Measurement Computing DBK Part 2 - Manual (Page 197)

Vehicle Testing and Noise Reduction
Power Connections and Analog Common
To properly measure vehicle-attached thermocouples differentially, it is necessary to have an analog common
connection to the negative side of the vehicle’s electrical system. A jack labeled ACOM, located on the DBK101
front panel, provides a connection point for analog common. If analog common is not connected, true differential
readings cannot be obtained due to noise. For this reason, the chassis of the primary data acquisition device, e.g.,
DaqBook/2000 Series device, must also have a good connection to the negative side of the vehicle’s electrical
system.
All grounds should come together at the negative terminal of the test vehicle’s battery. Connecting the grounds at
any other point may introduce noise. One line, with a banana plug is used to connect the battery’s negative terminal
to the DBK101 ACOM jack. The ACOM jack connects internally to the DBK101 P1, pin # 28 (AGND).
Connections for a Vehicle Test
Note 1: The ACOM connector is a banana jack. A stripped wire can be secured by:
(1) unscrewing the banana jack housing, (2) inserting the wire sideways through the
hole, and then (3) tightening the housing.
Note 2: It is best to use a male DIN5 connector to connect the lines from the battery to the
DaqBook/2005 Series female DIN5 connector. A Switchcraft® male DIN5 Connector
(p/n 12BL5M) can be used for making your own cable.
DBK Option Cards and Module 907994 DBK100 Series pg. 9