Thermoformed plastic containers for food often include an EVOH vapor barrier layer to prevent flavor contamination during storage.  The plastic sheet consists of two layers of polyethylene separated by a thin layer of EVOH.  Infra-red gauges can not distinguish between the top and bottom layers, but only measure the total polyethylene present.  Examining the edge of the product under a microscope is currently the method to measure the layer thicknesses.  A single T-Gauge Sensor can simultaneously measure all three of these co-extruded layers.  If the environment around the online sensor is above 50°C, a thermal enclosure can be supplied that will allow the necessary cooling.

Plastic extruder
Scan of plastic

Typical Product Configuration: