Abstract: To determine in a simple and unequivocal manner whether measurement contacts at which a voltage is to be measured have been properly contacted in a measurement system, in the measurement system, after a discharge switch connecting a charging circuit to a voltage measurement device is closed, the charging circuit is discharged via an internal resistance of the voltage measurement device. When the discharge switch is closed, after a measurement switch connecting the voltage measurement device to the measurement contacts is closed, it is established whether the electrical system is contacted with the measurement system by analyzing the voltage curve at the voltage measurement device after closure of the measurement switch. Advantageously, after the discharge switch is closed, the charging circuit is discharged via a discharge resistor connected in series or in parallel with the voltage measurement device and via the internal resistance.

Abstract: A device for maintaining an air conditioner, in particular, for air conditioners using CO2 or R744 as a coolant. The device has a low-pressure side region (A), which is connectable to a service port on the low-pressure side of the air conditioner via a low-pressure side coupler (1), and a high-pressure side region (C), which is connectable to a service port on the high-pressure side of the air conditioner via a high-pressure side coupler (1?). A compressor (4) is provided between the low-pressure side region (A) and the high-pressure side region (C) and between the compressor (4) and the high-pressure side region (C) an over-pressure region (B) is provided, which is connected to the high-pressure side region (C) via a throttle device (5).