Each C5B 42 two-wire transmitter interface module provides a single channel of analog input which accepts 4 to 40mA process current input and provides a standard +1 to +5V or +2 to +10V output signal. An isolated +20VDC regulated power supply is provided to power the current transmitter. This allows a two-wire loop powered transmitter to be directly connected to the C5B 42 without requiring an external power supply. The regulated supply will provide a nominal +20VDC at a loop current of 4mA to 20mA.
The C5B 42 modules will provide a 1500V isolation barrier for non-isolated two-wire field transmitters. They can also be used when additional isolation is required between an isolated two-wire transmitter and the input stage of the control room computer.
The voltage output is logic-switch controlled, which allows these modules to share a common analog bus without the requirement of external multiplexers.
The C5B 42 modules are designed with a completely isolated computer-side circuit which can be floated to ±50V from Power Common (pin 16). This complete isolation means that no connection is required between I/O Common and Power Common for proper operation of the output switch. If desired, the output switch can be turned on continuously by simply connecting pin 22, the Read-Enable pin, to I/O Common (pin 19).
A precision 20-ohm current conversion resistor is supplied with the modules. Sockets are provided on the C5BP panels to allow installation of this resistor and extra resistors are available. All field inputs are fully protected from accidental connection of power-line voltages up to 240VAC. The modules have a 3dB bandwidth of 100Hz. Signal filtering is accomplished with a six-pole filter, with two poles on the field side of the isolation barrier, and the other four on the computer side.