long lasting wiring of many ds18b20 sensors
(Is) 2 conductor + braid cable ... the right choice?



Perhaps if it meets your specs for cost, flex and EMI reduction, environment and rodent-proof ?  it all depends on many things unspecified



  Is it OK to get tin plated wires to crimp?


Not for gold plated contacts.  WHy do you think it is tin plated?

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Read the "TIN Commandments"

Then you will probably choose only lubrication over Au plating over Ni plating.

I believe going up over 0'C increases the rate of condensation and oxidation from evaporation.

If this was for a hot surge connection, then I might suggest tin-tin contacts with cap discharge wetting the contacts clean each use.

Cables


Shielded twisted pairs (STP) is best for EMI CM rejection with the shield only terminated at the unit yet worst for high impedance "1-wire" bus length due to the added capacitance.  So UTP gives faster rise times but lower immunity.
UTP capacitance is about 52pF/m at 1-Wire speeds limited by Vcc/R current T=RC and you need about 10x bit rate for rise time for best performance.
STP can be up to 325 pF/m which limits the rise-time x cable length product.
Unshielded twisted pair (UTP) may be considerably less cost for power and signals but may need more EMI testing for susceptibility from ambient transients, SMPS, motor noise, arc welders, distant lightning, ESD, etc. depending on your impedance imbalance.


For better immunity Bus drivers are used.

Maxim guidelines for cable

Connectors

Other choices are those commonly used for telecom such as RJ-11, RJ-45 with Au contacts.

ESD protection

Must be considered to limit current from hiV cable charged connections.