Solinst® Interface Meter Model 122

Solinst Oil/Water Interface Meters give clear and accurate measurements of product level and thickness in wells and tanks.

Determination of both light (floating) non-aqueous phase liquids (LNAPL) and dense (sinking) non-aqueous phase liquids (DNAPL) is quick and easy. The factory-sealed probes are pressure proof and tapes are available in a range of lengths from 65 - 1000 ft (20 - 300 m).

The 5/8" (16 mm) diameter P1 Probe allows easy access through tight spaces and into narrow wells. The Probe is designed for use in various monitoring applications.

Hazardous Locations Use

The Model 122 Interface Meter has been approved by the Canadian Standards Association (CSA) for use in explosive environments. It is suitable for use in hazardous locations Class I, Groups C&D.

The grounding strap is a safety essential when the meter is used in potentially explosive environments. It also ensures that the electronics are properly protected.

Operating Principles

Product (Non-conductive liquid) = Steady light and tone
Water (Conductive liquid) = Intermittent light and tone

To detect liquids, Solinst Interface Meters use an infra-red beam and detector. When the probe enters a liquid the beam is refracted away from the detector which activates an audible tone and light. If the liquid is a non-conductive oil/product the signals are steady. If the liquid is water (conductive liquid greater than 50 µ/cm), the conductivity of the water completes a conductivity circuit. This overrides the infra-red circuit, and the tone and light are intermittent.

Both sensors use exactly the same zero point, giving accuracy as good as 1/200 ft or 1.0 mm. The high accuracy enables the sensors to detect the slightest sheen of oil on the surface of the water; this is indicated by a rapid intermittent tone.

Mini Interface Meter Model 122M

The 122 Mini is a convenient small version of the Solinst Interface Meter, small enough to fit in a backpack. A custom carrying bag is also an option.

The Mini is available in 65 ft or 20 m lengths. The 5/8" (16 mm) diameter probe is attached to narrow 1/4" (6 mm) tape, which is accurately marked each 1/100 ft or millimeter. Enhanced electronics allow operation for up to 300 hours of on-time, using one 9V battery.

Close block

Accurate, Reliable, Robust

  • Designed for rugged field use
  • Stable electronics with automatic circuitry testing
  • Sturdy free-standing reel with carrying handle
  • Tape uses stranded stainless steel conductors:
    • non-stretch; does not corrode
    • resists kinking and breaks
    • easy to repair and splice


  • Sensor accuracy to 1/200 ft or 1.0 mm
  • Certified intrinsically safe
  • 5/8" (16 mm) diameter probe
  • Easy access batteries: minimum 120 hours of life
  • Automatic shut off after 10 minutes
  • Inexpensive, simple repairs
  • 3 year warranty

Interface Meter Model 122

Mini Interface Meter Model 122M