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ADU71 User Manual
7. ADU71 Connection Diagrams
The ADU71 USB to Current Output Interface is a USB bus powered current loop source for driving 4-20mA or
0-20mA input devices. The ADU71 can also be used with external resistors to provide 1-5VDC, 0-5VDC or 0-10VDC
signals for variable frequency drives, valves etc. The ADU71 internally generated 24VDC loop supply eliminates the
need for an external loop power supply.
7a) Connecting to 4-20mA Current Input Devices.
The first connection example shows the correct method to connect a device which has a 4-20mA current loop
input. Figure 1 shows the correct connections. Note that the "+" of the LOOP output is connected to the "+"
of the device under control and, the "-" of the LOOP output is connected to the "-" of the device under control as
shown in Figure 1.
Figure1: ADU71 connection to a 4-20mA current loop input device such as a variable frequency drive ( VFD )
motor controller.
If the application requires two current input devices they can be connected in series as shown in Figure 2.
Figure 2: ADU71 connections to multiple 4-20mA current loop input devices.