Oximeter red and IR zero calibration control

• US 20050187449A1
• Filed: 02/25/2004
• Published: 08/25/2005
• Est. Priority Date: 02/25/2004
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Inventors: Petersen, Ethan, Chew, Bradford B., Shea, William
• Granted Patent: US 7,373,192 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes

Abstract

A pulse oximeter with drive lines for driving red and IR LEDs, and a drive circuit for driving those drive lines. A processor controls the drive circuit using a red zero output line and an IR zero output line directly connected between the processor and the drive circuit. This allows a control signal to directly control the turning off of either the red or IR drive transistors to prevent forward current flow through the red and IR LEDs by overriding the ongoing programmable logic state machine control of the drive transistors. The effects of crosstalk and capacitive coupling are reduced as a result.

Claims

1. A pulse oximeter comprising:

a red drive line for a red light emitting diode (LED);

an infrared (IR) drive line for an IR LED;

a drive circuit coupled to said red and IR drive lines;

a processor for controlling said drive circuit, said processor having a red zero output line and an IR zero output line coupled to said drive circuit, wherein a control signal on said zero output lines turns off a red or IR drive transistor providing forward current flow through said red and IR LEDs, respectively.

2. The pulse oximeter of claim 1 further comprising:

a logic circuit, having inputs connected to said red and IR zero drive lines, and outputs providing control signals to said drive circuit.

3. The pulse oximeter of claim 2 wherein said logic circuit is programmed.

4. The pulse oximeter of claim 2 wherein said red and IR drive transistors comprise red and IR source transistors and red and IR sink transistors in an H-bridge arrangement coupled to a return line from said red and IR LEDs.

5. The pulse oximeter of claim 3 wherein said LEDs are arranged back-to-back, such that said drive line for said red LED is said return line for said IR LED, and said drive line for said IR LED is said return line for said red LED.

6. A pulse oximeter comprising:

a red drive line for a red light emitting diode (LED);

an infrared (IR) drive line for an IR LED;

a drive circuit coupled to said red and IR drive lines;

a logic circuit, having inputs connected to red and IR zero drive lines, and outputs providing control signals to said drive circuit; and

a processor for controlling said programmed logic circuit, said processor being coupled to and driving said red zero output line and said IR zero output line, wherein a control signal on said zero output lines causes said programmed logic circuit to turn off a red or IR drive transistor providing forward current flow through said red and IR LEDs, respectively.