Appropriate cable for MDT with an analog output

Hello, I wonder what is the recommended cable to use with MDT Balluff with 4-20 mA on distance cca 400 mesters?
We have used the following cable: JE-Y(ST)Y 2x2x0.8.

However, we see noise on the receiving side about ±0.1% of measuring range. This is not an issue that is making problems, but I guess it could be better.
What cable is usually used with such application?

Thank you!

Jasner,

We don’t have any specific cable recommendations. I understand that a braided shield may be better for low to medium frequencies and foil for higher frequencies, so a combination braided and foil cable may perhaps be better. Otherwise, for a typical 4-20 mA signal, I don’t believe other wire characteristics such as impedance are very important for noise concerns.

We always recommend SSI instead of analog for magnetostrictive sensors. The digital RS-422 signal is much more noise immune, and I believe the sensor cost is the same. In addition, with magnetostrictive sensors, SSI allows the internal measurement to be synchronized with the RMC’s loop time, resulting in less jitter.

Typical other causes of analog current noise are:

  1. Incorrect shield connections
    The common recommendation is to connect the shield at one end, usually the transmitting end. However, other methods have been used in various situations to reduce noise.

  2. Incorrect wiring for differential analog input
    The RMC analog input is differential. The current should go into the +In. The current should return from the In- and go back to the sensor, not be directly connected to common at the RMC. This can be tricky. How is yours wired?

  3. Proximity to high-frequency wiring
    I am sure you already know this, but if possible (and often it’s not), move wire away from high-frequency wiring.

Best Regards,
Jacob Paso

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