3. Setup
ADI16-4(USB)
21
Making a connection using the differential input format
This is a method of measuring the voltage of signal source by connecting the 3 wires (2 signal wires-
plus input pin[+] and minus input pin[-], analog ground[AG]) of the module.
How to connect:
(1)
Connect the analog ground to the signal source ground.
(2)
Connect [+] input to signal source plus pin (Point A).
(3)
Connect [-] input to signal source minus pin (Point B).
Minus pin and ground are both connected to a same point for the signal source. In this case, connect
both module’s minus input and analog ground to signal ground. You must connect 3-wires to take an
accurate measurement.
Even when the module ground and the signal source have a potential difference in between, using a 3-
wire connection eliminates its effect from the measurement results. In addition, the 3-wire input offers
better noise immunity than the 2-wire input (single-end input).
Figure 3.7. Connecting an Interface Connector and Connectors That Can Be Used
As shown in Figure 3.7, when several signal sources are measured, the potential differences between the
module’s ground and signal source’s ground may be different, such as 0.1V or 0.2V. 0.1V offset
voltage higher than the voltage of the signal source is added on CH0[+] and 0.2V on CH1[+]. Similarly,
the offset voltage of the potential difference between grounds is added on CH0[-] and CH1[-]
individually. However, with the connecting of 3-wires differential input, the value of voltage to be
converted is the value between point A and point B, the potential difference between grounds can be
canceled, so the measuring without error can be performed.
Although the maximum value of voltage on each input pin is ±20V, you should use the module with the
potential difference of ±2V between grounds.
CH0[+]
CH0[-]
AG
Potential difference between grounds: 0.1V
ADI16-4(USB)
CH1[+]
CH1[-]
AG
Signal source ground(1)
Point A
Point B
Point A
Point B
Signal source ground(2)
Signal source (2)
Signal source (1)
Potential difference between grounds: 0.2V
