122 Interface Meter: Field Measurements
- IMPORTANT: To meet safety requirements and to protect the electronics from damage, always ground the meter by attaching the grounding clip to the metal well casing or to a suitable ground rod.
- Push the ‘START/OFF’ button. Five brief tones and green light indicate that the meter is functional and the flashing green light indicates that the meter is on. The meter automatically turns off after 5 minutes. Press the ‘START/OFF’ button as necessary during operation to turn the meter back on.
- Place the slotted part of the tape guide onto the edge of the well casing. Lay the Interface Meter laser-marked PVDF flat tape into the groove on the top of the tape guide. Measurements are read at the V-notch on the tape guide.
- A steady tone and re light indicates a non-conductive liquid (e.g. product). An intermittent tone and red light indicates a conductive liquid (e.g. water).
- For floating product (LNAPL), take the air/product interface measurement on the way into the liquid, and the water/product interface on the way up. When passing through product into water, some product may adhere to the probe sensors due to surface tension. Therefore, when water is detected below product, the probe should be raised and lowered rapidly in a short vertical motion to remove any product that may have been carried down with the probe.
- The water/product interface should then be measured as the probe is raised very slowly back up. Once the interface is detected the probe can be raised and lowered in small increments to precisely determine the interface.
- Repeat measurements to confirm water/product interface.
- To determine the thickness of product, subtract the water/product interface from the product/air interface.
- To determine if there is any sinking product (DNAPL) in the well, continue lowering the probe slowly. If steady signals activate, determine the top of the sinking layer by reading directly from the PVDF flat tape. Continue lowering the probe slowly until the tape slackens when the well bottom is reached. Read the level directly from the PVDF flat tape and subtract one from the other to determine thickness.
- Upon completion of readings clean the tape and probe; as described in the Cleaning and Maintenance section.
When using the tape guide, remember to subtract the compensation factor stamped onto the side of the guide from each measurement.