• My recent DI contribution ( Another silly simple precision 0/20mA to 4/20mA converter ) used the LM337 regulator in a novel circuit arrangement to translate an input 0-20 mA current source into a 4-20 mA two-wire transmitter current loop (a standard two-terminal industrial current source) • The circuit can also be flipped over to perform the same operation using the LM317, which is more widely used, hence easily available, and lower priced • As before, it relies on tapering off an initial 4 mA current to zero in proportion to the input 0-20 mA, and adding the input and the tapered off 4 mA signal to create a 2-wire 4-20 mA output loop • The operation is identical, only with the current directions reversed • Figure 1 An input external boost transistor is used to limit U1 dissipation • Wow the engineering world with your unique design: Design Ideas Submission Guide At 0-mA input, the series combination of Rs and Rz sets the 4 mA “zero” value in the 4-20 mA output loop, set using Pz

Article Summaries:

  • My recent DI contribution ( Another silly simple precision 0/20mA to 4/20mA converter ) used the LM337 regulator in a novel circuit arrangement to translate an input 0-20 mA current source into a 4-20 mA two-wire transmitter current loop (a standard two-terminal industrial current source). The circuit can also be flipped over to perform the same operation using the LM317, which is more widely used, hence easily available, and lower priced. As before, it relies on tapering off an initial 4 mA current to zero in proportion to the input 0-20 mA, and adding the input and the tapered off 4 mA signa

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