DC POWER & NOISE
Many of the Kemo products are available with DC power input for portable applications. Typically 9 - 30 V DC power input, where 12 V or 24 V DC is available from batteries or a vehicle supply.
Most DC powered units use DC - DC converters, these are switching devices and they generate high frequency switching energy. Depending on the devices used and their type the level of this energy varies, but in low quality units it can be several volts on a typical unsmoothed 15 volt supply. The energy is typically a high speed switching pulse of several MHz frequency content which repeats at about 100 kHz. This energy will get into most signal circuits as some of the content is radiated.
We use a number of techniques to minimise this noise. Good quality DC-DC converters from a reputable and stable manufacturer. Then we use the best practice possible in our circuit board layouts, wiring, and power filtering around the DC-DC converters. Typically we attenuate any DC-DC power noise by a factor of over 50. However some of this energy still gets into the signal paths, and is seen as high frequency 'noise'. So if you require a portable system, there may be a higher noise level than with a 'mains' powered unit. Our experience is that in low frequency (<20kHz) systems with signal levels above about 100mV DC-DC related issues are not a problem.