SensorMote Battery & Accuracy Question

[G550_Pilot]

I am currently using a resistance based eTape product to measure the water level in my pool and I was interested in trying the SensorMote to see if it is more accurate. I had a couple of questions:

1) What kind of battery life can I expect using the kit if I were to measure once per minute using the 3.7V 2000mah using the 433Mhz HW radio? I plan in using it like the wireless sump pump water level monitor?

2) What is the effective sensor range? Where I read my water level I have a basin 9" in diameter and 11 1/4" deep where the water level in the basin will be between 3 1/4" from the bottom at the water's lowest point (where I need to start adding water) and 6 1/4" inches from the bottom when full:


--------------                                               <----------------
|    |      |    |   <--- SensorMote                                          |
|    -------    |                                                                     |
|                 |                                                                     |
|~~~~~~~| Water High Level 6 1/4" From Bottom          11 1/4"
|                 |                                                                     |
|~~~~~~~ | Water Low Level 3 1/4" From Bottom              |
|                 |                                                                     |
|-------------|                                              <----------------

<--- 9" ---->

I could not find the exact dimensions of the SensorMote enclosure, but assuming 2" tall that would leave 5" from the top of the water at it's highest to the bottom of the SensorMote.
Would this be too little distance for accurate measurement and can the SensorMote accurately measure a 3" change in water level?


3) It looks like from the pictures that you had two different sized batteries in the case. Adafruit has a 2500mAh battery
that is 2.4" x 1.4" x 0.03". Would this fit in the case with the SensorMote and Moteino?

[perky]

Just throwing this out there if the SonarMote won't cut it
http://howmuchsnow.com/waterlevel/

[G550_Pilot]

Just throwing this out there if the SonarMote won't cut it
http://howmuchsnow.com/waterlevel/

Interesting....using light instead of sound...

[TomWS]

I am currently using a resistance based eTape product to measure the water level in my pool and I was interested in trying the SensorMote to see if it is more accurate.
[\quote]
I use eTape to measure the liquid level in my man-made stream pond area and it is very accurate, reliable (even when the whole unit is splashed with water and have a thick layer of ice built up on it) and currently the batteries in the unit (2xAAA) have been running over 22 months using 10 minute sampling rates and an RFM69HW radio.   The batteries still have plenty of life left in them and will probably be replaced when I winterize the stream this year.

If you don't have any grunge that will build up on the sensor (ie, don't use it directly in a sump well), then the sensor is good and the sampling circuit is very simple (search for liquid level sensor on this forum).

Tom

[G550_Pilot]

I am currently using a resistance based eTape product to measure the water level in my pool and I was interested in trying the SensorMote to see if it is more accurate.
[\quote]
I use eTape to measure the liquid level in my man-made stream pond area and it is very accurate, reliable (even when the whole unit is splashed with water and have a thick layer of ice built up on it) and currently the batteries in the unit (2xAAA) have been running over 22 months using 10 minute sampling rates and an RFM69HW radio.   The batteries still have plenty of life left in them and will probably be replaced when I winterize the stream this year.

If you don't have any grunge that will build up on the sensor (ie, don't use it directly in a sump well), then the sensor is good and the sampling circuit is very simple (search for liquid level sensor on this forum).

Tom

Tom -

I am having issues with my eTape where the resistance returned by the tape fluctuates. Because of this, it makes it unusable for my pool project. That is why I am looking for something more accurate.

BTW - searching for "Liquid Level Sensor" on this forum just returns our conversation :-)

Would you care to share your setup and configuration?

Here is how I am reading mine:

digitalWrite(ETAPE_POWER, HIGH);                          // Turn on the power to the eTape circuit
pool.resistance = analogRead(ETAPE);                      // read etape resistance
digitalWrite(ETAPE_POWER, LOW);                           // Turn off power to the eTape circuit


Attached is a graph of the readings that I am getting back from the eTape.

[TomWS]

The circuit that I posted in https://lowpowerlab.com/forum/projects/moteino-liquid-level-sensor-using-etape/msg13511/#msg13511 compensates for temperature/drift variations in the eTape.  It provides a constant current in the reference leg, based on the resistance value of the reference leg, and measures the voltage, using that same current, of the measurement leg.  It's been stable for me, but is susceptible to short term changes due to waves and splashing.

Tom

[perky]

The circuit that I posted in https://lowpowerlab.com/forum/projects/moteino-liquid-level-sensor-using-etape/msg13511/#msg13511 compensates for temperature/drift variations in the eTape.  It provides a constant current in the reference leg, based on the resistance value of the reference leg, and measures the voltage, using that same current, of the measurement leg.  It's been stable for me, but is susceptible to short term changes due to waves and splashing.

Tom

You could encase it in a tube, it would have the effect of filtering waves as the pressure would come from the bottom of the tank to support the column of water in it and splashes would be eliminated.

Mark.

[TomWS]

You could encase it in a tube, it would have the effect of filtering waves as the pressure would come from the bottom of the tank to support the column of water in it and splashes would be eliminated.

Mark.

If it was a rigid tube and the eTape could be supported solidly within it, yes, you're right.  However, having done two generations of this, where the first Gen was simply placing the eTape inside a heavy PVC conduit and the second gen uses eTape's polycarbonate protection tube, neither of these completely isolated the splashing effect.  My case is probably extreme, however, as the sensor is placed off to the side of the bottom of a waterfall on a man-made stream - lots of splashing.  It also won't prevent waves from affecting the reading as the water level does, in fact, change.  Long term averaging is probably the simplest and most reliable solution.

Tom