Nivus OCM PRO CF, Инструкция по эксплуатации

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Instruction manual
OCM Pro CF
page 148 OCM Pro CF - Rev. 09 as of 07.06.2016
®
Auto calculation Automatic self-calculation is used as soon as, in addition to the standard
condition, lowest discharge volumes at very low filling levels (e.g. nightly
discharge, extraneous water or similar) are to be detected.
A prerequisite for the use of this function is that the application is
FREE OF
BACKWATER !
The detection principle is that the level in the channel decreases to a level
which no longer allows flow velocity detection. This happens with sensor type
POA as soon as the water level above the sensor falls below approx. 40-50
mm, with sensor type CS2 at a level of approx. 60-70 mm (2.36-2.76 in), with
sensor type CSM at a level of approx.10 mm (0.394 in).
Please make sure to reliably detect level 0 (e.g. by using an external level
measurement device, see also chap. 6.4).
If due to the constantly decreasing level (which hence at some point will be too
low) it is no longer possible to detect a flow velocity, the OCM Pro CF creates
an internal table of Q/h values by using the flow velocity value prevailing at the
minimum flow level h_crit (flow level which is barely sufficient to reliably detect
flow velocities) previously set. The exponent of the programmed channel shape
will be considered automatically to calculate this curve.
This table uses assumes a flow velocity corresponding with the measured level
for calculation even if this velocity cannot be measured any longer..
Due to hydraulic uncertainties this method may cause errors which may be
significantly higher than if measuring by using flow velocity and level.
The function is only appropriate for minimum rate measurements in channels
free of backwater and sedimentation and cannot be used apart from that! (risk
of partly significant measurement errors!)
Depending on the setting selected the entered values will be verified and cor-
rected if required in the course of the next measurement procedure (automatic
>YES<). Another possibility is to permanently use the value set in "v-critical"
(automatic >NO<). In this case however changes in flow behaviour e.g. caused
by roughness on the measurement point or changes in viscosity will not be con-
sidered. On the other hand possibly faulty measurement values, e.g. caused by
h_crit set too deep or vorticity, will not be saved at the moment of measuring and
hence will not be used for calculation below h_crit.
Fig. 9-154 Auto calculation
Manning-Strickler The theoretical discharge curve is calculated using the settings under
>Dimensions<, >Slope< and >Roughness<.
This function may be combined with the automatic mode (auto calculation YES).
This setting corrects the theoretical discharge curve after modifying the Strickler
coefficients.