MPL3115A2 absolute accuracy

[evacuate]

The absolute pressure accuracy for the MPL3115A2 is -400Pa to +400Pa as per the datasheet.

Would it mean that the output will always be offset by any value between -400 Pa to +400 Pa and I would need to do a offset correction to get it accurate.

What absolute accuracy for pressure can I get with the MPL3115A2 is something within +/- 20 Pa possible?

I am using the MPL3115A2 to measure absolute pressure.

Any hints at getting highly accurate pressure data from the MPL3115A2 would be highly appreciated.

[darioarias]

Hello,

Then my advice would be to use gauge pressure instead. This type of sensor is zero referenced with the atmosphere. It truly depends on which is the maximum pressure of the system, but that some parts that you could use is the MPXV4006 or MP3V5004G this devices range from 0-6 kPa and 0-4 kpa respectively with an accuracy of +/- 2.5% and +/- 1.5%. The second one can reach an accuracy of +/- 50 Pa (Probably the best accuracy). This sensors have analog output and also come in differential configuration.

Regards,

Darío

[evacuate]

Thanks Dario,

First of all can the sensors that you recommened MPXV4006 or MP3V5004G measure pressures below atmosphere. My measuring range is mostly from atmosphere pressure to around 10kPa below atmosphere.

If i record the offset once and store it in external memory and then subtract it from the live reading would I get accurate readings?

You see for this application I need to measure pressure from atmospheric pressure (approx 100kPa) to 10kPa below atmosphere so lets say 90 to 100kPa and I want this range to be sufficiently accurate and I don't mind storing the offset in external memory.

As I said earlier a accuracy of +/- 50Pa... so with the offset subtraction shouldn't I get accurate readings.

My other option is to actually go with a guage pressure sensor like MPXV7007 which has a range of -7 to +7kPa and +/-5% error of full scale span (4V) which comes to 0.2V, even here I'm planning to do offset correction.

Which of this is a good option MPL3115A2 or the MPXV7007?

Thank Again!

[darioarias]

Hi,

1.  Since the adjustments are stored in volatile registers, they are lost once the device is off, the device does not have any memory registers, only configuration registers. If you want to store back the data it would be necessary  to have an external memory.

2. The value of +/- 0.4 kPa is the best accuracy this device is capable of. One key factor to consider is how much pressure your container will handle? In other words, which is maximum pressure at which the container is exposed? Because is the range is small, you can consider using a pressure sensor with lower range and better accuracy. The MPL3115A2 has a range of 50 kPa to 110 kPa, so 20 Pa or 50 Pa are very small in comparison.

Actually the MPL3115A2 is an special unique type of sensor, and is the only pressure sensor we offer with that packaging. There is also the MPL115A but it is an absolute sensor as well.

Dario

[evacuate]

Thanks Dario,

That was indeed very helpful. So in summary the MPL3115A2 will not be

the right sensor for this application ? What about simple baromteric

pressure sensing, suppose I want to measure pressures near atmosphere

quite accurately, is there a way to calbrate this sensor to +/- 20Pa at

pressures near atmospheric?

Regards,

[darioarias]

Thank you for writing,

Yes there is always this typical offset of +/- 0.4kPa and this is the maximum accuracy that is possible to get with this sensor and it's a very high accuracy. For example if you are measuring 1 ATM (101,325 Pa), you'll get a measurement between the range 100,925 Pa to 101,725 Pa, this means an accuracy of roughly +/- 0.4%. The accuracy of +/- 20 Pa is nearly impossible, because if you try to measure the same 101,325 Pa this would imply  an accuracy of  +/- 0.02%.

This device is factory calibrated for sensitivity, offset for both Temperature and Pressure measurements. Trim values are stored, on-chip, in Non-Volatile Memory (NVM). In normal use, further calibration is not necessary; however, in order to get the highest possible accuracy, the device allows you to override the factory set offset values after power-up. This adjustments are stored in volatile registers. The factory calibration values are not affected, and are always used by default on power-up.

Dario

[evacuate]

Thanks for the extensive answer.

I am using this sensor to measure absolute pressure in a container, so I

need higher accuracy.

If I have understood your answer correctly:

User can override the factory calibration and this has to be done

everytime the device power's up.

1. is there a way to store the recalibrated value back I mean we do some

calibration inhouse at our factory .. we would need an external eeprom

for that right?

2. After overriding the factory calibrated value is it possible to get

an accuracy of +/- 50 Pa.

This sensor is in a small form factor and well suited for my application

I wonder if there are guage pressure sensors available in the same form

factor.

Thanks again