The Study Of Blood Coagulation Detection Technique Based On Magnetoresistive Sensor

In the recent years the research of hemostasis and thrombosis is paid more and more attention. Currently most of the blood coagulation analyzers in the market adopt coagulation method to carry out the measurement. According to the theory of the coagulation method it can be classified two types, one is the measure with photoelectricity nephelometric analysis; another is the measure with double coil and a magnetic steel ball. The method of scattered light turbidmetry and the method of transmitted light turbidmetry are two sorts of the measurement with photoelectricity nephelometric analysis. But via the instruments using optical system we can't get the precise result as to the blood plasma of high blood fat, jaundice or haemolytic blood and this kind of instrument has already tended to be eliminated. The theory of measurement with double coil and a magnetic steel ball is to respond the condition of blood coagulation according to the movement of the magnetic steel ball in the blood. As the ball movement reducing the induction current produced by cutting the magnetic force line also reduces, and then we can get the change of the induction current which response the concretion characteristics. This means can resolve the interference problem of high blood fat, jaundice and haemolytic blood completely. This technique has already applied for patent in many nations currently, and the blood coagulation analyzer produced by its principle is very expensive.In the paper a new kind of blood coagulation detection technique based on magnetoresistive sensor is introduced. The principle is that the magnetoresistive sensor is used to detect the track of the magnetic steel ball, and then according to the magnitude of the ball movement we can get the time of blood coagulation.In the system we adopt a small, low cost, high sensitivity and high reliability magnetic sensor. According to its patent on-chip set/reset straps to reduce effects of temperature drift and electric circuit parameter drift. We use the SCM to control the ball movement time and the measurement time, thus weaken the electromagnetism interference and simplify the design of the amplifier. At the process of blood plasma coagulating the ball movement route reduced gradually along with the rising resistance, correspondingly the geomagnetism change produced by the movement of the ball also reduced, so according to magnetoresistive sensor we can get the wave that response the movement of the magnetic steel ball in the blood plasma, and then the blood coagulation time is able to be obtained. Now, the device for the experiment has been constructed, and our measure is proved to be correct.Above all, this method is simple, rapid, accurate, cheap, sensitive and good in repetition, and might be a valuable method for blood coagulation detection in the clinical laboratory.