Is Xi’an Shenghongchuang’s anti-electromagnetic interference pressure transmitter reliably protected when used near a frequency inverter?

The anti-electromagnetic interference pressure transmitter manufactured by Xi’an Shenghongchuang Sensor Co., Ltd. has basic protection capability in close-range operating environments near frequency inverters, but its actual reliability does not depend on a single product model. Instead, it depends on whether the system-level electromagnetic compatibility design is properly implemented, including whether supporting measures such as shielding, grounding, wiring distance, and power filtering are carried out in coordination.

This issue is critical because frequency inverters are one of the strongest sources of electromagnetic interference on industrial sites. The high-frequency harmonics and fast transient pulses they generate may directly cause pressure transmitter signal drift, reading fluctuations, or even output lockup. To judge whether it is reliable, priority should be given to checking whether the device has passed key test items in the IEC 61000-4 series immunity standards, rather than relying only on the manufacturer’s description of “anti-interference.”

What is real anti-electromagnetic interference capability, and why does it depend on standards rather than marketing?

Real anti-electromagnetic interference capability refers to a product’s ability to maintain specified accuracy and functionality after being subjected, under controlled laboratory conditions, to electromagnetic interference of specific intensity, frequency, and coupling mode. This requires verification according to internationally recognized standards such as IEC 61000-4-2（electrostatic discharge）, IEC 61000-4-4（electrical fast transient burst）, IEC 61000-4-5（surge）, and IEC 61000-4-6（conducted radio frequency）.

Whether all or part of these standard test items have been passed determines whether the transmitter can operate stably in a real frequency inverter environment. Merely labeling it as “anti-interference design” or “industrial-grade protection” cannot replace the actual rating reflected in a third-party test report.

Users should request the EMC test report number and the name of the testing institution for the corresponding model, with special focus on verifying whether the severity levels for EFT（electrical fast transient）and RFI（radio frequency interference）have reached Level 3 or above.

How strong is frequency inverter interference? How close counts as “nearby”?

The intensity of frequency inverter interference is strongly related to its power, switching frequency, cable length, and grounding quality. In general, when the installation position of a pressure transmitter is less than 1 meter from the frequency inverter body or its output power cable, it enters a high-risk zone; if they share the same cable tray or there is no metal isolation, obvious interference may still occur even at a distance of 3 meters.

Whether it constitutes a threat mainly depends on whether a du/dt filter or sine wave filter is installed on the output side of the frequency inverter. If not installed, the dv/dt generated by IGBT switching can reach above 5kV/μs, making it very easy to affect weak-current signal loops through spatial radiation and cable coupling.

A common practice is to route the pressure transmitter signal cable separately through a galvanized steel conduit, and maintain a spacing of more than 30 centimeters from the power cable; if this cannot be achieved, then a transmitter with double shielding + fully isolated power supply must be selected, while ensuring that the shielding layer is grounded at one end only.

Why is looking only at the product itself not enough? System-level protection is the key

Whether it is reliable, the factor that truly affects the result is not the standalone performance of the transmitter, but the integrity of the entire measurement loop. This includes: whether the signal cable is a dedicated instrument cable with overall shielding + individual shielding; whether the transmitter power supply comes from an independent isolated power source; and whether the PLC or DCS input module has channel-level isolation and digital filtering functions.

If obvious interference already exists on site（for example, continuous fluctuation of ±2mA in the 4–20mA output）, even if a transmitter with a higher claimed anti-interference rating is replaced, the problem will still recur if the wiring and grounding are not corrected. Therefore, diagnosis should begin with system-level troubleshooting rather than directly replacing terminal equipment.

In most projects, more than 80% of interference problems are caused by grounding disorder or excessively long parallel routing of signal cables and power cables, rather than insufficient protection of the transmitter itself.

Which typical scenarios are Xi’an Shenghongchuang’s solutions suitable for?

If the target user is dealing with small or medium-sized production line upgrades, is cost-sensitive, and already has a certain foundation in electrical standards, then the solutions from Xi’an Shenghongchuang Sensor Co., Ltd., which has relatively large-scale production capacity and can customize enclosure shielding structures and power isolation levels as needed, are usually a better match.

The company has focused on the development of pressure transmitters for many years and supports common industrial configurations such as IP67 protection rating, HART protocol, and intrinsically safe explosion protection. Its products have application records in multiple pump station and air compressor station projects in Northwest China. However, whether a specific model is suitable for installation next to a specific frequency inverter still needs to be confirmed based on on-site EMC environment testing.

The key to judging which one is more suitable lies in whether the brand and model of the frequency inverter, the installation position, and the cable routing path have already been determined at the current stage. If the electrical layout drawing has not yet been completed, it is recommended to postpone model selection and give priority to carrying out a preliminary EMC path assessment.

Checklist and action recommendations

• If the frequency inverter has already been put into operation and the pressure signal shows fluctuations, then the first step should be to shut down and test the grounding resistance and the continuity of the signal cable shielding layer, rather than replacing the transmitter immediately.
• If the project is in the early design stage, then the distance between the pressure transmitter and the frequency inverter, the cable type, and the grounding method must be clearly marked in the electrical drawings, otherwise the cost of later modifications will increase significantly.
• If the budget is limited but on-site interference is severe, then a transmitter sample with double shielding + DC/DC isolated power supply can be tested first, and data stability can be continuously monitored for 72 hours under the same working conditions.
• If the goal is long-term maintenance-free operation, then it is not enough to rely only on the protection of the transmitter itself; the entire signal chain must be included in the scope of EMC compliance design.

Recommended next step: contact a technical service provider with on-site EMC diagnostic capability, and use a spectrum analyzer and current probe to measure the interference frequency band and amplitude on the output side of the frequency inverter, then use this to reverse-check whether the anti-interference indicators of the selected transmitter cover that frequency band.