Eurotherm Mini8 Controller Integration Guide

AO8/AO4 can only be installed in slot 4.

RL8 can only be installed in slot 2 or 3, but two (slot 2+3) can be installed simultaneously to obtain 16 relay outputs.

CT3 is only one piece per unit and is usually used for monitoring heater current.

If the heater fault detection function is required, the CT3 module and the controlled output module (DO8 or RL8 or fixed relay) must be configured simultaneously, and the current monitoring algorithm must be configured in the software.

2.3 Communication interface options

The communication function of Mini8 is a mutually exclusive option, and one must be specified when ordering:

Modbus RTU：RS485， Dual RJ45 interface, switchable between three wire or five wire system.

DeviceNet: CAN interface, speed 4800/9600/19200.

Profibus DP：RS485， 9-pin D-sub or RJ45, maximum 12M.

Ethernet/EtherNet/IP/Modbus TCP: standard RJ45, 10/100BaseT.

EtherCAT：100BaseT， Dual port.

All communication versions support multi station networking, making it easy to exchange data with PLC, SCADA, or DCS systems. In addition, the device also provides an independent configuration communication port (RS485 Modbus RTU) for connecting to iTools software for engineering debugging.

Deep analysis of control functions

3.1 PID Control Loop

Mini8 can be configured with 0 (pure data acquisition), 4, 8, or 16 PID loops. Each circuit is equipped with:

Control modes: On/Off (two position), single PID, dual channel PID (heating/cooling).

Output types: analog (4~20mA), time proportional logic output (for solid-state relays), relay output.

Cooling algorithm: Linear, water-cooled, fan or oil cooled options are available.

Setting method: Three independent PID parameters, supporting one click self-tuning (automatic tuning).

Disturbance free switching: automatic/manual disturbance free switching, or forced manual output.

Auxiliary functions: setting slope limit, output change rate limit, feedforward control, input tracking, sensor disconnection output preset value, circuit disconnection alarm, two internal setting values, etc.

This control performance is comparable to the Eurotherm 3000 series panel controller and can meet high-precision applications such as extruders, heat treatment furnaces, and environmental testing chambers.

3.2 Setpoint Programmer

This function is a software option (choose 1PRG or XPRG when ordering). Allow users to create slope/insulation programs:

Number of programs: Up to 8 independent programs.

Number of segments: Each program can have up to 16 segments (a total of 128 segments), and each segment can be set with target values, time, and slope.

Event output: Each segment can trigger up to 8 events (out of a total of 64 event outputs), which can be used to switch auxiliary devices such as alarm lights and fans.

Digital input control: can allocate functions such as running, holding, resetting, program stepping, jumping, synchronization, etc.

Power outage recovery strategy: You can choose to restart the ramp, reset the program, or continue running.

Servo start: You can choose to start the program with the current PV value or set SP value.

Typical applications: temperature curve of heat treatment, sterilization cycle, material aging testing.

3.3 Heater Failure Detection

By using the CT3 input module (3-channel current transformer input) and corresponding output module (DO8 or relay), it is possible to achieve:

Detection type:

Partial Load Failure - For example, some branches in a group of heaters are open circuited.

Over current.

SSR short circuit (causing continuous heating) or open circuit.

Measurement method: The cyclic algorithm measures the current of each heater in sequence, with only one heater measured at each measurement interval.

Current range: 0~50mA rms (from CT secondary side). The CT ratio can be set from 10:0.05 to 1000:0.05.

Alarm output: The upper and lower limits of the current for each heater can be set in the software, and an alarm will be triggered if it exceeds the limit.

This feature is crucial for scenarios such as plastic processing and hot runner systems where heating failure is not allowed to result in waste.

3.4 Toolkit Blocks

Mini8 has rich built-in soft logic function blocks, allowing for simple machine control without the need for an external PLC

Mathematical operations (24 blocks): addition, subtraction, multiplication, division, absolute value, maximum/minimum, power, square root, logarithm, exponent, toggle switch.

Logical operations (24 dual input blocks, 4 eight input blocks): AND, OR, XOR, latch, equal to, greater than/less than comparison.

Multiplexing device (4 blocks with 8 inputs): Select one of the 8 inputs based on the parameters.

BCD input decoding (2 blocks): decodes 8 digital inputs into 0-99 numerical values.

Input monitor (2 pieces): Record the maximum value, minimum value, and threshold exceeding time.

Signal conditioning: 16 point line fitting, polynomial fitting, smooth switching.

Timer (8 pieces): pulse, conduction delay, monostable, minimum conduction.

Counter (2 pieces): add/subtract, with directional signs.

Accumulator (2 blocks): Alarm when threshold is reached.

Real time clock (1 block): Date and time, up to 2 times can trigger an alarm.