Angle Indicator

Turck angle sensors are used in the aerial platforms of Ruthmann to measure the rotation angle of the working cage

The aerial platforms built by Ruthmann are based on quality and innovative technology. To guarantee at any time the safety of the STEIGER® aerial platform with a maximum working height of 100 meters, sensors detect each position change – right through to the swivel angle of the working cage. This task is mastered by Turck‘s Ri360-Q14 inductive angle sensor, which made a big impression with its compact design, simple teach function for the sensing range and intelligent response at the measuring range end points.

As aerial platforms carry people, they must meet special safety requirements. The safety-related sensors and the controller in particular must have a redundant design. This is the case with all Ruthmann models. The swiveling of the working cage is also monitored by a sensor underneath the cage. “Only if the jib is in the correct position can the working cage itself be swiveled fully. If it is too steep, the cage with the control console may hit the jib,” Dr.-Ing. Klemens Post, head of electrical control technology at Ruthmann, explains the task of the sensor. “To prevent this, the controller continuously monitors the swivel angle of the jib and ensures that it is only moved as far as the actual position allows.”

Behavior in the limit range
“There had been problems with the angle sensor that we had previously used,” Post explains. The sensor was taught with a sensing range of 180 degrees.” It outputs a 0.5 volt signal at the starting point of the measuring range at -90 degrees, and the maximum value of 4.5 volts at the end point at +90 degrees. If the stop at 4.5 volt was slightly overshot, the sensor signal jumped to 0.5 volt. This immediately caused the controller to lock the movement of the working cage in the direction of the 0.5 V signal. We had to go on the safe side and teach the old sensor within a safer range, i.e. from -85 to +85 degrees,” Post describes how they dealt with the previously used angle sensor.

Turck‘s Ri360-QR14 inductive angle sensor is better adapted to this. If a position is reached that is outside of the taught start or end point, the 0.5 volt signal is still output at positions before the start point and the 4.5 volt signal at positions after the end point. The signal does not jump until the intended limit point has moved between the two end points. If therefore – as with Ruthmann – the sensor is taught from the start point at 9 o‘clock to the end point at 3 o‘clock, and the sensor is at 4 o‘clock, it continues to output the maximum signal of 4.5 volts until the limit has been reached at 6 o‘clock. Only then does the signal jump to the start value of 0.5 volts.

Straightforward sensor offset
This behavior was not the only reason for using the Turck sensor. “A major benefit for us is the tolerance provided when the positioning element is offset. Vertically and horizontally, the sensor can be offset by three millimeters. This is very helpful because a few millimeters of offset frequently occur when the sensor is fitted. The teach functionality is also really child‘s play,” Post describes the benefits of the sensor. “We move to the first position, press the teach adapter button for two seconds, move to the end position, press once more for two seconds and that‘s it.”