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SC-2060: Frequently Asked Questions

Hardware: Signal Conditioning Other>>SC Digital Accessories>>SC-2060

Problem:
I was looking through the specifications and user manual for the SC-2060 optically-isolated digital input boards, but some points are still unclear, especially with regard to the voltage reference inputs. Where can I find more information?

Solution:
The following is a list of questions and answers that should reconcile most SC-2060 issues left out of the user manual.

  1. What should be connected to the +Vccx terminal?

    1. Ideally, connect to the same power supply used by the TTL or CMOS circuitry whose outputs are being connected to the SC-2060 inputs.


    2. If the suggestion above is not possible (or extremely inconvenient), use an external power supply having the same Vcc voltage and ground reference as the TTL or CMOS circuitry whose outputs are being connected to the SC-2060 inputs.


  2. Where should the ground reference of the power supply be connected on the SC-2060?

      For either a. or b. above, no ground reference connection is needed.


  3. The SC-2060 specifications given in the catalog and user manual seem to bear little relation to each other. Which one should be used?

      The specs in the catalog are the most current and complete.


  4. The digital logic levels given in the specs seem to make little sense. Please explain.

      The specs say that the input low voltage range extends from Vcc - 9V up to Vcc - 4V. For example, for a 5V reference voltage, any input voltage between -4V and +1V (with respect to the ground reference) will be interpreted as a logic low.

      The specs say that the input high voltage range extends from Vcc - 3V to Vcc + 5V. For example, for a 5V reference voltage, any input voltage between +2V and +10V (with respect to the ground reference) will be interpreted as a logic high.


  5. What are the minimum and maximum voltages that can be applied to SC-2060 channels without damaging the optoisolator input circuitry?

      If the input voltage is less than Vcc - 9V, then the 20 mA maximum input current limit (mentioned in the user manual) will be violated.

      If the input voltage exceeds Vcc + 5V, then the diode reverse breakdown limit for the optoisolator may be violated.

      Remember, exceeding these voltage limits will only endanger the SC-2060. Violating the 400 Vrms channel-to-channel or channel-to-ground common-mode isolation specification may damage an attached DAQ device or PC.


  6. The catalog says: "A digital signal 9V below the reference is registered as a logical low while input signals 3 V below the reference reads as a logical high". Is this true?

      Yes, it is true, but incomplete. For a more complete description of the logic-high and logic-low voltage ranges, see item 4) above.


Related Links:
SC-206X Series User Manual

Attachments:





Report Date: 09/12/2005
Last Updated: 09/30/2005
Document ID: 3PBF5KS9

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