analog TBXs
3.2
TBX AMS 620 Module
At a Glance
Aim of this section?
What's in this
Section?
This section introduces the TBX AMS 620 remote module.
This Section contains the following Maps:
Topic
Introducing the TBX AMS 620 module
Timing of measurements on inputs
Under/overshoot monitoring on inputs
Filtering of measurements on inputs
Displaying measurements on inputs
Characteristics of the outputs
Fault handling
Monitoring under/overshoots on the TBX AMS 620 module outputs
Calibrating the TBX AMS 620 module
Sensor alignment
Page
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108
109
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111
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113
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Introducing the TBX AMS 620 module
General The TBX AMS 620 base unit is an analog output module containing 6 high-level noninsulated channels and 2 insulated outputs. It must be associated to a TBX LEP 030 communicator.
l l
This module supports the following ranges on each input :
High-level voltage,
High-level current.
l l
This module supports the following ranges on each output :
High-level voltage,
High-level current.
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Overview Overview of the TBX AMS 620 module associated to the TBX LEP 030 communicator: processor
Input 0
Input 1
Channel 1
Channel 0
Input 2
Input 3
Input 4
Input 5
1
Analog
Digital conversion
2
Processes:
- range selection
- overshoot
- filtering
- display
6
4
5
3
Channel 7
Channel 6
Bus interface
Time base
FIPIO
Output 0
Output 1
Channel 6
Channel 7
Digital
Analog conversion
10
Processes:
- refreshing
- error handling
- range selection
8
7
9
24/48V
Supply
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Description analog TBXs
The TBX AMS 620 module associated with the TBX LEP 030 communicator supports the following input functions :
Address Function
1
2
3
4
5
6 l l l l l l acquisition of the 6 channels using multiplexing,
12 bit + sign analog digital conversion, range selection for each input: voltage, current, thermocouple, input under/overshoot monitoring, measurement filtering, user-defined measurement formatting.
The TBX AMS 620 module associated with the TBX LEP 030 communicator supports the following output functions:
8
9
Address Function
7 refreshing the digital values transmitted by the processor,
10 processing PLC dialog faults, range selection for each output: voltage, current, digital analog conversion.
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Timing of measurements on inputs
Introduction
Breakdown of the cycle time
The cycle time for the TBX AMS 620 module is fixed at 42.4 ms.
The measurements are sequenced in the following manner: channel 0, channel 1, channel 2, channel 3, channel 4, channel 5 then acquisition of two internal reference voltage channels, required for cyclical calibration.
Scanning time values:
Type of time
Scanning time for a channel
Acquisition time for a complete cycle
Time l l
5.3 ms,
42.4 ms.
Illustration:
Channel 1
Channel 0
Channel 3
Channel 2
Channel 5
Channel 4
Int.
T channel channel
Int. channel
Channel 1
Channel 0
Channel 3
Channel 2
T cycle = 42.4 ms
Note: l l
The cycle is always identical, even when some channels are not in use,
The time required for the program to access the measurements also depends on the transmission times on the FIPIO bus and on the PLC task period.
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Under/overshoot monitoring on inputs
Introduction
Measurement zone
The TSX AMS 620 module provides a choice between voltage or current ranges.
The module checks for under/overshoot corresponding to the selected range: it checks that the measurement falls between a lower and upper limit.
The measurement zone is in the nominal zone.
Beyond the nominal zone, under/overshoot is tolerated up to the under/overshoot limits:
Illustration: undershoot limit overshoot limit nominal zone undershoot zone overshoot zone
Under/overshoot indications
If values provided by the application fall outside the limits, then saturation will occur at the value of the limit exceeded.
The module continues to supply the converted value until saturation of the converter or of the display format (+32767/-32768), even though the validity of the measurement is not guaranteed.
The user can use the under/overshoot bit as a means of elminating these measurements.
Under/overshoot bit:
Bit name
%I\p.2.c\m.i.ERR
Meaning
When = 1, indicates a range over/undershoot on the channel.
Electrical range under/overshoot values
For voltage ranges, the module allows an overshoot of 5% on the positive electric part of the range.
Under/overshoot values according to the type of input
Range
+/-10 V
0..5 V
0..20 mA
4..20 mA
Lower limit
-10.5 V
Upper limit
+10.5 V.
0 V: this under/overshoot cannot be detected +5.25 V.
0 V: this under/overshoot cannot be detected +21 mA.
+3.2 mA +20.8 mA.
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Filtering of measurements on inputs
Introduction
Mathematical formula
Values for the
TBX AMS 620 module
The system uses first order filtering. The filter coefficient can be modified from a programming terminal and by program (See Modifying the filter value of analog
module channels, p. 189).
The mathematical formula used is as follows :
Mesf n = α × ( – 1 ) + ( 1 – α ) × Valb n with:
α =filter efficiency,
Mesf(n)=measurement filtered at moment n,
Mesf(n-1)=measurement filtered at moment n-1,
Valg(n)=gross value at moment n.
On configuration, the user selects the filter value from 7 possible values.
The filter values are as follows:
Efficiency
No filtering
Low filtering
Medium filtering 3
4
High filtering 5
6
0
1
2
Value to be selected
Corresponding
0 s
170 ms
339 ms
678 ms
1.35 s
2.71 s
5.42 s
α
time constant
0
0,750
0,875
0,937
0,969
0,984
0,992
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Displaying measurements on inputs
Introduction This process is used to select the display format depending on which formats are provided in the user program.
Standardized display of electrical ranges
The values are displayed in standardized units (in % with 2 decimals, also with symbol °/
°°°
):
Type of range Display unipolar range
0-10V, 0-5V, 0-20mA, 4-20mA bipolar range
+/-10V from 0 to 10000 (0 °/
°°°
to 10000 °/
°°° from -10000 to +10000 (-10.000 °/
°°°
°°°
).
).
to +10.000 °/
User-defined display of electrical ranges
The user can select the value range in which the measurements are expressed, by selecting: l the minimum limit corresponding to the range minimum: 0 (or - 10000 °/
°°°
), l the maximum limit corresponding to the range maximum: + 10000 °/
The minimum and maximum limits are between -31128 and +31128.
°°°
.
Example:
Use of a 2/20 bar pressure sensor supplying a 0/20 mA signal and having a linear characteristic.
The user is interested in the pressure rather than the current value. The best resolution is obtained by selecting user display: l l for minimum limit: 2000, for maximum limit: 20000.
The user-program then uses values expressed directly in the physical unit, the millibar.
Illustration:
Pressure
20.000 bars
2.000 bars
20 mA
Current
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Characteristics of the outputs
Output writing
Refreshing outputs via the module
The user has access via the program to 2 words (1 16-bit word per channel) in which the values of the analog outputs are given.
l l from 0 to 10000 (that is 0 °/
4/20 mA,
°°°
to 10000 °/
°°°
) for unipolar ranges 0/20 mA and from -10000 to +10000 (-10000 °/
°°°
to +10000 °/
°°°
) for bipolar range +/-10 V.
Outputs are refreshed every 5 ms
The response time between writing the output via the program and updating the outputs to the module limits depends on the PLC task period in which the module is configured.
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Fault handling
Dialog faults with the PLC
This type of handling groups together: l l l l l setting the PLC to STOP mode (or the task in which the module is configured), a PLC fault, a link fault between the PLC and the module.
In the above cases, the user has two options for each output: maintain the output at the current value, fallback to a defined value. The value must be selected between the normal display limits (0/10000) for unipolar ranges or –10000/10000 for the voltage range. By default, the module is configured in fallback to 0 mode.
Internal errors in the module
When the module has an internal error the outputs are forced to 0.
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Monitoring under/overshoots on the TBX AMS 620 module outputs
At a Glance
Characteristics of the ranges
The TBX AMS 620 module includes an under/overshoot monitoring device.
The limits and precisions of the various ranges are as follows:
Range
+/- 10V
0.20mA
4.20mA
Lower limit
-10000
0
0
Upper limit
+10000
+10000
+10000
Precision conversion on 11 signed bits of -
2048 to +2047 pulses conversion on 11 bits of 0 to
+2047 pulses conversion on 11 bits of 0 to
+2047 pulses
Illustration
Analog output value
+10 V
-10000
20 mA
Analog output value
10000
Numerical value
-10 V
20 mA
Analog output value
4 mA
0
10000
Numerical value
10000
Numerical value
Under/overshoot identifiers
If the values provided by the application are outside the limits, saturation occurs at the value of the limit exceeded. The overshoot is shown by:
Bit name
%I\p.2.c\m.voie.ERR
Meaning
When equal to 1, shows a range overshoot on the channel.
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Calibrating the TBX AMS 620 module
At a Glance Calibration (See
Calibration function for an analog module, p. 213) is carried out
globally for the module on channel 0.
It is advised that you calibrate the module outside the application. Calibration can be done with the PLC task linked to the channel, in RUN or STOP mode. Calibration is a full scale calibration
Full scale calibration is done on the 0 channel by placing the standard reference source scaled to +/-0.01% directly on the input limits of the 0 channel of the base.
Full scale calibration
Precautions When in calibration mode, measurements for all channels in the module are declared invalid, filtering and alignment are prevented and channel acquisition cycles may be lengthened.
As inputs other than the 0 channel will not be acquired during calibration, the value transmitted to the application for these other channels is the last value that was measured before switching to calibration.
How to calibrate the module
Step
1
2
3
4
5
6
7
The following table shows the procedure for calibrating the module:
Action
Access the calibration adjustment screen
Double click on the 0 channel.
Result : A question appears ‘Do you wish to switch to recalibration mode?’.
Reply to this question with Yes .
Result : The calibration window appears.
Then perform the full scale calibration.
According to the range to be calibrated, connect a reference voltage to the voltage input of channel 0: l l reference voltage = 10 V (precision +/- 0.01%) in order to calibrate the module on the +/-10 V ranges reference voltage = 5 V (precision +/- 0.01%) in order to calibrate the module on the 0..5 V ranges
Once the reference has been connected to the voltage input (e.g. 10 V), use the Reference drop-down list box to select this value. Wait, if necessary, for the reference voltage connected to stabilize, then confirm the selection using the Confirm command button. The ranges linked to this reference are then calibrated automatically.
Calibrate the module for other ranges, if applicable.
the command button Return to Factory Settings allows you to cancel all calibrations previously carried out and to return the module to the initial calibration settings configured in the factory.
Click on the Save command button in order to recognize and save the new calibration in the module. If you exit the calibration screen without saving, a message is displayed indicating that the new calibration values will be lost
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Sensor alignment
At a Glance Alignment consists of eliminating systematic deviation observed with a given sensor around a given operating parameter. An error linked to the process is compensated for. For this reason, replacing a module does not necessitate a new alignment, whereas the replacement of the sensor or modification of the operating parameter of this sensor does necessitate a new alignment.
Conversion line after alignment
Initial conversion line
Example
Alignment values
Let us suppose that a pressure sensor, linked to a conditioning unit (1mV/mB), indicates 3200 mB, whereas the actual pressure is 3210 mB.
The value measured by the module in standardized scale will be 3200 (3.20 V). The user can align the measurement to the value 3210 (value required).
After this alignment procedure, the measurement channel will apply a systematic offset of +10. The alignment value that must be entered is 3210.
The alignment value can be modified from the PL7 screen, even when the program is in RUN mode.
For each input channel, the user can: l l l view and modify the required measurement value, save the alignment value, see if the channel already possesses an alignment.
The alignment offset can also be changed by program.
Alignment is performed on the channel under normal usage, without affecting the module channel operating modes. The maximum difference between the value measured and the value required (aligned value) must not exceed 1000.
The alignment offset is stored in the word %Mwxy.i.8.
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