Swan Analytical Instruments AMI Turbiwell, Руководство оператора

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AMI Turbiwell
Instrument Setup
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4.3. ppm Calculation, e.g. “Oil in water”
Note:
If ppm is chosen, the matching and verification function is
not available.
General The AMI Turbiwell is also suitable for the measurement of other liq -
uids of which the turbidity correlates with the concentration of a sus -
pended solid or an emulsified liquid. In such applications, the
turbidity is normally displayed in ppm. Not recommended for drinking
water applications.
A submenu allows the user to perform a calibration of such process -
es.
The calibration line is defined by 2 points: zero point and a scale
point (slope). For the determination of the zero point, a sample with -
out the opacifier (x = 0) must be supplied to the AMI Turbiwell. The
average value over a defined time period is automatically saved as
the zero point.
For the determination of the slope, the AMI Turbiwell must be sup -
plied with a sample with a known concentration of turbidity material
(opacifier). The concentration of the opacifier must be entered into
the transmitter (i.e. 2.5 ppm). The average value over a defined time
is automatically saved as a slope (scale point).
The calibration line is calculated from this data.
Note: Two restrictions regarding this calibration method must be
considered:
• The reading is only valid if the zero does not change. This
means that the background turbidity which is caused by
different properties or different suspended solids must be
constant!
• In general, the correlation of the displayed value (ppm) and
content of the opacifier is only approximately linear in a limited
range. Due to that fact the sensitivity is strongly dependent on
the chosen concentration (scale point). If the scale point is
chosen so that it is close to a limit value or a control point (i.e.
setpoint), the error caused by non-linearity in this range can be
minimized.
It must also be taken into consideration that the turbidity of a sample
does not only depend on the concentration of the suspended solid or
emulsified liquid, but also on the drop size, respectively, particle size
distribution function. This property of the sample should not differ
substantially.