S7 Battery; S8 User Interface Pcb (Uif - Nellcor NPB-190 Service Manual

S7 BATTERY
S8 USER INTERFACE PCB (UIF)
S8.1 Regulated DC Power Supply
S8.2 Controlling Hardware
A lead-acid battery is used in the NPB-190. It is rated at 6 VDC 4 amphours.
When new and fully charged, the battery will operate the monitor for 12 hours. A
new battery will last 15 minutes from the time the low battery alarm is declared
until the unit is shut down due to battery depletion.
The battery can withstand 400 charge/discharge cycles. Recharging the battery to
full capacity takes 14 hours.
Change over from AC to battery power will not interrupt the normal monitoring
operation of the NPB-190. When the unit is running on battery power, the serial
port will be turned off along with the Nurse Call.
The UIF PCB is the heart of the NPB-190. All functions except the unregulated
DC power supply, display, and keypad reside on the UIF PCB. The following
text covers the key circuits of the UIF PCB.
The UIF PCB receives the Main_DC unregulated voltage of 7 to 18 VDC from
the Power Supply, or 5.8 to 6.5 VDC from the internal battery. The Power
Supply on the UIF PCB generates +10.0, -5.0 and +5.0 VDC.
Two microprocessors reside on the UIF PCB. The CPU is an Intel 80C196KC
(196) running at 10MHz. The second microprocessor is referred to as the PIC
and is controlled by the CPU.
CPU
The 196 is the main controller of the NPB-190. The 196 controls the front panel
display, data storage, and the SpO
controlled by the 196 with the exception of the Nurse Call. The user interface is
controlled by the CPU with the exception of the power button.
The SpO function is controlled by a pulse width modulator (PWM) function
2
built into the processor. PWM signals are sent to control the intensity of the
LEDs in the sensor and to control the gain of the amplifiers receiving the return
signals from the photodetector in the sensor.
Analog signals are received from the SpO
function in the 196 converts these signals to digital values for %SpO
rate. The values are then displayed and stored.
User's interface includes the front panel display and the keypad. By pressing any
of five keys on the keypad the operator can access different functions of the
NPB-190 (the power switch is not controlled by the 196). The 196 will recognize
the keystroke and make the appropriate change to the monitor display to be
viewed by the operator. Any changes made by the operator are used by the
function. Serial port communication is
2
circuit on the UIF PCB. An A/D
2
Technical Supplement
and heart
2
S-5