Liquid Level Pressure Sensor

Other Hardware Sensors
1

All,

I'm having some issues with a pressure sensor that I am using (Honeywell ABPMLNV060PGAA3).

It seems that even when I submerge the housing into a foot or so of water I am not seeing the change I would expect to see in pressure. The sensor is on the other end of ~200ft of wiring, but I should not be seeing too much voltage drop across it.

Below I have attached the necessary code as well as a data sheet....can someone just verify that I have this coded correctly.

int offset = 97;     // zero pressure adjust
int fullScale = 998; // max pressure adjust

P = (((0.8 * 3.3) / (fullScale - offset)) * (analogRead(4) - offset) * 3.3) * 2.31;
//2.31 is the conversion from psi to ft

Data Sheet

Thank you

2

Well your calculations are wrong to start with, but I wouldn't expect to read 0.33 volts over 200 ft of wire. Since you already have the wire run, I would use it to supply power for a remote Arduino with 433MHz radio transmitter.
The code could be (untested):
In theory the offset should be 1023 * 10% = 102 (97 may be OK). adcFullscale, 1023 * 90% = 921 (you have 998?), adcSpan, (adcFullscale - offset) = 824, sensorFullscale = 60.

float feetOfWater = 2.31 * (analogRead - offset) * sensorFullscale / adcSpan;

What is the maximum water depth? 60 PSI is 26 ft.
Well, that was a grand foul up, HUH? It's 60 DIVIDED by 0.434 PSI per foot. >:( SHEESH!

3

Below I have attached the necessary code as well as a data sheet....can someone just verify that I have this coded correctly.

In my interpretation of the datasheet the calculation is as follows:

int16_t offset = 67; // 10% * 3.3V / 5V * 1024
float range = 0.8 * 3.3 / 5 * 1024; // 80% * 3.3V (Vsupply sensor) / 5V (ADC Volt. of UNO) / 1024 (10bit)
float psi_fact = range / 60; // sensor range is 60psi
float foot = (analogRead(4) - offset) / psi_fact * 2.31;

200 ft of standard wire has a resistance of several Ohms, so this will most probably influence your result considerably.

It seems that even when I submerge the housing into a foot or so of water I am not seeing the change I would expect to see in pressure.

I wouldn't expect a serious measurement if such a sensor is submerged without a water proof casing.

4

Sensor is not submersible, board mount only.

5

All,

Thank you for the thoughts on the calculation, I will try them as soon as I'm able and update y'all.

As far as the sensor not being submersible, I created a housing that seals the electronics off and only allows the actual pressure port to be exposed, so it should not be an issue.

6

If I read your part number correctly ABPMLNV060PGAA3 you have a 0 to 60 PSIG sensor. With that in mind 1.0 PSIG = 27.7076 inches of water or 2.308 feet of water. This is where you get your 2.31 in your calculation to get from PSIG to Ft of water. Your 60 PSIG would be about 138.5 feet of water. Unless you are submerging your sensor quite deep I doubt you will see much change in output, especially if only a foot or two in depth.

Rather than submerge the sensor to read depth you may want to consider using a bubler method. A Google of "bubler method depth measurement" or "bubler method of water measurement" should get you started. Additionally you may wish to just try applying a pressure through a regulator to your sensor proportional to inches or feet of water in depth.

Ron

7

Ron,
I'll have to try it in the community pool tomorrow to test it....you may be right in the sense that there just isn't enough sensitivity to detect the foot of water I'm testing it in. Although purely math based I should be able to detect somewhere between an inch / three inches change.

I have some analog bubblers I'm currently using, but the goal of this is a low power, transmitting unit to send me water levels. Currently the unit has been running for about two weeks off my small solar cell and super capacitor....figuring out a good way to get these depths that has very little power usage has been my issue though....hence why I'm not sure that a bubbler is feasible for my purposes, just because of the draw required to force air through the tubing.

Any other potential thoughts though?

8

I would be curious how it does in the deep end of the pool. Also I wouldn't rule out applying some pressures if you can equivalent to depths.

Ron