lps27hhw problem with negative temperature

[DPesk.1]

Hello

We use the lps27hhw in our devices. When temperature is positive - all right. But when temperature is negative - the sensor sends the temperature less than it actually is (example -40* instead -20*).

I put the appliance in the freezer, the temperature is -19*, and show data from the sensor via BLE app.

0 byte - status reg

1-3 bytes - pressure reg

4-5 bytes - temperature reg

The sensor send -38 degrees of celsius.

After that I put the device in the oven, the temperature is +50*. All right.

 

What is the problem?

[Eleon BORLINI · Accepted solution]

Hi @DPesk.1​ ,

Did you have the possibility to try some other lps27hhw devices in the same conditions, in order to check whether it is a common effect or the device under test is just an outlier?

The negative temperature range (in Celsius), is commonly the most tricky to be handled, since there is the possibility of condensation of the water on the sensor if the humidity is not controlled.

In particular, the freezer doesn't usually control the humidity, so a condensation effect is common.

My suggestion is to try the device (which is a pressure sensor, so whose target is the pressure measure, not the temperature one) in a humidity-controlled environment.

But in case the effect is constant (constant gain among many sensors), you might think to compensate it via software (with a first order coefficient compensation).

-Eleon

[DPesk.1]

Hi

Thank you for your answer

We have this problem in all our devices.

We haven't humidity-controlled environment. And coefficient may vary from 1.5 to 2.0 for negative temperature (according to our observations)

[Eleon BORLINI]

Hi @DPesk.1​ ,

understood. But is the pressure measure ok?

I would suggest you to try to compensate the temperature gain by software, if the pressure measured is ok.

-Eleon

[DPesk.1]

Yes, pressure is ok. But temperature have a problem. Thank you for answer