OSI's patented Laser Level Meter (LLM) is a compact industrial sensor that utilizes an infrared laser and advanced micro-processor to measure levels in in industrial storage tanks, large commercial process bins and agricultural silos. The LLM-100 uses an eye safe pulsed infrared laser and measures distance using time of flight of a very narrow laser pulse. The sensor uses a very sensitive Avalanche Photodiode, which is coated with a bandpass filter to block out all ambient light. This enables the LLM-100 to be used indoors and outdoors on sunny days. The sensor can be used as a stand-alone sensor requiring only 12.5-36 VDC and out puts RS232 and 4-20 ma outputs or with optional control box.

The optional remote control box can accept up to 4 LLM sensors and allows the user to quickly configure each of the sensors and provides the power, display, a keypad, fault relay output and current loop connections for each of the sensors.

As with all Optical Scientific sensors, the LLM- 100 is easy to install, needs almost no maintenance, and is equipped with continuous self-diagnostics.

The LLM-100 cage houses all electronics and modules for the LLM to function.

  • Micro Processor Unit – Controls laser pulse and process Receiver signal.
  • Transmitter Unit – fires 20 ns laser pulses 4000 times a second.
  • Receiver unit – Receives return laser beam

OSI includes a visible Pilot laser collinear with the measuring laser to help with alignment. The pilot laser can be turned off to conserve power. The sensor also comes standard with a 4-line LCD display to aid checking the data and performance of the sensor, which can also be turned off to conserve power.



  • Eye safe pulsed infrared laser
  • Built in algorithms to handle dust flares Heated windows
  • Easy installation and optical alignment.
  • Works indoors and outdoors on sunny days Long-term reliability: no moving parts;
  • operates unattended - 24 / 7 / 365.
  • Ultra low maintenance design.
  • Rugged; designed for harsh environments. Built in continuous self-test diagnostics.



  • Order Z-Purge Option for Class I Div I/II applications.
  • LLM-4-channel Control Box (P/N 2013-300) 4-20 ma output standard.
  • Optional 4-20 ma output available (up to four 4-20 ma outputs).



  • MZ-1179-00 Fiber Optic Modems(FOM) for distance to 1 mile(2 required)
  • MZ-0649-00 Limited Distance Modems (LDM) for distances 100 feet to 3 miles. (2 required)
  • 1910-804 Laptop DB9 serial communications cable 


Measurement Technique

N/A Time-Of-Flight (TOF)


N/A 1 to 100 Meters

Accuracy (absolute)

N/A 0.01 Meters or 1% whichever is greater


N/A 0.01 Meters

Time Constants

N/A 4000 Samples/Sec updated @ 1 sec. interval


N/A Continuous Self Testing


Ambient Temperature

N/A -40 C t0 60C


N/A 0 to 100% RH Condensing



Physical Specifications

Light Source

N/A Infrared laser w/ visible pilot laser

Sensor Head

N/A 9 x 9 x 13 inches, 13 lbs. (15 x 15 x 14 cm ea 5kg ea)

Control Unit: NEMA4 Wall Mount

N/A 12 x 14 x 8 inches, 15 lbs. (30 x 40 x 25 cm. 7kg)

Electrical Specifications

User Interface

N/A RS-232 serial I/O and up to four 4-20 mA isolated current loops. Two sets of relay contacts for fault and error indication.

Power for Sensor Head

N/A 12-5 to 36 VDC @0.4 AMP

Power for Control Unit

N/A Universal 100-240 VAC, 50/60 Hz, 40 VA (fused & surge protection)

Cable between Control Unit & Sensor Head

N/A 25 foot fixed (shielded, 10 cond., 22 AWG)