Calibration

# Calibration of level trol – Displacer level meter calibration

A level trol is used to measure and control the level of a tank, where the tanks are in the isolated area.

The displacer level transmitter works under Archimedes principle. A force measuring mechanism senses changes in the buoyant force and converts this force into an indication of level.

## Calibration of level transmitter:

Uncovered picture of transmitter:

The basic procedure used in this calibration is the same for any type of displacement level transmitter. It is possible to calibrate this unit using weights instead of the sensor. You will calibrate the transmitter using water to set the required level.

Remember the final calibration must be done on the job. This final calibration depends on where the transmitter is fitted.

There is wet calibration and dry calibration. And usual for all transmitter there are zero adjustments for low liquid level and span adjustment for displacing immersed in the liquid which is maximum level.

### Wet calibration:

#### zero:

When the water level is below the bottom of the displacer, set the zero adjustments. Check that the output gauge reads 3 psi.

#### Span:

1. Fill the displacer housing with water until the level is above the displacer. Adjust the S.G. dial until the output reads 15 psi
2. Repeat zero and span steps until both are correct.
3. Raise the water level until it reaches the centre line (L) The output pressure should be 9 psi
4. 0%, 25%, 50% , 75% & 100%. Mark on chamber.Fill up & Drain water to check 0%, 25%, 50% , 75% & 100%. Check output.Check function two three times.

### Dry Calibration with Weights:

Using weights, find out the weight of the displacer first and arrange weight similar to the weight of the displacer.

#### Zero:

For 0% Hang displacer or weight equal to the weight of displacer on torque tube arm rod. Adjust Zero to 3 psi
Span:
For 100% Hang weight= Displacer weight – Volume X Specific gravity.

For the volume of displacer:  3.14 X r² X h

h is height, here it is Length of Displacer. Do the span procedure for 25%, 50%, 75% 100%, by changing the weight by subtracting weight ÷ 4 weight from hanging weight for each 25% step.

### Sivaranjith

Instrumentation Engineer