How Is Vibrating Wire Piezometer Installation Done?

Vibrating wire piezometer is used to measure the pore pressure in heavy structures like earth/rock fill dams and mass concrete during construction and for long term monitoring after construction is over.

The vibrating wire piezometer installation procedure requires complete knowledge and assistance. Before starting with the procedure, let’s first look at the list of tools needed for the installation.

Tools & Accessories Required for Vibrating Wire Piezometer Installation

1. Soldering iron 25 watt
2. Rosin 63/37 solder wire RF-3C, 30 swg
3. Thread sealant (Loctite 577 or equivalent)
4. Cable jointing compound
5. Acetone (commercial)
6. Spanner 20/22 and 26/28 and pliers 160 mm
7. Hacksaw with 150 mm blade
8. Cable Cutter
9. Surgical blade with holder
10. Wire stripper
11. Bent nose plier (internal)
12. Pouring funnel
13. Stainless steel rod 5 mm φ, 150 mm length and Spatula
14. Rotary tin cutter
15. Fixture for jointing up to six piezometers
16. Toothbrush
17. Cloth for cleaning (lint less)
18. Geo-textile bag (150 mm x 250 mm) with integral tying lace to contain the piezometer
19. Digital multimeter
20. EDI-51V portable readout unit

Vibrating Wire Piezometer Installation Procedure

Preparation of sensor before Vibrating Wire Piezometer installation

Here are the general instructions for Encardio-rite Vibrating Wire Piezometer Model EPP-30-V.

• To give access to the four-pin terminal, it is required to remove the cable joint housing from the cable end of the sensor. The terminals marked with red and black colors are internally wired to the coil of the magnet assembly which, exists inside the sensor. On the other hand, the other two terminals are used to measure temperature with the help of a thermistor. The terminals can be cleaned using a toothbrush.

NOTE: Acetone can be used to clean the sensor except the terminals. Using acetone for cleaning the terminals as it destroys the glass to the metal seal.

| Also Read: Vibrating Wire Piezometer — Types and Operating Principle

Checking the working of the sensor

• The coil resistance measured by a digital multimeter between the red and black pins should lie between a particular ranges for each kind of Vibrating Wire Piezometers. For Model EPP-30V, the resistance should lie between 120–150 Ohm. On the other hand, for Model EPP 40-V and VW Piezometer EPP-50V, the resistance should lie between 130–170 Ohm. It is important to determine the resistance at room temperature from the thermistor temperature resistance chart. To judge the resistance accurately, it should be equal to the resistance between the pins marked green and white. For example, if the room temperature is 25oC, the resistance would be 3,000 Ohm.
• Make sure that the resistance between any lead and protective armor is greater than 500 M Ohm.
• The next step is to connect the sensor with Encardio-rite Model EDI-51V Portable Readout Unit and switch it on. The display should show the reading in the following manner- Freq: 2629.8 Hz. The frequency measure may vary according to the transducer connected to the indicator.
• When working with vibrating wire piezometer installation, the initial reading (offset) of the frequency displayed on the portable readout unit should be stable.
• A cross-check can be done for Encardio Model EPP-30V to verify whether the sensor is reacting to the changes in pressure. This can be done using the following steps:
• With the help of a locking nut spanner, remove the filter of the vibrating wire piezometer.
• Put pressure on the diaphragm using your thumb. Verify whether the frequency reading on the indicator decreases.
• The change in the reading assures that the pressure on the diaphragm is successfully transmitted to the vibrating wire sensing element.
• Every Encardio-rite sensor is provided with a test certificate which lays down the relationship between output and applied pressure. To start with this procedure, change the readout unit display to frequency2 mode.

The Zero Reading in Frequency2 for Vibrating Wire Piezometer Model EPP-30V and EPP-40V should not vary from current zero reading by more than 100 (x 103) divisions and 250 (x 103) divisions respectively after consideration made for the difference in temperature, barometric pressure, height above sea level, and [Continue Reading…]