Guided Wave Radar (GWR) level transmitters have become one of the most preferred choices for continuous level measurement in process industries — especially in applications involving interface level, high pressure, steam, and changing dielectric properties. While selecting the right GWR level transmitter, understanding its datasheet is critical.
In this blog, we’ll break down the datasheet section-by-section, helping you interpret specifications effectively and make informed decisions for instrument selection, installation, and integration.
- Introduction to GWR Level Transmitters
What is a Guided Wave Radar Level Transmitter?
GWR level transmitters use microwave pulses sent down a probe (guide) that reflects off the process media surface. The time-of-flight of the signal is converted into level information. Since it’s guided, it performs better in vapor-rich, turbulent, or low-dielectric environments compared to non-contact radar.
- Key Sections of a GWR Datasheet
A typical GWR level transmitter datasheet includes:
- Product Identification & Model Code
- Measurement Range & Probe Length
- Process Conditions (Temp, Pressure, Dielectric)
- Output & Communication Protocols
- Accuracy & Resolution
- Process Connection Details
- Wetted & Non-Wetted Materials
- Electrical Connections & Power Supply
- Certifications & Approvals
- Diagnostics & Features
- Decoding the Datasheet – Section by Section
3.1 Product Identification & Model Code
Example:
Model: RDR-GWR-2500-A1B2C3-D4
Each letter and number in the model typically corresponds to a configuration option — such as probe type, length, material, flange size, electronics housing, and communication protocol.
What to do:
- Always request the model code breakdown table from the OEM.
- Match probe style (rod, cable, coaxial) with your application.
- Confirm communication protocol (e.g., HART, Profibus PA, Foundation Fieldbus).
3.2 Measurement Range & Probe Length
| Parameter | Example Value |
| Measuring Range | 0.3 m to 20 m |
| Probe Length | 200 mm to 20,000 mm |
Interpretation:
- Minimum Level Detection: Often limited by probe style and dielectric constant of the medium.
- Maximum Length: Dictated by probe strength and mechanical support.
Practical Note:
- For short-range tanks (<0.5 m), ensure the dead zone near probe end is considered.
- For tall vessels, verify probe sagging, mounting restrictions, and insertion depth.
3.3 Process Conditions
- Temperature Range
-40°C to +200°C
- Pressure Range
Vacuum to 100 bar (g)
- Dielectric Constant (DK)
Minimum DK: 1.4
Importance:
- Dielectric constant affects reflection strength. Low-DK media (e.g., hydrocarbons) need coaxial or twin rod probes.
- Pressure and temperature ratings must match process conditions and tank design pressure.
3.4 Output Signal & Communication
| Parameter | Value |
| Output | 4-20 mA, HART (2-wire) |
| Optional | Foundation Fieldbus, Profibus PA |
| DTM/EDD Available | Yes |
Explanation:
- 4–20 mA + HART is the most common for analog/digital hybrid loops.
- FF/PA is preferred in digital networks (e.g., offshore platforms or FPSOs).
- Availability of Device Type Manager (DTM) or EDD is critical for integration into host systems like AMS or PDM.
3.5 Accuracy & Resolution
| Accuracy | ±2 mm |
| Resolution | 1 mm |
Application Tip:
- Accuracy is affected by mounting nozzle length, turbulence, and foam.
- In interface applications (oil/water), accuracy depends on DK difference between phases.
3.6 Process Connections
| Parameter | Example |
| Threaded | 1½” NPT |
| Flanged | 2″ 150# RF, DN50 PN40 |
| Hygienic | Tri-Clamp |
Best Practices:
- Choose flanged connections for high-pressure or safety-critical applications.
- For interface or long probe types, consider 3″ or larger nozzle for installation ease.
- Avoid narrow nozzles or long standpipes unless guided by the OEM.
3.7 Probe Type and Material
| Type | Application |
| Rod | Clean liquids, short tanks |
| Cable | Long-range or solids |
| Coaxial | Low-DK liquids, high precision |
Material Options:
- SS316L (standard)
- Hastelloy C, Monel (corrosive service)
- PTFE-coated probes (sticky or aggressive media)
Selection Guidance:
- Match wetted materials with chemical compatibility chart.
- For aggressive tanks, consider corrosion allowance or double-walled probes.
3.8 Electrical Supply & Connection
| Voltage | 12–36 VDC |
| Cable Entry | M20, ½” NPT, or PG11 |
| Housing | Aluminum, SS, or Plastic |
What to Check:
- Ensure power supply is adequate for loop load.
- Select explosion-proof housing for Zone 1 or 2 applications.
- For outdoor or marine use, prefer SS housing with IP68 ingress protection.
3.9 Certifications & Approvals
| Type | Example |
| ATEX | Ex d IIC T6 Gb |
| IECEx | Zone 0/1 |
| SIL | SIL2 Capable (per IEC 61508) |
| Marine | ABS, DNV-GL, BV |
Critical Insight:
- Always cross-check Hazardous Area Classification of your site.
- If used in SIS loops, ensure transmitter is SIL certified and has FMEDA report available.
3.10 Diagnostics & Smart Features
Modern GWR transmitters include:
- Echo Curve Display
- Level and Interface Monitoring
- Dielectric Constant Tracking
- Event Log and NE107 Status Alerts
- Remote Configuration via HART or FDT/DTM
Field Tips:
- Use echo curve to diagnose false echoes or foam interference.
- Use mobile HART communicator or software like AMS/PACTware for commissioning.
- Application-Specific Considerations
4.1 Interface Level Measurement
In oil-water separators, GWR can track the top oil level and interface water level.
Selection Tips:
- Ensure probe supports interface mode.
- Required DK difference between upper and lower media >6.
- Tank conditions (emulsion, foam) can affect reliability.
4.2 Bypass Chamber Mounting
For level measurement in bypass chambers or external cages (e.g., on vessels):
- Use coaxial probes or chamber-specific designs.
- Always align chamber process connections to match liquid movement.
- Avoid mounting transmitter on very short chambers — causes poor resolution.
4.3 Foam, Vapors & Agitation
Although GWR handles foam better than non-contact radar:
- Heavy foam may dampen signal — coaxial probe helps.
- Agitation may require stilling wells or heavy-duty rod probes.
- Installation Notes from Datasheet
Many datasheets provide critical installation diagrams:
- Dead Zones: Top and bottom “blind” zones where accurate detection isn’t possible.
- Probe Mounting Angle: Must be vertical. Avoid tilted installation.
- Nozzle Effects: Long nozzles (>150 mm) can cause false echoes.
- Grounding: Required for cable probes in non-metallic tanks.
- Troubleshooting from Datasheet Values
If you face measurement issues:
| Symptom | Likely Cause | Datasheet Hint |
| Signal loss | Low DK or foam | Use coaxial probe |
| Erratic reading | Agitation or buildup | Check max probe coating spec |
| Interface not detected | Low DK difference | Datasheet DK limits |
| No reading in short tank | Dead zone too long | Check min level limit |
- Checklist Before Finalizing Datasheet
Here’s a handy checklist for reviewing a GWR datasheet:
✅ Probe style suits tank height and media
✅ Process temperature & pressure match spec
✅ DK of media is within measurable range
✅ Flange/nozzle dimensions are compatible
✅ Housing & enclosure are suitable for the area classification
✅ SIL or approvals are available if required
✅ Output type and protocol are compatible with DCS/PLC
✅ Installation diagram and accessories included
- Conclusion
Guided Wave Radar level transmitters are powerful tools for accurate and reliable level measurement in challenging process environments. But their success hinges on proper selection — and that starts with correctly interpreting the datasheet.
Whether you’re an instrumentation engineer, project consultant, or maintenance specialist, decoding the datasheet allows you to:
- Select the correct configuration
- Avoid costly installation or measurement errors
- Ensure long-term reliability and compliance
By following this guide, you can confidently analyze a GWR transmitter datasheet and apply it effectively in your plant.
- Downloadable PDF & Resources
If you’d like a downloadable version of this guide with diagrams and a checklist, feel free to [Request PDF Version] or email your datasheet queries to: instru.nexus@gmail.com