Endress+Hauser Analytik Jena multi N/C, Руководство по эксплуатации, Страница: 28 / 106

Function and setup multi N/C pharma UV
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3.4 Calibration
3.4.1 Calibration strategies
For most applications a single point calibration is permitted for the multi N/C pharma
UV – the blank value of the device is low and the NDIR detector linear.
To minimize sources of error during a single point calibration due to an incorrect
standard preparation, the following procedure is recommended:

Preparation of 3 standards with identical concentration

Measuring these standards

Calculation of the calibration curve from the mean of these standards
When using a single point calibration the blank value of the preparation water must be
taken into account.
For some applications a multiple point calibration with
variable metering volumes
and constant concentration can also be used.
A standard solution for the range to be calibrated is prepared measured for different
volumes in accordance with the settings in the selected method. The lowest volume of
1.6 ml must not be fallen below.
The calibration should be verified using a second independently prepared standard to
preclude the incorrect preparation of the calibration standard.
For measurements in the range of low concentrations (< 10 mg/l) the blank value of
the preparation water must be taken into account.
Especially for measurements in the lower concentration range (< 1 mg/l) a multiple
point calibration with variable metering volumes and constant concentration can be
used.
The syringe pump is highly linear. Due to the large metering range of the syringe
pump a wide calibration range can also be covered.
A multiple point calibration with constant sample volume and variable
concentrations can also be carried out.
The concentration series for the ranges to be calibrated are prepared and the settings
measured in the selected method. The calibration range should be defined in
accordance with the expected sample concentrations.
3.4.2 Day factor
Via the day factor it is possible to check and correct the calibration with a standard
solution. All subsequent measurement results are multiplied by this factor.
The day factor is calculated in accordance with the equation (3).
𝐹𝐹 =
𝑐𝑐
𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛
𝑐𝑐
𝑛𝑛𝑎𝑎𝑎𝑎𝑎𝑎𝑛𝑛𝑛𝑛
(3)
Single point calibration
Multiple point calibration
with constant
concentration
Multiple point calibration
with constant sample
volume