An improved method and apparatus for monitoring and studying blood clotting times are disclosed. The method includes the step of passing a direct current through a blood or plasma sample and observing the electrical resistance of the sample during the clotting process. The electrical resistance, when plotted against time, is found to form a sigmoid curve having distinct inflections which signify the occurrence of both gellation and fibrin cross-linking within the clotting sample. The apparatus of the present invention includes a sample container which is preferably a disposable cup having a pair of electrodes suitably mounted in it and connected to an electrical connector. A current source is provided for supplying a constant current to the plasma or blood sample, and is equipped with an electrical coupling for mating with the connector on the disposable sample container. A chart recorder is coupled to the constant current source for providing a continuous indication of the sample resistance.
A measurement method for determining the state of coagulation of raw milk in a production process for, for example, cheese or yogurt. According to this method, the state of coagulation of milk can be determined by placing a metal wire in the milk and, while feeding an electric current continuously or intermittently to the metal wire, measuring the temperature of the metal wire over a given period of time.
Disclosed are several embodiments of a disposable sample card for testing fluids such as blood and the like. A generally planar card contains a chamber, or well and supports two insulated electrodes which terminate in the region of the well. Various electrode configurations are disclosed, each adapted to associate with an instrument for applying an electric voltage between the two electrodes, and across the sample under study. Also disclosed is an instrument for receiving the specially shaped sample cards.
A paraffin monitor includes a pair of probes which are immersed in a medium having paraffin contained therein. A circuit is connected to the probes which provides an output voltage. The characteristics of the electric circuit changes over a period of time, causing a corresponding change in the voltage output, in accordance with a change in the amount of paraffin on the probes.
The present invention provides a method for initiating a responsive signal to a predetermined processing condition. The method relies upon generating sufficient processing data about a desired processing condition to establish a processing profile reflective of the condition. The predetermined processing condition is indexed or inputted onto the profile which, in turn, allows for automatically initiating the signal when subsequent processes achieve the indexed condition. The method is particularly applicable for determining a proper curding point in a cheese manufacture using a control computer to store and compare an indexed processing profile with an on-going plant run.
Aggregation of blood-platelets is detected by using a test cell which contains two electrodes which extend into the sample. So as to maximize the change in resistance between the electrodes which occurs as platelets aggregate on them, they are each rod-shaped and of not more than about 0.25 mm in diameter. The resistance between the electrodes is detected using an AC signal to avoid polarization effects. The test cell may be constructed so as to be a disposable item.
