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Liquid Level Interface with a Free Space / Non-Contacting Radar

Level and Pressure Instrumentation Forum

Create, collaborate, and share your information regarding radar, buoyancy, d/p level, d/p flow, purged bubble tube for level, multi-variable, differential pressure, absolute pressure and gauge pressure. Please post tips and tricks, ask questions of the community and share new information.

Schneider Alumni (Retired)
Schneider Alumni (Retired)

Liquid Level Interface with a Free Space / Non-Contacting Radar

A free space radar can be used as part of a liquid level interface solution.  The radar cannot work alone to accomplish this.  By using one of two solutions, a free space radar can solve this challenging application that stymies many solo-operating guided wave radars.


Solution #1: Free space radar with d/p level and a PLC (SCADAPack™ RTU) or DCS do the interface equation.  Here, the d/p is actually calculating the interface; when coupled with radar, the level can fluctuate in a relatively normal fashion.  


Solution #1: Free space radar with SCADAPack™ 4102.  The SCADAPack™ 4102 Modbus™ Multivariable Transmitter has a built-in PID controller.  It does the job of both a d/p level and a PLC.  It generates an analog or Modbus output.


As radar becomes more popular in the marketplace (fastest-growing level technology) I believe more customers are looking for additional uses.


Interface with dp and Radar and PLC #2.PNG


Interface with dp and Radar and PLC #1.PNG


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2 Replies 2

Re: Liquid Level Interface with a Free Space / Non-Contacting Radar

Nice overview and easy to follow

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Schneider Alumni (Retired)
Schneider Alumni (Retired)

Re: Liquid Level Interface with a Free Space / Non-Contacting Radar

When guided wave radar is applied properly for interface measurement, it's great.  The only issue is that there are quite a few criteria that must be met in order for the radar to operate properly.  Please see this excerpt from the operating instructions from a typical guided wave radar:

Upper medium (L2)
• The upper medium must not be conductive
• The dielectric constant of the upper medium or the actual distance
to the interface must be known (input required). Min. dielectric constant: 1.6.You can find a list of dielectric constants on our home page
• The composition of the upper medium must be stable, no varying
products or mixtures
• The upper medium must be homogeneous, no stratifications
within the medium
• Min. thickness of the upper medium 50 mm (1.97 in)
• Clear separation from the lower medium, emulsion phase or detritus layer max. 50 mm (1.97 in)
• If possible, no foam on the surface

Lower medium (L1)
• The dielectric constant must be 10 higher than the dielectric
constant of the upper medium, preferably electrically conductive.
Example: upper medium dielectric constant 2, lower medium at
least dielectric constant 12.

Gas phase (L3)
• Air or gas mixture
• Gas phase - dependent on the application, gas phase does not
always exist (d2 = 0)


Source: https://www.binmaster.com/_resources/dyn/files/76563709za5f81c72/_fn/925-0386%20Manual%20GWR-3000%20... on Oct. 6, 2020


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