Learn about Optical Measuring Principles.
Hover mouse over icon for application notes.
Optical Capabilities
| Technology |
Model/
Series |
Gas Flow |
Liquid Flow |
Steam Flow |
Line Size |
Temperature |
Pressure |
Viscosity |
Accuracy |
Considerations |
| Optical |
AOFM |
 |
 |
|
|
|
|
|
|
Excellent for pollution control |
SmartMeasurement's ALOFS Optical Flow meters are a line of advanced optical gas flow sensors that offer numerous advantages over traditional mechanical and ultrasonic type sensors.
Optical Flow Meters are easier to use, more accurate, and more cost-effective than other sensors traditionally used for gas flow measurement. This advanced technology, which is approved by the US EPA, employs a control unit paired with an optical transmitter and optical receiver which are easily installed on opposite sides of a smokestack, duct, vent or other confined space. The flow meter resides outside the stack chamber behind optical windows for easy access, more accurate measurements, and greater durability. The instrument mounts on the same level, in order to transmit the LED beam directly across and perpendicular to the flow.
The ALOFS optical scintillation technique measures the movement of turbulence found in exhaust flow streams to provide highly accurate, path-average air velocity measurements. Using fast and highly efficient digital signal processing (DSP), the control unit processes the data, and then transmits it to a PC, PLC, DAS or other data collection device that accepts 4-20 ma or serial digital input. The ALOFS uses built-in self-test and diagnostics routines to monitor its own performance to alert the user to any maintenance issues. In addition, the ALOFS can be easily installed temporarily with “C” clamps, facilitating its use if your existing flow sensor fails (existing angled flanges can be used). Some key advantages are:
Revolutionary, non-intrusive setup: The ALOFS is a patented, advanced, continuous flow measurement system for large and small stacks or ducts. The instrument is isolated from the flue gas. This non-contacting method ensures reduced maintenance over traditional flow sensors.
Exceptionally accurate, true cross-stack/path-averaged result: The ALOFS provides true, average velocity across the diameter between the optical sensors along this path. The accuracy of the ALOFS is traceable back to the NIST wind tunnel standards. Long term drift for the system is less than ±1% over the entire life of the instrument.
Calibration and other checks verify all system components: ALOFS meets all 40 CFR 75 requirements, including daily calibration zero and span checks. System components and interference checks are completed on a continuous basis.
Velocity measurement independent of temperature, pressure and density of flue gas: ALOFS measures flue gas velocity. Path angle and gas composition, whether wet or dry, hot or cold, has no adverse effect on the velocity measurement.
In addition:
- The ALOFS gives a true cross-stack/duct flow measurement of the process.
- Costly 45 degree angle offset installations or extra platforms are not required.
- The path-averaged result is far more representative than point sensors.
- No moving parts, non-intrusive, non-contacting measurement technique. No parts are directly exposed to stack gases.
- ALOFS measurement is independent of stack diameter, media, temperature, pressure, moisture, or opacity levels