Dear friends.
I would like to measure the VACUUM, inferior pressure to the atmosphere. (Example, the depression provocated by a recycled fridge compressor for example...)
Is the differential pressure sensor Mpx5010dp is OKAY to do this? Is someone has done this?
Regards.
The maximum measurable differential pressure is 1.45 psi or 10 kPa. Not much of a vacuum.
jremington:
The maximum measurable differential pressure is 1.45 psi or 10 kPa. Not much of a vacuum.
OK... to measure the vacuum produced by a re-used fridge compresor which "cheap" sensor you can recommend? I don't need much precision...
The SDX15A2 is an absolute pressure sensor but it's a bit expensive and so much good for what I need...
Can someone make a guess about the pressure by a refrigerator pump ?
I found a few numbers, going as low as 3% (30 millibar) or even 0.2% (2 millibar). I found that hard to believe, a refrigerator pump that I used in the past was not even close to those numbers.
The MPX5010 is a nice pressure sensor that goes very well with a 5V Arduino board.
The "Dual Port" version can probably be used to measure negative pressure.
It is not a good choice, since its range is wrong and the sensor is not meant for vacuum. It wil break at 40kPa.
Normal atmospheric pressure is 100kPa. When using a differential pressure sensor, and one port is open, then it must withstand 100kPa if the other port is 100% vacuum.
I think that means that a MPX5010DP will break.
There are better similar sensors. See NXP vacuum sensors.
They suggest a 15kPa to 115kPa dual port differential pressure sensor. I did not check what the different specifications are. There are more than 20 of those.
The SDX15A2 has a full span output of 90mV and is designed for 12V. You need to amplify its signal, and because of that, you probably lose accuracy.
There are also vacuum sensors on Ebay/AliExpress with a "industrial" look.
It won't be close to an absolute vacuum for sure (then you need a very different kind of pump than you find in a fridge), so maybe the MS5803-01BA is an option, it has a range of 10-1,300 mBar (absolute pressure).
Koepel:
There are better similar sensors. See NXP vacuum sensors.
They suggest a 15kPa to 115kPa dual port differential pressure sensor. I did not check what the different specifications are. There are more than 20 of those.
Yeah those are great especially the MPXV6115V6U this one sohuld be the correct one, but there is a problem : Unalvaiable... Only comprar a big quantity, Mouser or shops like those don't have the sensor...
But I found another one more easy to find, the MPX2200DP
This one have a bigger range then the MPX5010DP...
Do you think this one is okay for a fridge compressor vacuum measure? Another problem, I'm ignoring how much depression I have with this fridge compressor...
The ones that go well with an Arduino are the sensors with internal amplifier, temperature compensated, ratiometric output, and more.
The MPX2200 has a output with a span of only 40mV and is typically used with 10V. I don't see the MPX2200 in the list that NXP suggests.
I did not check the MPX4115AP datasheet, but I can find it at Conrad.com and at Amazon.com. However, the prices are ridiculous.
[Update] I checked the datasheet, and there seems to be no "Dual Port" version. Then it can not measure vacuum.
Perhaps those sensors with a "industrial" look is the best option.
I think that depression is the same as vacuum. Pulling the air apart and making the air thinner, that is vacuum.
I found this one:
https://www.agelectronica.com/detalle.php?p=BPS120-AD01P0-2DG*
The BPS120-AD01P0-2DG
The BPS120 -> i2c output
The BPS110 -> Analog output (apparently amplified and ready to be connected directly to the analog pins)
What do you think of those?
That could work, but the pressure range is weird: 1.03 to 6.89 KPa.
They don't start at zero. When the pump starts, the sensor is not working yet.
The I2C interface is easy.
int n = Wire.requestFrom( 0x28, 2);
if( n == 2)
{
uint16_t rawData = Wire.read() << 8;
uint16_t rawData |= Wire.read();
int status = rawData >> 14;
Serial.print( "status: ");
Serial.print( status);
int sensorData = rawData & 0x3FFF;
Serial.print( ", sensorData: ");
Serial.println( sensorData);
}
else
{
Serial.println( "Sensor not found");
}
Where do you buy things ? Then I can try to find more sensors.
Yes for me the i2c is not the problem thanks for sharing the code btw 
Tehre with A4 A5 SDA SCL and wire.h here we go!
The documentation of the BPS120-AD01P0-2DG says it's 0.15PSI to 1PSI, as I understood 1PSI is the atmosphere or the 1013 Hpa is correct?
So I can measure from 1 PSI downto 0.15 PSI (Near absolute vacuum)?
When you make a link, do your really tick the box to not open a new window ? Please don't. I clicked the link to the sensor for the datasheet and lost what I wrote. Luckily I found most of it in the "Drafts".
PSI ? Really ?
In Europe, we think that this is what you do all day: American Chopper vs The Metric System- Why mechanics should not work in inches. VIDEO] - YouTube.
Normal atmospheric pressure is 1 bar, 100 hPa, 15 psi.
Atmospheric pressure - Wikipedia.
If you have a sensor and keep one port open and have total vacuum at the other port, then the sensor detects 15 psi.
That is why NXP advises to use a sensor up to 115 kPa.
I'm sorry that I did not see that before :-[ I should know that 6.89 kPa is far too little.
You may want to give this a read. Using a refrigeration pump as a vacuum pump things like lubrication may need to be addressed. Most pumps like this will pull down to about 75 Torr, 10 Kilopascal, 1.45 PSI (starting from atmosphere of about 14.7 PSI) or 27 inches of HG (Mercury).
As to a vacuum transducer? Really depends on your pocket book and how accurate you want to get. A 0 - 15 PSIA transducer should be all you need. It will start at atmosphere and pull down. You could even use an old Bourdon tube vacuum gauge unless you want the electronics. Companies like Honeywell and Sen Sym have some reasonably priced transducers out there. Again, depends on what you want to spend if features like temperature compensation are not important you can get by inexpensive.
Ron
Koepel:
When you make a link, do your really tick the box to not open a new window ? Please don't. I clicked the link to the sensor for the datasheet and lost what I wrote. Luckily I found most of it in the "Drafts".PSI ? Really ?
In Europe, we think that this is what you do all day: https://www.youtube.com/watch?v=EUpwa0je6_Y.Normal atmospheric pressure is 1 bar, 100 hPa, 15 psi.
Atmospheric pressure - Wikipedia.If you have a sensor and keep one port open and have total vacuum at the other port, then the sensor detects 15 psi.
That is why NXP advises to use a sensor up to 115 kPa.I'm sorry that I did not see that before :-[ I should know that 6.89 kPa is far too little.
Dear friend, unfortunately, the "Open link in new TAB" doesn't appear, here is the proof: :o If you can tell me how I can get it it should be cool.
Btw I found another Differential sensor, this is the HSCDRRN600MDAA3.
I think it complies to measure what I need!
What do you think of it, I want to ensure before buying it.
Regards.
Sorry that I assumed you clicked that box :-[ The problem is on my side (PEBCAK).
A link without selecting the option to stay in the same window: https://forum.arduino.cc/
A link with selecting the option to stay in the same window: https://forum.arduino.cc/
Result: They are the same ! they both open in a new Tab in Firefox. It is just a Firefox setting, I think I override that setting, but it seems that sometimes that override fails. I can add it to my forum annoyances.
Those Honeywell sensors should work. Both analog and with I2C is okay. The analog version is easier.
The 'Gage' can not measure a negative pressure.
The 'Differential' should work, use 1.6 bar or 2.5 bar.
The 'Absolute' should work, use 1.6 bar or 2.5 bar.
Koepel:
Sorry that I assumed you clicked that box :-[ The problem is on my side (PEBCAK).
A link without selecting the option to stay in the same window: https://forum.arduino.cc/
A link with selecting the option to stay in the same window: https://forum.arduino.cc/
Result: They are the same ! they both open in a new Tab in Firefox. It is just a Firefox setting, I think I override that setting, but it seems that sometimes that override fails. I can add it to my forum annoyances.Those Honeywell sensors should work. Both analog and with I2C is okay. The analog version is easier.
The 'Gage' can not measure a negative pressure.
The 'Differential' should work, use 1.6 bar or 2.5 bar.
The 'Absolute' should work, use 1.6 bar or 2.5 bar.
To avoid this I always open a link with the wheel clic and it always open on a new tab xd
So, I will buy this one:
AG │ Detalles HSCDRRN600MDAA3*
When I receive it and I will make my tests, I will give feedback soon there!
Thanks a lot!
Why would you buy a 0.6 bar version ?
Suppose air is 100% air.
And complete vacuum is 0% air.
Then that sensor can measure down to 40%. If your pump is stronger, then that sensor can not measure it.
As I mentioned before, you will need an absolute pressure sensor, as otherwise you have to compensate for atmospheric pressure. Vacuum is an absolute pressure of zero, so 1000-1100 mbar lower than atmospheric. Maybe less if you're at elevation.
Also you never specified what final pressure you expect. The best vacuum we know of is in outer space, and even that is not absolute. The highest vacuum I ever worked with required multiple stage pumping over a rather long period of time, with the last stage a turbomolecular pump. I doubt you have such equipment, as if you would have it and know how to use it you wouldn't be here asking about it.
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