Bruno HÉNON - Automation & Control Engineer Freelance
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HART - Digital signal modulation by frequency modulation (bit is 1 : frequency = 1200 Hz ; bit is 0 : frequency = 2400 Hz) with a level of 10 mA, that is ± 0,5 mA around the analog signal of the measure over the 4-20 mA current loop.
  • When a bit is high (1) the period is long (around 0.8 ms).
  • When a bit is low (0) the period is short (around 0.4 ms).
  • The analog value of the measure is the mean value of the modulated digital signal.
  • The range value of the digital signal is about 1 mA (± 0.5 mA around the analog signal).

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