The input of the voltage divider is connected to the traction voltage of the vehicle. The divider output is connected to the input of the voltage/current converter. The output from this converter is a current in the interval from 4 mA to 20 mA, which is proportional to the magnitude of the traction voltage measured. For safety reasons, the high-voltage part and the safe low-voltage part of the converter are galvanic insulated.
The traction current drained by the vehicle is scanned on the shunt of the vehicle. Similarly as in the case of the traction voltage measurement, the voltage on the shunt is connected to the input of a voltage/current converter. The output from the converter is a current within the range 4 mA to 20 mA, which is proportional to the measured traction current. Also in this converter, the high-voltage part is galvanic insulated from the safe low-voltage part.
The two current signals from the converters are transmitted to the analogue inputs of the recording unit of the recording tachometer TTZ, which uses these parameters together with the distance travelled and the time to calculate the total electric energy consumed. The energy consumption measured in this way is then recorded on the memory card of the recording tachometer. At the same time, pulses are generated at one of the outputs of the recording unit, whereby a pulse corresponds to an increment in the energy consumed by 0.1 kW. The pulses allow for displaying the energy consumption on a mechanical counter located on the displaying unit of the recording tachometer.
The energy consumption information can be read up from the record of the recording tachometer using the “Evaluation Program of TT-Series Recording Tachometers”, available from the manufacturer.
