ORP-3500 series is a kind of popular and cost-effective online pH and ORP controller , with plug-in pH/ORP-1220 sensor, which have good measurement accuracy, anti-interference,easy to install and operation features. Characteristics Ø White backlight LCD screen,several operations, easy for operation. Ø Be compatible for six kinds of buffer solution(10.00,9.18,7.00,6.86,4.00,4.01) which suitable for international standard. Ø Selectable temperature sensor which reduce the replacement cost. Ø Manual calibration is easy for on-site calibration. Ø EMC enhancement type could run smoothly under kinds of industry environment. Ø （4~20）mA output support instrument/transmitter modes and satisfy all （4~20）mA receiving unit. Ø Double relay high/low and delay control function could fulfill pH or ORP interval control and adjustment. Ø Several power supply to be selection according to the different models.Input AC/DC power, no polarity connection. Model selection model Power supply frequency（Hz） Current mode Sensor selection pH/ORP-3500 DC 24V ------- Instrument/transmitter pH-1220B plug-in sensor; ORP-1220B plug-in sensor or other sensors; TE-1230-14 temperature sensor