Temperature sensor accuracy

Hi Nico,

If required, these types of boards are quite neat to act as a sort of semi-reference. The accuracy is claimed to be +- 0.1 degrees C within a certain range. I have an older model that claims +- 0.3 degrees C I think.

They can be accessed via Bluetooth on mobile, and can show historical data as well. Link: https://www.newark.com/sensirion/sht4x-smartgadget/ref-design-board-temp-humidity/dp/74AJ2003 

Thanks for pointing that out, that's really accurate!
That would solve the problem of which sensor to trust as a baseline.

A man with a watch knows what time it is. A man with two watches is never sure

I've added it to my wishlist

ntewinkel said:

that's really accurate!

Looks like the reference design module uses the SHT40 sensor

Looks like the accuracy takes a bit of a deviation at around the freezing point, which you are interested in.

For comparison, the performance plot for the DS18B20 sensor

From the specs the performance is not much better, it's just different, at zero degrees for the sensor. But I think the problem is, without a reference design, the discrepancy will easily exceed those charts (for instance having the sensor powered up will warm it, or if its on a board then other components or drafts will heat or cool it. I observed that with a SHTxx chip too, where my layout was not the same as the reference board, and the measurement was off by more than the datasheet curve (by about 1-2 degrees from memory). The Sensirion board is their reference design, so should be more accurate - hopefully!

Edit: This was my layout, but it was not fit for purpose, the measurement was off by several degrees. Subsequently I changed the board shape to more closely reflect the reference design, but I've not tried the new layout yet.

New layout:

From the specs the performance is not much better, it's just different, at zero degrees for the sensor. But I think the problem is, without a reference design, the discrepancy will easily exceed those charts (for instance having the sensor powered up will warm it, or if its on a board then other components or drafts will heat or cool it. I observed that with a SHTxx chip too, where my layout was not the same as the reference board, and the measurement was off by more than the datasheet curve (by about 1-2 degrees from memory). The Sensirion board is their reference design, so should be more accurate - hopefully!

Edit: This was my layout, but it was not fit for purpose, the measurement was off by several degrees. Subsequently I changed the board shape to more closely reflect the reference design, but I've not tried the new layout yet.

New layout:

shabaz said:

I changed the board shape to more closely reflect the reference design

A half-way house might be something more like this

https://sensirion.com/products/catalog/SHT85

shabaz said:

for instance having the sensor powered up will warm it, or if its on a board then other components or drafts will heat or cool it.

It's super windy just now...

And the sensors are both reporting a similar temperature now... the light blue line is the DHT sensor that is inside of a 3D printed housing and usually shows a few degrees warmer... maybe I need to rethink that setup!

I have ice cubes in the freezer that should be ready soon, so I can test the freezing point with both sensors.