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13. Ensure the shroud is on all EC Probes. Place the probes in the stream in
moving, but not turbulent or aerated, water. Ideally place the Ch0 and
Ch1 probes on opposite banks, 10-20 channel widths downstream of the
point of injection. If not possible, then place one probe in the center of
the channel and the other on the near shore. If not possible, place one
probe near shore and the second probe 2-3 channel widths downstream.
a. If using Ch2 as the 3rd U/S Probe (this is the default if Ch2 is
active), then place it in moving, but not turbulent or aerated water
upstream of the point of injection and ensure it has >1min to sta-
bilize its temperature
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.
14. Wait for the EC.T and temperature to stabilize. It may be necessary to
lightly knock the shroud to release any entrapped air. Ensure there are
no upstream water inflows. This will show up as noise in the EC and likely
only on one channel. It may be due to unseen groundwater inflows. Push
the button to begin calculating the background EC.T
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. By default, QiQuac
uses a 15-point Pre- and Post- average for BG EC.T
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. The Post-BG EC.T is
a moving average of the last N points, thus the QiQuac will begin calcu-
lating the Post-BG EC.T immediately after the Pre-BG EC.T. The area under
the curve is calculated by either
a. The difference between the ECT trace and the line between Pre-BG
ECT and Post-BG ECT or
b. The difference between the ECT trace and the estimated BGECT
derived from the 3rd U/S Probe.
15. Inject the required amount of salt
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a sufficient distance upstream
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in
sufficiently turbulent flow
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.
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If not using Ch2 at all, then no changes are necessary if it was turned off or not present. The QiQuac will handle the SDIQ as a 2 probe scenar-
io. If using Ch2 as a 3rd D/S probe, after starting the measurement and Pre-BG N has reached zero, push the button again, select “Use 3rd U/S BG” from
the context menu. This will change the setting for the Displayed (either D or S) channel. If Ch2 is selected, the wording changes to “Use Ch2 AS 3U/S?”
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Note that if 2-3 EC.T probes are being used, turning the dial counter-clockwise will toggle the values between the channels. The currently
displayed channel is indicated by Ch0D, or Ch1D, or Ch2D for multi-plot display or Ch0S, Ch1S, or Ch2S for Solo display.
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The number of BG points can be changed in settings or from the context menu. More BG points should reduce the associated uncertainty, but
will require more time. Use 15-30 points if relying on the regression line, use 5-10 point is using the 3rd U/S sensor.
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The rule of thumb dosing guideline is 1 kg per m³/s and should not exceed ~5 kg per m³/s. There are more detailed dosing guidelines in the
references. The required amount can be reduced for lower BG EC.T values, or for shorter transit times. We built the QiQuac with the aim to reduce the
dosing to 0.1 kg per m³/s but often 0.2 kg per m³/s results in a Grade A measurement.
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A sufficient distance is typically 10-20x the channel width. This can be reduced for very turbulent reaches or where there is a constriction.
The mixing distance must be increased for less turbulent flow and may not work at all for calm flow. Placing one of the two EC.T probes in the channel
center and the other on the bank should help determine if complete mixing did not occur. Averaging the two derived Q’s should be more accurate than
if both probes are placed near the same bank.
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The salt should be injected in very turbulent flow. Ensure there is no salt left on the bottom of the channel. The salt can be injected slowly
over time or spread out over the channel width to assist in mixing. The salt can also be pre-dissolved in stream water before injection. In cold water
(<5°C) this is recommended.
C H A P T E R 3: OPE R AT ION
Содержание QiQuac M5
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