NI 9403 Over Current Protection Hardware: CompactRIO>>Digital Input Modules>>cRIO-9403
Problem: When I tie several of my NI 9403 DO lines to ground, the module no longer functions. If I remove the shorts the module will then function as expected. Why does this behavior occur? Solution: This behavior is due the over current protection on the NI 9403 module. Each channel also has a pull-down resistor and includes overvoltage and over current protection. The over current protection allows only a specified amount of current through the output channels. If the channels go into an overcurrent state, the NI 9403 tri-states all the DIO channels for approximately 280 milliseconds. When the channels are in this state, the NI 9403 can accept new line direction configuration and output state data but cannot pass valid input data to the software. After the channels return to a normal state, the NI 9403 automatically recovers to the latest direction configuration and output state. If the overcurrent condition still exists, the module again tri-states the channels. This cycle continues until the over current condition is removed or the current returns to an acceptably low level. Typically shorting 1 output to ground will not cause an over current condition to occur but will increase the likely hood that it will trip the NI 9403 overcurrent protection circuit. Related Links: Attachments:
Report Date: 06/17/2007 Last Updated: 07/02/2007 Document ID: 4AGDH1LX |
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