• Control through analog output (single set point) or relay
• Fully customizable
• RS485 interface
• Differential input for ground loop protection
• Automatic three point pH calibration
• Last calibration data
• Automatic Temperature Compensation
• Password protection
• Fail Safe Alarm System
• Overdosing safeguard

The HI 21 controllers are simple to operate, microprocessor-based pH process controllers packed with features. With HI 21 quick one, two or three point calibration at pH 4.01, 7.01 and 10.01 comes standard and you can choose from ON/OFF, proportional and PID control to save on chemicals. These instruments have a differential input, extending electrode life by eliminating ground loop current through the reference.

Password protection prevents unauthorized modifications in settings or calibration. The Fail Safe Alarm System protects the HI 21 against the pitfalls of process control, like power interruption or line failure.
Wiring the controllers is simple with extractable terminal modules. A host of self-testing features and user-friendly functions make HI 21 a great value.

For more flexibility and better resolution for chart recorders, any two points between 0 and 14 pH can be chosen to correspond to the analog output spans. Some HI 21 models are equipped with a bi-directional RS485 port, which allows remote control of the instrument from a PC.

Order Information:
Each HI 21 model is supplied with instructions.

• Manual
• Literature