HyQual Multi-probes User Manual v3, 08.07.2022
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4.
Wait a few minutes for the temperature to equilibrate and the sensor to arrive at a steady read-
ing.
5.
Follow the calibration instructions on the screen.
7.3.11
Depth and Vented Depth
Depth is measured by a strain-gauge transducer as hydrostatic water pressure. The deeper you go in
the water, the higher the pressure.
HyQuest
Solutions’
Depth sensors are usually buried inside the instrument, with a small pressure port
that can be seen on the outside of the HyQual probe bottom cap. They require no regular maintenance,
but you might check occasionally to make sure the pressure port is not clogged. If it is, use something
soft, like a toothpick, to clear the port of obstruction.
Depth calibration is nothing mor
e than “zeroing” the sensor in air, where one assumes the water depth
to be zero:
1.
Make sure the HyQual probe is not in the water.
2.
Open the Calibration menu and select “Depth”.
3.
Now just follow the calibration instructions on the screen.
Please notice that the Depth sensor cannot distinguish between water pressure and the air pressure
over that water (i.e., barometric pressure). After you have zeroed the sensor, any change in barometric
pressure will be measured as a change in water pressure.
Another choice is using Vented Depth (Stage). Vented Depth uses the same transducer as does Depth,
except that there’s a
small hole in the back of the transducer. There is a tube inside the cable (i.e., a
Vented Cable) to connect the Stage sensor to the atmosphere so that changes in barometric pressure
will not affect the Depth reading.
Vented-Depth cables have a desiccant-filled housing at their surface end. The desiccant keeps water
from condensing in the vent tube by letting vapor escape through a small Gortex patch. Keep that hous-
ing clean and replace the desiccants every year.
7.3.12
Turbidity
Turbidity is measured as the fraction of an infrared light beam that is scattered at 90° to that beam.
More particles in the water mean more of that light is scattered, so the Turbidity reading is higher.
Any material that accumulates on the optical surfaces of the Turbidity sensor is indistinguishable from
material in the water, so most Turbidity sensors have little wipers to clean the window(s).
Turbidity sensors require no regular maintenance, but you might check occasionally to make sure the
optical window (i.e. the little glass port on the front of the sensor) has not been damaged by overzeal-
ous wiping.
Turbidity uses a two-point calibration; one point is zero turbidity and the other point should be a stand-
ard approximating the turbidity of the water you intend to monitor.
Make sure you use enough calibration standard to cover the sensor’s “optical volume” –
imagine a golf
ball stuck on the end of the sensor; make sure there are no objects in the volume represented by that
ball. One common method is keeping calibration solutions in one-litre, dark, wide-neck bottles with a
non-reflective finish (such as Nalgene 2106 bottles in amber).
For the zero calibration:
