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.

© National Instruments Corporation

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SCC-CO20 Isolated Current Output Module User Guide