Dangerous-electricity annunciator and detector

Investigations into electrical accidents in hospitals have shown that the hazards are usually associated with the simultaneous use of two or more instruments. Recognizing this, several groups have written safety standards which limit the allowable potential difference between any two conductors near or connected to the patient. Implementing such a standard may be difficult since there may be a large number of such conductors and they must be tested using all combinations of two conductors. A simple scanning circuit using programmable operational amplifiers (PRAMs) and MOS digital circuitry makes the series of safety checks quickly and efficiently. The design includes both the ability to detect dangerous conditions and a digital annunciator to indicate which of the many leads being checked simultaneously is at fault. The scanning rate is rapid enough to allow the detection of dangerous transients. Preliminary results indicate that this portable, battery operated device is useful in providing an electrically safe environment for patients.