Does a flameproof level switch require an external power supply?
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It seems to be from E+H; it says “Made in China” and “Exd II CT6”. I remember that devices with explosion protection requirements need an external power supply, right?
It mainly depends on your on-site needs
Is the level switch of E+H a fork-type switch? There are several wiring methods for the fork switch of E+H, and currently two main types are in use. The first is the two-wire system, which requires an electronic module; power is supplied from the control room. The second is the four-wire system, which is easy to understand – two wires are used for power supply and two wires for signals. In any case, power supply is necessary in both cases, only the method differs.
Reply to 3#: OHA is a level switch used to measure the level of oil in the sealing system. But can an explosion-proof version function without external power supply? As far as I remember, explosion-proof level switches all require an external power supply, that is, they operate on a 4-wire system. ? ? ? ? ? ? ?
Flameproofing has nothing to do with power supply. Thermocouples/resistors also have explosion protection ratings!
Whether explosion protection is required and whether external power supply is needed are completely separate matters.
All mechanical switches do not require a power source on their own, while intelligent ones need a power source to function. Typically, switches provide dry-contact outputs; the output signals are sent to the DCS, which can be powered with 24V internally. Of course, there are also those that use 220V to power the contactors. Relays, etc. When the switch operates, arc discharge occurs, so explosion protection is certainly necessary.
Reply to 7# mingyao1987: Level switches can also be made intrinsically safe
The last edit to this post was made by mingyao1987 on 2010-11-26 at 12:09. Yes, some smart switches can generate their own output signals; for example, some photoelectric switches produce an output signal of just over 2 mA. Such signals must be converted into digital outputs using an isolation barrier