YSI 1003A [605324] Amplified pH/ORP Sensor. The YSI 1003A pH and combination pH/ORP sensors have an internal, battery-powered pre-amplifier designed for use in difficult environments. The available extension adapter attaches to the bulkhead, so the longer sensors fit in the probe guard for the Pro1010 and Pro1020 cables (not needed on the Pro Plus Quatro cable). All YSI flow cells work normally with the YSI Professional Series line of handheld instruments.