HyQual Multi-probes User Manual v3, 08.07.2022
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5.
Access your app’s calibration function by navigating from the Home Screen to
the calibration
section. Select the parameter to be calibrated, and then enter the calibration value in the type-
in box, and press enter. When the reading has stabilized, press enter to calibrate. The HyQual
probe will report the resulting Sensor Response Factor (SRF; see below). For most apps, you
then press Y to accept the calibration, N to back up one step, or Exit to leave the sensor uncali-
brated.
7.3.2
Sensor Response Factor (SRF)
Near the end of the calibration routine, you will be asked to
accept or decline the calibration based on the Sensor Re-
sponse Factor (SRF). Suppose that a “typical” Conductivity
sensor puts out 100 μA in a 1413 μS/cm standard. If your
Conductivity sensor reports 100 μA in that same calibration solution, then your SRF is 100% (some
pa-
rameters, such as pH, have a more complex SRF calculation, but the effect is the same). If your response
is 80 μA, your SRF would be 80%. When you press the OK button to accept a calibration,
the HyQual
probe automatically accepts your calibration if the SRF is between 60% and 140%. If the SRF falls out-
side that range, you will be cautioned to check your standard value, make sure the sensor is clean, make
sure the reading has stabilized, etc. But you can elect to accept any SRF.
7.3.3
Choosing Calibration Standards
For best results, choose a calibration standard whose value is close to what you expect to see in the
field. For example, calibrate with a 1413 μS/cm Specific Conductance standard if you expect to see Spe-
cific Conductance readings between 500 and
1000 μS/cm in the field. Calibrating with a sea water stand-
ard or a very low standard would not be appropriate. Similarly, if your waters tend toward the acidic,
calibrate with a 4-buffer instead of a 10-buffer.
If you are moving The HyQual probe across wide ranges of water conditions, you may wish to recalibrate
to match the new situations. For instance, if you are measuring a clear lake during the morning and a
high-sediment stream in the afternoon, you might consider recalibrating at noon with a high-value tur-
bidity standard.
The table below shows common calibration practices.
Table 1
–
Common Calibration Practices
Sensor
Standard Method of Calibration
Available Calibration Solutions
Comments
Temperature
never requires calibrating
N/A
pH / pH reference
2 or 3 points
pH 4, pH 7, pH 10
pH7, pH 10 most common
ORP
1 point
ORP Standard 200 mV
Conductivity
1 point
CD Standard, 0.5 Molar, 58670 Micro S
CD Standard, 0.1 Molar, 12856 Micro S
CD Standard, 0.01 Molar, 1412 Micro S
CD Standard, 0.001 Molar,147 Micro S
brackish/saltwater
borderline brackish typical
freshwater very pure
fresh/glacial
Reference Electrode
calibration not required
N/A
replace pH electrolyte
solution at routine
calibration
Depth
adjust for barometric pressure
N/A
recalibrate at deployment
site for best accuracy
