National Instruments Isolated Current Output Module SCC-CO20 - Manual (Page 5)

© National Instruments Corporation 5 SCC-CO20 Isolated Current Output Module User Guide
Note If your load is grounded and you are using the internal supply, connect the load
ground to the current sink terminal at pin 2 on the SCC-CO20. Do not connect the load
ground to the isolated ground terminal because doing so could defeat the module isolation.
Driving Higher-Resistance Loads with the SCC-CO20
In order to calculate the supply voltage your application requires, multiply
the load resistance by the current you need to sink, then add 2.5 V for the
voltage drop across the protection diode and the current-sink MOSFET.
If you need a higher voltage than the 15 V provided by the internal loop
supply, you can either add a second SCC-CO20 module or provide an
external loop supply.
Adding a Second SCC-CO20 Module
You can add another SCC-CO20 loop supply to create a supply of 30 V,
as shown in Figure 3. Do not use more than two SCC-CO20 modules on
a single circuit, because the resulting voltage can cause overheating and
damage the modules and other equipment.