Rockwell Automation T7420A User Manual

ICS Regent+Plus

PD-7023

Analog Input Modules

60 Hz Rejection and Fast Response

(T7420A and T7420AF)

Issue 1,

Analog input modules provide data input for a maximum of 16 field analog signals per module. Two types of modules are available: one for high noise immunity (60 Hz rejection) and one with low noise immunity (fast response).

Features

Sixteen single-ended or eight differential Interface to current current to voltage conversion (resistors are provided as part of the I/O Termination Assembly - see PD-7901).

inputs using external 250 ohm resistors for

voltage

March, 06

inputs.

Fault tolerant operation when connected in parallel with redundant modules of the same type.

Hot replaceable.

Jumper-selectable input ranges.

12-bit analog to digital resolution (1 part in 4096).

Sample rate of all channels in 1.8 msec (differential) or 3.6 msec (single-ended).

60 Hz rejection (T7420A) and fast response (T7420AF) versions available.

2500 volt isolation between analog and digital logic cir

Individual front panel indicators on each module show module active and fault status.

TÜV certified for safety, Risk Class 5.

Each module’s triplicated I/O Safetybus interface ensures that no failure in the module can affect the operation of the Regent system or other I/O modules in the system. Extensive fault detection and annunciation of critical redundant circuits help

cuits.

Industrial Control Services

Analog Input Modules

prevent the controllers from receiving erroneous data from a faulty inpu

Three analog input modules can be connected in parallel to obtain fault tolerant input sensing. In this triple module configuration, a failed module can be removed and replaced without interrupting the input signals.

(T7420A, AF)

t module.

Module Operation

A block diagram of the analog input module is shown in Figure 1.

Figure 1. Block Diagram of Analog Input Module.

Analog field signals are conditioned and multiplexed into an analog-to-digital (A to D) converter and converted into 12-bit digital data. These digital values are stored in the module’s RAM. The digital logic circuits are optically isolated from the analog field signals to protect the logic circuits from external field signal transients and over voltages.

Industrial Control Services

Analog Input Modules

The processor modules send triplicated read data requests to the analog input module over the I/O Safetybus. The processors’ addressing data and data read requests are voted by the module (preventing I/O Safetybus failures upstream from the module from affecting module operations). The voted result is then passed to the I/O bus interface logic.

After receiving the voted data read request, the I/O bus interface logic retrieves the analog data values from the RAM and places the data into the module’s three bus drivers. Each of the three bus drivers is independently powered and controlled (by the I/O transceiver modules) — preventing failures in a single driver from propagating to the other two /O busses. The bus drivers then transmit the data via the backplane I/O Safetybus to the I/O transceiver modules which, in turn, transmit the data to the processors.

The 12-bit analog input data is packaged as a 16-bit integer. In this format the analog data is the least significant bits, providing analog input data ranging from 0 to 4095. Two of the remaining four bits are used to flag alarms as shown in Figure 2.

(T7420A, AF)

Figure 2. Analog Input Data Format.

Testing and

Each module’s voter circuits are periodically tested by the processor modules. Discrepant data are sent through one of three legs of the I/O Safetybus to determine whether the module’s voter is able to outvote the incorrect data. A failure to return the correct majority-voted result to the processors

Diagnostics

PD-7023

Mar-06

Analog Input Modules

produces an I/O module error indication at the processor modules and a module fault indication at the I/O module.

Each type of module has a unique identification code that is read by the controll which type of module is installed in each I/O chassis slot and how to address that module and its points specifically. If a module is removed, or is replaced with a module of a different type, the processor modules will indicate an I/O module error.

Loopback logic tests periodically write data to the module and then read it back to determine whether the module’s I/O bus interface logic is functioning correctly.

(T7420A, AF)

er. This code lets the controller know

Front Panel Indicators

Figure 3 shows the physical features of the analog input modules. The front panel of each module contains active and fault status indicators.

Active and Fault Status Indicators

These green and red LEDs indicate the overall health of the module. During normal operation the green ACTIVE indicator flashes at the controller's scan rate. If a module fault occurs the red FAULT indicator turns on and the green ACTIVE indicator turns off.

Industrial Control Services

Analog Input Modules

(T7420A, AF)

PD-7023

Mar-06

Figure 3. Analog Input Module.

Voltage Ranges

Current Ranges

(using external 250 Ohm resistor)

0 to 5 Vdc

0 to 20 mA

1 to 5 Vdc

4 to 20 mA

5 to +5 Vdc

20 to +20 mA

0 to 10 Vdc

0 to 40 mA

10 to +10 Vdc

40 to +40 mA

Analog Input Modules

(T7420A, AF)

Application

Analog Input Range Selection

The possible input voltage ranges are the same for both differential and single-ended modes. Since current measurements are converted to voltages using external precision resistors, the same voltage ranges apply. Choices of input voltage ranges include unipolar, bipolar, and offset ranges. All ranges are selected by setting jumpers located inside the module.

Table 1. Analog Input Ranges.

Input Out of Range Detection

If the analog signal is well beyond the normal operating range selected, the NOSIG contact associated with the analog point will be enabled. Note that there are some out-of-range signals that do not set the NOSIG bit. The out of range thresholds for each input range are shown on page 27.

Absolute Signal Ranges

The absolute workin from -10.3 volts to +10.3 volts with regard to AGND (analog ground). The acceptable common mode voltage range (either differential or single-ended with regard to its appropriate analog reference input) is from -10.3 volts to +10.3 volts.

g range for any analog input signals is

Industrial Control Services

Analog Input Modules

(T7420A, AF)

Sampling Speed

The rate at which each of the analog input channels is sampled depends upon the mode of operation. Each channel is given a 225 msec time slot during the multiplexing process. During that time s measuring system, the measuring system is allowed to settle, the settled value is sampled (and held), and is then converted to a 12-bit value by an analog-to-digital converter. The channels are sampled in numerical order. In single-ended mode, the 16 channels are sampled in 3.60 msec on a continuous repeating basis. In differential mode, the eight channel pairs are sampled in 1.80 msec on a continuous repeating basis. Converted data are stored in the module’s R

AM and can be accessed by the controller. Data for a given channel is available at the previously stored value until an updated conversion replaces it.

Sampling speed is unrelated to internal access speed within the Regent system. Programming and other features determine how often the Regent system can access the converted data. There are no “lockout times” when the Regent system is prevented from reading the current stored values of the converted data.

lot, the input voltage is connected to the

PD-7023

Mar-06

Single-Ended References

When single-ended input mod reference for all eight signals on the same input field wiring terminal block is AREF1 on the top terminal block and AREF2 on the bottom. This ground reference may be different from the external I/O analog ground AGND also available on the same connector. When used with the I/O Termination Assembly (see PD-7901), both AREF1 and AREF2 are isolated from AGND by 1K Ohm resistors.

When the single-ended signals are measured, the appropriate ground reference for the signal is selected by another multiplexer on the board, and becomes the reference for the measurement. In differential mode, AREF1 and AREF2 are not used as references.

e is selected, the ground

Analog Input Modules

(T7420A, AF)

Input Over Voltage Protection

All analog inputs, regardless of mode and analog references (AREF1 and AREF2), are protected from over-voltages (these ranges are shown on page 27).

Current Measurement Considerations

Precision resistors external to the module are required to convert currents to voltages that can be measured directly by the module. The resistors can be mounted on field marshaling terminals or are provided using the appropriate analog input termination blocks. For differential current measurements, both sides of the external resistor are brought onto the module.

It is possible to mix current and voltage measurements on the same module as long as they can work with the same voltage range selected. In the case of single-ended measurements, this either requires that both current and voltage measurements are referenced to the sa (AREF1 or AREF2), or that voltage inputs be on one set of eight inputs and current inputs on the other set.

me reference point

Input Range and Mode Selection Jumpers

The jumpers that determine the mode and input range for the module are set at manufacturing time for an input range of 1 to 5 volts and the 16-channel, single-ended input mode. If other input ranges or another mode is desired these jumpers must be repositioned to the appropriate settings.

There are 17 jumper locations that are used. They are summarized in Tables 2 and 3, below. The module’s cover must be removed to access and reposition the jumpers.

Industrial Control Services

Analog Input Modules

Jumper

Single-Ended

Differential

J251

J252

J501

J502

J503

J504

J505

J701

Jumper

0 to +10

10 to +10

+1 to +5

0 to +5

5 to +5

J551

J552

J553

J601

J602 n

J651 n

J652

J653

J654 n

(T7420A, AF)

Table 2. Mode Selection.

Table 3. Input Range Selection.

Input Low-Pass Filters

Two rows of jumper connections (J506 and J507) allow selection of onboard capacitors to create single-pole low-pass input filters on the board. Jumpers are placed on these connections to select either single-ended or differential filters as appropriate.

n single-ended mode, the filtering is done with respect to the appropriate AREF1 (or AREF2) input line. A 10K Ohm resistor is in series with each analog input line (this resistor is also a part of the over voltage protection system for the module as well), and the capacitor is on the multiplexing side of the resistor. There are four rows of eight pins labeled J506 and J507, for single-ended mode filtering install jumpers across row J506 and row J507 (for a total of 16 jumpers).

PD-7023

Mar-06

+ 20 hidden pages