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nkwai

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Posts posted by nkwai

  1. Hi,

     

    another question, the scan time in SI0 is between 11-14ms. The plc has 19 inputs used out of 20. As I understand SI0 gives the scan time of 1 cicle eg. in that time it reads 1 channel. Assuming that the total scan time should be around 200-250ms?

    Without the immediate read, using only the 2.5ms interrupt the plc will check the input every 2.5ms or every 200-250ms?

     

    Thank You.

  2. Hi,

     

    I have a problem trying to read the power from a power meter reading pulses. I already did a search on the forum and found 2 or 3 topics but would still like to ask if someone can give me any suggestions to increase accuracy.

    At the moment the power meter is set to output 1imp/Wh. The output is connected to a V120, not to the high speed input because they are already all used, but to a normal input and at 15kW the error is of 2.5kW which is to much.

    At the moment in the 2.5ms subordinate I'm reading the value of SDW3 (2.5ms counter) at every pulse to get the time between pulses, and then in a normal subordinate calculate the kW from that. I tried to use immediate read but VisiLogic says it not compatible with the hardware (is it only for high speed inputs or it's not supported by the V120?).

    If it helps I can also set the power meter to output 1 imp/10Wh if the 1imp/Wh is to fast for the normal input. The power meter works in the range between 5kW and 20kW so from 1.38 to 5.55 imp/sec.

    Is there any "trick" to improve accuracy?  Or what am I doing wrong?

     

    Attached is a sample of how I'm doing the reading and calculations.

     

    Thank You

    PowerMeter.vlp

  3. Ok, after some hours I think I understood what it does.

    The first 20 bits of DW3 covers the digital imputs from I2 to I20

    The bits of DW6 covers the MB from 340 to 371

    And the bits of DW4 covers the MB from 300 to 331

    And the three DW are use to comunicate with the scada software

    Now I just need to find the "pinout" of the three DW.

    I think this was used as a workaround for the 24 tag limit of the licence, this way only 3 tags are consumed.

  4. Hi,

     

    A friend asked me to modify him a scada software, he wants to change some controls. The scada software comunicates by modbus with a V120 which is conected to a V130.

    The person who wrote the program is unreachable and he didnt leave any comments in the program. At least there is a subrutine named Scada.

    At the begining of the subroutine is this piece of program that I don't understand what it does (see attachment).

    If someone can explain me what is going on there I would be greatefull.

    Thank You.

     

    Best Regards.

    post-16999-0-77993600-1384195494_thumb.jpg

  5. Hi,

     

    maybe this will be a stupid question, but I don't want to burn something.

    I have a Vision 120 with transistor outputs, two of the outputs are turning on two relays.

    The relays have a common 0V and then the +VO from the PLC.

    If I connect a switch using the same +VO to manually control the relays, do I have to put a diode

    on the wire coming from the PLC? or there is no problem if current comes backwards?

    There is also the possibility that the output will turn on while using the manual switch is this a problem?

     

    Thank You.

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