GE AquaTrans AT600 User Manual page 66

Chapter 4. Initial Setup and Programming
Totalizer Pulse Setting Guidelines
When programming the pulse totalizer, a smaller pulse value generally results in higher totalizer accuracy.
However, the minimum practical pulse value is limited by the resolution of the pulse counter being used.
Thus, one must find the proper balance between the desire for a small pulse value and the capability of the
pulse counter to accurately read the pulses output by the AT600.
The best way to illustrate this process is with the following example calculation:
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The parameters set on the previous page are the Pulse Value ( PV = the volume of flow per pulse) and
the Pulse Time ( PT = the width of each pulse).
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Program the Pulse Measurement as a Forward Batch Totalizer.
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Consider a process where the volumetric flow rate ( VR ) fluctuates near 4.6 liter/sec.
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As a typical value, try a PV of VR/20 = 4.6/20. Thus, set PV = 0.23 liter/pulse .
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Then, the duration of each pulse is PV/VR = 0.23/4.6 = 50 ms. As the Pulse Time (PT) is defined as half
the pulse duration, then the correct PT = 25 ms.
•
Program the AT600 frequency output with PV = 0.23 liters/pulse and PT = 25 ms . If your frequency
counter correctly reads the AT600 pulse output, then these settings are appropriate. If not, you need
to try different calculations for PV (instead of VR/20) until you find a set of values that can be
properly read by your frequency counter. In general, the smallest PV value that is within the
resolution specification for your frequency counter will provide the best accuracy for the batch
totalizer.
54 AquaTrans™ AT600 User's Manual