Circuit Description; Amperometric Circuits - Bayer HealthCare RapidPoint 400 Series Service Manual

Output Signal
ID_PWR
ID_RET

Circuit Description

Amperometric Circuits

Because the amperometric circuits (oxygen, glucose, lactate, and
creatinine) are nearly identical, a description of only the glucose circuit is
provided.
The glucose sensor connects to P1-5, P1-6, P2-5, and P2-6 on the Contact
board. This sensor requires that a bias potential be forced to exist on P1-6,
with respect to P1-5 and P2-6 of -400 mV.
Pin 1 of U9 forces a voltage on GLU_CN until the voltage sensed on
GLU_RF equals REFV_GLU. The voltage on REFV_GLU is -400 mV, with
respect to 5_RTN_GLU.
Limited by a diffusion rate, the electrode reaction dominates the current
output. The concentration of glucose in the sample limits the diffusion rate,
so that the output current is proportional to the glucose concentration in the
sample.
Another current output, GLU_WA, is from the inactive electrode of the
sensor. This current corrects the glucose signal current for interfering
substances and for diagnostics. To prevent leakage currents from
corrupting the electrode current output, the entire electrode current output
net is guarded by 5_RTN_GLU.
The oxygen sensor does not have an inactive output, so that
NOTE:
circuitry is deleted.
74
Description
Power supply for the EEPROM in the sensor module. It
supplies +5.000 V ±5% at a current of 5 mA. This signal is
generated on the Multiplexer board and is a pass-through to
the sensor module.
Power supply return signal for the EEPROM. This is a pass-
through signal from the Multiplexer board to the sensor
module.
Rev. C