Gravity: Analog Water Pressure Sensor (SEN0257)

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This is a water pressure sensor adopts DFRobot Gravity 3-pin interface. It supports standard 5V voltage input and 0.5~4.5V linear voltage output. It is compatible … read more

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I have an urgent question about this Gravity: Analog Water Pressure Sensor.

I want to measure the water pressure of a river and transduce it with a Pi or Arduino into Water depth. So my questions are:

  1. How can I extend the cable?
  2. Is the sensor good for permanent use in deep water?
  3. If not is there an alternative sensor I could use?

Thanks in advance

Hi Katharina

The cable can be replaced with a longer 3 wire cable, or extended with a waterproof cable extender. how long are you wanting to make the cable? The limits to the length of the cable will be most affected by the resistance of the cable.

I’m not sure but it seems to be fairly durable.

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Hi Clinton,

sorry it took me a while to find out the depth of the water. It’s about 3.5 m deep and it should be mounted together with the Pi a little bit higher…so maybe 5-6 m. Do you think I could get reliable data through this distance?

You should still get a good signal from that length. Your biggest worry will be the cable resistance but at that length it should be low enough to ignore. I would recommend putting the ADC on the pi side as long cables can cause problems at high frequency.

Hi Clinton,

thanks for your help. So I could buy 3 of this and connect it with a waterproof cable gland to the original wires, is that right?

Yes, that should do the job, just make sure there are no leaks.


Hey, I am wanting to use one of your pressure sensors for a water tank project where I use the pressure to determine the depth of the water, but I am not sure how suited the sensor will be under these conditions? The max depth of the tank is 3.5 meters which corresponds to a max pressure of 34 kpa where the max pressure of the sensor is 1.6 Mpa, Will it give an accurate reading at this pressure?

Hi Alexander,

This sensor would work fine for that. It’s not meant to be submerged, so you will need to mount it external to the tank near the bottom. It measures from 0-1.6 MPa. 1.6MPa is equal to 1600KPa, so you will get accurate readings at that pressure.

You can find all the details for this product here:

I hope that helps! Good luck on your project!

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On the product it specifies that the Sensor is accurate to 0.5-1%FS, and by full scale I am assuming by that it means any reading can deviate by 0.5% of 1.6 MPa? This leads to an error of 0.8 meters head if the error in the reading is 8 KPa (0.005*1600= 8 KPa, --> P = pgh … ∆h = 0.81 meters). Can I be expecting that the sensor will be giving me this much error in my project or have I interpreted the error scale incorrectly?
Cheers, Alex

Hi Alexander,

Sorry I missed that. Yes that you give you an error factor of 8-16 KPa. Or up to 2.3 PSI.

Hi there, I’m looking for a cheap effective sensor to measure the water depth of my watertank. The maximum water depth is around 2.2 m and I can get down to as low as about 100 mm. At first glance, The sensor seems ideal but then I noticed that it has an error of around .8 m and it says in the comments here that you can’t be submerged at the water depth I need of 2.2 m. All this makes me wonder what the heck this sensor can do and under what circumstances? I can’t imagine many applications we would be reading at the maximum pressure as 1.6 Mpa equals 163 m of water depth, and yet this means that the error is around 0.8 m which makes it useless for shallow water depth measurements? I’d still really like to use this sensor but would need to know it is going to work for my application. If not, do you know of any other reasonably priced water depth senses I could use? Cheers, Nick

Hi Nick,

This water pressure sensor is not suitable for water tank pressure, but is well suited for pressureized systems such as mains water supply or high pressure applications. To measure the depth of your water tank I would suggest taking a different approach, such as measuring the distance to the water surface with an ultrasonic sensor, or by using a barometer in a pipe, with the top sealed and the bottom open and in the water. As the water level drops the pressure of the air in the pipe will be reduced.

Good luck with your project!

Hi Stephen

You may have read about the tsunamis that have hit Indonesia in recently months. I want to try and help and build a tsunami early warning system can can be deployed easily and monitored in real time to help warn people. I can get all the software bits done but i have little expertise in hardware but i was hoping a raspberry pi based system with a combination of solar cells plus a data transponder will work. Do you think you have the hardware for this?


Hi Mohan,

We would have all the parts for that. Please start a new forum thread about this and we can discuss it there!

Thanks Stephen, I think this should do the job. what do you think? cheers, Nick

Hi Nick,

I think the error factor with this sensor will be too great to get meaningful readings from 2.2 meters of water. You could probably get more valuable data from three float switches mounted at different heights in the tank.

Hi Stephen,

Do you guys stock this one? It would seem to be accurate enough. what do you think?



Hey Nick,

Yes we do stock this item.

Do you think it would do the job with enough accuracy? It would seem so from the specifications as apparently it yields a +/-5 mm error.