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Two photo sensing elements generate a photocurrent proportional to the amount of
light. These currents are then converted to the voltage signal in the I/V converters.
These voltage signals will then be sent to the signal processing circuit where their
Balance will be precisely converted into the digital signal corresponding to the
refractive index.
This digital signal will go through (1) Sensitivity calculation, (2) Response time calculation,
(3) Auto Zero / Base line shift calculation, (4) Range attenuation for recorder output
and (5) Event Marker processing in that order and will finally be converted back to
analog signal for integrator output terminal and recorder output terminal.
The signal processing circuit does also following jobs:
① Parameter settings via Display or Keyboard (Recorder Range, Integrator Sensitivity,
Temperature Control, Response Time, Polarity, Base Line Shift).
② Commands requested via Keyboard (Purge On / Off, Event Marker and Auto Zero :
Optical Auto Zero is carried out by activation of the null Glass driver and fine
adjustments are made through calculation).
③ Execution of commands given via external device (e.g. purge on / off,auto zero).
④ Displaying data and status information such as Refractive Index, Temperature.
⑤ Signal outputs (displays various error messages such as Temperature control,
Light Intensity control, Auto Zero and contact closure signal for output terminals).
⑥ Data display and setting for maintenance.
⑦ LAN communication processing.
Light Intensity Control circuit controls a load current to the light source to keep
intensity signal (sum of the two I/V converters output voltage) constant.
This feature prevents unexpected reductions in detector sensitivity due to such
problems as dirty flow cells, decreased lamp intensity.
Based on the data from temperature sensors of the optical system and the external
heater plate, the temperature control circuit adjusts the current in the heating
elements (transistors) so that the temperatures of the optical system and the external
heater plate reach their designated values.