Servo gauge level transmitters are unique in that this type of level sensor uses the principle of displacement to measure level. Their high accuracy makes them very popular in custody transfer and inventory control. Endress+Hauser and Honeywell have most of this market tied up, but you can still find other companies competing. So let’s talk about how a servo type gauge level transmitter works.
The device makes contact with the product using a displacer connected to a measured wire around a wire drum. It counts the rotations of the drum, then calculates the distance to the displacer when it touches the product’s surface. It detects the surface by monitoring the change in the displacer weight as it begins to float. The drive motor adjusts the displacer’s position as the level changes.
The wire drum works with a stepping motor, which comes in a few different flavours. Some vendors have patented products that use magnetic couplings between the drum and the motor. How these types of level sensor find their level can vary depending on vendor and technique, but the principle remains the same.
As an added bonus, a servo level transmitter can measure interface, spot, and profile densities!
This video will show you more about these types of level sensor: