Controller R251 is an in-built programmable controller intended for temperature regulation of electric ovens and warming systems using contractors and solid state relays (SSR). According to its settings, the controller allows programming of arbitrary temperature cycle consisting of one to eight segments and one final segment. Each segment is defined by time of growth or decline to goal value, and by the goal value itself. The type of final segment can be infinity hold, controlled decay, or uncontrolled decay.
The controller R251 offers a wide range of options for highquality regulation, delayed start, etc. Parameter settings are achieved by five-keys foil keypad in dialog mode. Temperature and time are displayed on 5-character LED display, the cycle progress is portrayed on LED bracket, consisting of four LEDs. Another four LEDs are used to indicate current state of controller outputs.
Temperature can be measured by resistive sensors (Pt100, Pt1000, Ni1000) or by thermocouples (B, C, E, J, K, N, R, S, T, voltage 0–39 mV and 0–78 mV). The input sensor can use current output 0-20 mA or 4-40mA as well. It is necessary to state the requested sensor type (voltage, resistive, current) in your order, the type of thermocouple or range of input current can be adjusted from controller keypad, after entering a service password.
The output part of the controller R251 consists of three relays (two of them with N.O./N.C. contacts 230V / 2A, one with N.O. contacts 230V / 2A) and one 12V / 10mA output for the solid state relay (SSR) actuation. The function of each relay can be selected from controller keypad, after entering a service password. It is also possible to add a voltage or current output for proportional elements actuation.
Operating the controller, adjusting of parameters and diagnostic functions are presented by system of wellarranged menu views, showing textual acronyms on red 7-segment LED display, guiding the user through all options and settings of the controller.
Access to controller settings is divided into five levels, according to impact on regulated system. To avoid unauthorized intervention, access to the lowest three levels can be secured by passwords. Passwords for upper two levels are compulsory and can not be changed.
In case when the controller is equipped with communication module, entire settings can be performed through PC.
During a power supply failure (blackout) all parameters remain preserved and after power recovery the controller continues in the process.