1. Connect "+" voltmeter to output "+1", and the voltmeter to the output "EW".
2. Connect "+" battery to the output "+V", A "-" to conclusions "EW" And "+S".
3. Switch the wiper to position "INT".
4. Within 5 seconds, move "+" battery to the output "S+".
5. Connect "-" battery to the output "+S", and check the voltage change between the terminals "+1" And "EW", when the purifier works when adjusting the interval.