Gravity: Analog Water Pressure Sensor (SEN0257)

Hi Nick,

As we discussed earlier on in this thread, the error factor would be about .8 meters. I’m not sure where the 5mm error comes from. I do not think that this is suited for your application.

Hi Stephen,

As per the screenshots below, the error range i’m seeing is +/- 5mm. Where are you getting 0.8m?

Cheers,

Nick

Hi Nick,

You didn’t include your links until just now. This is essentially just a switch. It will tell you if it is submerged in water or not. If that is what you are after you should consider this as well:

Hi Stephen

realised that it was a switch just yesterday. Only really clear once I saw the installation diagrams.

Back to square one. What do you stock in the way of measuring the distance to the water surface with an ultrasonic sensor? Would these experience interference from echoes in the tank? What about capacitance wire loops down into the water whose capacitance varies linearly with water depth? As you can see I prefer the non-contact solutions.

Cheers and appreciate your patience.

Nick

Ps what’s the minimum order for free shipping with you guys? I’m developing associate degrees and short courses for the Uni of Tas down here and we’ll need to order bulk electronics kit.

The specs on this sensor are very good for the price but it would be nice if there were other variants that were for much lower pressures. For measuring the level in a water tank this device is not suitable (unless your water tank is 160m high :slight_smile: ). What’s needed is a full scale pressure of 20 or 30 kPa.
Any chance of pressuring (!) DFRobot to produce other variants?

Hey Folks,

I see a few people disagree with the idea that this would be useful in measuring the depth of water in a water tank. Doesn’t the +/- 0.5% error equate to 0.5% of the reading? ie… if my water tank were full, it’d read roughly 30kpa (tall tank, approx 1kpa per metre of water height). Taking the error into account, it could be between 28.5-31.5. Is there reason to believe this isn’t the case? (Admittedly, that’s +/- 14,000L in my case, but I can live with that)

I’ve got one unit on backorder, so I’ll eventually find out for myself :wink: Which brings me to my next question - I can’t find the cable length in any of the specs. Can anyone help?

Cheers,
Matt

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Hey Matt,

It’s a little hard to test this sensor as it requires a high-pressure water system, but I’d err on the side of caution and assume they’ve calculated the 0.5% error at close to the 1.6MPa, and thus having a significant error at the ranges you’re talking about. You may have luck calibrating this one, as others have reported it can be quite a bit off out of the box.

We don’t have any in stock to measure the cable, but if you need it to be longer, I believe a servo extension cable could work well: Servo extension cable 600mm Australia

Let us know how you go! We’ll definitely update our product page if you find anything interesting.
-James

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I am looking at the following sensor:

Gravity: Analog Water Pressure Sensor SKU: SEN0257

The accuracy is quoted as follows:



Measurement Accuracy: 0.5%~1%FS (0.5%, 0~55°C)



I’m uncertain how to interpret this specification.

My application will be dealing with pressures ranging from 0 to 0.4 mPa. Will the accuracy always be better than 1% within this range?

Reading a few more comments I conclude the FS means full scale ie. 1.6 mPa. So it seems the error is up to 0.016 mPa which I think I could live with. Confirmation of my final conclusion would be helpful.

Can I use the DF robot gravity water pressure sensor with the lopy4?

I bought a level shifter too but not sure if it can only shift digital signals?

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Hi Hilton,

Welcome back :slight_smile:

Unfortunately level shifters are only good for digital signals like I2C, UART, etc.

Certainly, there is an ADC on the LoPy, you could remap the 0.5-5V with a resistor divider to something that the LoPy can take

Is the sensor only for water? Or it can be used on other liquids like oil etc. too?

Hi Tepalia,

Good question, while you might get a reading the sensor itself might not last as long as expected: Avnet: Quality Electronic Components & Services

I’m no materials expert but I imagine the engineering team has a specific use-case in mind when developing a particular sensor, if the liquid its being used on is more inert than water it might last longer, might not?

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Thanks a lot for answering, dear.