yes the pH probe needs to be polarized and calibrated before use. It is suggested to put in a pH buffer before calibration.

to be brief / short:

cf: http://www.hannacan.com/FAQ_en.html

>

also contained in:

HANNA Knowledge Base [http://hannainst.com/knowledge-base], see

[http://hannainst.com/knowledge-base#dissolvedoxygenion] 

cf.: https://www.fondriest.com/pdf/thermo_ph_electrode_hb.pdf :

p.18: "Between buffers, rinse the electrode with distilled water and then with the next buffer. To reduce the chance of error due to polarization, avoid rubbing or wiping the electrode bulb. Use a lint-free tissue and gently blot the bulb"

Also perhaps (general information) see: http://www.broadleyjames.com/faq