The mechanical indicator type 50 from the company Leutert GmbH is one of the last devices of this type on the world market.
Mechanical indicators can only be used up to speeds of max.
800 … 1000 min-1. The indicator is screwed with a nut on the indicator valve. When the valve is opened, the pressure from the cylinder immediately enters the indicator and moves there the indicator piston.
This piston is in connection with a calibrated measuring spring, so that its way, under the counterforce of the spring, is proportional to the pressure exerted on it and registered on the writing drum.
On the piston rod, the writing unit is connected, with the pin at the top. This records the pressure curve. The drum, in which the paper is mounted for recording, moves back and forth under the influence of the cord tension on pressure-piston-stroke indicator.
On the writing unit, the variable pressure in the cylinder chamber is recorded above the piston path. The well known indicator diagram.
From the area-equivalent rectangle the mean indicated pressure can be calculated.