13 Description Of The N20pa Portable Pulse Oximeter

The Nellcor N-20PA portable pulse oximeter provides noninvasive measurement of, and continuous information about, the percent of oxygenated hemoglobin compared with total hemoglobin and pulse rate. A pulse amplitude indicator provides a qualitative indication of pulse activity and patient perfusion. Patients are connected to the instrument by a Nellcor sensor. The sensor LEDs are driven by the SpO2 analog section, which also conditions the incoming signals, and provides CPU-adjustable gain...

2

Power Supply Power Control Circuitry Power supply circuitry is located on the auxiliary PCB and consists of the Batteries Four 1.5-V alkaline C size batteries provide 4-6 VDC power. Power control circuitry Power control circuitry is connected to the batteries. It senses any press of the On Off button and switches on the power supplies. Reverse current limiting protects the N-20PA from damage if batteries are inserted incorrectly. Power shutoff circuit This circuit controls power to all circuits...

22 Cleaning

The N-20PA requires no routine maintenance, routine service, or calibration. If service is necessary, contact qualified service personnel or your local Mallinckrodt representative. Use only Mallinckrodt-approved test equipment when running a performance test on the N-20PA. The user's institution, local or national agencies, or both may also require testing. Dampen a cloth with a commercial, nonabrasive cleaner, and lightly wipe the surfaces of the N-20PA. Do not spray or pour liquid on the...

27c1024l

The memory system external to the CPU consists of an 8 K x 8 static RAM (U14) and a 64 K x 16 EPROM (U15). The EPROM is 16 bits wide to enhance CPU performance. Because RAM is infrequently accessed, it is only 8 bits wide. U14 is a standard 8K x 8 static RAM. Test point TP 43 is used during testing to disable the output. The program that the CPU runs is stored in U15. U15 is a 16-bit wide output, one-time programmable (OTP) EPROM. During 16-bit wide bus accesses, the CPU uses address line AO...

44 Replacement Level Supported

The replacement level supported for this product is to the printed circuit board (PCB) and major subassembly level. Once you isolate a suspected PCB, replace the PCB with a known good PCB. Check to see that the trouble symptom disappears and the device passes all performance tests. If the trouble symptom persists, swap the replacement PCB and the suspected malfunctioning PCB (the original PCB that was installed when you started troubleshooting) and continue troubleshooting as directed. 4.5...

62

7.2 Repacking in Original Carton 7.3 Repacking in a Different Carton Should you need to ship the N-20PA monitor for any reason, follow the instructions in this section. Pack the monitor carefully. Failure to follow the instructions in this section may result in loss or damage not covered by the Mallinckrodt warranty. If the original shipping carton is not available, use another suitable carton or call Mallinckrodt Technical Services to obtain a shipping carton. Prior to shipping the device,...

96 Digital Circuitry

The digital hardware and related circuitry, which is illustrated in Figure 9-14, includes the following subsystems CPU A 16-bit microcontroller that includes a serial port, watchdog timer, A D converter with an 8-input analog multiplexer, 3-pulse width modulators, and a high speed I O subsystem. System memory System memory is external to the CPU and consists of an 8K x 8 static RAM and a 64K x 16 EPROM. Real-Time Clock (RTC) The RTC keeps track of date and time, which is printed on each...

961

The CPU circuit is illustrated in Figure 9-15, at the end of this section. The Intel 80C196KC CPU is a 16-bit microcontroller with built-in peripherals including a serial port, watchdog timer, A D converter with an 8-input analog multiplexer, three pulse width modulators, two 16-bit counter timers, up to 48 I O lines, and a high speed I O subsystem. The CPU is capable of running up to 16 MHz however, it is run at 10 MHz for decreased power consumption. All unused inputs are tied to either Vcc...

Adv

Momentarily click the On Off button 9O appears in (or shuts off) the Oxygen Saturation display. 2. Press the battery-check button bAt appears in the Oxygen Saturation display. 3. Press the printer ON button On appears in the Oxygen Saturation display. A printer test pattern prints out the following is an approximate example of the test pattern ABCDEFGHIJKLMNQP QRSTUVIiIXVZpz -0123456789 _ ', < > I IVFV VWWVW Examine the test pattern to verify that all dots print with a uniform darkness....

Ale

U13 and U33 are transparent latches that latch the address portion of the AD bus data on the falling edge of ALE the outputs are always enabled. The outputs of U13 and U33 are always the address portion of the AD bus. The address decoding circuit is illustrated in Figure 9-17. The CPU has a 64 Kbyte address range of 0-FFFF. RAM, EPROM, and I O ports share this space. The address decoding circuit splits up this space and output enable lines to the RAM, EPROM, and I O ports. U30A generates the...

C20

In order to achieve a specified level of oxygen saturation measurement and to still use a standard-type combined CPU and A D converter, the DC offset is subtracted from each signal. Because the DC portion of the signal can be on the order of one thousand times the AC modulation, 16 bits of A D conversion would otherwise be required to accurately compare the IR and red modulations between the combined AC and DC signals. The DC offsets are subtracted by using an analog switch to set the mean...

C63 01uf

Diode D8 is a photodiode that is used to measure ambient light. Q8, R68, and R136 provide current gain for D8's photocurrent. The amplified photocurrent flowing through R136 creates a voltage drop, which is measured by the CPU. The CPU continually monitors the light source output at AMB_LIGHT (TP72). Under low-ambient light conditions, the CPU automatically switches on the display backlight. The ambient temperature circuit is illustrated in Figure 9-29. TEMP SENSOR

Contents

SECTION 1 1.1 Manual 1.2 Warnings, Cautions, and 1.3 Description of the N-20PA Portable Pulse SECTION 2 Routine 2.3 Periodic Safety and Functional SECTION 3 Performance 3.2 Required Tools and 3.3 Performance SECTION 4 4.2 How to Use This 4.3 Who Should Perform 4.4 Replacement Level 4.5 Obtaining Replacement 4.6 Troubleshooting SECTION 5 Disassembly 5.2 Beginning 5.3 Disassemblying the Printer Flex Circuit SECTION 6 Spare 6.2 Spare Parts SECTION 7 Packing for 7.1 General

Darkest

Note The parenthetic line description is not printed. Button presses are ignored whenever the printer is printing. 1. Press the ADV button to change the darkness setting. The printer prints a line with each button press, and the setting increments from lighter to darkest and then wraps back to lighter. 2. Allow the N-20PA to switch off (about 30 seconds). The last printer darkness setting is remembered when the N-20PA is switched back on. Test this by repeating the procedure and skipping step...

Info

Momentarily press the DAY DATA button and verify that the 85 in the SpO2 display stops flashing and that the 40 Rate Default starts flashing. 26. Momentarily press the DAY DATE button and verify that the monitor returns to the normal monitoring display and indicates the live subject's saturation and pulse rate. 27. Press the MEASURE button until the monitor turns off. 3.3.2.3 Neonate Defaults and Alarm Limit Ranges The following procedure will allow verification of the monitor NEONATAL...

Tables

Table 4-1 Troubleshooting the (This page intentionally left blank) 1.2 Warnings, Cautions, and Notes 1.3 Description of the N-20PA Portable Pulse Oximeter This manual contains information for servicing the N-20PA portable pulse oximeter. Only qualified service personnel should service this product. Before servicing the device, read the operator's manual carefully for a thorough understanding of its operation. 1.2 WARNINGS, CAUTIONS, AND NOTES This manual uses three terms that are important for...

Test

BZ1, a piezo ceramic sounder, is the audio output device. Due to its low drive current of 2 mA maximum, no drive circuitry is needed and is driven directly from the external output port. The audio output device is differentially driven with 2 square waves 180 degrees out of phase. The drive frequency is approximately 1480 Hz or 740 Hz and is generated by the CPU. BZ1 is differentially driven to obtain maximum audible volume. The display control circuit is illustrated in Figure 9-23, at the end...

V

This circuit is illustrated in Figure 9-25, Power Supply Circuit. The batteries (VBAT) provide the input power for the high-voltage supply. The high-voltage supply is a switched-inductor voltage regulator (U26) that operates in conjunction with a capacitive voltage doubler to output 72 VDC 5 . To protect against a runaway voltage condition, CR25 clamps U26 output to a safe level. The analog reference voltage circuit is illustrated in Figure 9-27. U32 provides an accurate, regulated voltage that...

Vcc

Figure 9-17 Address Decoding Circuit U30B and U28 are used to generate the input port and output port active low enable signals EXINEN and EXOUTEN. When address lines A15, A14, A11, and A10 are high, and A13 is low, U28 becomes enabled. With U28 enabled, one of the 8 outputs is set low. The output to go low is selected by pins A, B, and C. They form a 3-bit binary number with pin C being the most significant bit. So when address line A12 is high, WR active (low) and RD inactive (high), a binary...

Low

The monitor must operate for at least 37 hours with no printer activity. 5. Verify that the LOW BATTERY indicator lights sometime after 35 hours of operation. 6. Verify that the LOW BATTERY indicator starts flashing after 36 hours of operation. 7. Verify that the monitor turns off approximately 1 hour after the LOW BATTERY indicator starts flashing. 8. Allow the monitor to continue operation until power-down due to low battery. Monitors with the same software must demonstrate identical startup...

Ds1202s

Figure 9-21 Real-Time Clock Circuit The RTC has two functions (1) it provides nonvolatile memory that is used to remember whether the printer should be enabled at power-on, and (2) to keep track of time and date for the N-20PA printer. The N-20PA does not require or use the RTC it is disabled via software. The RTC chip U29 uses a 3-wire synchronous serial interface to communicate with the CPU. The CPU brings signal RTC_RST high to activate communication with the RTC. RTC_CLK clocks data into...

Vref

The two variable gain circuits are functionally equivalent. The gain of each circuit is contingent upon the signals received level and is controlled to bring each signal to approximately 3.5 V. Each circuit uses an amplifier and one switch in the triple SPDT analog multiplexing unit U2. The gain in each of the circuits is accomplished by means of a feedback loop, which includes one of the SPDT switches in U2. The PWMs control whether the feedback loop is connected to ground or to the amplifier...

Tp78

Figure 9-9 Differential Synchronous Demodulation Circuit Figure 9-9 Differential Synchronous Demodulation Circuit The same line that controls the on off pulsing of the LEDs controls U6D, a single-pole-single-throw (SPST) analog switch. When either of the LEDs is on (the line is low and the switch is closed), U35 is used as a noninverting amplifier. When the LEDs are both off, U35 is used as an inverting amplifier. The signal at the output of amplifier U35 is then demultiplexed. The CPU HSO...

Test Results

3.3.2.2 Adult Defaults and Alarm Limit Ranges 3.3.2.3 Neonate Defaults and Alarm Limit Ranges 3.3.3 Hardware and Software Tests 3.3.3.1 Operation with a Pulse Oximeter Tester I certify that the monitor listed in this form has successfully passed all of these tests. Technician _Date _ I certify that the above signed technician has performed the tests listed on this form and the monitor performs satisfactorily. 4.4 Replacement Level Supported 4.5 Obtaining Replacement Parts This section explains...

601

Category 7 Watchdog-Timer Errors Error in the watchdog-timer circuit of the CPU (main PCB). Likely action is replacement of the CPU. Error in the printer. If a printer error condition occurs, the display reads Pr Err. See the Troubleshooting section for further information on this error. 5.3 N-20PA Disassembly Procedure The device can be disassembled down to all major component parts, including chassis enclosures Tools required small, Philips-head screwdriver small flat-head screwdriver WARNING...

24

Figure 5-4 Printer and Flex Circuit Assembly Figure 5-4 shows how to disassemble the printer and flex circuitry. 1. Remove the printer button stiffener (37). 2. Disconnect the two flex-circuit headers of the printer (29) from the connectors on the printer flex circuit (28) by slowly pulling them outward from side to side at alternating ends of the connectors. 3. Remove the printer button strip (7) from the printer flex-circuit. 4. Remove the printer flex-circuit insulator (24). 5. Remove the...

74hc573

U16 is the input port external to the CPU. The logic levels on the inputs (pins D1-D8) are output to the CPU via the AD bus while EXINEN is strobed low. All of the user control buttons are input via U16. Also, the battery type is senses via U16 a high on signal BAT_TYPE signifies to the CPU that rechargeable batteries are being used. If the optional printer head is in the home position, PR_HOME will be a logic high. Pin D8 (RTC_IO) and an output bit of the external output port are connected....

21

(This page intentionally left blank) 3.2 Required Tools and Equipment This section describes performance verification and safety testing for the Nellcor N-20PA pulse oximeter (monitor) and all options, following troubleshooting and repairs. The tests can be performed without removing the monitor cover. All tests except Battery Operation must be performed before the monitor is returned to the user. If the monitor fails to perform as specified in any test, repairs must correct the discrepancy...

85 Physical

Block Diagram Pulse Oximeter

8.5.1 Weight with batteries installed 19.0 cm high x 7.6 cm wide X 6.35 cm deep 7.5 in. x 3.0 in. x 2.5 in. This page intentionally left blank 9-1 Introduction 9-2 Functional Overview 9-3 Definition of Terms 9-4 Overall Block Diagram 9-5 SpO2 Analog Circuitry 9-6 Digital Circuitry 9-7 Circuitry Illustrations This Technical Supplement provides the reader with a discussion of the N-20PA circuits. This discussion is supported with applicable illustrations, including graphics that have been placed...

97 Circuit Illustrations

Circuits Diagram Oximeter Multisim

The foldout graphics referenced throughout the Technical Supplement text are as follows Figure 9-10 N-20PA HSO Timing Diagram Figure 9-13 AC Variable Gain Control Circuit Figure 9-23 Display Control Circuit Figure 9-32 Printer Interface Circuit Figure 9-34 N-20PA Main PCB Schematic Diagram Figure 9-35 N-20PA Auxiliary PCB Schematic Diagram Figure 9-36 N-20PA Flex Circuit Schematic Diagram This page intentionally left blank Figure 9-10 N-20PA HSO Timing Diagram Figure 9-13 AC Variable Gain...

93 Definition Of Terms

The CPU has a 10-bit A D converter on board. Up to eight different analog inputs can be provided to the A D converter for measurement. Central Processing Unit CPU . An Intel 80C196KC 16-bit microcontroller. The CPU sends and receives control signals to the SpO2 analog section, display, and optional printer. Content Addressable Memory CAM . The CPU controls the HSO lines with the CAM. CAM is controlled by software and programmed with events scheduled relative to...

N20PA Portable Pulse Oximeter

Caution Federal law U.S.A. restricts this device to sale by or on the order of a physician. To contact Mallinckrodts representative In the United States, call 1.800.635.5267 or 314.654.2000 outside the United States, call your local Mallinckrodt representative. 2001 Mallinckrodt Inc. All Rights reserved. 062153C-0701 Nellcor Puritan Bennett Inc. 4280 Hacienda Drive Pleasanton, CA 94588 USA Telephone Toll Free 1.800.NELLCOR