March 24, 2020

Portable Tiltmeter (MEMS) – Operating Principle & Taking Readings

Tiltmeters are used to monitor deflection, vertical rotation, and deformation in the diaphragm and retaining walls.

Encardio Rite Model EAN-70M is a portable tiltmeter that uses an anodized aluminium housing which contains an accurate accelerometer and suitable signal conditioning circuit.

Tiltmeters are used to monitor deflection, vertical rotation, and deformation in the diaphragm and retaining walls.

Encardio Rite Model EAN-70M is a portable tiltmeter that uses an anodized aluminium housing which contains an accurate accelerometer and suitable signal conditioning circuit.

The accelerometer picks up the force of acceleration due to gravity which reaches its highest when the accelerometer is rotated to full 90o tilt position and touches zero when the title angle of the accelerometer is 0o.

For other angles, the force of acceleration is calculated by equating the product of the sine of tilt angle to the acceleration due to gravity.
Portable-tiltmeter
The tilt sensor produces a bipolar DC voltage output proportional to the sine of tilt angle measured by the tiltmeter. The voltage output measures zero volts for a truly vertical sensor. The sensor presents a relatively low-cost tilt measurement solution with superior resolution, long term stability and low thermal sensitivity.

Tiltmeter is used to monitor the change in the tilt of any horizontal floor or vertical surface by setting it on a fitting tilt place, which is accessible separately.

The portable tiltmeter is not made for absolute determination of tilt of structures.A reference tilt plate is attached to the structure through which the change in the tilt of the structure is measured.
Once the tilt plate is mounted, initial tilt reading for each tilt plate is monitored and recorded. The change in the tilt of a structure is then calculated by subtracting the initial tilt reading from the subsequent tilt reading.

Tilt Plate

Tilt plate is a disc-like structure of 142 mm in diameter made from Aluminium. It is attached to the structure using a four Hilti anchors HPS 1-6/15×40 # 260350 or equivalent. If the structure has a smooth surface like marble or granite, the tilt plate is bonded to it by epoxy. The four pegs on the tilt plate are used to position the tiltmeter.
Tilt-plate
Horizontally mounted tilt plate allows tilt readings in two planes that are at 90o to each other. Vertically mounted tilt plate allows tilt readings along one vertical plane only.

Tiltmeter

Portable tiltmeter, as the name suggests is shifted from one tilt plate to another to monitor the reading. With the help of alignment bars which are provided on the front, the bottom, and the rear side, the tiltmeter is precisely placed on the tilt plate.
Horizontal-vertical-tilt-plate
For each tilt plate, the readings are taken twice. One reading in plus direction and another in the minus direction. The base of the tiltmeter has proper + and – marks to provide complete guidance.

Taking readings

Before taking the reading of the portable tiltmeter, allow it to be adjusted to the ambient temperature. If it is feasible, store the tiltmeter at the same temperature as at the time of taking the reading.

The next step is to connect the tiltmeter to the readout unit and switch it on. Take readings as stated.

Also Read: What is a Portable Tiltmeter & How is it Installed?

Reading horizontal tilt plates

  • The first step is to take the reading in plane A, the direction of which is determined by pegs 1 and 3. Place the “+” end of the on Peg 1, and capture the reading after stabilizing it. Rotate the tiltmeter 180 degrees to place the “-” end of tiltmeter on peg 1, and capture the reading.
  • Repeat the above the step at least 2-3 times to be assured that the correct readings are recorded. The “+” and the “-” reading should be identical except for their signs. With Encardio Rite Readout Unit, there can be a difference up to 0.0003 due to bias of sensor and small irregularities in tilt plate.
  • The above procedure for taking readings is illustrated in the pictures below.

  • The next step is to take the reading in Plane B, which is determined by the direction of pegs 2 and 4. Similarly, like the Plane A readings, place the “+” end of tiltmeter on peg 4, capturing the reading after stabilization. Rotate tilt meter 180o and place “-“end of tiltmeter on peg 4, doing the same.
  • The “+” and the “-” reading for plane B should be identical except for their signs. As with Plane A readings, there can be a difference up to 0.0003 due to bias of sensor and small irregularities in tilt plate.
  • The above procedure for taking readings is illustrated in the pictures below.

Horizontal-tilt-plate-plane-B
Reading vertical tilt plates

Similarly to the horizontal tilt plates, Vertical tilt plate’s readings are defined by the direction of pegs 1 and 3. Using alignment bars at the end of tiltmeter, the instrument is aligned.

  • The positive “+” end of the portable tiltmeter is placed against peg 1 while taking the reading.
  • Similarly, the negative “-” end of the instrument is located against the peg 3. The readings are taken after they are stabilized.
  • Repeat these steps three times to ensure that you have good repeatable readings.
  • Repeat the above steps two to three times to ensure readings are repeatable.
  • In theory, readings should be identical except for different sign (+/-). In practice, there is a difference up to 0.003 on Encardio Rite readout unit between two readings due to bias of sensor and small irregularities in tilt plate.
  • Refer the figures below to get a better understanding.

Reading-vertical-tilt-plate

This was all about Encardio Rite EAN-70M Portable tiltmeter operating principle and taking readings. If you have any doubts or queries, feel free to drop it in the comment section below.

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