Power Supply Isolation

Tech Note

MAQ20 data acquisition and control system Low voltage DC to DC converters, in many cases, need electrical isolation from input to output. Low voltage is defined as Safety Extra Low Voltage (SELV) and Functional Extra Low Voltage (FELV). These refer to DC voltages below 60VDC, and are deemed be safe for human contact.

In modern systems, the supply load is often delicate, low voltage devices such as microprocessors and associated storage and signal conditioning circuits. These can be expensive and need protection from power main spikes. Isolation prevents ground loops that occur when different circuits share the same ground. Current may then circulate in the ground of an interconnected circuit. Since wires are never perfect short circuits at DC and certainly not at high frequency AC, unwanted voltages are excited in each circuit. Such a circulating current may cause galvanic corrosion of wiring eventually causing failure of one or multiple circuits. Thus power supplies in consumer, industrial, military, and communications systems almost always have isolated supplies. Power main voltages are usually reduced and rectified to DC voltages less than 60VDC. Then isolated DC to DC converters make the final low voltage DC such as 1.8, 3.3, 5.0, etc. for multiple functional circuits.

Dataforth's MAQ®20 and I/O modules all feature power supply Isolation.

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