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Why Does My [c]FP-CTR-50x Module Miss Pulses?

Hardware: FieldPoint>>Discrete I/O Modules>>FP-CTR-500, FieldPoint>>Discrete I/O Modules>>FP-CTR-502, Compact FieldPoint>>Discrete I/O Modules>>cFP-CTR-500, Compact FieldPoint>>Discrete I/O Modules>>cFP-CTR-502

Problem:
Why does my [c]FP-CTR-50x counter module fail to count the first few pulses of my source signal?

Solution:
This is a known issue that affects the following revisions of the [c]FP-CTR-50x counter module:
  • Revision C and earlier of the cFP-CTR-500 module
  • Revision F and earlier of the FP-CTR-500 module
  • Revision D and earlier of the cFP-CTR-502 module
  • Revision D and earlier of the FP-CTR-502 module
The particular revision is identified by the letter within the part number. For example, a revision C cFP-CTR-500 module will have part number 185503C-02. You will find the part number on the label affixed to the side of the module.

While configured to the 50 kHz filter setting, these modules may fail to count a few source signal pulses under two conditions. The details are in the table below.

Channel Filter Setting
200 Hz
50 kHz (Default Setting)
No Issues                                                                                   
  1. If a channel's filter setting is changed from 200 Hz to 50 kHz on the fly (while acquiring data), the counter may miss one or more pulses immediately after changing to the 50 kHz setting. After missing these initial pulses, the counter will continue to function normally.

  2. If a channel input remains idle at either low or high voltage for more than 25 minutes, the counter may miss one or more initial pulses when the source signal starts up again. After missing these initial pulses, the counter will continue to function normally.

To work around these problems, leave your counters configured to the 200 Hz filter setting (i.e. do not change the setting on the fly while acquiring data), or if you must use the 50 kHz filter setting, ensure that the inputs do not remain idle for more than 25 minutes.

Please accept our apology for the inconvenience. National Instruments is committed to your total satisfaction and to maintaining your confidence in our products. If you have any technical questions or concerns, please call 1-877-493-2406 and ask to speak with an Applications Engineer.


Related Links:
KnowledgeBase 3KEAE473: (c)FP-CTR-500 Destroyed When Applying External Power

KnowledgeBase 3V2EL1IH: [c]FP-CTR-50x External Power Supply Voltage Specification is Incorrect



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Report Date: 02/27/2006
Last Updated: 09/15/2006
Document ID: 3TBGIBPT

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