INTERCONNECT CIRCUIT BETWEEN NON-COMPATIBLE OXIMETER AND SENSOR

摘要

An oximeter sensor adapter which allows a sensor without a resistor in parallel with its LEDs to operate with an oximeter expecting such a resistor in parallel. The adapter has a switching circuit which has inputs connected to the LED drive outputs of the oximeter. The switching circuit has two pairs of outputs, one connected to the LED drive lines of the sensor, and the other connected to a resistor in the adapter itself. The switching circuit is controlled by a sensing circuit which senses when a signal on the input lines drops below a predetermined level, such as 0.5 volts. The sensing circuit, in response to a low voltage (corresponding to an attempt to read a resistor in parallel with the LEDs), will provide a signal to a switching circuit. The switching circuit will switch the resistor onto the input lines so that it can be read. When a higher voltage returns to the input lines, the switching circuit switches back to the LEDs themselves.