Gotta say,.. i much prefered the very old analouge controllers that used the pressure switch instead of dead end detection - (Not the new "Analouge" ones which are just a dial connected to a digi board!),.. there was none of this messing around & they did the job just fine!
Around 2005 we were approached by a local cleaning company in the South East to address these problems. They recognised that if the speed of the pump could be controlled there were many benefits:
Less wear and tear on the pump
Extended life of the pump motor
Less current drawn from the battery means the charge lasts longer
Reduced pump speed means less water is used
Less water used per job means more jobs from the same tank
The first pump controller was named in house as the V1 it was an analogue controller which turned the pump on or off and regulated the speed of the pump. There was an immediate effect in that the cleaner was now using less water and was able to cover more work per tank added to this pump reliability improved as it was no longer running flat out. Downtime was reduced and connectors and fittings lasted longer.
The early analogue relied on the pressure switch to stop the pump when flow was stopped, This meant that the system built up very high pressure:
http://www.thehub360.com/spring-pressure-comparison.htmlAs the pressure switch cuts out the pump is operating at maximum, working as hard as it possibly can and therefore drawing maximum current from the battery. As the switch opens it is under great strain. The high current and the fact that the pump is an inductive load (with stored energy) means that the pressure switch contacts are likely to arc and eventually they will fail.
So as in any development solving one issue showed different issues. As such The next development brought a control which did not rely on the pump pressure switch to stop the pump when the water flow stopped. Having the control manage the pump stopping meant there was no longer stored energy arcing across the pressure switch contacts. Referred to as Dead End (DE) the control stops the pump when the water flow is stopped. The pump is no longer under full load when it stops this has an advantage as less energy is drawn from the battery. Also as the controller stops the pump well before the pump pressure switch would have done, we have reduced the strain on the pump motor as it is no longer working against a restriction.
The V3 analogue control came into being with a dial to control the speed of the pump and a second switch on the side to adjust DE calibration.
Ever since the V3 we made a decision to design the control to operate with a pressure switch. If for any reason the control did not stop the pump the pressure switch would. all be it at much lower pressure than if no pump regulator was used.