The resistance of the incandescent globes increases as the current through them increases, so under normal conditions (where the device under test does not draw a large current) the globes will not light up.
This graph indicates voltage drop across the globe with respect to current.
Maximum current (at short circuit) can be calculated:
For one 100W bulb
I = P/V = 100W/240V
I = 0.4167A
The unit can be constructed from several batten fixtures.
4* 100W incandescent globes is enough to provide idle current for a very large amplifier.
If a lower current limit is required, simply unscrew a few globes.
Current limiting bulbs installed on test bench.
Example of fault in device under test
(here provided by a short circuit).
Alternatively, this device can be constructed as a rack unit.
Switches are wired such that each bulb can be taken out of circuit in order to provide the correct current limit.
A meter displays output voltage and current.
Bulbs are mounted in lamp-stand fittings.
Please note, this method cannot be employed on some "universal" switch mode power supplies, as the supply may enter a mode designed for a different voltage mains supply (ie; a 240V supply might think it's receiving 110V). I have found this only rarely to be problematic.
For one 100W bulb
I = P/V = 100W/240V
I = 0.4167A
The unit can be constructed from several batten fixtures.
4* 100W incandescent globes is enough to provide idle current for a very large amplifier.
If a lower current limit is required, simply unscrew a few globes.
(here provided by a short circuit).
Switches are wired such that each bulb can be taken out of circuit in order to provide the correct current limit.
A meter displays output voltage and current.
Please note, this method cannot be employed on some "universal" switch mode power supplies, as the supply may enter a mode designed for a different voltage mains supply (ie; a 240V supply might think it's receiving 110V). I have found this only rarely to be problematic.
