Method and arrangement for making contactless distance and pressure measurements within an air spring

A pulse/echo method for making contactless measurements of the spacing between the axle and the chassis of an air spring suspended vehicle and to measure the pressure present in the air spring, the method comprising the steps of:

• providing an ultrasonic arrangement including a transmitter/receiver component mounted on the chassis, a first reference reflector disposed at a first distance to said transmitter/receiver component and an end reflector fixedly mounted at the axle;
• providing a second reference reflector disposed at a second distance to said transmitter/receiver component with said second distance being different from said first distance;
• determining said spacing from a relative value of the running times of the ultrasonic pulses traversing said first and second distances;
• converting sound reflected from said first and second reference reflectors into first and second sonic signals;
• providing a control unit for controlling one of the transmitting signal power and the receiving amplification of said sonic signals to determine the pressure in said air spring;
• adapting said control unit to control said one of said transmitting signal power and said amplification of said sonic signals so that the amplitude of the sound waves reflected from said first reference reflector remains at a constant value;
• measuring the echo amplitude of said second reference reflector utilizing a first unit;
• and,
• determining the pressure in said air spring from the echo amplitude measured from said second reference reflector with the aid of an amplitude/pressure characteristic line and said instantaneous temperature.