YSI 1500 Sport, User Manual, Page: 38 / 134

5 5 5 5----4 4 4 4
5.3 Measurement Methodology
The algorithm used to calculate results allows the SPORT to process samples as
quickly as possible while maintaining high accuracy and reliability. The result is
calculated from a group of four readings, depending on the chosen operational
mode:
•
Initial baseline current
•
Sample / Calibrator plateau current
•
Reference plateau current (Auto mode only)
•
Calibrator concentration value current
For initial calibration, 25 microliters of calibration standard is dispensed into the
chamber, which already contains approximately 500 microliters of buffer. The
sensor response increases until it reaches a plateau, approximately 30 seconds.
The reference pump then flushes the chamber for approximately 33 seconds and
the sensor response changes to a different value. At this point the instrument
calculates the relationship of the known standard to the reference solution and
stores this information until another calibration injection is performed. The
Buffer Pump then flushes the chamber for approximately 33 seconds and the
sensor response decreases to the normal baseline value.
During each subsequent sample cycle, the reference solution is again measured
and then internally compared to the reference solution concentration measured
during the initial calibration. If a variation exists, the calculation of the sample
concentration will be compensated accordingly.
The profile of probe current response is shown in Figure 5.3 (Auto Mode) and
Figure 5.4 (Manual mode).