ORP standard solutions allow you to test the precision of ORP electrodes. For example, by immersing the electrode in HI 7022 solution, you should read 470 mV @ 25°C/77°F
If the reading is outside the indicated interval, clean and condition your ORP electrode in HANNA® pretreatment solution. Use HI 7092 for oxidizing or HI 7091 for reducing pretreatment.
HI8733 EC Meter with Multi-Range 0.0 to 199.9 mS/cm ATC
HI733 Checker HC ® - Ammonia, HR 

