MDD measures the wheel diameter using a three-point measurement. Two of the points being established by fixed rollers, the third point is measured using an inductive position transducer.

The measured diameter can directly be read on the two displays, one on each side. The measuring result can be stored in the memory of the device, together with the running ordinal number and the date. An eight-digit ID number allows the identification of the loco, wagon or car and of the wheel.

The memory has capacity for 1800 measurements. The data transfer from the device to a PC is made through a cable to the PC’s serial port. The data are received in ASCII format and can easily be integrated in Company’ s other programs.


Technical Specifications

The body of the device has been manufactured of black anodised aluminium. The device is attached onto the wheel by means of two permanent magnets (holding strength about. 70 N/each) and it lies on two support rollers of hard metal. The distance of the centre points of the rollers is measured with an accuracy of 0.002 mm. The measuring is made by a transducer, which is furnished with a hard metal, r 7, measurement point. The maximum linear error of the transducer is 0.1 %. The device is equipped with three rechargeable, removable batteries with capacity of approx. 8 hours’ active operation.

The black and white LCD screen displays two lines with 16 characters on each. With its optional back lightning it is perfectly visible in day light as well as in dark environment.

Individual calibration stand and calibration pieces, made of steel and precision cut on the calibration planes, are included in the delivery.

Measurement Ranges

The total measurement range is divided in four subranges, individually designed for each customer. This position is adjusted on the calibration stand using the corresponding calibration piece.

MDD is manufactured in two types: MDD-350 for bigger wheels and MDD-315 for smaller ones with the following measuring ranges: MDD-350 between 1255 and 750 mm, MDD-315 between 1050 and 590 mm.

The standard distance between the reference line, i.e. wheel inner side, and the taping line is 70 mm, but at request devices with different distances can be delivered.



The reading accuracy shown on the display is 0.1 mm. The true measurement accuracy is in the range of 0.2 mm, if the wheel is round and has good reference plane and running surface.


Length: MDD-350 380 mm, MDD-315 345 mm.

Height from the tread level: 151 mm. Depth 106 mm.

Weight: measuring unit 1.8 kg, total weight with calibration unit, tools, adapter and storing bag 6.8 kg.

Operating temperature -5°...+45°C.

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