This is an instrument specifically designed to measure the reflectance of smoke stains on filter papers. This measurement is then used to estimate the concentration of black smoke or particulate matter in the air. The instrument works by shining a controlled light source onto a smoke stain collected on a filter paper and then measuring the amount of light reflected back. This is an EEL model 43 reflectometer with a Kemtronix digital readout. It's tested and working and comes in a lovely leather carry case
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