2. Features
The AL808/AL809 is a versatile, high stability temperature or process controller, with selftuning, in 1/4 and 1/8 DIN sizes. It has a modular hardware construction with the option of two control outputs, two alarm relays and a communications module. Two digital input are included as standard. The hardware is configurable for heating, cooling or alarm. Precise control An advanced PID control algorithm gives stable straight-line control of the process. A on-shot tuner is provided to set up the initial PID values and to calculate the overshoot inhibition parameters. On electrically heated loads, power feedback is used to stabilise the output power and hence the controlled temperature against supply voltage fluctuations. Dedicated cooling algorithms ensure optimum control of fan, water and oil cooled system. Universal Input A universal input circuit with a advanced analogue to digital convertor samples the input at 8Hz and continuously corrects it for drift. This gives high stability and rapid response to process changes. High noise immunity is achieved by rejection of 50/60Hz pick-up and other sources of noise. Sensor diagnostics are also provided. The input will accept all standard thermocouples, the Pt100 resistance thermometer and linear millivolts, milliamps or DC volts. Input filtering from OFF to 999.9 seconds is included. Easy to Use A simple LED display provides a bright, clear display of the process value and setpoint. Tactile pushbuttons ensure positive operation. Access to other parameter is simple and easy to understand and can be customised to present only those parameters that need to be viewed or adjusted. All other parameters are lock away under password protection. Alarms Up to four process alarms can be combined onto a single output. They can be full scale high or low deviation form setpoint, rate of change or load failure alarms. Alarms messages are flashed on the main display. alarms can be configured as latching or non-latching and also as blocking type alarms which means that they will become active only after they have first entered a safe state. Digital Communications For communications with a host computer system the instrument can be fitted with either an EIA485 or EIA232 digital interface. This enables the automatic recording of measured values on a printer.

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