近年來隨著抗凝血藥物的使用，藥物的副作用會使血液凝結時間不正常。因此監控凝血時間為當前重要指標，而如何使凝血時間監控更方便、快速且簡單，成為了現今凝血監控的一大挑戰。當凝血反應發生時，阻抗中大部分的變化都會被全血中的電容變化所等效，當阻抗的變化最劇烈時，便可以推出凝血反應時間，因此藉由電阻抗法來得到阻抗的變化。本文使用電阻抗法之自動平衡橋法監控人體凝血時間內的阻抗變化，但微量的血液與所相對應的較小阻抗變化會使凝血變化較難被偵測出來以及所選用的電極與血液反應的氧化還原現象皆為影響阻抗變化，因此高精準地量測系統及活性低的電極可以更有機會判斷出凝血變化。平衡橋法有高準確地量測誤差以及活性極低的金電極為測量血液電極，選用此架構來實現並與市售阻抗量測晶片AD5933比較量測精準度，最終實作量測自動平衡橋法與AD5933皆可達到誤差約5 %以內，驗證平衡橋法有相當的準確度。平衡橋法之設計可藉阻抗一階微分最大加速點判斷出凝血時間，藉由定頻100 kHz的訊號並透過電流互相抵銷，進而反推出待測阻抗值，其精準的阻抗範圍及快速的收斂時間，可準確的量測微量血液阻抗凝血變化，並與透光度法量測結果互相比較。目前電阻抗分析量測18管數據，相關係數為0.88，手撈與平衡橋電路量測凝血實驗平均誤差為2.6秒，運用此一量測凝血系統可以達到具有可攜式、成本低廉、使用簡單、直接偵測全血等功效，使其達到居家照護的概念。

With the usage of anti-clotting drugs in recent years, the side effects of drugs will make the blood-clotting time abnormal. Therefore, monitor the blood-clotting time becomes an important target nowadays , and it is a great challenge that how to make monitor easily、quickly and simply. It can be defined as PT time when the acute variation of impedance is measured. This thesis implemented the Auto-Balance Bridge of electronic impedance method to monitor changes of impedances in the human blood-clotting time. But the tiny impedance variation due to small amounts of blood will make it difficult to detect the PT time. The chosen electrode and reaction of Redox phenomenon will both influence the impedance variation. So the high accuracy measurement systems and low reactivity could judge the PT time with more probability. The design of Auto-Balance Bridge can calculate the blood-clotting time by the 1st differential equation of impedances. Through a fixed frequency (100 kHz) and canceling out the current each other, we can calculate the impedance of device under test (DUT). Compared with the method of light transmittance, the more precise range of impedances and faster coverage time of the Auto-Balance Bridge can measure the impedance of blood much more accurately for observing changes of blood-clotting time. We had measured data of 18 tubes of blood, the correlation coefficient is 0.888, the manual method and Auto-Balance Bridge circuit measuring the average error was 2.6 sec.

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