Hoefer DQ300 - Manual (Page 27)

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8. What is the %FS (% of full scale) of blank and
calibration standard?
Press <DIAG> and <ENTER> to display the %FS
values (see 3.8 on page 14). If you calibrated the
instrument with the highest concentration stan-
dard and the %FS of the standard is too close to
the %FS of the blank, you might be reading the
samples out of the instrument’s detection limit.
5.2 High or Over Reading
Dilute samples and standards.
5.3 Fluctuating Results
1. Check for spills in the sample compartment.
2. Check the volume of the sample.
The minimum volume is 2 mL for a 10 × 10 mm
cuvette, or 50 µL for a Minicell.
3. Check if the reagents and cuvette material are
compatible.
4. Check temperature (see 4.3 on page 17).
5. Confirm that the %FS STD is greater than %FS
BLK by factor of 2 or 3.
5.4 Solid Standard
The optional Solid Standard can be used to deter-
mine if the instrument is functioning properly.
The Solid Standard is designed to effectively
verify the stability of the instrument or if any
instrument settings have been changed. After
calibration, insert the Solid Standard into the
sample compartment of the DQ300 Fluorometer
(Note: always insert it with the tab away from
you), and record the reading. You can check the
calibration or the stability of the instrument by
reading the Solid Standard again in the future.