X20 Sprayer Reference Manual
Problem 15
Rate Unstable
Information
The rate is determined from the pulses received from the Flow Meter. These pulses are processed along with the Sprayer width, speed, and target rate and a determination is made as to how to drive the Regulator Valve to achieve the target rate. Most unstable rate displays are due to erratic signals coming from the Flow Meter. With a Centrifugal pump, air can be sucked into the pump through seals, loose hose fittings, faulty hoses etc. This air can dramatically increase in volume in the pump due to cavitation, and when this air pocket passes through the Flow Meter, it will cause erratic operation, as well as giving fluctuating pressures due to poor pump efficiency.
If using a Positive Displacement pump, Piston, Diaphragm etc, a faulty valve in either the suction or pressure side will give a pulsating flow which will also give erratic readings. If there is 5 or less pistons, the pump will have an Accumulator (Air Pressure reservoir) that is designed to smooth out the pulsing from the pistons. The pressure in this accumulator is critical and should be as determined by the pump manufacturer.
Problem 16
Rate Unstable
Information
A faulty Flow Meter can give erratic readings as well. The Flow Meter fault can vary depending on the design of the meter. The most common problem is wear. As the components in the Flow Meter wear, the inpeller will move around and can drag on the side of the housing, giving poor readings. Also, it can become jammed or sticky due to contamination, foreign objects or poor cleaning routines. These causes will also give incorrect volume used readings, which could be corrected by changing the FCAL, but this only masks the problem of a failing Flow Meter.
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