# The installation of the HK-1100C water pressure sensor to measure height

I hope that all of you are doing well.

I would like to know, if and how, can someone use the HK-1100C water pressure sensor to measure the height of the water inside an overhead water tank. The pressure sensor is an analogue sensor that produces an output voltage ranging from .5 volts to 4.5 volts after detecting the pressure (Further details are in the link).

I would also like to know as to where on the tank should i install it ; should it be at the bottom of the tank (externally fixed on its side [1]) , or should it be installed on (screwed in) the outlet (the supply pipe to the house [2])
Is the pressure sensor in contact with the water ?

2-

I would like to know, if and how, can someone use the HK-1100C water pressure sensor to measure the height of the water inside an overhead water tank.

1.2MPa is about 120 meters of water.
The sensor, with Arduino's 10-bit resolution, can detect about 820 different levels (4/5 * 1024).
That's about 15cm of water per A/D value.
If your tank is 1.5 meters tall (water level difference), then you can only detect about 10 levels of water.

So that sensor seems to be ok to measure water pressure (0-12bar), but not so much water level in an open overhead water tank.
Leo..

What type of tank do you really have? Your diagram shows a pressure tank with a rubber bladder and a sealed air chamber. However your project wants to measure water level. If you want to measure water level of a tank that is vented to the atmosphere, your pressure gauge will allow you to compute that.

But if your tank is sealed with a rubber bladder, it is designed to maintain pressure on the water, as the water level is lowered with use. The sensor will not function to measure water level. This is the type of pressure vessel used with our water well to maintain pressure and keep the well pump from cycling on-off rapidly.

What is the purpose of measuring water level?

Paul

A pressures sensor is a good way of measuring water levels, and millimeter accuracy is possible, if:

• the water surface is open to the air, and
• you compensate for atmospheric air pressure.

When using a differential pressure sensor you don't have to worry about the second part, as the sensor measures pressure relative to the atmosphere.

As pointed out above, you do have to get a sensor with a range that's not too much more than the range you're measuring, or you start losing accuracy.

Paul_KD7HB:
What type of tank do you really have? Your diagram shows a pressure tank with a rubber bladder and a sealed air chamber. However your project wants to measure water level. If you want to measure water level of a tank that is vented to the atmosphere, your pressure gauge will allow you to compute that.

But if your tank is sealed with a rubber bladder, it is designed to maintain pressure on the water, as the water level is lowered with use. The sensor will not function to measure water level. This is the type of pressure vessel used with our water well to maintain pressure and keep the well pump from cycling on-off rapidly.

What is the purpose of measuring water level?

Paul

hi paul
the water tank is covered with a lid but isn’t airtight , it is vented . i am working on a project which is to design a water level monitor with two level sensors : the sonar and the pressure sensor.
the arrangement of the sensors on the tank are displayed in the attachment .
i am still unsure as to where the pressure sensor needs to be installed , is it on the outlet (like in the diagram) or is it at the bottom of the tank

wvmarle:
A pressures sensor is a good way of measuring water levels, and millimeter accuracy is possible, if:

• the water surface is open to the air, and
• you compensate for atmospheric air pressure.

When using a differential pressure sensor you don't have to worry about the second part, as the sensor measures pressure relative to the atmosphere.

As pointed out above, you do have to get a sensor with a range that's not too much more than the range you're measuring, or you start losing accuracy.

the max tank height is 2m and the tank is not airtight , just has a plastic lid that can be screwed on.
is there really a way to get millimetre accuracy using the sensor i have mentioned.

Not with that sensor, nor with the Arduino's ADC.

Sensor: get one with a range of 0-25 kPa or so (that's 2.5 meters of water) and a resolution of better than 10 Pa (10 Pa = 1 mm of water).

Preferably digital output, makes it a lot easier.

If analog output, you have to get an ADC with 16-bit resolution. The Arduino's ADC has 1024 steps, so with a 2500 mm range you can never get better than 2.5 mm per step, in practice more like 7.5 mm due to the ADCs error. You also have to design a circuit that's pretty low noise to even get to that resolution.

wvmarle:
Not with that sensor, nor with the Arduino's ADC.

Sensor: get one with a range of 0-25 kPa or so (that's 2.5 meters of water) and a resolution of better than 10 Pa (10 Pa = 1 mm of water).

Preferably digital output, makes it a lot easier.

If analog output, you have to get an ADC with 16-bit resolution. The Arduino's ADC has 1024 steps, so with a 2500 mm range you can never get better than 2.5 mm per step, in practice more like 7.5 mm due to the ADCs error. You also have to design a circuit that's pretty low noise to even get to that resolution.

https://www.ebay.com/itm/BMP280Atmospheric-Pressure-Sensor-Temperature-Humidity-Sensor-Breakout-Arduino-/132767394766?_trksid=p2349526.m4383.l4275.c10#viTabs_0

and does the width of the tank have anything todo with the pressure , such as the tank is 1.5 meters tall but more than 2meters wide , will the aforementioned sensor be able to detect the height and not be crushed

I don’t think an atmospheric pressure sensor like the BMP280 is going to survive submersion in water… though you could mount it inside a pressure pipe or so. It’s an absolute sensor so you need a second one for atmospheric.

If you want to use a pressure hose or so, the MPX5100 may be useful. It can do up to 10 meters of water so you only use the bottom 20% of the scale (so the first 1V of the 0-5V scale).

And no, width has no effect on pressure.

wvmarle:
I don’t think an atmospheric pressure sensor like the BMP280 is going to survive submersion in water… though you could mount it inside a pressure pipe or so. It’s an absolute sensor so you need a second one for atmospheric.

If you want to use a pressure hose or so, the MPX5100 may be useful. It can do up to 10 meters of water so you only use the bottom 20% of the scale (so the first 1V of the 0-5V scale).

And no, width has no effect on pressure.

by hose type attachment do you mean something like in the diagram i have attached . the pressure sensor is going to go on the outlet (supply pipe to the house). i assume that the sensor is going to be in contact with the water. This is analogue sensor if i am not wrong

No, separate pressure hose or pipe. One end open at the bottom of the tank, the other end sealed. Air pressure inside is a direct measure for the water level (after correction for atmospheric).

Pressure at the bottom of a 1 meter column of water is 9.80665 kPa, what will be the maximum depth of water in your tank?

outsider:
Pressure at the bottom of a 1 meter column of water is 9.80665 kPa, what will be the maximum depth of water in your tank?

the tank height varies from 1.5m to 2m

the issue is that i am trying to construct a fault tolerant water level sensor for the overhead tanks found in most the houses here.

i am using a sonar sensor and a pressure sensor as the two level sensing devices , so that if one fails , the other sensor would take over the monitoring process .

i have managed to calibrate the sonar to detect 1mm changes , but i can’t seem to decide upon the pressure sensor that can do the same . the ones that are currently available to me are the hk-1100c 1.2Mpa pressure sensor (it is threaded , so i thought i would screw it on to the outlet of the tank) and the BPM 280 atmospheric pressure sensor .

the latter’s circuitry isn’t water proof but its resolution is better (according to its data sheet, it can handle upto 2Mpa before getting damaged). This sensor is digital, but can not be screwed on (i might have to change my design ).
i have already attached the basic design showing where the sensors are going to be on the tank (i’ll attach it again).

Make sure your sonar is weather proof. Don't bother with the cheap HC-SR04 ones (other than maybe for testing); get one of the sensors that are used for cars as reverse collision alarm.

wvmarle:
Make sure your sonar is weather proof. Don’t bother with the cheap HC-SR04 ones (other than maybe for testing); get one of the sensors that are used for cars as reverse collision alarm.