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A dielectric value copied from a material table can look precise while describing the wrong product or test conditions. Using dielectric constant for radar selection requires more than identifying a familiar chemical name. A dilute mixture, changing recipe or laboratory value measured at another frequency may not represent the liquid in the tank.
Keep the value with its conditions
Ask where the number came from and what material was measured. Retain composition, concentration, temperature and measurement frequency where available. If the source does not give those details, record the number as screening information rather than a confirmed process property.
| Source detail | Reason to retain it |
|---|---|
| Composition | A pure chemical is not necessarily representative of a mixture or contaminated process liquid. |
| Temperature | The cited condition may differ from storage, operation or cleaning. |
| Frequency | Dielectric behaviour can depend on the frequency at which it was characterised. |
| Recipe range | One value may omit the product variation the installed instrument must handle. |
A single number does not identify the wanted reflection
The surface return depends on the electromagnetic contrast between media as well as the installation and process condition. A weak liquid-surface reflection may compete with the tank bottom or internal structures. Conductivity, layers, foam and deposits can also affect the observed result; a scalar table entry does not describe every relevant behaviour.
Do not estimate a mixture's dielectric behaviour by averaging two constituent values unless that model has been justified for the mixture and conditions. Likewise, a radar that detects one interface is not automatically qualified to measure the thickness of a second layer.
Use dielectric constant for radar selection as part of an evidence request
The METRAVON MV-RD12 is a non-contact liquid radar. Its published page does not establish a universal minimum dielectric value for every liquid, nozzle and distance. Provide the actual material information and ask what evidence supports the intended configuration at the longest required distance and relevant surface conditions.
When material data are uncertain, useful evidence can include representative operating observations or an agreed trial. Record sample preparation and whether temperature, foam or layering can be reproduced. A small bench vessel may establish a response for its conditions without reproducing the reflections and path length of the real tank.
Q1. Is a value from a safety data sheet sufficient?
It can support identification, but check whether it actually provides dielectric information for the relevant composition and conditions. Do not infer that property from density or a broad product classification.
Q2. Can a successful water test approve an unrelated solvent?
No. It may confirm basic operation, but the target reflection and material compatibility can differ. Qualify the intended liquid and assembly separately.
Summary
Retain the origin and conditions of material data rather than treating an isolated number as approval. Submit the liquid specification, property source and operating range for an MV-RD12 assessment.
