Libratherm offers 6 Zone Ramp/Soak PID Temperature Indicator/Controller (Model PRC-8000) for accurate temperature control of multiple zone gradual heating and cooling. PRC-8000 is ideally suitable and is most economical as it eliminates the need for a number of individual PID or ON/OFF Temperature Controllers required per zone. Each zone can be independently programmed for 16 steps of Ramp/Soak profile. Each loop parameter like PID, Hysteresis, Deviation Hold, Facility to skip unused channel, etc can be programmed from the user-friendly front panel membrane keyboard. The programmed profile and other parameters are retained in the non-volatile memory in the event of power failure.

This Multizone Programmer PRC-8000 can accept 6 Thermocouples or RTD(Pt-100)3 wire inputs and can provide switching PID or ON/OFF Control output in the form of DC Pulses or SSR or relay to drive external load contactor drivers for heating and cooling. It can simultaneously provide 6 analog PID control outputs in the form of (4-20)mA or (0-5)volt, which can be used to control heater power through Thyristor power pack (for the electrical heating system) or to control the position of a modulating motor valve (for oil or gas-fired heating systems). The analog outputs can be directly connected to a single-phase/three-phase SCR phase angle fired power controller which is ideally suitable for both resistive and inductive heating load.

Open or Faulty sensor indications for each zone are also displayed with the respective Zone No. It also provides common High and Low alarm relay outputs, which can be used for external temperature-dependent, interlocking, or audiovisual alarm. The display scan rate is programmable from 1 to 99 seconds, whereas the internal control scanning is at the rate of 100ms. Separate displays are provided to indicate simultaneously the Process temperature, Set temperature, and the channel/zone number. There is a provision to view on demand the online status of the running program viz, Percentage control output, balance time of the current process, set point of the current step, step no. in progress, etc. In case of power failure, the internal non-volatile memory back up ensures automatic resumption of control from the last point on power resumption.

This Multi-Channel Profile Controller PRC-8000 is ideally suited for the online pre and post welding heat treatment cycle. Where the large size jobs are heated by local heating pads. Temperatures are sensed using 6 to 8 K type thermocouples welded at different points. The common ramp/soak profile is run for all zones. To ensure the uniform heating cycle of all the zones, the PRC-8000 offers special features of common or individual deviation hold facility, thereby the guaranteed ramp/soak controlled is achieved. All 6 zones heating cycles can be synchronized with this feature. Since, for PWHT applications, thermocouples are welded on the job, all the thermocouples become grounded and may cause ground loop problems and may cause a jump in the temperature reading. To eliminate this effect, Libratherm offers and recommends thermocouple to thermocouple signal isolators.

PID SSR Programmer PRC-8000 can also be configured for controlling the average or uniform temperature of the large heating system, with a maximum of 6 sensors and 6 independent control outputs, following the common ramp/soak profile.

For a graphical representation of the actual process in progress, a duplex thermocouple can be used which can be connected to a multi-point recorder. PRC-8000 is available in standard 1/2 DIN (192 x 96 x 200mm) for 4 zones, 6 zones or 8 zones. It operates on 230 VAC with built-in high and low supply voltage trip circuits. It is also protected against industrial RFI/EMI Interference.

The serial interface of RS-485 in Modbus protocol is also optionally available for the computer interface. The supporting window-based software allows users to monitor the behavior of all the heating zones in both graphical and tabular form. This PWHT Stress Relieving Controller model PRC-8000 is a field-proven model in the industry and performing satisfactorily since 1994.