Theory Of Operation; Introduction; Power Supply Board - Novametrix Medical Systems 515 Service Manual

Service Manual: Model 515
Theory of Operation:lntroduc
1.0 Theory of Operation
1.1 Introduction
The Novametrix Model 515 Pulse Oximeter is a non-invasive portable (
meter designed to provide reliable continuous measurement, display,
alerts for, oxygen saturation (Sa02) and pulse rate. The monitor can be p(
ered by AC line voltage or by its internal battery.
The Model 515 Pulse Oximeter utilizes sensors that contain two li
emitting diodes (LEDs) and a photodiode. Each LED emits a specific p
wavelength of light (660 and 940 nanometers) through a pulsating vasci
bed to the photodiode. Because oxygen saturated blood absorbs differ
amounts of light at each wavelength as compared to unsaturated blood,
amount of light absorbed by the blood in each pulse can be used to calcul
the ratio of oxygenated hemoglobin to total hemoglobin. This is displayed
Sa02. Pulse Rate is calculated by measuring the time period between detec
peaks of the waveform. The inverse of the time period, the frequency, is c
played as Pulse Rate. The oxygen saturation measurement and the pulse i
(beats/minute or bpm) are displayed on the monitor's Vacuum Fluoresc
Displays and are updated once a second. Presence of a pulse is indicated v
bly by a bar graph and audibly (user selectable) by a tone.
The Model 515 contains four main assemblies. These assemblies inch
the Power Supply Unit (PSU), the Digital Board, the Analog Board, and
Bezel Assembly (which includes the VFD Display, and the Membrane K(
panel). The operation of each is discussed in detail in this section, referet
the last section of this manual for the schematics and assembly drawings t
correspond to each discussion.
1.2 Power Supply Board
Circuitry for mains or battery operation, turn on control circuitry, isolai
supplies, and RS232 interface are contained in the power supply board. Ope
tion of the power supply board can be easily described in a block diagram n