A leak detector comprising a base appliance provided with a gas detector, a vacuum pump, and a control device. A sniffer probe is connected to the base appliance. A test leak device containing the supply of test gas is arranged in a separate sub-housing. The sub-housing also contains a temperature sensor, a processor, and a data memory. The processor corrects the measured temperature according to a sample, and modulates the light of a light barrier. The processor is connected to the control device in the base appliance by a data cable.