Essentially, I have to measure the pressure of a water filled bucket, and evaporate water in order to see change of pressure.
Put a 500 ohm resistor across the output of a 4-20 sensor, read it as 2-10VDC.
Would a load cell to weigh the bucket not be easier, or is this another one of those wacky projects and ideas your boss has come up with that you "have" to do it this way ?
How tall is your bucket?
I have used an electronic sensor from IFM to measure liquid in a drum about 3 feet tall with good success. At low head pressure, you need a sensitive instrument and onboard filtering is a good feature to include.
http://www.ifm.com/products/us/ds/PN2298.htm
Correct me if I am wrong, You have used this pressure sensor to measure the level of liquid? How much was this sensor for?
I was measuring a liquid in a chemical drum (non-corrosive) with a specific gravity slightly higher than water (~1.2). There is a pump that pulses and causes some spikes on the suction line where the sensor port is fitted, but the signal filtering built into the sensor made that "noise" vanish.
Not sure I fully understand your last question...
The drum is about 40" tall, usually filled to at least 24"(60cm) of head pressure on the sensor.
The sensor cost about US $400