May 2004System Integration & Control Systems Design
Baumer Electric, the suppliers and manufacturers of a large variety of sensors, has offered the following useful information on how to use sheet glass, acrylic (or any other transparent sheeting) as a cover in the optical path of a laser distance sensor, because there are some precautions that must be taken.
Firstly, the optical path must be covered - both the laser outputs as well as the receiver optics. The red front glass of the sensor defines the position of the receiver optics. The cover must be kept outside the measuring range. If the cover is inside the measuring range, then any dust or dirt that accumulates on the cover could be detected as a valid object within the range, and will lead to a constant, but wrong output.
The cover must be parallel to the front sensor (±5° is tolerable). The reason for this is because the cover might cause disturbing reflections. Larger angles cause linearity errors. Even direct reflections back into the receiver are possible and spoil the results.
The cover must always be flat in an optical sense. If the cover shows 'waves' or curvature, then it will affect the laser beam and the optical path of the detection. The linearity will be affected in a strong and unpredictable way. Normal sheet glass or acrylic glass or macrolon sheets are plane. A simple test can be done to show uneven plane surfaces, by looking with one eye through the sheet and looking at a regular pattern of lines. Then turn the sheet. If the pattern is warped or deformed, the sheet has some optical effect this affects the sensor. This sheet must NOT be used. The pattern must remain stable through rotation.
There is a constant error in absolute distance. Every cover will affect the measured distance! The measured value will always be smaller than the real distance. The following rule is a good approximation for the error:
Change in distance = (thickness of material)/(constant for the material)
Constants:
Glass - 2,5
Acrylic - 2,8
Water - 3,5
Example:
3 mm acrylic leads to a constant error throughout the measuring range of 3/2,8 = 1,07 mm
This affect can be used to indirectly measure the height of transparent and undisturbed fluids by measuring the distance through the liquid down to the bottom of the container.
Modernising Vertical Filter Press Machines with Future-Focused Control Systems
System Integration & Control Systems Design Project and Industry
Pressure Filter Specialists approached us to modernise vertical filter press machines for the Minerals and Metals industry. The goal was to improve reliability, reduce downtime, ...
Read more...Project & industry
System Integration & Control Systems Design Project and Industry
This project involved delivering a complete electrical, instrumentation, and automation solution for a new OEM drum-twister machine, replacing an ageing unit in a major cabling production ...
Read more...It’s a risky business not to challenge standard language
System Integration & Control Systems Design
On the surface, contracts all look alike. Once you’ve seen one, you’ve seen them all, or so it seems. Maybe so, but hidden within the standard language can be language that shifts the other party’s risk to you.
Read more...Control system upgrade: Smelting SAM Systems Automation & Management
System Integration & Control Systems Design
Systems Automation & Management recently completed a major control system upgrade in the smelting industry. The project was delivered on budget and achieved a positive ROI for the client.
Read more...Gottwald drives upgrade: Ports and harbours Abacus Automation
System Integration & Control Systems Design
In the ports and harbours sector, Abacus Automation completed a significant modernisation of a Gottwald crane, improving both operational reliability and serviceability.
Read more...Agogo Integrated West Hub Project: FPSO/subsea offshore Angola Moore Process Controls
System Integration & Control Systems Design
The Agogo Integrated West Hub project represents a historic milestone in the FPSO and subsea industry, achieving first oil offshore of Angola. This project is the first FPSO deployment since ANPG’s establishment in 2019, and the first major project for Azule Energy since 2022.
Read more...Project and Industry
System Integration & Control Systems Design
The Sicomp Control System Upgrade focused on modernising a 1985 power generation control system with more than 3 000 I/O points. The plant faced increasing system failures and risk to operational continuity, ...
While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.
printer friendly version