Troubleshooting Guides · Free Tool

Guided Wave Radar Fault Finder

Choose what the GWR transmitter shows and get the likely causes, with checks on the echo curve and the fixes.

Lost echoEnd of probeInterface wrongCoating

What do you see?

SymptomReads end of probe or empty when not

Most likely causeDielectric too low for probe type

First checkWeak level peak on echo curve

Cause	How to check	Fix
Dielectric too low for probe type	Weak level peak on echo curve	Use coaxial or single lead in chamber; adjust thresholds
Wrong probe length setting	Compare with measured probe	Correct length
Probe disconnected or broken	No reference pulse	Repair or replace probe

Before You Start

Work under a permit, inform the control room and put the loop in manual or bypass the trip before touching a live instrument.
Save the echo curve before changing anything.
Check probe type, length, reference point and dielectric settings.
Compare with a gauge glass or manual dip.

Likely cause	How to check	Fix
Dielectric too low for probe type	Weak level peak on echo curve	Use coaxial or single lead in chamber; adjust thresholds
Wrong probe length setting	Compare with measured probe	Correct length
Probe disconnected or broken	No reference pulse	Repair or replace probe

Likely cause	How to check	Fix
Condensation or buildup at nozzle	Peak near top on echo curve	Clean; adjust upper blocking or threshold
Probe touching nozzle wall	Inspect installation	Centre probe; use larger nozzle
Level truly in upper dead zone	Compare with gauge	Reconfigure range

Likely cause	How to check	Fix
Wrong upper liquid dielectric	Check settings	Enter correct dielectric
Emulsion layer	Sample at several heights	Accept emulsion or use other technology
Upper layer too thin	Check minimum layer thickness	Accept limit or change method

Likely cause	How to check	Fix
Coating along probe	Multiple peaks on echo curve	Clean probe; choose coated probe type
Turbulence or foam in vessel	Correlates with agitator or filling	Use stilling well or chamber
Interference from chamber inlets	Peaks at nozzle heights	Adjust thresholds; centring disc

Key insight: the echo curve is the truth: save it at commissioning and compare whenever the reading looks wrong.

Can GWR measure interface?

Yes, if the upper liquid has a lower dielectric and the layers are clear.

Why does coating matter?

Buildup along the probe creates echoes and can mask the real level.

Is GWR affected by density?

Not for total level, which is a major advantage over DP and displacers.

Guided wave radar vs non contact radar

A practical, field focused guide on instrumentationblog.in that explains the theory behind this tool and how engineers apply it on real plants.