Measurement Computing ADAC/5500 Series - Manual (Page 19)

ADAC Series PCI Boards 795 - 14 - ADAC/5500 Series User Manual
4. EXTERNAL CONNECTIONS
WARNING
Always turn the computer power OFF and unplug it before connecting or disconnecting a screw
terminal panel or a cable to the PCI card. Failure to do so could result in electric shock, or
equipment damage.
The ADAC/5500 cards bring out ±15 V and +5 V to the main I/O connector J1, and +5 V to the auxiliary digital I/O
connectors P3 and P5. These power lines are individually fused to protect the ADAC/5500 card. Connecting or
disconnecting cables or screw terminal panels (as well as any user connections to these power lines) may blow a fuse,
or worse, cause damage to the board. If you are getting incorrect data readings on your ADAC/5500 card, check all
fuses to make sure they have not blown. Replacement fuses can be obtained from the factory, or from most electronics
stores (such as Radio Shack in the USA). Fuse values on the ADAC/5500 card are as follows:
Fuse # Power Line Fuse Value Manufacturer’s p/n IOtech p/n
F1 -15 V to J1 1.0A, 63 V LITTLEFUSE # 0433001.NR FU-7-1
F2 +15 V to J1 1.0A, 63 V LITTLEFUSE # 0433001.NR FU-7-1
F3 +5 V to J1 1.0A, 63 V LITTLEFUSE # 0433001.NR FU-7-1
F4 +5 V to P3 3.0A, 63 V BUSSMAN # TR/3216-FF-3A FU-7-3
F5 +5 V to P5 3.0A, 63 V BUSSMAN # TR/3216-FF-3A FU-7-3
4.1 CONNECTING USER WIRING
Incorrect connection of user wiring is one of the most common problems experienced by users of data acquisition
boards. To ensure proper results, you must first determine what type of signal source you are measuring (Ground
Referenced Source or Floating Source), and then choose the appropriate input configuration on your data acquisition
card (Differential, Pseudo-Differential, or Single-Ended).
4.1.1 Signal Types
Floating Sources
A Floating Source is a signal that has no connection to the building's power ground. Examples of Floating Sources are
batteries, battery powered devices, and signals from optically isolated devices. When connecting Floating Sources to a
data acquisition card, the ground reference of the signal must be tied to the analog ground (AGND) in order to establish
a common reference point.
Ground Referenced Sources
A Ground Referenced Source is one that is connected to the same common ground as the host PC, and therefore has the
same ground as the data acquisition cards. An example is equipment that plugs into the same building power source as
the host PC.
Due to differences in a building's power system, the Ground Referenced Source and the data
acquisition board's ground may be at different voltage levels. This difference is referred to as a
Common Mode Voltage. Common Mode Voltage can be eliminated by using either Pseudo-
Differential (PD) or Fully-Differential (DI) input configurations on the data acquisition board.
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