17
For making higher or lower concentrated H
2
S calibration solutions,
make reagent 1 more or less concentrated with Na
2
S .
r
e
-
calibration
Check the calibration at appropriate time intervals and repeat
it, if the sensor exhibits significant drift . When the sensor is
new, you may need to calibrate it every two hours . An older
extensively used sensor may require calibration only every 24
hours or less . To minimize the need for calibration, keep the
sensor polarized between measurements if possible (unless the
time between measurements exceeds several days) . If the signal
does not stabilize or remains too high or too low, refer to the
“Troubleshooting” section in this manual .
The response of the H
2
S microsensor does change with time, and
a decrease in signal of up to 50 % pr . month is to be expected . This
does not affect the quality of the measurements as long as the
sensor is regularly calibrated .
