| 摘要 |
The present invention relates to instrumentation and method for determining the distance between a dental probe located in a root canal of a tooth and the apical constriction. Two excitation signals are applied between the dental probe and an electrode located in electrical contact with oral mucosa and using these two signals comprising alternating voltages of different frequencies a signal is measured and a lower frequency signal is used to cancel errors due to media dependencies by applying an error signal obtained from a low frequency signal to the high frequency component using an analogue negative feedback system. The high frequency signal then contains all distance information and is error eliminated. Thus by sampling only the high frequency signal an accurate and stable measure of the distance is obtained. |
