Connect Tech NT960/PCI - Manual (Page 76)

4-24 Chapter 4: Appendix E - 20mA Current Loop Option
Intellicon-NT960/PCI User's Manual, ver. 0.02
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(R
L
) is:
Note:
1. S = the number of stations in the loop (TX’s and RX’s).
2. V
D
= the voltage drop for the HP opto couplers on the SLIM.
V
D
= 2.3 V for the HPCL 4100 and HPCL 4200. When you
use other manufacturers’ equipment in the loop the value of
V
D
may differ.
3. V
OC
= the open circuit voltage of the current source.
Max R
L
= V
OC
- (S x V
D
)
0.020