METSO Isolated Input Module IOP301

METSO Isolated Input Module IOP301

This module, featuring 16 isolated input channels, can be configured for any mix of voltage or current inputs. The current loop can be powered from a field supply or from a system loop supply provided via the backplane edge connector. For current inputs, this module is pin and function compatible with the IOP302 input module.  

LED Indication

A green LED, labeled Active at the bottom of the module front panel, is on when system power is present and the module is communicating with the DPU. This LED blinks on and off when the module is not being scanned by the DPU.

Bus Address

This module supports two modes of operation selected by jumper setting. For use as a replacement for a Model 564 module this module requires 16 bus addresses and provides 15 channels.   The addressing rules specified in the Model 564 manuals still apply. When used as a maxPAC module, the module only requires two bus addresses and provides 16 channels.   Each module address must be on an even boundary (i.e. 32, 34 50 etc.) in the range of 32 to 252.    Addresses 0 to 31 are reserved for digital input modules.

Jumper Configuration

The module contains two jumpers, located near the address switches. Refer to the following table for jumper setting information.

Program Resistors

Jacks are provides at the front of the module for the installation of a pair of resistors per channel. These resistors can be used to scale a voltage input to the 2.4V span of the A/D measurement. These resistors are identified as follows:

The input circuit configuration for each type of input is shown in the following sketch. An electronic fuse protects the 24-volt loop power to the transmitter. A 200-Ohm thermistor in series with the 4-20 mA input provides current limiting for voltages up to 100 Volts. The 24-volt loop supply is available to the module from the backplane. For current inputs with external shunt the channel is configured for voltage input and Rs = 0.

Module Operation

This microprocessor-based module supports up to 16 isolated high level inputs. A sigma delta A/D and precision reference is provided for each pair of inputs. The A/D reads the voltage generated by the selected input and converts the differential measurement to a 15-bit plus sign binary value representing the voltage input, which is read by the microcontroller. The microcontroller initiates the conversion and waits for the conversion to complete.   The digital filter in the oversampling A/D provides excellent 50/60 Hz normal mode rejection. Prior to starting each conversion, the microcontroller selects one of the two input channels by means of two solid-state, optically coupled relays. The two inputs are multiplexed with optical relays to provide channel to channel isolation. Immediately following each measurement, open input and over range conditions are checked.   A separate DC/DC converter provides isolated power to each A/D converter measuring circuit. Communication between the microcontroller and each A/D is serial at 100kHz. A separate group of optical isolators provide the isolation between each A/D and the serial logic circuits. The microprocessor provides the input data to the DPU on demand via the bus FPGA. The FPGA provides the I/O bus interface logic; its program is loaded from the FLASH on power up.   Module calibration is done automatically at power up following startup diagnostics. Calibration is repeated periodically online to compensate for temperature effects.  

Diagnostics

The module executes diagnostics on power up. When an error is detected on power-up or during online operation, the front-panel green LED, labeled Active, blinks the first digit at a slower rate and the second digit at a faster rate. During normal operation the active LED is on continuously or flashes at a steady one-second rate when the module is not being scanned. The diagnostic codes are as follows:

Field Wiring for Redundant Modules with Common Transmitter

The following figure shows the recommended wiring for two redundant IOP301 analog input modules that share a common two-wire or four-wire transmitter.   Redundant inputs must be configured as voltage inputs with an external 100 Ohm shunt resistor. The recommended maximum distance between the shunt and the I/O module is 10 meters. The +24V connection should be independently fused to each transmitter.   The connection to the (-) terminal of the 24v supply must be made at the (-) side of the shunt resistor. The voltage that is developed across each 100-Ohm shunt by the 4-20 mA signal from the transmitter is wired to the AI module using twisted pair cables. A PTC thermistor is recommended between the transmitter output and the 100-Ohm shunt. This protects the 100-Ohm shunt against over voltage and provides additional resistance to increase the transmitter load to 250 Ohms. Kit IOP306 supplies 16 pairs of 100-Ohm shunts and thermistors to support two IOP301 analog input modules.  

Overview

The IOP302 module features sixteen 4-20 mA common input channels. The IOP305 module features 16 voltage input (not current input) channels. Transmitter loop power is available to the module via the backplane, providing individually fused 24V transmitter power for each channel.