Roche Diagnostics April 2007
A-34 Service manual · Version 2.0
4 Description of modules 91xx pH/Electrolyte Analyzers
Description of modules
Valve drivers The solenoids are activated by transistors Q9 - Q13. To open the solenoid, a 0.5-
second pulse of 22 V is applied, then the voltage drops down to 12.5 V (16 V on the
9110) to hold the solenoid open.
Pump motor driver/cover sensor The pump driver circuit IC U9 and IC U10 provide the drive and control for the
peristaltic pump. Signals PUMPEN, Pump Enable and PUMPSTEP, Pump Step Pulses
enable IC U10 to provide the necessary control to driver IC U9 which supplies pump
drive signals PHASE A through PHASE D to control peristaltic pump operation.
IC U11 operates with signal DCLOSED from the sample door light gate to provide
signal DOOR which detects the status of the sample door (open or closed).
Input amplifiers IC U13, U14 and U15 (9110/9180/9181: U13 only) provide high to low input
impedance matching for each Electrode input. Offset generator IC U12D and
amplifiers IC U12A, U12B and U12C provide the necessary gain and offset for each
electrode channel. TP9, TP10 and TP11 provide test points for the Na
+
(TP9: pH on
the 9110), K
+
and Cl
–
/Ca
2+
/Li
+
channels respectively.
9110 only: IC U300 is used as the input amplifier for the reference electrode, IC U12A
is used for the subtraction of the reference electrode signal from the pH electrode
signal. For sample detection, the reference electrode is switched to ground (relay
K300) during aspiration.
Temperature sensor This circuit is used in the 9110 pH Analyzer to amplify the signal of the temperature
sensor in the preheater. This is an optional circuit which is used in the 9140, 9180 and
9181.
The circuit creates a temperature-dependent voltage which is converted by software to
degrees Celsius. R54 can be adjusted for correct temperature display.
Analog channel selector and A/D
converter
Analog inputs from the input amplifiers are selected via signals ADSEL0 through
ADSEL2 and are multiplexed by IC U19. This multiplexed signal is then fed to the A/
D Converter IC U20. IC U21 supplies the necessary reference voltage (2500mV) for
the A/D Converter and can be measured at TP14.
Microprocessor Microprocessor IC U31, EPROM IC U25 (9180/9181: U40) and MOSTEK Real Time
Clock/RAM IC U22 form the components of the central processing system. IC U23
Address Demultiplexer, IC U24 Programmable Array Logic (PAL) and IC U28
provide serial data buses (9180/9181: U23, U24 and U28 not present). IC U34
through IC U38 convert serial data to parallel data and provide printer data, display
data, solenoid valve control and peristaltic pump control (9110: U34 not present).
This fashion of serial to parallel data conversion is used to prevent analyzer lock-up by
peripheral devices. The RS232 serial interface is a direct input/output from the
microprocessor utilizing interface driver and receiver U29 and U30.
SnapPak Sensor (9180/9181
only)
Optical detector ISO1 provides a signal indicating if the ISE SnapPak™ is in place.
This signal is fed to U41 which converts the light gate input to a digital logic output
indicating SnapPak position (IN or OUT).
Lamp board
The lamp board contains the LED array used to illuminate the measuring chamber
and the interconnectors used for all solenoids, the peristaltic pump, door sensor and
sample turntable (9181 only). A ribbon cable from the SBC Board supplies the
electrical connection for each signal through connector JP6.
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