Our Donut sensors - suitable for all load-carrying means

The Donut load sensors have been developed for use in lifts with their installation spaces becoming smaller and smaller. Together with the elastomer spring buffers or the compression springs the sensors are fitted to the rope suspension (dead centre), and thus are suitable also for very small shaft heads. It does not matter whether conventional steel cables or belts are concerned here as both supporting devices use similar mechanical suspensions.
The Donut sensors come in two variants, i.e. a cost-efficient version with weights to be calibrated, “Donut LIGHT”, and a very comfortable, absolute measuring version.

DONUT VariantenThe Donut sensor series presented during Interlift 2015 in the German town of Augsburg already has been supplemented with the new types of sensor. Apart from the standard Donut sensor, there is also Donut LIGHT sensor now. With respect to installation, handling and the mechanical construction, the two types of sensor are almost identical. The difference between the two sensors is that Donut LIGHT has to be calibrated with weights after installation. Thus, the advantage of the standard Donut sensor has been dropped that no weights are required for the installation. On account of this fact, we save costs in the production of Donut LIGHT sensors for certain electronic modules and time for the calibration. We pass this cost advantage on to our customer completely so that they can decide for themselves which variant is more advantages for them.
Common features of the product variants
Bild_en.jpgRange of application
The two types of sensor are identical with respect to their range of applicaiton. Both come in four different models, which in the end depend on the suspension means used and its maximum load. Thus, the internal diameter of the Donut sensor, through which the threaded rod of the terminal connector of the suspension means is passed, is decisive for the selection of the suitable model and the maximum load of each individual suspension means.
Resistance and durability
DonutInst_kl.jpgIn all load bearing parts of the sensor, considerable attention is given to the load-bearing capacity. Consciously we have decided against aluminium in the load-bearing parts and use hardened steel instead. There are two important reasons for this: Firstly, after the safety catch has been triggered and thus after release of immense forces the sensor must not be deformed, thus requiring a re-calibration, and second, the components of the sensor rub against each other minimally only during every movement of the cabin. This friction almost inevitably leads to abrasion of the aluminium and thus to falsification of the measuring signal and potentially to an obstruction of the diagonal pull compensation, for example.
Diagonal pull compensation
schraegzug.jpgAn equally important aspect in a sensor, which is used in the terminal connector of the suspension means, is the possibility of compensating the diagonal pull. Especially in 2:1 suspended lift installations which have been designed without machinery room, a massive diagonal pull of up to 7 deg. occurs on the thin ropes in the upper stopping place as a rule. This diagonal pull is naturally passed on to the threaded rod of the suspension means, but must have no effect on the sensor by any means. If this would develop diagonally to the rope place, the flow of forces in the sensor would develop abnormally and would lead to massive measurement errors in parts. For this reason we have developed the so-called “wobble plates” which are fitted between sensor and rope plate. They make sure that the sensor remains parallel to the terminal connector of the suspension means and thus produces valid measuring results. The wobble plates compensate a diagonal pull of up to 10 deg., which occurs on the lift market at present.
Differences between the product variants
Weights for installation
Gewicht.jpgDue to the fact that cost-producing electronics and pre-calibration has been dispensed with in Donut LIGHT sensors, they have to be calibrated with weights after installation. If a new lift is installed, they are on site already in any case and do not cause any extra costs. In this case Donut LIGHT is a good because inexpensive variant. 
Gewicht durchgestrichen.jpgThe standard Donut sensor, however, can be used “plug ‘n play”. As soon as the terminal connector of the suspension means has been installed no other work is required - the load in the individual suspension means and thus the overall load can be read off immediately. Weights must not be transported to the site.
Absolute single rope loads
wiegung.jpgThe standard Donut sensor permits the measurement of the absolute single rope loads. This means that it is known which suspension means carried out how much load each. Apart from the rope setting (see below), this means also that the absolute total weight of the cabin is known. Thus, the empty weight of the cabin can be determined which may be very helpful for modernisation, for example.
Unfortunately Donut LIGHT is not able to do so.
Minimizing rope wear
einstell.jpgWhen the standard Donut sensor is used and thus the absolute single loads can be measured, free software of Henning Company permits easy setting the rope tension. Everybody who has adjusted a rope already knows how difficult that can be. Due to the fact that the change of the rope tension of one rope immediately cause the change of the rope tension of all other ropes of the set, the adjustment of a rope set of four or six ropes is relatively difficult and costs a lot of time, even if a measuring device can measure the tension of each rope. The human brain is able to approach the solution of the problem iteratively only: By trial and error, the human approaches the ideally adjusted rope set by tensioning and/or de-tensioning each rope in small steps (several times often enough). This process requires a lot of time in case of rope sets with about half a dozen of ropes.
einstell_2.jpgEspecially for this problem our devices and sensors provide a possibility of carrying out adjustments precisely, documented and effectively and thus inexpensively: The software leads the fitter through rope setting step by step. In the process, each rope of the set is adjusted to the ideal tension calculated by the software. This means that each rope needs to be touched by the fitter once only, and thus the setting of a complete rope set takes only a few minutes, even if it consists of twelve ropes.
light_gew.jpgDonut light. The cost-effective variant to carry out overload measurements in rope suspension. After installation these sensors are calibrated with weights and used with an evaluation unit AE16 or AE8.
more on Donut light sensors ...
donut_nogew.jpgThe Donut Sensor These sensors are able to measure the absolute weight of each rope, belt or other load-carrying means, thus omitting the calibration with weights after installation. Thus, the sensors can be used immediately and are simply connected up to an evaluation unit AE12.