800.727.5646 atcdigitec.com Digitec Division 750-J2/M2 Series Tachometers/Generators // 750-J2/M2 Series 331 The Model 750 DC Tachometer-Generator embodies a permanent magnet field surrounding a rotating armature. The commutator segments are made from a special non-corrosive alloy which has an exceptionally long life. The brushes are of a self-lubricating material and are carried in a self-aligning holder which equalizes the pressure of both brushes. The armature shaft rotates on ball bearings which under normal operation do not need lubrication for 15,000 hours running time or approximately 3 years, whichever comes first. Maximum recommended speed is 5,000 rpm. Brush life is greatest at the lower speeds. Dust-proof aluminum alloy housing. S.A.E. 7/8" screw type steel mounting with 3/16" drive dog. Used on Diesel and gas engines where a standard S.A.E. screw type tachometer outlet is available. Two binding posts for electrical connection. Approximate torque: 3.0 oz.-in. starting, 4.0 oz.-in. running (1000 RPM). Screw Moun t e d T a ch o m e t e r - G e n e r a t or BINDING POST COVER BOX \\\DIMENSIONS (INCHES/MILLIMETERS) \\\SPECIFICATIONS VOLTAGE OUTPUT AT 1000 RPM 6 Volts ±1% Per 1000 RPM ACCURACY ±1% EMF LINEARITY 1 ±0.15% PERMISSIBLE CURRENT DRAIN 50 mA MAX RMS VALUE OF AC RIPPLE 2% ALLOWABLE END PLAY .005" MAX OPERATING TEMPERATURE 250°F INTERNAL RESISTANCE AT 25°C 20 ½ ±2% J2R: 200 ½ ±2% NUMBER OF BRUSHES 2 Per Set COMPOSITION OF BRUSHES Palladium Silver Alloy ARMATURE 12 Bars, 12 Slots INSULATION Insulation Class 105 HI-POT TEST 500 Volts for 1 Min. BEARINGS Ball TEMPERATURE COMPENSATION 0.1% Per 10°C Change NORMAL CONTINUOUS SPEED 2000 RPM MIN TOP SPEED 100 RPM MAX SPEED 2 5000 RPM STARTING TORQUE J2, J2R 3.0 oz. ins. M2 1.0 oz. ins. RUNNING TORQUE AT 1000 RPM J2, J2R 4.0 oz. ins. M2 1.0 oz. ins. SHAFT DIAMETER 3/16" SHAFT CONNECTION Direct SHAFT LENGTH .47" ADJUSTABLE MAGNETIC SHUNT RANGE ±4% DIRECTION OF ROTATION EFFECT ±0.6% MOUNTING SAE 7/8" Screw ENCLOSURE Dust Resistant MEASUREMENTS 5.61"L x 2.91"H x 3"W WEIGHT 1.8 Ibs. (.82 kg.). Approximate \\\ORDERING INFORMATION MODEL NUMBER DESCRIPTION 750-9906000 750 Type J2 Tachometer-Generator 750-9906002 750 Type J2R Tachometer-Generator 750-9906001 750 Type M2 Tachometer-Generator ACCESSORIES 9933-0143156 Binding Post Cover Box 249302.901 Replacement Brush Kit Type J2R: Same as Type J2, except internal resistance is 200W. Type M2: Same as Type J2, except front bearing seal has been eliminated to reduce torque burden. Recommended for use with a low-torque gear box. Approximate torque: 1.0 oz.-in. starting, 1.0 oz.-in. running (1000 RPM). Binding Post Cover Box: Provides protection for the terminals, and has a 1/2" NPT connection for conduit. Replacement Brush Kit: Metallic leaf brushes are of an alloy which will wear before the commutator bars. Brush replacement is a simple field operation.