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if it is 0 ______ MD Phd it is 2 degrees below zero if it is 0 ______ MD Phd it is 2 degrees below zero
If it were a 0 and not an O it would mean 'three degrees below zero'.
three degrees below 0
3 degrees above 0
The 4-20 ma is used more often in analog signaling than 0-20 ma because sufficient power dissipation. The hence is the upper rage and was reduced to 20 ma.
3 degrees below 0
42° 47′ 0″ N, 71° 5′ 0″ W42.783333, -71.083333
42° 19′ 0″ N, 71° 3′ 0″ W42.316667, -71.05
42° 22′ 0″ N, 72° 31′ 0″ W42.366667, -72.516667
4-20ma is a standard range used in process controls to indicate measured values. For instance, a pressure instrument may output 4ma to indicate 0 psi, up to 20 ma to indicate 100 psi, or full scale. Or, to control a variable-speed motor drive, 4 ma may mean to stop the motor, and 20 ma to run at full speed. The reason that 4ma is chosen instead of zero is for fail safe operation. A broken wire always results in 0 ma. Suppose our signal right now is 12 ma, and this causes a ventilation fan to run at 50% speed. Suddenly the signal drops to 0 ma. Now, if our range was 0-20 ma, does this change mean stop the fan? Or does it mean the signal wire just broke? There would be no way to tell. With a 4 ma low range, we would know that 0 ma was a broken wire. Then instead of stopping the fan, we could set it to some default speed, or simply continue at the previous speed until the wire was repaired.
In the UK it BS 476 and is usually FR 0 or FR 1. This is retardent but not fire proof.