Measurement Computing USB-1608GX-2AO - Manual (Page 13)

USB-1608GX-2AO User's Guide Functional Details
13
Internal pull-up/down configuration
Unconnected inputs are pulled low by default to 0 V through 47 kΩ resistors via jumper W1 on the circuit
board. The pull-up/pull-down voltage is common to all 47 kΩ resistors. Complete the following steps to
configure these inputs to pull high (+5V).
Caution! The discharge of static electricity can damage some electronic components. Before removing the
device from its housing, ground yourself using a wrist strap or touch the computer chassis or other
grounded object to eliminate any stored static charge.
1. Turn the device over and rest the top of the housing on a flat, stable surface.
2. Peel off the four rubber feet on the bottom of the device to access the screws.
3. Remove the four screws from the bottom of the device.
4. Hold both the top and bottom sections together, turn the device over and rest it on the surface, then
carefully remove the top section of the case to expose the circuit board.
5. Configure jumper W1 for either pull-up or pull-down. The jumper is configured by default for pull-down.
Figure 8 shows the location of the jumper on the board.
Figure 8. W1 jumper location
Figure 9 shows the jumper configured for pull-up and pull-down.
Figure 9. W1 jumper configurations
6. Replace the top section of the case, and fasten it to the bottom section with the four screws. Replace the
rubber feet onto each screw.
For more information about digital signal connections
For general information about digital signal connections and digital I/O techniques, refer to the Guide to Signal
Connections (available on our web site at
www.mccdaq.com/signals/signals.pdf ).
Trigger input
The TRIG terminal is an external digital trigger input. The trigger mode is software selectable for edge or level
sensitive.
 Edge sensitive mode is configurable for rising or falling edge.
 Level sensitive mode is configurable for high or low level.
The default setting at power up is edge sensitive, rising edge.
Retrigger mode
Retrigger mode lets you set up repetitive analog input or output trigger events. The trigger is automatically re-
armed after it is activated. Use software to set the A/D or D/A trigger count (the number of samples you want
per trigger).