1. incoming inspection for new encoders,
2. repair and trouble shooting of equipment,
3. and identifying good encoders from those previously removed during repair
   efforts, and returning them to the spare parts inventory.

For maximum flexibility, the current software revision allows for testing both installed encoders using their drive motors, and for testing uninstalled encoders by turning them manually. There are tradeoffs involved in each kind of testing which will be discussed. Please refer to the PulsePro User's manual for operational details.

Why Test with the PulsePro?
It can be tricky to test an encoder (especially an installed encoder) by conventional means. Typically an oscilloscope is used to observe the pulses while the encoder is turning. This is a good approach in many respects because improper signal levels, noise pulses, intermittent connections, and other electrical problems can often be discovered. Oscilloscope use does have its shortcomings, however. Unless the encoder rotational speed can be kept very constant, it can be very difficult to set up the scope to accurately measure phase angles, and the pulse width measurement and conversion to degrees is typically time consuming. While many times it is possible to observe glitches, extra or missing pulses, and other problems, such events may easily be missed even by the most conscientious observer when they are intermittent or the event time is small compared to the sweep time. Automating these tests by using the PulsePro's built-in test functions, eliminates tedium for the user by providing easier setup and faster testing; and it makes the results less subjective by displaying definitive results. Not only will the test functions help identify faulty encoders, but they will likewise help identify good encoders, which may have been removed during substitution in previous repair efforts.

The Count Test
The fundamental question in encoder integrity is, "Does it produce the correct number of counts in the correct direction when moved through a given angle?" A very basic test can help answer that question by simply counting pulses between encoder index pulses which occur once per revolution. For example, a 500 line per revolution encoder should produce 2000 counts from one index pulse to the next. The count displayed at the end of the test can be compared with the expected count to determine whether the correct number of edges in the correct sequence are being generated by the encoder.

The PulsePro provides two such tests, one called the COUNT TEST and the other called the CONTINUOUS COUNT TEST. The former can be performed by turning the encoder manually to determine its resolution or confirm that it is working properly. The latter allows for turning the encoder many revolutions with a motor to determine whether an incorrect count occurs during repeated revolutions.

The Angle Test
Quadrature pulse phase angles are commonly measured with an oscilloscope to insure that an encoder is performing within the manufacturer's specifications. Two angles typically specified by encoder manufacturers, the A/B phase angle and the symmetry angle, may be measured for comparison with specifications. Out of tolerance angles can indicate encoder problems. An effective phase measurement scheme measures the time between pulse edges. The A/B phase angle, symmetry angle, or other angles may be computed from the time between pulses multiplied by 360 degrees and divided by the time of the pulse period as shown in Figure 1.