Guided Wave Radar Probe Selection: Differences Between Cable, Rod, and Coaxial Tube
In industrial liquid and material level measurement, guided wave radar instruments with measuring probes often face probe selection issues. Cable, rod, and coaxial tube probes have different structures and clearly different applicable conditions. This article uses E+H guided wave radar as an example to help engineers and procurement teams quickly understand the selection logic.
Rod Probe: Sturdy and Durable, Suitable for Harsh Conditions
Rod probes are the most common type of guided wave radar and are mainly divided into 8mm and 12mm diameters. The thicker the probe, the larger the measuring range and the stronger the structure.
- 8mm rod: Most commonly used, suitable for general liquid and solid level measurement.
- 12mm rod: Suitable for harsh conditions such as stirring, easy buildup, and high-viscosity media.
Thick probes are less prone to swinging, and buildup is more likely to fall off, so they can be used stably even in stirring conditions. Summary: The severity of the working condition is proportional to the measuring rod diameter.
Cable Probe: Flexible Installation, Adapts to Complex Tanks
The tail structure of cable probes is clearly different, and they are divided into three cases according to the weight method. Cable diameters generally include 2mm and 4mm.
| Type | Function | Application Scenario |
|---|---|---|
| With weight | Straightens the cable to ensure accurate measurement | Liquid measurement |
| With centering weight | Keeps the probe centered and prevents buildup | Foam, slurry, and dust environments |
| Without weight | Adapts to lightweight media or limited space | Lightweight media, limited installation space (less commonly used) |
Coaxial Tube: Strong Anti-Interference, More Stable Measurement
The coaxial tube consists of two coaxial metal tubes, inner and outer, with the middle being the measuring area. It is mainly used in guided wave radar to guide electromagnetic waves along the tube, eliminating interference inside the tank, such as from agitators, foam, and steam, ensuring stable measurement.
- The diameter is generally 20mm or more, with multiple options.
- Opening types are divided into single-hole and multi-hole.
- The larger the opening, the better the medium flow and the less likely buildup occurs.
Supplement: The Role of the Top Centering Rod
The top centering rod is a short rod or bracket installed at the top of the probe (near the flange/connection) to "prop" the probe in the center of the connection. Its functions include:
- Preventing the probe from tilting or touching the wall inside the connection.
- Avoiding radar wave interference caused by hitting the pipe wall.
- Reducing probe swinging caused by medium flow or stirring.
- Improving measurement stability, especially suitable for short connections and short-section installation.
Selection Recommendations and Consultation
Overall, rod type is suitable for harsh conditions, cable type is suitable for complex tanks, and coaxial tube is suitable for strong interference environments. During selection, medium characteristics, tank structure, and installation conditions must be considered. For more information, you can add the WeChat below for consultation, or join the instrumentation exchange group. You can also call 153 2371 3323, or visit the official account and website http://ainstru.com/ for more content.