Bayer HealthCare RapidPoint 400 Series Service Manual page 76

Simultaneously, a similar process is taking place with C16 and C21. U5 and
feedback resistors R35 to 38 form a differential amplifier with a gain of 51.
The HCT_SIG signal is the peak-to-peak voltage at HCT_HS minus the
peak-to-peak voltage at HCT_LS multiplied by a gain of 51.
Hematocrit circuit 2 is identical to the circuit 1, except that C50, a capacitor
AC, couples this hematocrit circuit to prevent a ground loop in the sample
path.
76 Rev. C