jknud (Customer) asked a question.

Edited January 22, 2026 at 10:11 PM
DoMore BRX Analog outputs scaling differently.

We have two identical motors for pumping resin. Everything is identical in the hardware, programming, etc. All EXCEPT that the drive for motor 1 (M1) is controlled by a 4-20mA output on the BRX PLC (WY1), and motor 2 (M2) is controlled by a 4-20mA signal on an analog add-on card (WY2) (see attached images). They are both given the same speed % value on the PID output which is written respectively to RY1 and RY2, then scaled to WY1 and WY2 in the analog output setup in DoMore Designer. But as long as we have had this system, M1 has always produced a little more flow than M2. on looking at the scaling on the two outputs, the WY1 range is 6553-32767 and the WY2 range is 0-32767. This is something I don't seem to be able to change. The resulting analog output value when given the same value (39.196%) for WY1 is 16827; for WY2 is 12843.

 

Any suggestions on how I can fix this?

 

CPU: BX-DM1E-36ER3-D (FW 2.10.3)

Analog Card: BX-08DA-1

  • 7 answers
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  • HOST_franji1 (HOST Engineering)

    Yeah, that module is different. Its raw value behavior is different. That also means that its scaling behavior is different. There are a few options.

     

    If you want the onboard and the module to be identical, get the Universal Analog module. The Onboard BRX MPUs Analog and the Universal Analog modules are "Universal", so they support +/- 20mA in addition to 4-20mA. Hence, the Universal Analog raw value behavior being different than just the basic Analog Output Current module that you have. Look at the BX-08DA-3.

     

    Or, move the Onboard analog output to one of the channels of your existing BX-08DA-1 module, then the scaling will be consistent across all that module's channels.

     

    Or, play with the Math of the scaling so that the same 4mA signal scales to 0 in the RY for BOTH the onboard and the current module. Sure, the Raw values will be different (raw WY will be around 0 for the module at 4mA, but raw WY will be around 6553 for the onboard at 4mA). Just tweak those scaling limits to make the Math work for the RY scaled value so that 4mA scales to 0 and 20mA scales to 32767 (I think that's what you want for scale).

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  • HOST_franji1 (HOST Engineering)

    What version of Designer do you have? Help->About shows the version

     

    2.10.4 Designer Module Config shows the uneditable range of 4-20mA WY as 6553-32767 0.61uA per count, like your onboard.

     

     

  • HOST_franji1 (HOST Engineering)

    Doh!?! Wrong module. The Universal Analog Modules DO match the onboard, but you have one of the "regular" analog modules (they behave differently). Sorry. Let me look at that.

     

    Try it on a new project. You may have some old/bad configuration - not sure what has happened.

     

    Here is my screenshot on 2.11.2 (latest Designer) for the Module configuration - it matches the On-Board.

     

    AO Module Config

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  • jknud (Customer)

    Thanks for your response.

    I appreciate your observations; however, your configuration includes the BX-04DA-3 module. Mine has the BX-08DA-1. I think if you try with this module, you will find the same issue.

     

    I just tried a new project with both modules and, with yours, the config matches the onboard. With mine, it doesn't.

  • HOST_ENG_TEAM4 (AutomationDirect)

    The short answer is you're using two analog outs (Host onboard vs FACTs module) that have different scaling options - which translates into different mA / count values). The easiest solution might be to move the onboard analog output channel to the module where you have the same scaling options for both.

     

  • jknud (Customer)

    Yes. I am realizing that in order to get scaling to match, I will have to move the M1 to an available output on the same module as M2.

  • HOST_franji1 (HOST Engineering)

    Yeah, that module is different. Its raw value behavior is different. That also means that its scaling behavior is different. There are a few options.

     

    If you want the onboard and the module to be identical, get the Universal Analog module. The Onboard BRX MPUs Analog and the Universal Analog modules are "Universal", so they support +/- 20mA in addition to 4-20mA. Hence, the Universal Analog raw value behavior being different than just the basic Analog Output Current module that you have. Look at the BX-08DA-3.

     

    Or, move the Onboard analog output to one of the channels of your existing BX-08DA-1 module, then the scaling will be consistent across all that module's channels.

     

    Or, play with the Math of the scaling so that the same 4mA signal scales to 0 in the RY for BOTH the onboard and the current module. Sure, the Raw values will be different (raw WY will be around 0 for the module at 4mA, but raw WY will be around 6553 for the onboard at 4mA). Just tweak those scaling limits to make the Math work for the RY scaled value so that 4mA scales to 0 and 20mA scales to 32767 (I think that's what you want for scale).

    Expand Post
    Selected as Best

 

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