HDA 5500 Intelligent Display Unit:
The HDA 5500 is a microprocessor controlled display and control unit in standard control panel module housing. A single-chip microprocessor controls all functions. A maximum of 3 analog inputs and 1 analog output is possible. The analog input signals are converted by a 10 bit A/D converter and displayed according to the measuring scale selected by the user. Each of the 4 maximum possible relays can be allocated to each of the 3 analog sensor inputs or the differential between sensor signals 1 and 2. All operating parameters such as switching points and switch-back (i.e. hysteresis) points can be programmed by means of the MODE and SET keys. The relays switch as soon as a pre-set switching point is reached, or after a programmed delay. This function suppresses the reaction of the relays to short-term and irrelevant variations such as pressure spikes.