When regulating flatfield mask lighting for astronomical CCD cameras, fluctuation-free and extremely short exposure times in the (sub) millisecond range are required. Unfortunately, conventional dimmers cannot be considered for this, but only a so-called PWM with an on and off frequency of 25 kHz or even faster!
In theory, it would be enough to reduce the voltage with an ohmic resistor if we wanted to dim incandescent lamps instead of LEDs. However, we absolutely need a dimmer with pulse width modulation, which regulates the time interval in which the full voltage acts: the regulating instrument is switched on and off in quick succession.
Depending on the switch-off / switch-on frequency, various accessories can be operated: for a heating jacket, switching on and off once per second would be enough, or even less, because its inertia is very large. In everyday life for such dimmed LED lamps (e.g. living room lighting), about a hundred cycles per second are sufficient because the human eye hardly notices the fluctuation from 25Hz. For flatfield masks, which were built for astronomical CCD cameras, at least 25kHz are required in order to be able to guarantee evenly illuminated surfaces even in a short lighting time.
- Input: RCA and 5.5 / 2.1mm (note polarity: middle positive)
- Output: RCA and 5.5 / 2.1mm (note polarity: middle positive)
- Frequency: over 30 kHz, typically 31-36 kHz (guaranteed to switch on and off more than 30,000 times per second)