A photo electronic sensor based instrumentation system was developed to match the tractor drawn seed planters to quickly assess the seed metering rotor performance. The data thus collected and logged using instrumentation system without manual interference while in operation could quickly subjected to analysis, to identify defects in critical components, so that such machine components be redesigned to improve precision. Inclined and horizontal rotor plate metering mechanisms were test using a grease belt test rig in laboratory conditions fitted with the instrument system. The developed electronic sensor based instrument seed counting accuracy ranged between 96.88 to 99.55 percent of the actual seeds metered. The mean number of seeds counted by the sensor at different forward speeds for maize varied from 257.54 to 253.88, 267.45 to 265.82 for inclined and horizontal rotor plates respectively, whereas for castor in the range of 258.52 to 254.74 and 266.40 to 265.28 against the theoretical number of seeds to be dropped is 270. Seeding rate obtained for maize and castor for horizontal and inclined plate at forward speed of 3.5 km h-1 were 11.13 and 11.18 seeds m-2 and 5.58 and 5.63 seeds m-2 .Seed spacing interval observed for horizontal rotor at the forward speed of 3.5 km h-1 was 201.33 mm for maize and 201 mm in case of castor and 207.01 mm for maize and 207.66 mm in case of inclined plate meters mechanism. Horizontal metering plate recorded more consistent seed to seed spacing interval when compared with the other mechanism. Sensing the seeds flowing through the seed tubes helps the operator to observe functioning of the planter.