Pilot lamp
Miniature incandescent lamp · 12 V 25 mA · about 48 Ω cold, 480 Ω hot: tungsten resistance rises tenfold as it heats · thermal time constant ≈ 50 ms
Try it on the benchThe lab drops it on an empty bench and opens its datasheet card.
Typical part: 12 V 25 mA pilot lamp
Pins
- Lead 1
- Lead 2
Ratings and limits
| Cold R | ≈ 48 Ω |
|---|---|
| Hot R | ≈ 480 Ω at 12 V |
| Thermal time constant | ≈ 50 ms |
How to use it
A tungsten filament’s resistance rises about tenfold from cold to white hot. That makes it a self-adjusting resistor: the amplitude stabiliser in Hewlett’s Wien-bridge oscillator, and the reason lamps draw a big inrush current at switch-on.