According to ISO 8655, all channels of multi-channel pipettes are to be tested. All channels have to be filled but only the channel to be tested is measured. Because of the high number of measurements (8-channel pipette: 240 measurements, 12-channel pipette: 360 measurements), it makes sense to send the multi-channel pipette to a professional calibration lab. These labs have special constructions for balances to ensure that all channels are filled but only one channel is measured.