What products are involved?

Rheonics inline process density meters and viscometers (sensor probe, sensor cable and sensor electronics).


What is the purpose of this article?

This article explains how Electromagnetic Interference (EMI) affects Rheonics sensors and how to reduce the EMI effects.


Table of Contents

1. Overview

When working with various electronic systems, Electromagnetic Interference (EMI) issues are not uncommon and can adversely affect nearby electronic devices, leading to problems such as serial communication loss, disturbances in output signals, and cross-talk.


Electromagnetic Interference (EMI) is a widespread issue with diverse sources, posing potential challenges to the reliable functionality of electronic devices. Common sources of EMI include devices with switching power supplies, Variable Frequency Drives (VFDs), electric motors, and voltage converters, as well as transmitters, power lines, motors, generators, and other sources of Radio Frequency Interference (RFI). Additionally, switching devices, digital electronics with rapid voltage changes, and wireless communication devices all contribute to EMI. [1]


Some of these are present in a large number of manufacturing, transformation and transport processes commonly used in industrial applications.


2. How Does EMI Affect Rheonics Sensors?

Rheonics sensors employ proprietary technology to achieve extremely high immunity from EMI. A properly connected Rheonics inline process density meter and viscometer can easily operate without performance degradation in high EMI environments like with large electric motors provided that the sensor probe and electronics are properly grounded following recommended procedure.


The table below gives general guidance on what symptoms a user would find when the sensor might be affected by EMI from computers and power lines - here the causes and mitigation strategies are discussed. These are items to take into consideration when doing a Root Cause Analysis (RCA) on sensor where performance degradation is taking place.


Rheonics sensors employ real-time detection technology that can highlight possible measurement issues, these are shown as error codes on the sensor output. When using the Rheonics Control Panel (RCP) software, these codes are often accompanied with descriptive text that highlight possible cause and solution.


E10 and E12 errors can be triggered by EMI, for example when the sensor cable runs along power lines or motor starters, or when one laptop controls a VFD over serial communication while talking to the sensor.


Symptom
  • E10 and E12 errors (Low Accuracy Error and Sensor Unlocked Error).
  • E10: the sensor is locked but the measurement may not be stable for accuracy [2], [3].
  • E12: the sensor is not locking properly to a measurement value.
Cause
  • This can be triggered if user uses serial communication and tries to control a VFD through a single Laptop.
  • Running the sensor along power lines/noisy data/motor starters.
Description
  • Due to EMI, sensor performance could be compromised and it may not provide reliable readings.
Solutions or checks
  • It is recommended to try Ethernet communication in these scenarios.
  • We recommend connecting the motor or VFD controller to a different laptop than the one used for communication with the sensor electronics over USB
  • Avoid usage of USB communication as those are heavily affected by EMI.
  • Verify wiring and ground loops. Do not run sensor cable along power lines.
  • Ensure the shield of the sensor cable is grounded properly - this ensures the signal is not affected by EMI between the probe and the sensor electronics (in particular when there is a long run length of cable between the probe and electronics)

Table 1. EMI symptoms, causes and solutions


3. How to Reduce the EMI Effects?

Signal grounding stabilizes the SME electronics and communication interfaces, reducing susceptibility to EMI and RFI [2], [3].


To reduce the impact of EMI we recommend the following:

  • Ensure the proper grounding of the panel (where sensor electronics is mounted) to the equipment ground (where sensor probe is mounted).
  • Ensure that the sensor (probe and transmitter) is properly grounded.
  • Ensure the sensor cable shield is properly connected to ground.
  • Connect all ground connections to a metallic common ground block.
  • Verify that all electronic components are adequately earth-grounded.
  • Maintain separation between power lines and sensor cable to prevent interference: at least 200 mm from high-power cables or VFDs.
  • Use shielded cables for all signal connections.
  • Do not install the SME adjacent to high-power contactors or radio transmitters.
  • In extreme cases, an EMI filter is also recommended.


DISCLAIMER

Pictures, photos and images used are for illustration purposes and do not constitute any warranty or assertions on suitability of use and should not be construed as an explicit or implicit recommendation or endorsement. All illustrations are given proper credit from our source of access and by their use here we do not specify or establish any copyright which belongs and stays unaffected with the existing copyright holder of that material.


4. References

  1. KEB America, "Introduction to Electromagnetic Interference with VFDs." [Online]. Available: https://www.kebamerica.com/blog/electromagnetic-interference-vfds/. [Accessed: Sep. 23, 2026].
  2. Rheonics GmbH, Rheonics SRV Inline Viscometer Manual, DocID SRV-G1-OP-2606, Jun. 2026.
  3. Rheonics GmbH, Rheonics SRD Inline Density and Viscosity Meter Manual, DocID SRD-G1-OP-2606, Jun. 2026.