4-20 ma is dc or ac?
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The 4-20 mA current loop has been the standard for signal transmission and electronic control in control systems since the 1950's. In a current loop, the current signal is drawn from a dc power supply, flows through the transmitter, into the controller and then back to the power supply in a series circuit.
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Most modern residential circuits are 15 or 20 amps, so we're looking at a max load of either (15A x 120V =) 1800 watts or (20A x 120V =) 2400 watts before the breaker trips.
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Most CPAP, APAP and BiLevel machines today are designed to operate on both AC and DC voltage. In the United States, the AC current from a wall outlet is 110 volts. Overseas, the AC current is usually 220 or 240 volt.
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Amps = Watts / Volts 4160 Watts / 208 Volts = 20 Amps.
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Typically, either 110-volt AC (110V) or 220-volt AC (220V) is used. Most countries use 50Hz (50 Hertz or 50 cycles per second) as their AC frequency. Only a handful use 60Hz. The standard in the United States is 120V and 60Hz AC electricity.
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A common source of DC is a battery. AC is short hand for Alternating Current, meaning the polarity is continually changing from positive to negative. In an AC circuit, it is generally said that current flows from the Active to Neutral.
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It is neither AC nor DC, but it is closer to being DC in waveform. PWM was often used to encode a RF signals with information. PWM in RF has been largely replaced with FM modulation.
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We need to convert AC to DC because of below facts: AC signals can not be stored and DC power or signals can be stored. Thus,to store the electrical energy we need to convert it into DC. ... AC can be transported over long distances because of it's frequency and dc can not be transported as dc has zero frequency.
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It is perhaps worth noting that 12/24V DC is just as deadly as 120/240V AC. There's naught deadly in voltage, it's the wattage that electrocutes you. A static shock is 6kV, as I recall, but the amperage is low enough that it doesn't hurt at all.
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AC is much easier (therefore cheaper) to step up and down in voltage than DC, and can be done more efficiently (typcially, currently) than the much more expensive and complex DC step-up/step-down systems. That is why AC is used for mains power transmission at a national level.
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A 2-ton AC at this SEER rating is approximately 15 amps; 3-tons is 18 amps; 4-tons is 21 amps. Next, calculate the wattage consumed. A typical whole-home air conditioner uses a 240-volt power outlet. Multiply the amps by 240 watts, which equals 4,320 watts.
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Basically, switching power supplies take the incoming ac voltage and turn it into a high-frequency 20- to 500-kHz ac voltage that is then stepped down to a lower voltage using a small transformer. The voltage is then rectified, filtered and regulated.
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AC is self-extinguishing since the current goes to zero 120 times every second. DC does not so the switch has to survive until the arc dies down on its own. So the DC switch has to be hardier and will therefore work with AC. However, the AC switch is not as hardy and should not be used with DC.
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For light bulbs and heating elements, both AC and DC will work as long but the fact is that though all electric devices require direct current, alternating current is what is used to deliver electricity with the help of transformers which convert AC to DC for the use of electric devices.
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For standard 5mm diameter LEDs the maximum current is usually 20mA, so 10mA or 15mA are suitable values for many circuits. The current must be in amps (A) for the calculation, to convert from mA to A divide the current in mA by 1000.
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AC vs DC (We only sell AC Ballasts): Both types of ballasts take the DC power from vehicles and power the HID bulbs for light. The difference in these ballasts is in the type of electricity being outputted to the HID bulb. AC ballasts output AC power, while DC ballasts output DC power.
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40 VA is "Volts times Amps," which is typically close enough to 40 Watts for hobbyist purposes. The reason they say "VA" instead of "W" is that if your voltage lags (or leads) current, you get (VA) times (cosine of the angle between the V and the A), instead of just VA.