Level Measurement

# Principle, Installation and trouble shooting of capacitance type level transmitter

## Principle of capacitance type level measurement:

A capacitance type level transmitter is a device used for measuring the level of liquids or solids in a tank, vessel or container. It works by utilizing the principle of capacitance, which is the ability of a system to store electrical energy in an electric field.

## How does capacitive pressure transmitter work?

In a capacitance type level transmitter, two electrodes (often referred to as “plates”) are placed in close proximity to the material whose level is to be measured. One electrode is kept at a fixed distance from the material, while the other electrode is connected to a movable probe. As the level of the material changes, the distance between the two electrodes also changes, causing a change in capacitance.

This change in capacitance is then converted into an electrical signal and transmitted to a control system or a display unit, which can then be used to determine the level of the material. The accuracy and reliability of a capacitance level transmitter are dependent on several factors, such as the material properties of the electrodes, the frequency of the electrical signal used, and the stability of the environment in which the measurement is taken.

Capacitance type level transmitters are widely used in a variety of applications, including chemical processing, oil and gas production, water treatment, and food and beverage production.

## What is the formula for capacitance level?

A capacitor made by two parallel plate electrodes has a capacitance of

Where,

C = capacitance

δ = dielectric constant of the insulating material

A = effective area of the conductors

d = distance between the conductors

1) Directly proportional to electrode area “A”

2) inversely proportional to the plates’ separation (d).

3) Directly proportional to the dielectric ‘ä’ placed between them

The metal container wall surrounding the level sensor and its probe form an electrical capacitor when the vessel is empty. This initial capacitance happens between the electrode level sensor and the metal wall. This capacitor’s value rises when the sensor is submerged in liquid, and the capacitance change is detected and transformed into an output signal proportionate to the capacitance change.

An incompletely or completely insulated flexible or solid rod probe is used depending on the application’s needs. The electronic capacitance current and transducer are located in the probe head.

## Installations and wire connection

• Carefully unpack the level indicator.
• Check that you have all the necessary equipment and tools, including the transmitter, a mounting kit, conduit, wiring, and appropriate electrical fittings.
• Choose a spot on the tank for the probe where there is the least amount of turbulence.
• Probe should be placed so that material doesn’t flow directly onto it.
• Make sure that the level transmitter’s process connection matches the one on the tank.
• The reference electrode or the side of the tank should be parallel to the sensing electrode.
• With the required gasket and bolts, secure the probe unit to the tank.
• In the event that an electronic device is installed outside, it is necessary to protect it from direct sunlight by enclosing it in sheets.
• When putting the flexible probe into the tank, do it carefully because rough handling could damage the probe and its insulation.
• According to the provided wiring code, connect the level transmitter.
• Connect the 24 VDC power to the appropriate polarity (+ve and ve) for the input power.
• The output may be examined by connecting the multimeter in series as shown below. This loop-powered transmitter can be linked to a PLC or a process controller.
• The transmitter is factory calibrated, so it doesn’t need to be calibrated, but if it does, follow the steps below.

## Troubleshooting of capacitance type level transmitter:

Here is some of the common troubleshooting guideline for a capacitance type level transmitter

### Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

Check Also
Close