Non-contact measurement with light

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LDM41AFor more than ten years ASTECH has offered laser-based distance meters for industrial purposes. From the beginning, the LDM41A was a part of the product portfolio.
Meanwhile thousands of these gauges are used to solve applications distributed over all branches of the industry. All of them share one common purpose – an accurate and reliable distance measurement.


When ASTECH first started to sell laser distance meters right after the millennium, nobody estimated the great extent of this success story. Devices of the earlier LDM30 series were still based on the electronics of simple handheld devices. Distance gauges like those where quite hard to find even on modern construction sites. Based on market monitoring and the requirements of well-known customers from the metal industry, the successor LDM40 and finally the LDM41 were developed. With its outstanding measurement capabilities and the well-known 4-20 mA interface the new model attracted great interest on the market. Additionally, the easy handling and the consistently proven reliability made the LDM41A really successful. For customers it was now easy to realize a highly accurate reflector-less distance measurement up to 30 m onto nearly every solid surface with affordable cost. With the use of targets made of special reflectors and reflecting foils the detection range of the gauge could be extended to more than 100 m.

Application-driven development

From now on the LDM41A replaced fault-prone cable extension encoders for fill-level measurement in silos or storages. Big parts of transportation machines for steel coils or paper rolls were moved exactly to the correct position by laser distance meters from ASTECH. With overhead crane position monitoring the LDM41A established a new special field of applications. Due to the comparative phase-shift principle the LDM41A provides a distance independent measuring uncertainty. No matter if the distance is 3 m or 30 m, the accuracy of the distance measurement is always ±2 mm. During the development of the LDM41 much emphasizes were put on the reliability and a robust construction. All internal optical parts are mounted in a solid metal bracket. The massive front tube prevents the receiver from extraneous light and prevents the lenses from scratches and damages caused by the harsh industrial environment. Over the yeas more and more new application cases were added. Today there are historic buildings like castles or old churches, where
ldm winkel the LDM41A monitors unwanted movements or changes of the constructions. In combination with programmable data logging devices the LDM41 observes the roof sag of big warehouses. The same setup is used to observe a street tunnel in the south of Germany for deformations of the concrete cover caused, by surrounding rocks. Not only the robust construction and the powerful measurement principle are responsible for the success of the LDM41 on the market. With the ongoing digitization and higher grade of automation the requirement for flexible and modern ways of communication arose. Therefore ASTECH presented a flexible concept of digital interfaces to transmit the measured distance values via fieldbus to the PLC world. The LDM41P with Profibus and later on the LDM41PN with Profinet interface spread the spectrum of the distance meter series. With the LDM42 ASTECH also presented an enhanced version with a faster measurement mode.

Worldwide use

For reasons of laser safety the LDM41 is not to be used if the inner temperature goes below 0° C. Therefore there is an option with an internal temperature controlled heating and a pressure regulation element available. This enables the device to be used in outdoor applications like fill level measurements on top of a grain silo in the north of Sweden. For a higher grade of protection ASTECH offers an additional protection case made of stainless steel in IP67. ASTECH and its distribution partners helped to provide worldwide success to the LDM41 series. In Australian open cast mines the depth of drill holes for explosive charges are measured by those devices. American saw mills measure the height of wood bins with the LDM41A, Chinese aluminum plants aquire the fill level of liquid aluminum or Danish flood protection facilities determine the position of big tide gates.

ldm caseCustomer-specific solutions

With much know-how about the different applications, ASTECH becomes capable to offer custom tailored solutions. Aluminum rolling mills use very aggressive and extremely penetrating rolling lubricants. For the standard LDM41 this would lead to disintegrated gaskets and the gauges would be destroyed within short time. Together with the customer, ASTECH developed a solution where all the gaskets of the LDM41A are made of Viton which is a very resistant sealing material. With this setup the customer is able to measure the correction position and diameter of freshly rolled aluminum coils despite of the ubiquitous influence of the aggressive rolling lubricant.

All these examples show that the LDM41A and its variations don’t belong on scrap heap yet. Based on the various solved applications and all the gained experiences over the years ASTECH offers a whole system of products around the LDM41A which enables to provide solutions for nearly every thinkable Application regardless how unusual they might be.