How does DCS detect absent signals and signals with a value of zero?
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For 4-20 mA signals sent to a DCS, what is the typical threshold below which it is considered that there is no signal at the field level?
It should be below 3.7mA. . . .
There is some volatility at zero point, so it’s normal for the value to be below 4 Ma sometimes; here it’s 3.8 Ma
It depends on one’s own settings; to eliminate the impact of gauge errors, setting it around 3.5mA is sufficient.
No signal means below 4mA, and a signal of zero means 4mA. When the 4~20mA standard was established, this concern of the original poster was taken into account, which is why the zero point was set at 4mA.