Abstract: Wheel type electronic sheet material area measuring machine has means arranged to emit a test start signal, which may be manually operated or automatically operated at a particular stage in the machine cycle, and test means actuated by the signal which cause all of the detecting means of the machine to emit a signal normally indicating presence of sheet material for a predetermined period of such a length that, in the normal operation of the machine, the signalling means of each wheel should generate at least one pulse. Should a pulse not be received from one of the wheels in the allowed time, a signal is given indicating that the machine is faulty. The invention includes means to indicate which of the arm and wheel assemblies is faulty.

Abstract: Electronic wheel-type area measuring machine has manual or automatic operating means, arranged to emit, at a predetermined point in the machine cycle, a test start signal, the operating means includes test means, which upon receipt of the test start signal, feeds signals to computing means of the machine until the computing means registers a predetermined number whereupon a stop signal is emitted. The test means has duplicate computing means which also receives the test signals until the stop signal is emitted, whereupon the number of signals received by the duplicate computing means is compared with the predetermined number and an alarm signal is given if the number recorded by the duplicate computer means differs by more than a predetermined tolerance from the predetermined number. The counter check system also preferably provides a visual test on a visual test display unit and an output printer.

Abstract: Wheel type electronic sheet material area measuring machine comprises means for emitting a test start signal, operated either manually or automatically at a particular point in the machine cycle, and test means actuated by the test start signal to cause material detecting means associated with each wheel to emit a signal normally indicating presence of sheet material for a predetermined length of travel of a conveyor surface on which the material is normally supported, the wheels running on the conveyor surface. Thus each of the signalling means associated with the wheels should, if the machine is operating correctly, emit a number of test signals. The signals emitted by the signalling means of each wheel of a group of wheels are added and compared with an acceptable range of numbers of test signals which would be emitted in respect of that group if the machine is functioning within the predetermined tolerances.