Abstract: Apparatus for wiping the optical window of a sample cell in a turbidimeter or other particle measuring instrument for analyzing a liquid sample. The wiping apparatus is operated by the pressure of the source of supply of the liquid sample and avoids the necessity of liquid seal bearings.

Abstract: An auto-ranging glucose measuring system including a device capable of mixing a glucose containing solution and a diluent in a variable ratio, a glucose oxidase enzyme converter column for converting the diluted glucose solution to hydrogen peroxide as one of the products, an amperometric detector for producing an analog electric signal proportional to the concentration of hydrogen peroxide, a high-low limit circuit for producing a pulse output when the analog electric signal is greater than the preset high limit of the linear span of the detector or is less than the preset low limit of the noise level of the detector, an electronic motor speed changing circuit interposed between a source of alternating current and a pump motor in said mixing device, having a frequency dividing network controllable by a register whose contents may be incremented or decremented by a pulse from the high-low limit circuit.