ASD offers a variety of transmission probes for various contact dip, absorbance, and transflectance measurements. Applications requiring a transmission probe include liquids such as biofuels, petroleum, and other chemicals. 
Shown above: 2MM Dip Probe. This probe is suitable for liquid measurements. 
If using this probe with a spectrometer such as a TerraSpec mineral analyzer or a LabSpec lab analyzer without an integrated light source, a Fiber Optic Illuminator is necessary. The Fiber Optic Illuminator provides