â·ÃÊͺ¶ÒÁÃÒ¤Ò The Extech 461891 tachometer is designed for high precision Contact measurements. 461891: High Precision Contact Tachometer Fast and accurate rpm and surface speed measurements to 20,000rpm Features: 0.05% basic accuracy Make contact measurements of rotating objects Measure linear surface speeds in ft/min or m/min using three accessory wheels provided Recalls Last/MAX/MIN values Specifications: Range: 0.5 to 19,999rpm; 0.2 to 6560ft/min; 0.05 to 1999.9m/min Resolution: 0.1rpm (0.5 to 999.9rpm); 1rpm> 1000rpm Accuracy: +/-(0.05%rdg +1d) Sampling Time: 1 sec> 6rpm Dimensions: 6.7 x 2.8 x 1.5" (170 x 27 x 37mm) Weight: 9.2oz (260g) 461891 Extech Tachometer à¤Ã×èͧÇÑ´¤ÇÒÁàÃçÇÃͺ ẺÊÑÁ¼ÑÊ