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

Level and Pressure Instrumentation Forum

A forum dedicated to sharing information, tips and tricks or ask/answer questions regarding radar, buoyancy, d/p level and flow, differential/absolute and gauge pressure and more! 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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