Users’ Manual
ESM-12S Digital seepage monitoring system
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The distance from the sides of the weir to the sides of the approach channel should preferably be at
least twice the depth of water above the crest, but not less than 30 cm.
The overflow sheet (nappe) should touch only the upstream edges of the notch.
The maximum water level in downstream pool should be at least 6 cm below crest elevation.
The head on the weir should be taken as the difference in elevation between the crest and the weir
surface at a point upstream from the weir.
The seepage sensor should be located at a sufficient distance upstream from the weir because the
flow at the brink of the weir is sloping down and curvilinear in nature. This curved surface/draw down
extends upstream a short distance from the weir notch. The head needs to be measured at a point,
beyond the effect of draw down. This distance must be at least four times the maximum head on the
weir. Thus, the seepage sensor is installed at a distance of 4~5 times the height of notch.
The seepage sensor position should be kept submerged in water, lower than the vertex of weir.
4.3 Installation of moisture trap assembly and junction box
As described earlier, moisture trap and junction box are supplied mounted on a wall mounting plate. This
assembly is installed near seepage sensor location.
Fix the wall mounting plate on a vertical surface/wall, near the sensor location, by means of the two
Hilti expandable fasteners HPS-1 5/5x25 or equivalent (see figure 4-2 and 4-3).
Check colour of desiccant in desiccant capsule. It should be blue. It needs changing if it is pink in color.
Remove cap from cable vent tube and plug from quick connect coupling at top of moisture trap
assembly. Insert cable capillary tube in quick connect coupling to make a secure connection.
Turn vent screw at bottom of moisture trap assembly to open it to the atmosphere. Ensure connectivity
between the vent tube running from inside the sensor to the outside atmosphere such that sensor
reading is unaffected by any change in barometric pressure (there should not be any sharp bend).
Air vent tube
from sensor
Digital signal
3 core cable
from sensor
Desiccant unit
(Moisture trap)
Wall mounting plate
Size: 150x300
Mounting holes Ø5
C/C: 130x280
3 core cable
to datalogger
Junction box
Quick fitting
connector for air
vent tube
Hydrophobic Filter
Expandable
anchor
HPS-1 5/5x25
Side View
(Only plate mounting)
Front View
Wall
A
B
C
A
B
C
Clamps
Vent screw
Figure 4-3 Wall mounting plate with moisture trap and junction box
