22mm small digital tube led round mini digital display hertz frequency meter electronic indicator lamp measuring type: AD101-22Hz place of origin : Zhejiang Province,China(Mainland) brand name : NIN mounting diameter : 22mm color : white green red yellow blue display type : digital display frequency measuring range : 0-99HZ supply voltage : AC 50V-380V display resolution : 1HZ sample rate : about 1 time/s no input signal hint message : display 000