GTA04b7/Neo900

Issue 827: Very low temperature (-25C) on ds18b20 precision

Reported by mozo bata, Jul 18, 2017

I'm busy building a multi-probe temperature sensor and log system 
using a couple of ds18b20 probes on a Raspberry Pi.

They will be monitoring freezer temperatures that should be between 
-23°C and -18°C.

I'm a little concerned about the precision of the probes though as 
the datasheets only give the precision between the -10°C to +85°C 
Range (±0.5°C).

There's an error curve on page 18 here, and another almost identical 
one on page 20 here. Both of them however start a 0°C and only go 
up.(Here is the datesheet of ds18b20
http://www.componentschip.com/pdf/6a-DS18B20-T-R.pdf


As I'll be operating outside of this range, how/where can I find the 
expected accuracy?

The freezers that the probes will be monitoring are used for storing 
human tissue, and I'll need this before I can put forward a 
tender/proposal. Any Ideas?

Comment 1 by mozo bata, Jul 18, 2017

I'm busy building a multi-probe temperature sensor and log system 
using a couple of ds18b20 probes on a Raspberry Pi.

They will be monitoring freezer temperatures that should be between 
-23°C and -18°C.

I'm a little concerned about the precision of the probes though as 
the datasheets only give the precision between the -10°C to +85°C 
Range (±0.5°C).

There's an error curve on page 18 here, and another almost identical 

one on page 20 here. Both of them however start a 0°C and only go 
up.(Here is the datesheet of ds18b20
http://www.componentschip.com/pdf/6a-DS18B20-T-R.pdf


As I'll be operating outside of this range, how/where can I find the 

expected accuracy?

The freezers that the probes will be monitoring are used for storing 

human tissue, and I'll need this before I can put forward a 
tender/proposal. Any Ideas?

Created: 1 year 2 months ago by mozo bata

Updated: 1 year 2 months ago

Status: New

Labels:
Priority:Medium
Type:Defect