A bit of a math problem

[richard]

number of pumps = ((discharge rate) /(individual pump capacity))+1

if the rate of change of tank level is not linear with discharge rate then use a lookup table

[Ioannis]

Thanks Richard.

My problem is to find that rate of change.

I have a sensor that gives me the level of the tank. Also a variable 'rate' that is set by the user.

Now I have to combine these two and decide how many pumps should work at a time.

Ioannis

[pedja089]

Take measurement ever XYZ sec.
Discharge rate is First-Second.
Eg do something like this:

RunFirstTime:
ADCIN SensorValue' or whatever
OldSensorValue=SensorValue' initialization at beginning of program
return

SubRoutineToRunEveryXYZsec:
ADCIN SensorValue' or whatever 
DischargeRate=OldSensorValue-SensorValue
OldSensorValue=SensorValue
RETURN

Depending on how often you call SubRoutineToRunEveryXYZsec you can get quicker response, or better resolution(wider range of values). That all depends how quick your process is.

[Ioannis]

Thanks Richard. I see what you mean.

Greet help on that small hour that my mind is almost in literary sleep mode!

Ioannis

[mpgmike]

Another approach would be:
SELECT CASE Level
CASE < 80 : HIGH Pump1 : LOW Pump2 : LOW Pump3 : LOW Pump4
CASE < 70 : HIGH Pump1 : HIGH Pump2 : LOW Pump3 : LOW Pump4
CASE < 60 : HIGH Pump1 : HIGH Pump2 : HIGH Pump3 : LOW Pump4
CASE ELSE : HIGH Pump1 : HIGH Pump2 : HIGH Pump3 : HIGH Pump4
END SELECT

[Ioannis]

Thanks mpgmike. Good one too!

Ioannis