Electron Machine Corp. Microprocessor Refractometer Sensing Head. Model: MPR-83 / MPR-83R. This sensing head fits the MPR-83 series of microprocessor refractometers that are typically used to measure the refractive indexes of process fluids. Microprocessor refractometers may also be used as error indicators or as part of complete process control systems and can be inserted directly into process lines or vessels for measurements and controls. Sample of applications include: fructose, glycol, NaOH, black and weak liquors, and coatings. Inlets/outlets: (2) 1-1/2 in. dia. S-line fittings. Overall dimensions: 12 in. L x 7-1/2 in. W x 13-1/2 in. H.(ACN80).