Carrying out the measurement
For the analysis of individual consumers or circuits in the test vehicle, automobile manufacturers, development service providers and suppliers often use MULTI-8 measuring modules, a millivoltmeter with 8 parallel, independent inputs. Different probes for current, voltage and temperature measurements can be connected to all inputs. These probes are automatically identified by the measurement module. In order to achieve the highest possible accuracy when calculating the measured value, the calibration value of the respective sample is transferred to the measuring module and used for the calculation. The measurement data is transmitted via CAN and/or Ethernet, a maximum of 8 kHz can be output per channel. A wide range of configuration options enable, for example, the reduction of the data volume via different operating modes and the averaging of measured values.
These modules are preferably installed in the vehicle interior and, for example, looped directly into a circuit via the vehicle fuse box - see Figure 1.
In order to protect the extremely expensive test vehicle against possible short circuits, the measuring circuits are protected by the original vehicle fuse. The arrangement of the measuring shunt in a separate housing ensures that the measured values are not falsified by thermal effects. This measurement technology is also used for measurements on laboratory vehicles, in which the complete electrical/electronic system is reproduced using the original wiring harnesses in a so-called board structure.
Along with the measured current and voltage values, a number of other measurement data are often recorded, which are evaluated using commercially available measurement data software. The transmission of the measured values with its own time stamp, independent of the CAN bus, enables the measured values to be assigned in terms of time and correlated with other measured data.
Thanks to this high-resolution measurement technology, which enables the precise measurement of electrical quantities over a very wide range, even the smallest power guzzlers can be identified. With up to 180 control units in a premium class vehicle, this results in considerable optimization potential.