Ultrasonic Level Switches

This type of level switch uses ultrasonic sound waves to detect the presence of process material either solid or liquid at one point.

The Working Principle

Sound waves pass back and forth within the gap of the probe, sent and received by piezoelectric transducers. The presence of any substance other than gas within the gap detects the received audio power, thus signalling to the electronic circuit within the bulkier portion of the device that process level has reached the detection point.

Fig 1

Fig 2

In Fig 1, the sound passes through the gap when filled with liquid (wet gap).

In Fig 2, the sound cannot pass through an air-filled gap (dry gap).

The lack of moving parts makes this probe quite reliable although it may be become fooled by heavy fouling.

You can also read: The Working Principle of Ultrasonic Flow Meters

Some of the industrial applications of Ultrasonic level  switches include:

• Leak detection
• As an overfill alarm
• Detection of presence of liquids in pipeline
• Pump Protection
• Engine oil level control

The Components that make up a 4-20 mA Current Loop

The 4-20 mA current  loop is an important aspect of process measurement and control circuits. The important components that make up this loop are:

• The Sensor
• The Transmitter
• The Power Source
• The Loop itself
• The Receiver

The following diagram shows each component with its function:

This is a simple illustration of a 4-20 mA current Loop System.

 You can also read:

• How to wire a 4-20 mA current loop with a PLC

Don't miss out on key updates, join our newsletter list here.