Reactive Air Level Monitor

The Reactive Air Level Monitor by Tesco Controls, Inc., is a trapped-air fluid level monitoring instrument designed for application in most liquids and slurries in wastewater, storm water, and fresh water systems. This technology offers and elegantly simple solution for measuring fluid levels with extreme reliability and accuracy, in liquids containing up to 30% solids.

TESCO’s Reactive Air Level Monitor consists of a compression bell connected by a sensing tube to a remotely mounted pressure transmitter. The principal of operation is based on the fact that a change in fluid level outside the bell will compress the trapped air column proportional to the change in fluid level.

Small changes in level within the bell, correspond with a significant change in pressure at the pressure transmitter providing superior accuracy. An integral compressor is used to purge the compression bell. During the purge cycle, the level seen by the pressure transmitter is frozen using onboard electronics. A solenoid valve automatically isolates the pressure transmitter from the sensing line during the purge cycle, eliminating undue shock to the pressure sensing element.

TESCO’s Reactive Air Level Monitor is immune to solids build-up and inaccuracies resulting from foaming or fluid separation. Since no electronics or electrical conductors are used between the bell and the pressure transmitter, high noise immunity is realized.


  • High suspended solids level measurement, including raw sewage (up to 30% solids)
  • Wet well level measurement
  • Open tank or basin level measurement


  • Simplified operation
  • Increased system reliability
  • Cost-effective
  • Simple installation
  • No maintenance

Standard Features

  • Choose from 120VAC or 12VDC
  • High-strength polymer bell resists corrosion and material build-up
  • Not susceptible to inaccuracies due to foaming or solids build-up
  • Self-cleaning utilizing manual or auto purge
  • High noise immunity
  • Operation can continue without power for compressor, for up to 30 days
  • Wide variety of pressure ranges available
  • Compression bell can be mounted up to 1000 feet from pressure transmitter
  • Output hold during purge, with adjustable duration
  • Optional surface mounted cabinet
  • Optional digit display provides visual indication of measured level
  • Optional manual purge switch


Standard Level Range 0 to 35 feet, optional ranges available
Operating Voltage 120 VAC or 12 VDC
Temperature Range 0 to 200 ° F
Accuracy +/-0.125 inches
Repeatability 0.2%
Interface Two wire analog current loop 4-20mA