The device includes a meter measuring the through flow volume and mounted in the line (14) between a hydraulic pump (16) and the free lift cylinder (10). An evaluator unit is connected to the meter and a calculates from the measuring signal of same the relevant lifting height. A detection device detects the end of the free lift movement and the start of the movement of the load lift cylinder and sends a signal to the evaluator unit for applying a modified factor to the calculation of the lift height. A reference point (22) on the lifting frame is detected by means of a switch, approach sensor or similar to produce a reference signal for the evaluator unit (18).
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