TACHOMETER Model DT-2234B DT-2235B Range 5 to 99, 999 RPM 0.5 to 19, 999 RPM Surface Speed ( m/ min.) :  0.05 to 1, 999.9 m/ min. Surface Speed ( ft/ min.) :  0.2 to 6, 560 ft/ min. Resolution RPM 0.1 RPM < 1, 000 RPM RPM 0.1 RPM < 1, 000 RPM 1 RPM 1, 000 RPM 1 RPM g1, 000 RPM 0.01 m/ mim. < 100 m/ min. Surface 0.1 m/ min. g100 m/ min. Speed 0.1 ft/ min. < 1000 ft/ min. 1 ft/ min. g1, 000 ft/ min. Display 5 digits, 10 mm ( 0.4 " ) LCD. 5 digits, 10 mm ( 0.4 " ) LCD Accuracy ± ( 0.05 % + 1 digit ) . ± ( 0.05% + 1 digit ) . Sampling Time 1 second ( 60 RPM ) . 1 second ( 6 RPM ) . Time base Quartz crystal . Quartz crystal . Photo Tach. 50 to 150 mm/ 2 to 6 inch. detecting * Typical max. 300 mm/ 12 inch distance depending upon ambient light. Circuit Exclusive one-chip of micro- Exclusive one-chip of microcomputer LSI circuit. LSI circuit. Battery 1.5 V AA ( UM-3) battery x 4 PCs. 1.5 V AA ( UM-3) battery x 4 PCs. Operating temp. 0 to 50  ( 32 to 122 ) . 0 to 50  ( 32 to 122 ) . Memory Last value, Max. value, Min. value. Last value, Max. value, Min. value. Size 190 x 72 x 37 mm ( 7.5 x 2.8 x 1.5 inch) . 208 x 72 x 37 mm ( 8.2 x 2.8 x 1.5 inch) . Weight 250g ( 0.55 LB) / including battery. 280g ( 0.62 LB) / including battery.