04-12-2013, 01:49 PM
It is pretty simple to work out.
At the normal working temperature the heater has a resistance and to double the currant you need a shunt resistor of equal value. So it needs to be the same value as the hot filament.
For conversion from 1.4 volts and 25ma to 1.4 volts and 50ma only only a little bit of maths needs to be done.
Divide the voltage by the currant and you have the value of the resistor you need to add.
1.4 volts divided by 0.025 amps gives 56 ohms.
A 56 ohm resistor will give you the extra 25ma you need for conversion.
At the normal working temperature the heater has a resistance and to double the currant you need a shunt resistor of equal value. So it needs to be the same value as the hot filament.
For conversion from 1.4 volts and 25ma to 1.4 volts and 50ma only only a little bit of maths needs to be done.
Divide the voltage by the currant and you have the value of the resistor you need to add.
1.4 volts divided by 0.025 amps gives 56 ohms.
A 56 ohm resistor will give you the extra 25ma you need for conversion.
