DS18B20 probes: stainless tip, waterproof cable
Sensor
DS18B20 waterproof probe
The classic stainless-steel waterproof temperature probe on a cable. Temperature only, a few dollars, and it can sit in a brine tank or a glycol bath all year.
The cheapest wired path and the toughest. One data wire plus power and ground; several probes can share a single pin, so one board can watch many points.
Where to get one
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Specs.
| Measures | Temperature only |
|---|---|
| Accuracy | ±0.5 °C between -10 °C and +85 °C |
| Accuracy, full range | ±2 °C across the whole -55 °C to +125 °C span |
| Measuring range | -55 °C to +125 °C; happy in any freezer |
| Resolution | 9 to 12 bits, your choice: 0.5 °C down to 0.0625 °C. Resolution is not accuracy |
| Conversion time | 93.75 ms at 9 bits, up to 750 ms at 12 bits |
| Address | A unique 64-bit code per probe, lasered in at the factory, so many can share one wire |
| Interface | 1-Wire: three wires (red power, black ground, yellow data), and every probe on the run shares them |
| Needs | One 4.7 k resistor between the data line and 3.3 V, for the whole bus. Without it there is no bus at all |
| How many per pin | No protocol limit; about eight to ten on a short run with the usual 4.7 k resistor |
| Probe | Sealed stainless tip on a waterproof cable; can sit submerged |
| Power | 3.3 V from the board; no batteries |
Numbers from the Analog Devices (Maxim) DS18B20 datasheet. The same figures are on the build page for the DS18B20 node.
How to pick a good one.
- Get the sealed stainless-tip version on a cable, not the bare transistor-style part.
- Multi-packs are the value play: the probes chain on one wire, so extras cost you nothing in pins.
- Temperature only. If you also want humidity in the cold room, that is the SHT-30 probe's job.