20mA Current Loop
The 20mA Current Loop module provides optically isolated 20mA passive Current Loop interfaces for four ports. For each port there is an optically isolated receiver, and an optically isolated transmitter.
Note:. Please refer to the Hewlett Packard Optoelectronics Manual/Catalogue for a complete description of HPCL 4100 and HPCL 4200 specifications.
To implement a passive interface, wire the transmitter and the receiver, to an external current source.
Please refer to Figure 22 for a 20mA Current Loop cable wiring configuration between one port of a ACM/Flex16 and another port of an external device.
WARNING
There is a maximum loop resistance for a Current Loop circuit. The calculation for Maximum Loop Resistance(RL ) is:
Max RL = VOC - (S x VD)
Note:
0.020
1.S = the number of stations in the loop (TX’s and RX’s).
2.VD = the voltage drop for the HP opto couplers on the SLIM. VD = 2.3 V for the HPCL 4100 and HPCL 4200. When you use other manufacturers’ equipment in the loop the value of VD may differ.
3.VOC = the open circuit voltage of the current source.