Blue Heat/PCI User’s Manual, Connect Tech Inc.
41 Revision 0.11
Current Source/Voltage Selection
When using the current source in a loop with low resistance, the transistor will run hot. This can
be avoided by increasing the loop resistance. The calculation for Maximum Loop
Resistance(RL ) is:
Where:
● VS = 22V when pins 2 and 3 on jumper blocks J1, J2, J3, J4 J5, J6, J7 or J8 are jumpered
● VS = 11V when pins 1 and 2 on jumper blocks J1, J2, J3, J4 J5, J6, J7 or J8 are jumpered
● S = the number of stations in the loop (TX’s and RX’s)
● 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.
Note:
For most applications, jumpering pins 1 and 2 on the
appropriate jumper block (J1, J2, J3, J4, J5, J6, J7 or J8) will
be satisfactory.
Jumpering pins 2 and 3 on the appropriate jumper block (J1,
J2, J3, J4, J5, J6, J7 or J8) may be required for applications
with multiple/many loads on the Current Loop network.
J1, J2, J3, J4, J5, J6, J7, and J8 are factory set with no
jumpers installed. (Please refer to Figure 7 for the locations of
J1, J2, J3, J4, J5, J6, J7, and J8)
0.020
V S - V
RMax DS
= L