Hello Olmec,
I have an idea that you may wish to at least investigate. This is just one idea.
I recently purchased a submersible pressure transducer from Stevens Water Monitoring Systems, Inc.
They are located in Portland, Oregon USA and can be found at
http://www.stevenswater.com/
This sensor can be dropped into the well string and supported by its own cable or it can be installed inside a PVC pipe.
The sensor I purchased is an SDX model with a 0-35 foot (~10M) depth range.
http://www.stevenswater.com/resources/datasheets/sdx_brochure_web.pdf
Accuracy (linearity) is +/- 0.3% of full scale, +/- 0.1% typical.
The output is a three wire analog 4-20 mA signal.
You must provide a 14 to 35 VDC power source and all external signal conditioning / monitoring electronics.
They offer the SDX sensor in 0-10 ft, 0-35 ft and 0-50 ft variations.
You must specify the cable length desired. Cable price is in addition to the sensor.
The cable is VENTED to atmosphere for pressure compensation.
You should also purchase a desiccant cartridge to attach to the vent tube to prevent moisture from condensing inside.
My purchase of the 35 foot SDX sensor with 50 ft of vented cable, the desiccant cartridge and shipping totaled $434.79 USD.
93720-035 sensor $295.00
44049 cable ($1.75 / foot) $87.50
93030-001 desiccant cartridge $30.00
My purpose for this sensor is to monitor the water level of the river at my remote cabin.
I will install the sensor at the bottom of a 1-1/4" or 2" pipe with a well screen at the bottom and a screened side vent higher up.
I am going to drive this pipe string into the sand at the edge of the river bank where my cabin is located.
If the river begins to flood, the rising water will fill the well pipe through the well screen from below as well as the side vent.
This will create a pressure increase at the sensor which will provide a corresponding increase in the current output.
I have also purchased a programmable pressure indicator display unit that will convert the 4-20 mA signal into a calibrated
digital readout of the actual depth, in feet, as well as provide programmable alarms that can activate sirens or lights and activate
a cellular device to send a text alert message to my computer or I-Phone.
You could use a 0-50 ft SDX sensor to control your pump operation, if you can create the electronic interface circuitry.
If the water level in the well drops below 46 - 48 feet (14 - 14.6M) the low current indication would disable your pump.
The maximum water depth the sensor can be installed at (submersed to) is approximately 68 feet or 20.7 M at sea level because the maximum overpressure the sensor is rated for is 45 psi.
You have to add the weight of the water column and the atmosphere above it to calculate the max depth.
RADAR