Efficiency Scientific Instrument Co., Ltd: ESI - Simply the best. Advanced and complete (energy dispersive X-ray fluorescence )XRF spectrometer solutions. Portable, handheld and benchtop XRF Element Aanlyzers. Leading manufacturer of XRF spectrometer to offer elemental analysis solutions include: XRF gold tester, handheld XRF metal alloy PMI analyzer, handheld XRF mineral analyzer, portable sulfur in oil analyzer, benchtop XRF RoHS compliance spectrometer, XRF coating thickness analyzer.