resistance values for such a voltage divider, it is important to select resistances in the high-megaohm range to avoid excessive current flowing through the circuit to ground.
Remember that the input resistance of the voltmeter is in parallel with R2. For an oscilloscope the value is typically 1 MΩ and for digital multimeters 10 MΩ, the exact resistance for a given instrument must be known before the measurements can be trusted. In some cases R2 can be dropped and the instrument's own resistance takes place of R2.
Use for measuring high frequency voltages
Example
With the above circuit diagram, with:
- Vin=100 kv
- R1=999 megaOhms
- R2=1 megaOhm
would result in Vout of 100 volts, which can be measured with a standard voltmeter.
With an input of 100kV and total resistance of 1 gigaohm, current through the voltage divider would be 0.1 mA.
