48
sure the standard covers the sensor entirely, and that it also covers the thermistor for those parameters that are
temperature-compensated.
6)
Watch the parameter readings until they have stabilized.
7)
Select the parameter to be calibrated by clicking on the calibrations button in the Scuba manager home screen,
then clicking on
Calibrate
, and then clicking on the parameter you wish to calibrate. For parameters that have
two calibration points, you will specify which you wish to calibrate (usually high or low). Enter the calibration
value and click on
OK
. The Scuba will report the resulting Sensor Response Factor (SRF); then click on
OK
to
accept the calibration or
Quit
to leave the sensor uncalibrated. (4.5)
8)
Each sensor calibration’s Sensor Response Factor (SRF) is automatically logged into the
Cal Record
with the
details of that calibration.
7
Can I use calibration solutions more than once?
If your QC protocol requires fresh calibration solutions for every calibration, then you might as well discard the once-
used solutions. If not, then your sensitivity cost and accuracy will determine whether you can re-use calibration
solutions. If, for instance, you really want your field conductivity readings to be within 1% of reading, then fresh
conductivity calibration solution, which is not very expensive, should be used for each calibration. If you are not so
keen on turbidity accuracy, then you can probably reuse your turbidity calibration solution once or twice because it’s
pretty expensive. (4.3)
8
What standard should I use to calibrate SC? What type?
For any parameter, use a calibration standard that is near the highest reading you anticipate in the field. For instance,
if your lake usually runs about 1000 µS/cm, then calibrate with the readily available 1413 µS/cm KCl standard. Note
that some sensors (not SC) have two calibration points; the second point should be set at a convenient low point,
usually zero. (4.3)
9
What is the different between calibrating % sat or milligrams per liter for DO?
Percent saturation tells you how much oxygen you have compared to how much you would have if the water were
saturated with oxygen. Milligrams per litre tells you just that: how many milligrams of oxygen are dissolved in one
litre of water. For instance, if your Scuba was reading 6.0 mg/l and the saturation tables told you that at that
temperature, salinity, and barometric pressure the saturation value was 8.0 mg/l, then your % sat would be 6/8 =
75%. You can use either measurement, or both, but % sat is helpful during DO calibration because it should always be
100%. (4.7)
10
What is the different between the Amco Clear turbidly standard and StablCal?
Amoco Clear is made of polymer beads while StablCal is a formazin compound. Most people want their turbidity
measurements referenced to formazin, and so use formazin or StablCal for calibrations. The polymer beads are
cheaper and more stable, BUT you must know the equivalent formazin value for any polymer bead standard. You
cannot rely on what’s written on the polymer-bead label; you must check it with your own instrument after it has
been calibrated with formazin or StablCal. (4.13)
11
How do I calibrate blue green algae?
There are several ways to calibrate fluorometers. Please read Standardizing Eijkelkamp’s Turner Fluorometers and
please read Calibrating Eijkelkamp’s Turner Fluorometers; they can be found on the Eijkelkamp flash drive. (4.14)
12
What is a good SRF?
Generally, and SRF between 80 and 120 is good, and 60 to 140 is acceptable. It your SRF is outside those limits, you
should check your standard value and the maintenance condition of your sensor. (4.5)
