Why Do I See an Incorrect Output on My NI 6624? Hardware: Counter/Timers (TIO)>>Devices>>PCI-6624
Problem: Why do I see an incorrect output on my PCI 6624? Solution: Reasons for an incorrect or no output include:
The NI 6624 counter/timer board has isolated outputs and need to be driven by an external power supply. An external power supply can have any voltage in the range of 5V to 48V. In order to hook up a power supply, wire the positive lead of the power supply to the Vdd terminal and the negative lead to the Vss terminal for the given counter. The output channel for each counter of the board is of sinking type (open drain). Therefore, there must be a load between the Vdd and OUT terminals in order for the signal to be generated. The load must also be chosen so as to keep the current below 100 mA. An inrush current is allowed, but anything above 600 mA may result in a short circuit protection of 250 ms to protect the 6624 and its load. When the NI 6624 is first powered up, the counter outputs will be high for 250 ms. See KnowledgeBase 4LT911D4: What is the Startup State for the Counter Outputs on the NI 6624? for more information. As a final note, you can add bypass capacitor(s) between the Vdd and Vss terminals at the load to reduce the chance of ringing when the output switches on and off, especially when the connecting wires are long. Related Links: Product Manuals: NI 6624 User Manual (December 2006) Attachments:
Report Date: 01/28/2004 Last Updated: 06/03/2008 Document ID: 35RHIHIO |
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