Absorption tester having ports and trapezoidal enclosure with provision for eliminating bubbles from the optical test path

Abstract

Abstract 1,189,081. Photo-electric colorimeters. SWEDEN FREEZER MFG. CO. Feb. 12, 1968 [Feb. 13, 1967], No. 6739/68. Heading G1A. [Also in Divisions G2 and G3] The flow cell of a photo-electric colorimeter comprises an upper wall sloping upwardly from an inlet port to an outlet port and means at a lower level for defining the optical path and permitting bubbles entrained in the sample fluid to flow unobstructed along the inner surface of the upper wall, by passing the optical path. Dialysis effluent from an artificial kidney machine is tested for the presence of blood by passing it through a photometer chamber 18 from inlet 20 to outlet 24. The chamber has a sloping roof 18 to keep bubbles from the light path and baffles 34, 36 to prevent stray reflections. ' Light from a lamp 82 passes via ports 50 and 52 through the effluent to a measuring CdS photoresistor 102 and also directly to a reference CdS photo-resistor 94. The photo-resistors are connected in a bridge circuit, and any out of balance indicative of blood in the dialysis effluent is detected by an instrument relay and used to operate an alarm. Circuits for supplying stabilized voltages to the photo-resistors and a stabilized current to the lamp are described. (see Division G3). Spurious signals due to bubbles are ignored by a time delay which prevents actuation of the alarm until a blood signal has persisted for a predetermined time. Initial calibration is effected by adjusting a screw 93 in front of cell 94 and by adjusting resistances in the bridge circuit. Silica gel dessicant 96, 104 prevents misting of the ports 50, 52. When the apparatus is not in use, the meter and alarm circuits may be switched off without switching off components which would require a warm-up period.

Inventors

• 👤 Robert W Pierce

Bibliographic Details