cytiva pH/C-902 Instructions Manual - Page 8

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Fig 4. pH electrode cross-section

Conductivity cell

The flow cell has two cylindrical titanium electrodes positioned in the
flow path of the cell. An alternating voltage is applied between the
electrodes and the resulting current is measured and used to
calculate the conductivity of the eluent. The monitor controls the AC
frequency and increases it with increasing conductivity between
50 Hz and 50 kHz giving maximum linearity and true conductivity
values.
The conductivity is automatically calculated by multiplying the
measured conductance by the flow cell's cell constant. The cell
constant is pre-calibrated on delivery but can be measured with a
separate calibration procedure. This procedure is described in
Section
Calibrating the conductivity cell,
One of the electrodes has a small temperature sensor for measuring
the temperature of the eluent in the flow cell. Temperature variations
influence the conductivity and in some applications, when highly
precise conductivity values are required, it is possible to program a
temperature compensation factor that recalculates the conductivity
to a set reference temperature.
Fig 5. Conductivity cell – principle
8
.
Technical specifications
Operating data
General
Operating temperature
4 – 40°C
for monitor
Operating surrounding
2 – 30°C
temperature for cells
Surrounding humidity
20 – 95% rH
pH measurement
pH range
0 to 14 (spec. valid between 2 and 12)
Accuracy
temperature
±0.1 pH within +4 to +40°C
1
compensated
not temperature
±0.2 pH within +15 to +25°C
1
compensated
±0.5 pH within +4 to +40°C
Response time
Max 150 s (0-95% of step)
Long term drift
Max 0.1 pH units/8 h
(constant conditions)
Flow rate sensitivity
Max 0.2 pH units within 50l/h - 200 l/h
20°C
1
Calibrated for 20°C
Conductivity measurement
Conductivity range
1 μS/cm - 999.9 mS/cm
Deviation from true
Max ± 4 % or ±10 μS/cm, whichever is
conductivity value
greater, in the range 1 μS/cm –
300 mS/cm
Max ± 2 % or ±10 μS/cm, whichever is
greater, in the range 0,1 μS/cm –
100 mS/cm (at room temperature)
Reproducibility
short term
Max ±1 % or ±5 μS/cm
long term
Max ±3 % or ±15 μS/cm
Noise
±0.5% of full scale calibrated range
Response time
Max. 120 s (0 – 95% of step)
Temperature sensor
Accuracy
±2.0°C
Drift
±1%/10 h
Flow rate sensitivity
±1% within 50 l/h – 200 l/h 20°C
Flow cell data
pH cell
Cell sizes:
6 mm
For use in:
6mm Polypropylene systems
3/8" Stainless steel systems
10 mm
For use in:
10mm Polypropylene systems
1/2" Stainless steel systems
22 mm
For use in:
1" systems (PP and SS)
pH/C-902 Instruction 14003958 AB