Analog Input Functional Description

Description

The Analog Input function offers the following range for each input according to the selection made during configuration:

±10 V
0…10 V
0…5 V/0…20 mA
1…5 V/4…20 mA
±5 V/±20 mA

The function operates with voltage inputs. It includes four read resistors connected to the terminal block to perform current inputs.

Measurement Timing

The timing of measurements is determined by the cycle selected during configuration (Normal or Fast Cycle):

Normal Cycle means that the scan cycle duration is fixed.
With the Fast Cycle, however, the system only scans the channels designated as being In Use. The scan cycle duration is therefore proportional to the number of channels In Use.

The cycle time values are based on the cycle selected:

Function	Normal Cycle	Fast Cycle
Analog input	6.5 ms	1.3 ms + (1.3 ms x N) where N: number of channels in use.

NOTE: Module cycle is not synchronized with the PLC cycle. At the beginning of each PLC cycle, each channel value is taken into account. If the MAST task cycle time is less than the module’s cycle time, some values would have not changed.

Overflow/Underflow Control

The Analog Input function allows you to select between six voltage or current ranges for each input. This option has to be configured in configuration windows for each channel.

The module checks for overflow depending on the selected range and verifies that the measurement falls between a lower and an upper threshold:

Designation	Description
Nominal range	Measurement range corresponding to the chosen range
Upper Tolerance Area	Varies between the values included between the maximum value for the range (for instance: +10 V for the ±10 V range) and the upper threshold
Lower Tolerance Area	Varies between the values included between the minimum value for the range (for instance: -10 V for the ±10 V range) and the lower threshold
Overflow Area	Area located beyond the upper threshold
Underflow Area	Area located beyond the lower threshold

The threshold values are configurable independently from one another. They may assume integer values between the following limits:

Range	Range
Range	Underflow Area		Lower Tolerance Area		Nominal Range		Upper Tolerance Area		Overflow Area
Unipolar
0…10 V	-1,400	-1,001	-1,000	-1	0	10,000	10,001	11,000	11,001	11,400
0...5 V/0...20 mA	-5,000	-1,001	-1,000	-1	0	10,000	10,001	11,000	11,001	15,000
1...5 V/4...20 mA	-4,000	-801	-800	-1	0	10,000	10,001	10,800	10,801	14,000
Bipolar
±10 V	-11,400	-11,001	-11,000	-10,001	-10,000	10,000	10,001	11,000	11,001	11,400
±5 V, ±20 mA	-15,000	-11,001	-11,000	-10,001	-10,000	10,000	10,001	11,000	11,001	15,000
User
±10 V	-32,768	-	-	-	User-defined	User-defined	-	-	-	32,767
0...10 V	-32,768	-	-	-	User-defined	User-defined	-	-	-	32,767

Measurement Display

Measurements may be displayed using standardized display (in %, to two decimal places):

Type of Range	Display
Unipolar range 0…10 V, 0…5 V, 1…5 V, 0...20 mA, 4…20 mA	From 0...10,000 (0% at +100%)
Bipolar range ±10 V, ±5 V, ±20 mA	From -10,000…10,000 (-100% at +100%)

It is also possible to define the range of values within which measurements are expressed, by selecting:

The lower threshold corresponding to the minimum value for the range: 0 % (or -100.00%).
The upper threshold corresponding to the maximum value for the range (+100.00%).

The lower and upper thresholds must be integers between -32,768 and +32,767.

For example, imagine a conditioner providing pressure data on a 4…20 mA loop, with 4 mA corresponding to 3,200 millibar and 20 mA corresponding to 9,600 millibar. You have the option of choosing the User format, by setting the following lower and upper thresholds:

3,200 for 3,200 millibar as the lower threshold
9,600 for 9,600 millibar as the upper threshold

Values transmitted to the program vary between 3,200 (= 4 mA) and 9,600 (= 20 mA).

Measurement Filtering

The type of filtering performed by the system is called first order filtering. The filtering coefficient can be modified from a programming console or via the program.

The mathematical formula used is as follows:

Measf(n) = α x Measf(n-1) + ( 1-α ) x Valb(n)

where:

α = efficiency of the filter

Measf(n) = measurement filtered at moment n

Measf(n-1) = measurement filtered at moment n-1

Valb(n) = gross value at moment n

You may configure the filtering value from seven possibilities (from 0…6). This value may be changed even when the application is in RUN mode.

NOTE: Filtering may be accessed in Normal or Fast Cycle.

NOTE: α=e-Tcycle/τ

where:

Tcycle = sampling period of the channel

τ = response time of the filter

The relation between the efficiency α and the Parameter k (0 to 6) is:

α = 0 for k=0

α = 1-1/2k+1 for k=1...6

The filtering values depend on the T configuration cycle (where T = cycle time of 6.5 ms in standard mode):

Desired Efficiency	Required Value	Corresponding α	Filter Response Time at 63%	Cut-off frequency (Hz)
No filtering	0	0	0	-
Smooth filtering	1	0.750	4* T	0.040/T
Smooth filtering	2	0.875	8* T	0.020/T
Average filtering	3	0.937	16* T	0.010/T
Average filtering	4	0.969	32* T	0.005/T
High filtering	5	0.984	64* T	0.0025/T
High filtering	6	0.992	128* T	0.0012/T

NOTE: Enter the valid value for filter between the ranges 0…6. If you enter an invalid value in Device DDT, MC80 PLC will consider the last value of the filter.

Sensor Alignment

The process of alignment consists in eliminating a systematic offset observed with a given sensor, around a specific operating point. This operation compensates for an error linked to the process. Replacing a module does not therefore require a new alignment. However, replacing the sensor or changing the sensor’s operating point does require a new alignment.

Conversion lines are as follows:

The alignment value is editable from a programming console, even if the program is in RUN Mode.

For each input channel, you can:

view and modify the desired measurement value
save the alignment value
determine whether the channel already has an alignment

The alignment offset may also be modified through programming. Channel alignment is performed on the channel in standard operating mode, without any effect on the channel’s operating modes.

The maximum offset between measured value and desired (aligned) value may not exceed ±1,500.

NOTE: To align several analog channels, we recommend to proceed channel by channel. Test each channel after alignment before moving to the next channel in order to apply the parameters correctly.

NOTE: Enter the valid value for the filter. The valid value is between the predefined ranges. If you enter an invalid value in Device DDT, MC80 PLC will consider the upper or lower limit from the predefined range.

Wiring Precautions

In order to protect the signal from outside interference induced in series mode and interference in common mode, we recommend that you take the following precautions:

Cable Shielding - Connect the cable shielding to the grounding bar. Clamp the shielding to the grounding bar on the module side.

For more details on grounding, refer to the chapter Grounding Bar ....

DANGER

HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH

While mounting / removing the modules:

Make sure that each terminal block is still connected to the grounding bar
Disconnect voltage supplying sensors and pre-actuators.

Failure to follow these instructions will result in death or serious injury.

WARNING

UNEXPECTED EQUIPEMENT OPERATION

Use a 24 Vdc supply to sensors and a shielded cable for connecting the sensors to the module.

Failure to follow these instructions can result in death, serious injury, or equipment damage.

DANGER

HAZARD OF ELECTRIC SHOCK

Sensors and other peripherals may be connected to a grounding point some distance from the module. Such remote ground references may carry considerable potential differences with respect to local ground. Ensure that:

potentials greater than permitted low limits cannot exist,
induced currents do not affect the measurement or integrity of the system.

Failure to follow these instructions will result in death or serious injury.

Electromagnetic Hazard Instructions

CAUTION

UNEXPECTED BEHAVIOR OF APPLICATION

Follow these instructions to reduce electromagnetic perturbations:

Use the BMX XSP 0400/0600/0800/1200 electromagnetic protection kit to connect the shielding.

Electromagnetic perturbations may lead to an unexpected behavior of the application.

Failure to follow these instructions can result in injury or equipment damage.

Wiring Diagram

The Analog Input Function is connected using the 20-pin terminal block (BMXFTB20x0).

This figure shows the terminal block connection and the sensor wiring:

IVx:

pole input for channel x

COM:

common pin for each channel

ICx:

current reading resistor + input

FG

functional ground

This table lists the suitable terminal block references for AnaIog Input function:

I/O Function	Reference Number
AnaIog Input function	BMX FTB 2000 BMX FTB 2010 BMX FTB 2020

LED Indicator

The LED indicator shows the status of the AI channels.

Use this table to perform diagnostics of the analog input function status according to the channel LEDs:

Status LEDs AMI Function	Function Status
IN Channel	Function Status
ON	Operating normally
OFF	Module is running with channels in stopped state
OFF	Module is inoperative or turned off
OFF	Module not configured or channel configuration in progress
OFF	Internal error in module
OFF	Not configured
BLK	Range under/overflow error
FLK	Sensor link error
Legends
ON	LED is turned on
OFF	LED is turned off
FLK (Flickering)	The LED is turned on for 50 ms then turned off for 50 ms, and then repeat
BLK (Blinking)	The LED is turned on for 200 ms then turned off for 200 ms, and then repeat

For more information, refer to “Fitting a 20-Pin Terminal Block” ....