Novametrix Medical Systems 515 Service Manual page 24

Theory of Operation:Analog Board #2288
Service Manual: Mode
A2
Al
AO
Channel Select
I/O Address
(HEX
0
0 0
INI AO
0
0 1
IN2
Al
0
1 0
IN3
A2
0
1 1
IN4
A3
1 0 0
IN5
A4
1 0
1
IN6
A5
1 1 0
IN7
A6
1
1 1
IN8
A7
Before a channel is read the address is written to A0-A2 lines anc
ALC (Address Load Control) and SC (Start Conversion) lines are brc
high. When the conversion is complete (25 psec) the EOC (End Of Co;
sion) pin will go high to inform the processor that the value can be used.
The REE+ line is tied to VREE+ and the REE- line is tied to ai
ground, this gives a digital value of 0-255 for the input range 0 - -i-4.1
The analog input range must never exceed the limit of -0.3 to -i- 5.0 volts c
chip will be damaged. In order to guarantee this, inputs to channels 1, 2, 4
6 are taken from IC12. This is a quad, single supply operational amplifier v
is supplied by -i-5.0 volts. Therefore the outputs cannot exceed the limi
ICll. Channels 3 and 5 are limited to approximately 4.7 volts by IC21 pin
13, 14, D6 and R39. Input channels 7 and 8 of ICll monitor levels whicl
referenced to -i-5 volts, this keeps the maximum level present to the ii
within limits.
The channel numbers and their corresponding input signals are listec
low.
CHANNEL SIGNAL
INI
IN2
IN3
IN4
IN5
IN6
IN7
IN8
AC NOISE
DC NOISE
RED DC
RED/IR AC
IRDC
V BATT
PROBE DETECT
VLED DETECT
NOTE:
In Production Test Software the displayed channel number in the SATURA
display does not correspond to the numbered channels listed above, reference section 2.6.
1.4.10 Noise Detection Circuits
Two channels of the A/D converter (ICll) are used to detect noise it
photodiode's signal. One channel (CH 1) detects AC noise which would 1