Siemens SC 7000 Service Manual page 36

Service Manual
7.3 LCD Backlight Invertor
Interface
7.4 Ambient Light
Interface
7.5 Local Rotary Knob/
fixed Keys Interface
7.6 Battery/power LED
Interface
8 MultiMed Front End
8.1 Introduction
8.2 Safety
20
• ambient light sensor
• base unit rotary knob and keypad interface
• battery and power LED's
• Jumper for selecting LCD power voltage (currently +5V)
The Backlight circuitry for the LCD backlight is resident on the front bezel
board. The backlight inverter converts VBUSS power from the main board
to the high voltage ac power used by the backlight. The voltage may be
controlled by a digital PWM input supplied by the processor board.
The base unit's ambient light sensor is mounted on the front bezel board.
The ambient light sensor is a photocell that exhibits a logarithmic change
in resistance vs. light intensity. The ambient light sensor is connected in
series to a 2kΩ potentiometer which is used to calibrate the ambient light
sensor at the factory.
The SC 7000 and SC 9000XL base units each have twelve fixed keys. An
additional key is dedicated as the power on/standby switch. The rotary knob
interface provides a 2-bit encoder output and also a rotary knob push button
signal output. All of the key/rotary knob signals are filtered. All of the keypad
switches have pulldowns except the power on/standby switch. Thus, the
power switch signal output from the Front Bezel board is pulled up by the
power switch interface located in the power supply section.
The battery LED is turned on or off via the associated LED control signal
from the main board. The power LED is connected to +5V. Both the battery
and power led's are green when turned on.
The power and battery LED's have been integrated into the membrane
switch interface used for the fixed key and power on/standby switch. The
LED on/off control signals are provided by the base unit's power supply
section. Thus, the LED control signals originate in the power supply,
The MutiMed front end section of the main board combines 6-lead ECG, 2-
lead respiration, temperature, and saturated oxygen data gathered by the
MultiMed Pod from transducers at the patient and converts them to digital
form for transmission through isolators to the computer section of the main
board. This section also houses the NBP pressure transducer which uses
the same acquisition system. See
The hardware design uses a single oversampling 16 bit converter to
measure all of the parameters. This allows bulky analog filters to be
replaced by software filters. Careful shielding and filters protect against
very high frequency interference from upsetting measurements.
• Patient isolation withstands 5kV during defib.
• Leakage currents are limited to safe values normally and during single
fault conditions.
• Patient is protected against electrosurgical burns at the electrodes.
• Defibrillation protection does not drain excessive current away from
the patient.
Siemens Medical Systems, EM-PCS, Danvers
NOT A CONTROLLED DOCUMENT
SC 7000 and SC 9000XL Patient Monitors
Figure 2-8 on page 21.
ASK-T898-03-7600
7k9kXLTM.c2.CD_ROM.fm/04-99/kaupp