Solinst 122M Interface Meter

Quick guide from the manual

The Solinst 122M Interface Meter is designed for measuring groundwater and surface water levels, specifically detecting the interface between water and non-conductive liquids (LNAPL or DNAPL). Before use, always perform an equipment check and ensure the meter is properly grounded to the well casing or a grounding rod to prevent damage or explosion from flammable gases.

Operating Principle

The meter uses a narrow 5/8" (16 mm) diameter probe and a laser-marked PVDF jacketed cable. An infra-red circuit detects liquid presence, while a conductivity circuit differentiates between conductive liquid (water) and non-conductive liquid (LNAPL or DNAPL product).

Equipment Check

Before heading to the field, verify the meter is functional:

• Press the 'On/OFF' button.
• A brief tone and red light indicate the meter is functional.
• The meter automatically turns off after 10 minutes to preserve battery life.

Field Measurements

1. Push the 'On/OFF' button to activate the meter.
2. Lower the probe into the well. If using a tape guide, lay the cable onto the groove on the top.
3. Measurements are read at the point of the V-notch on the tape guide. Remember to deduct 2/10 ft or 6.0 cm.
4. A steady tone and light indicate a non-conductive liquid (product). An intermittent tone and light indicate a conductive liquid (water).
5. For floating product (LNAPL), take the air/product interface measurement on the way into the liquid.
6. Measure the interface between LNAPL and water by raising the probe slowly.
7. To check for sinking product (DNAPL), continue lowering the probe slowly. If steady signals activate, determine the top of the sinking layer.
8. Continue lowering until the cable slackens at the well bottom to determine total depth.

Cleaning and Maintenance

Proper maintenance ensures the longevity of the probe and cable:

• Cleaning: After each use, wipe the cable clean and rewind it. Wash the probe with a non-abrasive mild detergent and lukewarm water. Do not use solvents. Use a soft cloth around the pins and prism. Rinse with distilled water and wipe dry.
• Battery Replacement: If tones become weak, replace the 9V alkaline battery. Push the battery drawer in and up, then pull out to eject. Ensure correct polarity during replacement.

General Tips

• Always use the grounding cable.
• Do not drop the probe.
• If storing for longer than two months, remove the battery to avoid leakage.
• The meter may sound when directed toward sunlight; this is normal and does not affect operation in a monitoring well.