The GEOKON 1900-11-150M (Model Code: 1900-11-150M / Model 1900 Series Reed Switch Settlement Probe) is a high-precision geotechnical vertical displacement and subsurface settlement monitoring instrument manufactured by GEOKON (USA) with 100% USA Origin. Pairing a high-sensitivity hermetically sealed reed switch probe with an accurate 150-meter polyethylene-jacketed steel measuring tape, this system accurately identifies the depth and settlement elevation of magnetic targets positioned inside subsurface access casings.

OPERATING PRINCIPLE:
The probe is lowered through an internal PVC access pipe or grooved Inclinometer casing. When the probe traverses the magnetic field generated by external magnetic targets (such as Spider Magnets anchored in soil strata, Plate Magnets at fill interfaces, or bottom Datum Magnets anchored in bedrock), the magnetic field actuates the internal reed switch. This closes the electrical circuit, instantaneously activating an audible buzzer and a bright visual LED indicator on the cable reel. The operator observes and records the exact depth marking on the precision graduated tape directly at the casing top collar to millimeter accuracy.

KEY PRODUCT FEATURES AND OPERATIONAL ADVANTAGES:
1. High-Tensile 150m Polyethylene-Coated Flat Steel Tape:
Constructed with a non-stretch stainless steel core ribbon encased in an extruded, wear-resistant Polyethylene (PE) jacket. Permanently marked with sharp millimeter (mm) graduations that resist abrasive friction, eliminating stretch errors across the entire 150 m depth profile.
2. Corrosion-Proof Stainless Steel Reed Switch Probe:
Machined from heavy-duty stainless steel to withstand high subterranean hydrostatic pressures. The internal glass-encapsulated reed switch delivers crisp, bounce-free contact closure, ensuring repeatable target center detection within ±1 mm.
3. Dual Audible & Visual Alert System (Buzzer & LED):
The cable reel faceplate features a loud audible buzzer and a high-luminosity LED for easy detection in bright outdoor sunlight. An integrated sensitivity control potentiometer allows fine-tuning for varying groundwater mineralization levels.
4. Heavy-Duty Industrial Aluminum Reel & Brake:
Built on a rugged aluminum stand with a smooth winding drum, an integrated friction drag brake to prevent uncontrolled tape spooling, and an onboard probe storage holder.
5. Standalone 9V Battery Operation:
Powered by a single, widely available 9V DC alkaline battery, delivering hundreds of hours of continuous field surveys and allowing tool-free on-site battery replacement.

TYPICAL GEOTECHNICAL APPLICATIONS:
• Stratified Foundation Settlement: Monitoring consolidation settlement rates across individual soil layers under highway fills, runways, and reclamation sites.
• Embankment Dams & Levees: Tracking internal core deformation and differential settlement profiles during staged reservoir impoundment.
• Large Storage Tank Foundations: Measuring vertical settlement profiles beneath large crude oil, water, and LNG storage tank pads.
• Deep Excavations & Tunnels: Detecting baseline heave at the bottom of deep urban foundation pits and monitoring ground convergence surrounding tunnel alignments.

• Manufacturer: GEOKON
• System Designation: Reed Switch Probe with Measurement Tape (Model 1900 Series)
• Model Code: 1900-11-150M
• Brand Origin: USA (100% USA Origin)
• Primary Function: Magnetic extensometer settlement and heave monitoring
• Measuring Tape Length: 150 meters (150 m)
• DETAILED COMPONENT SPECIFICATIONS:

1. REED SWITCH PROBE:
• Sensor Type: Hermetically sealed glass reed switch
• Housing Material: Stainless Steel
• Probe Diameter: Ø 19 mm (0.75") or Ø 16 mm (0.625")
• Probe Length: Approx. 150 mm to 190 mm
• Positional Repeatability: ±1 mm (±0.04")
• Ingress Protection: Submersible IP68 (Rated for continuous subterranean water head)

2. FLAT STEEL MEASURING TAPE:
• Standard Length: 150 m
• Construction: Non-stretch high-tensile stainless steel core with extruded Polyethylene (PE) coating
• Internal Conductors: Twin stranded stainless steel/copper conductors
• Graduations: Millimeters (mm), Centimeters (cm), and Meters (m)
• Scale Accuracy: Standard engineering tolerance (±1 mm over full length)
• Tensile Integrity: High resistance to stretching and mechanical elongation

3. CABLE REEL & INDICATOR MODULE:
• Reel Frame Material: Powder-coated cast aluminum / heavy-duty structural polymer
• Indicators: Loud audible buzzer + High-intensity red LED indicator
• Sensitivity Control: Rotary potentiometer for fine threshold adjustment
• Reel Brake: Integrated mechanical friction brake
• Power Supply: Standard 9V alkaline battery (NEDA 1604 / 6F22)
• Battery Life: Hundreds of operating hours in field conditions

4. ENVIRONMENTAL & ACCESSORY SPECIFICATIONS:
• Operating Temperature: -30 °C ... +80 °C
• Compatible Magnetic Targets: 3-leaf / 6-leaf Spider Magnets, Plate Magnets, Datum Magnets
• Compatible Casing Diameters: PVC access pipes (Ø 25 ... 50 mm) or Inclinometer casings (Ø 48 ... 89 mm)
• Standard Package Includes: 9V battery, aluminum reel, user manual, and factory inspection certificate