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A 26 GHz radar level transmitter measures the distance to a liquid surface using microwave reflections. The operating frequency does not tell a buyer whether the antenna fits the nozzle, whether the assembly is pressure-rated or whether the signal will remain usable during filling. For a liquid tank, begin with those differences between actual models.
Two 26 GHz radar level transmitter configurations
The METRAVON MV-RD901 and MV-RD902 illustrate why one set of "26 GHz specifications" is misleading. The former has a PTFE rod antenna and an atmospheric-tank configuration. The latter uses a stainless-steel horn with several diameter choices. Neither should inherit the other's material or pressure suitability.
| Item | MV-RD901 | MV-RD902 |
|---|---|---|
| Antenna | 44 mm PTFE rod, with listed lengths of 50-250 mm. | Stainless-steel horn; listed diameters are 46, 76 and 96 mm. |
| Distance interval | 0.3-10 m for the published atmospheric configuration. | 0.3-30 m for the published liquid configuration. |
| Process boundary | Atmospheric pressure; listed temperature -40 to 100 deg C. | Listed pressure -0.1 to 2.5 MPa; temperature version and seal must be confirmed together. |
| Main drawing check | Rod projection beyond the opening and exposed-material compatibility. | Horn clearance, position and the beam data for that horn size. |
These are product-page selection data, not interchangeable order codes. The MV-RD902 standard temperature configuration is listed at -40 to 120 deg C, with a separate high-temperature configuration up to 200 deg C. Request the allowable pressure at the required temperature for the supplied assembly; do not combine separate maxima into an assumed operating point.
Assess the signal path through the real nozzle
On the MV-RD902, a horn that passes through a flange may still be recessed inside unsuitable pipework. Supply the nozzle bore and length, reducers, lining and the intended horn position. Use the beam information for the selected antenna to check nearby walls and internal structures over the full measurement distance.
For a compatible chemical in an atmospheric tank, the MV-RD901 offers a different antenna route. Its projecting rod is a free-space radar antenna, not a guided-wave probe that must reach the liquid. Review the seals and connection materials as well as the visible PTFE.
Diagnose a jump before changing the measuring range
First establish whether the local distance jumps or only the PLC value changes. A stable local observation with an unstable receiving value suggests a different investigation from a target switch at the instrument. Record actual process movement, the time of the jump and any available diagnostic status.
If the radar itself changes target, compare the reported distances with the nozzle, internals and expected surface. Inspect deposits through a safe access procedure and observe whether the problem follows filling or agitation. A larger damping setting can smooth an error without identifying its cause.
Include the receiving input in the quotation
The documented two-wire electrical option uses 24 V DC and 4-20 mA/HART. An RS485 requirement needs its corresponding electronics and terminal documentation. State which variable the host expects and how unavailable measurements will be handled. A protocol label alone is not a wiring drawing.
Q1. Is a bigger horn always preferable?
Select the horn using both its documented beam data and the mechanical drawing. Confirm that it can be installed in the intended position and that the measurement path remains clear at the highest and lowest required surfaces. A larger horn that is recessed into unsuitable pipework or cannot be fitted correctly does not solve the installation. Review the proposed assembly before changing the nozzle.
Q2. Does the atmospheric MV-RD901 suit a pressurised tank with the same thread?
The shared connection size is not evidence of pressure suitability. The published MV-RD901 configuration here is atmospheric; a pressure duty requires a separately assessed assembly with documented ratings for the actual pressure-temperature conditions and exposed materials. Identify the required duty before ordering rather than treating a fitting that screws into place as a compatible pressure-rated replacement.
Q3. Is replacing 26 GHz with 80 GHz a guaranteed cure for jumps?
First separate a changing local distance from a fault confined to the receiving system. If the radar changes target, compare the fault-state distance with the nozzle, internals and actual surface before assessing another antenna. If local measurement is stable, investigate output and PLC interpretation. A frequency change alone cannot repair scaling, an incorrect reference or an unsuitable process installation.
Summary
Select the antenna and process assembly before finalising the electrical option. Send the liquid specification, nozzle section and operating distances for an MV-RD901 or MV-RD902 proposal.
