Radar/Ultrasonic Level Commissioning — Why False Echo Mapping Isn't Optional

-

Practical Procedure · Commissioning

Radar/Ultrasonic Level Commissioning — Why False Echo Mapping Isn't Optional

Applies to: Radar and ultrasonic level transmitters on silos, hoppers, and bins  |  Equipment needed: Transmitter's own configuration tool (HART/local display/software), knowledge of vessel internal obstructions

Real Echo vs. False Echo — See the Difference

Tap a tab to see why an unmapped vessel confuses the transmitter, and what mapping actually fixes.

Silo (internal view) Support beam Transmitter false echo off beam actual material surface Transmitter Output Erratic / Jumping Level confuses beam echo with real surface
Silo (internal view) Support beam (mapped & ignored) Transmitter actual material surface Transmitter Output Stable, Accurate Level beam echo excluded by the map
Without a false echo map, the transmitter can't tell the difference between the real material surface and a fixed obstruction like a support beam, ladder, or nozzle — both return an echo, and either one can get picked up as "the level."
A false echo map tells the transmitter to ignore echoes from known fixed obstructions at their known distances, so only the real, moving material surface is tracked.

Why This Step Gets Skipped

False echo mapping (sometimes called echo curve mapping) takes extra time during commissioning — the vessel often needs to be at a known, mostly empty level, and someone has to note the actual distances to internal obstructions. Under commissioning schedule pressure, this step is one of the first things skipped, with the assumption that the transmitter's own signal processing will sort it out on its own.

What Happens Without It

  • Ghost/jumping readings — the level appears to spike or drop suddenly and settle back, especially when the material surface passes near a fixed obstruction's distance.
  • Readings that look "mostly fine" during commissioning testing but become unreliable months later as material buildup on internal structures changes the obstruction's echo strength.
  • Technicians chasing what looks like a transmitter fault or antenna problem, when the transmitter is actually functioning correctly — it's just not been told what to ignore.

How to Do It Properly

  • Note the physical location and approximate distance of every fixed internal obstruction — support beams, ladders, agitators, fill pipes, nozzles — before commissioning.
  • Run the transmitter's false echo mapping/learn function with the vessel at a known level (commonly empty or near-empty), so any echo the transmitter records that doesn't match the known material distance can be identified as a fixed obstruction.
  • Review the resulting echo curve/map and confirm the mapped distances correspond to known obstructions — don't blindly accept an auto-generated map without checking it makes physical sense.
  • Re-verify the map after any internal vessel modification — added structure, new agitator, repositioned nozzle — since the map is only valid for the vessel configuration it was made against.

Common Mistakes to Avoid

  • Skipping the mapping step during commissioning to save time, assuming it can be "done later" — it rarely is, until a fault forces the issue.
  • Mapping only once at commissioning and never revisiting it after vessel modifications.
  • Chasing a suspected transmitter or antenna fault for weeks when the actual cause is an unmapped or outdated false echo map.

This is a general commissioning procedure — specifics vary by transmitter brand and vessel design. Adjust to your own SOP where needed.

🎥 Watch It Explained on PLC Key Channel

Prefer video? I break down topics like this with animations on my YouTube channel.

▶ Watch the full playlist on PLC Key Channel →

🛠️ Tools I Actually Use in the Field

A few affiliate links to tools that come up constantly in instrumentation work — I only list things I'd recommend to my own team:

As an Amazon Associate I earn from qualifying purchases. It doesn't cost you anything extra.

Got a specific instrumentation problem you're stuck on? Drop it in the comments — I answer based on real plant troubleshooting, not textbook theory.

Comments

Post a Comment

Popular posts from this blog

Belt weigh feeder Zero and Span Drift

-
Image
Fault Log · Field Report Schenck Weigh Feeder — Zero and Span Drift, Two Different Root Causes Plant: Cement  |  System: Schenck weigh feeder, belt scale, hopper load cells  |  Downtime: None Symptom A Schenck weigh feeder started showing both zero drift and span drift at the same time. Two separate accuracy problems showing up together made this a two-part investigation from the start — zero and span errors don't always share the same root cause, even when they appear together. Investigation — Zero Drift Started with the load cell loop and mechanical side of the belt scale: Load cell loop — checked the full loop, cleaned the load cell area. Idlers/rollers — checked the rollers for wear or misalignment. Belt tracking — with the belt empty, noticed it was drifting to one side. Zero was being tared in that empty, drifted position. Once material loaded onto the belt, the belt tracked back closer to center — meaning the zero reference had been tak...
Read more

Zirconia Oxygen Analyzer Reading Maximum O2

-
Image
Fault Log · Field Report Zirconia Oxygen Analyzer Reading Maximum O2 — Not the Cell, a Rusted Outlet Plant: Cement  |  System: Zirconia oxygen analyzer, sample extraction system  |  Downtime: None Symptom The zirconia oxygen analyzer started reading maximum oxygen — pegged at the top of the range rather than tracking the actual process value. A reading stuck at maximum on a zirconia cell usually means the cell is seeing something close to ambient air instead of process gas, which points straight at a sample delivery problem before you even think about the analyzer itself. Investigation Started at the sample path, from the process side inward: Probe, extractor filter, sampling line, pump — checked the full sample path from the probe through the extraction filter and sampling line, including the sample pump. Performed a leakage test across this section. All found ok. Panel-side tubing and membrane filter — checked all tubing inside the panel along...
Read more

Control Valve Positioner Calibration

-
Image
Practical Procedure · Calibration Control Valve Positioner Calibration — Full Stroke, Limits, and Auto vs. Manual Applies to: Pneumatic control valves with smart/digital positioners (e.g. HART-based) or conventional analog positioners  |  Equipment needed: HART communicator (for smart positioners), air supply/regulator, mA source or 4–20 mA loop calibrator Control Valve: Throttling the Flow ACTUATOR As the PLC output signal changes, the actuator rotates the internal disc — from fully open (parallel to flow) toward fully closed (perpendicular to flow). This is exactly why a control valve isn't just "on/off" like a block valve: it throttles anywhere between 0% and 100% to hold a process variable at setpoint. Before You Start Confirm the valve is safe to stroke — coordinate with operations, since a full 0–100% stroke will move the valve through its complete range on a live process line. Chec...
Read more