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1. Introduction ______________________________________________________
The Geokon Model 4675LV Weir Monitor is designed for the measurement of water
levels in streams, weirs, flumes, etc., where accurate measurements of very small
water level changes are required. The unit consists of a vibrating wire from which is
suspended a hanging cylindrical weight partially submerged in the water. As the water
level rises and falls, the buoyancy forces acting on the weight change causing
changes in the tension and vibrational frequency in the vibrating wire. Level changes
of as little as .001” can be measured. Ranges of up to 10’ are available.
2. Installation Procedures _____________________________________________
2.1. Preliminary Checks
Before installing the weight cylinder, there is an orange colored spacer which
lies between the base of the sensor and the nut on the hook assembly, this
needs to be removed. (This releases the tension in the sensor wire –put there as a
safety precaution to protect the sensor from damage during shipment.)
The gage and weight assembly can now be checked out on site by connecting the
sensor to the readout system and measuring the output of the sensor with the weight
hanging from it in air. The readings [in Readout box channel “B”] should coincide
within about 200 digits of the factory reading in air shown on the calibration sheet. Be
sure that the sensor is held firmly and allow the system to stabilize (no swinging of the
weight). Detach the weight after this preliminary check.
Always handle with great
care to prevent breakage
.
2.2 Installation
If the 4675LV is used in a weir box, a stilling-well is required. The stilling-well is
provided by Geokon, in the form of a slotted, 3 inch or 4 inch PVC pipe. This stilling
well must be installed in a
vertically plumb
position in an area where there is little
turbulence and positioned in such a way that
the bottom of the weight is slightly
lower than the tip of the V notch,
It is important that the well be vertical, because
any friction from the weight rubbing along the well will influence the sensor output
The installation is made by using two pipe-straps to hold the stilling well in place. Two
spacer bars are provided to hold the stilling well away from the wall so that the stilling
