LM75A LSB are always zero

Andy Brooker

Prodigy 30 points

Other Parts Discussed in Thread: LM75A

Hi Thank you for reading this.

I am working with a project that has 3 LM75A s on the I2C bus.

When it started all was fine but now I can only see temperature down to 0.5 of a degree.

Looking at the raw data I receive 10000000 or 0000000 on the LSB from all the sensors.

over 9 years ago

0 Aaron Heng over 9 years ago

TI__Mastermind 37260 points

Hi Andy,

Could you please provide me your schematic? Thanks.

Aaron

0 Ren Schackmann over 9 years ago

TI__Mastermind 43815 points

Hi Andy,

There are many competitor devices on the market that are compatible with LM75 temperature senor. LM75A always has 9 bit resolution, but other products have configurable resolution. Have you inadvertently swapped for another product?

The 9 bit resolution of LM75A translates to 0.5C temperature resolution. The first 8 bits correspond to the integer portion of the temperature on the left side of the decimal. The least significant bit corresponds to 0.0 or 0.5C.

Ren

0 Andy Brooker over 9 years ago in reply to Ren Schackmann

Prodigy 30 points

When I first put the project together I was receiving the full 0.125 resolution in the readings.
As part of my testing I have swapped one of the LM75As for a spare and at the moment that one is giving 0.125 but the other two are not.

0 Ren Schackmann over 9 years ago in reply to Andy Brooker

TI__Mastermind 43815 points

What is the package marking on your device?

Thanks,
Ren

0 Andy Brooker over 9 years ago in reply to Ren Schackmann

Prodigy 30 points

Ren Schackmann said:
What is the package marking on your device?

Thanks,
Ren
Hope this helps

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LM75A LSB are always zero