Uplift pressure measuring system
Users’ Manual
Rev. 0
Page 3-3
Summarizing, any variation in hydraulic pressure causes the diaphragm to deflect. This changes the ten-
sion in the wire thus affecting the frequency of vibration. Uplift pressure is proportional to the square of the
frequency and the read out unit is able to display this directly in engineering units.
3.2.3. Sp ecif icat io n s
Type:
Vibrating wire
Model:
TES-PU-20/21/22/23/24/25/26V
Range (kg/cm
2
):
3, 5,10,20,35,50, specify
Accuracy:
±
1 % fs; (non lin hyst repeatability)
Temperature limit
Operational:
-20 to 70
o
C
Compensated:
0 to 55
o
C
Over range limit:
150 % of range
Over range effect:
±
0.1% fs upto 150%
Enclosure:
Stainless steel, IP-68 enclosure
Read out:
Portable vibrating wire indicator
Thermistor:
YSI 44005 or equivalent (3,000 Ohm at 25
o
C)
3.2.4. D escrip t io n
The uplift pressure meter is manufactured in various capacities. Each transducer is provided with a ther-
mistor for making correction due to temperature induced frequency changes and the correlating data for
this is provided in the test report (see § 3.5). Thermistor may also be used to monitor the temperature.
A tripolar plasma surge arrestor inside the transducer housing protects the vibrating wire pluck and read
coils from electrical transients such as may be induced by direct or indirect lightning strikes.
3.2.4.1. Stainless steel body
The vibrating wire and coil magnet assembly is enclosed in a stainless steel body which is electron beam
welded to the diaphragm. This results in a vacuum of 1/1000 torr inside the sensor resulting in it becoming
immune to the effect of any ingress of water. As the uplift pressure meter is of stainless steel construction,
it is not affected by normal chemical corrosion at locations in which it is used. Once properly installed, it is
almost maintenance free.
Figure 3.2
3.2.4.2. Adopter
A ½” BSP adopter is provided for the pipe connection. The water oozing through internal pores or seams
in rock formations of dam foundations, mass concrete of structures, foundation soil of structures, re-
claimed land soil etc. percolates upward through the pipe to actuate the diaphragm.
