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Entry type: FAQ Entry ID: 81714201, Entry date: 02/15/2016
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How do you determine the current measuring value from the IO data of the energy meter?

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There are several ways of determining the IO data: cyclic reading of the IO data and acyclic reading via data records.

This FAQ response deals with the cyclic reading of IO data. Information about acyclic reading via data record 142 is available here:81715524.

Instructions

  1. Define which measurements are to be in the IO data. You have 10 different user data versions available with 400 VAC. You have 25 different user data versions available with 480 VAC. Detailed information is available in the manual of the Energy Meter in the section entitled User data versions.
     
  2. Table 1 shows the standard user data version 254 "Total power L1L2L3".
     
    ByteAssignmentData typeUnitValue range
    0User data versionBYTE-254 (FEh)
    1Quality information=
    QQ1 I3 U3 I2 U2 I1 U1
    BYTEBit sequenceqq xx xx xx
    2 to 3Current L1UINT1 mA0 to 65535
    4 to 5Current L2UINT1 mA0 to 65535
    6 to 7Current L3UINT1 mA0 to 65535
    8 to 9Total active power L1L2L3INT1 W-27648 to 27648
    10 to 11Total reactive power L1L2L3INT1 var-27648 to 27648
    12 to 13Total apparent power
    L1L2L3
    INT1 VA-27648 to 27648
    14 to 17Total active energy L1L2L3UDINT1 Wh0 to 4294967295
    18 to 21Total reactive energy L1L2L3UDINT1 varh0 to 4294967295
    22reservedBYTE-0
    23Total power factor L1L2 L3USINT0.010 to 100
    24Current scaling L1USINT-0 to 255
    25Current scaling L2USINT-0 to 255
    26Current scaling L3USINT-0 to 255
    27Total active power scaling L1L2L3USINT-0 to 255
    28Total reactive power scaling L1L2L3USINT-0 to 255
    29Total apparent power scaling L1L2L3USINT-0 to 255
    30Total active energy scaling L1L2L3USINT-0 to 255
    31Total reactive energy scaling L1L2L3USINT-0 to 255

    Table 1

  3. Use your user program in full operation to read out the relevant measured value from the IO data (example: Current I L1).
     

  4. In addition you read out the scaling factor for your variable (example: "Scaling Current L1").
       

    Fig. 1
     
  5. The measured value is calculated as follows:

    Measured value = "Value from IO data" * 10 ^ "Scaling from IO data"
       

    Example
    Current = "Current I L1" * 10 ^ "Scaling Current L1"

    Sample program (S7-1500):
     

  6. Fig. 2 and Fig. 3 show the sample program for an S7-1500 CPU:
       

    Fig. 2
       

    Fig. 3
     

Further Information
More information about the IO module Energy Meter is available in the following Entry IDs:
  • Manual:
    SIMATIC ET 200SP Analog Input Module AI Energy Meter ST (Entry ID 73098696)
  • FAQ:
    What should you watch out for when setting up and configuring an ET 200SP with an Energy Meter? (Entry ID: 81800892)
  • FAQ:
    Is there a way of reading out all the measured values of the Energy Meter at once? (Entry ID: 81715524)
  • FAQ:
    How do you reset the Energy Meter? (Entry ID: 81715807)
  • FAQ:
    How do you select a current transformer for the ET 200SP Energy Meter and how do you connect it to the module?
    (Entry ID: 85477190)
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