Mantracourt DCell, DSC User Manual
DCell
DSC
DCell & DSC
Strain Gauge or Load Cell Embedded Digitiser
Module MantraCAN – 2nd Generation
Software Version 3 onwards
User Manual
MICRON METERS
www.micronmeters.com
metersinfo@micronmeters.com
Mantracourt Electronics Limited DCell & DSC MantraCAN User Manual
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Contents
Chapter 1 Introduction ................................................................................................................. 4
Overview ................................................................................................................................... 4
Key Features............................................................................................................................... 4
Special Facilities .......................................................................................................................... 5
Version 3 Additions and Enhancements ............................................................................................... 5
The Product Range ....................................................................................................................... 6
Which Device To Use ..................................................................................................................... 6
Additional DCell & DSC Variants Available ........................................................................................... 6
Some Application Examples............................................................................................................. 7
Chapter 2 Getting Started with the Evaluation Kit............................................................................... 8
The Evaluation Kit ........................................................................................................................ 8
Contents............................................
........................................................................................ 8
Checking the Device Type............................................................................................................... 9
Connecting Up The Evaluation Kit ..................................................................................................... 9
Initial Checks .............................................................................................................................. 9
Instrument Explorer ...................................................................................................................... 9
What Can Instrument Explorer Do? .................................................................................................... 9
Installing Instrument Explorer .......................................................................................................... 9
Running the Instrument Explorer Software.......................................................................................... 10
Instrument Explorer Icon ............................................................................................................... 10
Instrument Settings......................................................................................................................11
Viewing Device Data .................................................................................................................... 12
Instrument Explorer Parameter List ..................................................................................................12
Connecting a Load Cell .................................................................................................................13
DSJ1 Evaluation Board Sensor Connections ......................................................................................... 14
Performing A System Calibration .....................................................................................................15
Chapter 3 Explanation of Category Items .........................................................................................20
Communications .........................................................................................................................20
ID, NODEIDL, NODEIDH..................................................................................................................20
Example ................................................................................................................................... 20
CAN Bit Rate, BPS........................................................................................................................21
Identifier Size, IDSIZE .............................
......................................................................................21
CAN Bus, CANTXERR, CANRXERR, CANSTATUS ......................................................................................21
CANTXERR.................................................................................................................................21
CANRXERR.................................................................................................................................22
CANSTATUS ............................................................................................................................... 22
Streaming ................................................................................................................................. 22
Configuring Output Message Streams ................................................................................................ 22
Message Streams .........................................................................................................................22
Streaming Types, STRMTYPE...........................................................................................................22
Starting and stopping Streaming, STRMON, STRMOFF ............................................................................. 22
Message Configuration .................................................................................................................. 23
Custom Start / Stop .....................................................................................................................24
Start Streaming ..........................................................................................................................24
Stop Streaming ...........................................................................................................................25
Data Types ................................................................................................................................26
Sub Formats ..............................................................................................................................26
Message Output Examples..............................................................................................................27
Streaming Start / Stop Examples ..................................................................................................... 27
Information ............................................................................................................................... 27
Software Version, VER ..................................................................................................................27
Serial Number, SERL and SERH .........................
............................................................................... 27
Strain Gauge .............................................................................................................................. 28
mV/V output, MVV....................................
...................................................................................28
Nominal mV/V level, NMVV ............................................................................................................28
mV/V Output In Percentage Terms, ELEC ...........................................................................................28
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Temperature Value, TEMP ............................................................................................................. 28
Output Rate Control, RATE ............................................................................................................ 28
Dynamic Filtering, FFST and FFLV ....................................................................................................28
Cell .........................................................................................................................................30
Temperature Compensation In Brief ................................................................................................. 30
Cell Scaling, CGAI, COFS ............................................................................................................... 30
Two Point Calibration Calculations and Examples .................................................................................30
Calibration Methods .....................................................................................................................31
Cell Limits, CMIN, CMAX ................................................................................................................31
Linearisation In Brief....................................................................................................................32
System ..................................................................................................................................... 32
System Scaling, SGAI, SOFS ............................................................................................................32
Example of calculations for SGAI and SOFS .........................................................................................32
System Limits, SMIN, SMAX............................................................................................................. 33
System Zero, SZ..........................................................................................................................33
System Outputs, SYS, SOUT............................................................................................................33
Reading Snapshot, SNAP, SYSN ........................................................................................................33
Control.....................................................................................................................................34
Shunt Calibration Commands, SCON and SCOF .....................................................................................34
Digital Output, OPON and OPOF ......................................................................................................34
Flags ....................................................................................................................................... 34
Diagnostics Flags, FLAG and STAT ....................................................................................................34
Latched Warning Flags (FLAG)......................................................................................................... 34
Meaning and Operation of Flags.......................................................................................................35
Dynamic Status Flags (STAT)...........................................................................................................36
Meaning and Operation of Flags.......................................................................................................36
Output Update Tracking ................................................................................................................36
User Storage .............................................................................................................................. 36
USR1…USR9 ...............................................................................................................................36
Reset.......................................................................................................................................37
The Reset command, RST ..............................................................................................................37
WARNING: Finite Non-Volatile Memory Life.........................................................................................37
Chapter 4 The Readings Process ....................................................................................................38
Flow diagram ............................................................................................................................. 38
Cell & System Scaling ................................................................................................................... 39
Calibration Parameters Summary and Defaults .................................................................................... 40
Chapter 5 Temperature Compensation ............................................................................................41
Purpose and Method of Temperature Compensation ..............................................................................41
Temperature Module Connections and Mounting (DTEMP) .......................................................................41
Control Parameters...................................................................................................................... 42
Internal Calculation ..................................................................................................................... 42
The Temperature Measurement.......................................................................................................43
How to Set Up a Temperature Compensation ......................................................................................43
Parameter Calculations.................................................................................................................44
Chapter 6 Linearity Compensation .................................................................................................45
Purpose and Method of Linearisation ................................................................................................ 45
Control Parameters...................................................................................................................... 45
Internal Calculation ..................................................................................................................... 45
How to Set Up Linearity Compensation..............................................................................................46
Parameter Calculations and Example ................................................................................................46
Chapter 7 Self-Diagnostics............................................................................................................48
Diagnostics Flags......................................................................................................................... 48
Diagnostics LED .......................................................................................................................... 48
Chapter 8 MantraCAN Communication Protocol .................................................................................49
Basic Command Structure ..............................................................................................................49
Read........................................................................................................................................49
Example of Read .........................................................................................................................50
Write .......................................................................................................................................50
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Example of Write ........................................................................................................................51
Execute A Command ....................................................................................................................51
Example Of Execute A Command .....................................................................................................51
Data Type Conversions and Rounding ................................................................................................ 52
Chapter 9 Software Command Reference .........................................................................................53
Commands in Access Order ............................................................................................................53
Chapter 10 Installation ................................................................................................................57
Before Installation....................................................................................................................... 57
Physical Mounting........................................................................................................................ 57
Electrical Protection .................................................................................................................... 57
Moisture Protection .....................................................................................................................57
Soldering Methods .......................................................................................................................59
Power Supply Requirements ........................................................................................................... 59
Cable Requirements.....................................................................................................................59
Strain Gauge input (DSC) ............................................................................................................... 59
Power and Communication.............................................................................................................59
Temperature Sensor.....................................................................................................................60
Identifying Strain Gauge Connections................................................................................................60
DCell Input Connections ................................................................................................................ 60
DSC Input Connections.................................................................................................................. 60
Identifying Bus-End Connections ......................................................................................................61
DCell Bus Connections ..................................................................................................................61
DSC CAN Versions-Bus Connections ...................................................................................................61
Strain Gauge Cabling and Grounding Requirements ............................................................................... 62
DCell Strain Gauge Wiring.............................................................................................................. 62
DCell Strain Gauge Wiring Arrangement ............................................................................................. 62
Key Requirements .......................................................................................................................62
Key Requirements .......................................................................................................................62
Communications Cabling and Grounding Requirements...........................................................................63
DCell Power and Communications Wiring ........................................................................................... 63
DCell Bus-End Arrangement............................................................................................................63
DSC4 Versions- Power and Communications Wiring................................................................................63
DSC4 Versions-Bus-End Arrangement.................................................................................................63
Key Requirements .......................................................................................................................63
Suitable Cable Types.................................................................................................................... 64
DCell/DSC CAN Bus Cable .............................................................................................................. 64
Indication Of Maximum Bus Length................................................................................................... 64
CAN Bus Connections for Multiple DCells ............................................................................................65
CAN Bus Connections for Multiple DSC Versions....................................................................................65
Key Requirements .......................................................................................................................66
Bus Layout and Termination ...........................................................................................................66
Loading .................................................................................................................................... 66
Strain Gauge Sensitivity Adjustment (DSC ONLY) .................................................................................. 66
Identifying the DSC ‘Rg’ Resistor .....................................................................................................66
Chapter 11 Troubleshooting .........................................................................................................68
LED Indicator .............................................................................................................................68
No Communications ..................................................................................................................... 68
Bad Readings ............................................................................................................................. 68
Unexpected Warning Flags ............................................................................................................. 69
Problems with Bus Baud Rate.......................................................................................................... 69
Recovering a ”lost” DCell/DSC ........................................................................................................ 69
Resetting to default ID.................................................................................................................. 69
First Command ...........................................................................................................................69
Second Command ........................................................................................................................69
Chapter 12 Specifications.............................................................................................................70
Technical Specifications DSC/DCELL High Stability................................................................................70
Technical Specifications DSC/DCELL Industrial Stability ......................................................................... 71
Mechanical Specification for DSC .....................................................................................................72
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Mechanical Specification for DCell ................................................................................................... 72
CE Approvals.............................................................................................................................. 72
Chapter 1 Introduction
This chapter provides an introduction to DCell/DSC products, describing the product range, main features and
application possibilities.
Overview
The DCell and DSC products are miniature, high-precision Strain Gauge Converters; converting a strain gauge sensor
input to a CAN output. They allow multiple high precision measurements to be made over a low-cost 2-wire link.
Outputs can be accessed directly by PLCs or computers, or connected via various types of network, all without
compromising accuracy.
The device is configurable via a proprietary MantraCAN protocol but is able to stream data in a customisable manner
to suit most CAN networks i.e. CANopen® or J1939.
This streamed data does not support any interaction, parameter writing or action commands. However all this can be
achieved using the MantraCAN protocol.
Customisable start and stop messages allow the instrument streaming to be controlled via the host CAN network.
Key Features
Ultra-miniature
The DCell ‘puck’ format can be fitted inside most load cell pockets, and similar restricted spaces. The DSC cards
are similarly very small, optimised for mounting as a component onto custom PCBs.
High-precision Industrial Version.
25ppm basic accuracy (equates to 16 bit resolution)
High-precision High Stability
5ppm basic accuracy (equates to 18 bit resolution) with comparable stability – far exceeds standard instrument
performance.
Low-power
Low-voltage DC supply (5.6V min), typically 40mA for RS485 and 52mA for RS232 (including 350R strain gauge).
Adjustable sensitivity
Configured for standard 2.5mV/V full-scale strain gauges as supplied.
A single additional resistor configures the input between 0.5 and 100 mV/V full-scale.
Temperature sensing and compensation (optional)
An optional temperature sensor module is available and advanced 5-point temperature-compensation of
measurement.
Linearity compensation
Advanced 7-point linearity compensation.
CAN Output
Lower-cost cabling, improved noise immunity, and longer cable runs with no accuracy penalty.
Device addressing allows up to 127 devices on a single bus, drastically reducing cabling cost and complexity.
Two-way communications allow in-situ re-calibration, multiple outputs and diagnostics.
No separate measuring instruments needed.
Digital calibration
Completely drift-free, adjustable in-system and/or in-situ via standard communications link.
Two independent calibration stages for load cell-and-system-specific adjustments.
Programmable compensation for non-linearity and temperature corrections.
Calibration data is also transferable between devices for in-service replacement.
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Self-diagnostics
Continuous monitoring for faults such as strain overload, over/under-temperature, broken sensors or unexpected
power failure.
All fault warnings are retained on power-fail.
Special Facilities
Output Capture Synchronisation
A single command instructs all devices on a bus to sample their inputs simultaneously, for synchronised data
capture.
Output Tare Value
An internal control allows removal of an arbitrary output offset, enabling independent readings of net and gross
measurement values.
Dynamic Filtering
Gives higher accuracy on stable inputs, without increased settling time.
Programmable Output Modes
Output rate control enables speed/accuracy trade-off.
ASCII output version provides decimal format control and continuous output mode for ‘dumb terminal’ output.
Unique Serial Number
Every unit carries a unique serial-number tag, readable over the communications link.
Communications Error Detection
CAN transmit and receive error counts along with CAN bus status can be read from the device.
External Temperature Sensing (optional)
An external temperature module for improved accuracy (especially tracking changing temperature conditions).
Software Reset
A special communications command forces a device reboot, as a failsafe to ensure correct operation.
Version 3 Additions and Enhancements
The following are an outline only more detail will be found further on in this manual
DCell
• E
asy mounting via a 2mm screw
• Connection via solder holes to either side of PCB
• Lower profile, dual PCB construction
DSC
• Additional I/O
• Easier shielding connection at load cell connector end
DCell & DSC
• Bit rates to 1 Mbps
• Higher sampling rate. Sampling to 200Hz can now be achieved. Also more sampling rates are available as
follows 1, 2, 5, 10, 20, 50, 60, 100 & 200Hz
• Lower cost. With new technology and further use of miniaturisation the cost is now lower
• Real mV/V calibration. Instead of % full scale the base measurement is in mV/V and is factory calibrated to
within 0.1%. the % of FS output “ELEC” is still available
• Extreme Noise Immunity, 5 x heavy industrial level
• Diagnostics LED. An LED is used to indicate that the device is powered and working correctly. The LED is also
used to indicate which protocol the device is
• Remote shunt cal. A 100K 1% 50ppm/Deg C resistor can be switched across the bridge to allow load cell
integrity to be established
• Peak & Trough Measurements. Added to allow the faster rates to hold a peak or trough readings. These are
stored in volatile memory & are therefore reset on power up
• Programmable dynamic filtering. The filtering is the same as used on Version 2 but with the advantage of
being able to set the characteristics using the communications
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• Wide Operating Voltage. The operating voltage is now 5.5 to 18V allowing the device to be powered from a
wider range of available system supplies
• DC Excitation. DC excitation has now been employed allowing longer cable lengths for the load cells which is
particularly useful for DSC. This is a 4-wire measurement
• Scaling implementation has been changed for both “CELL” and “SYS”. The gain is applied before the offset
thus following the more standard approach. This allows for an offset change to be made easily as the offset
is not a component of gain
The Product Range
Devices are available in two physical formats:
Which Device To Use
It is important to select the correct product for your application.
First choose DCell or DSC based on your physical installation needs
Common Features
Both physical formats offer identical control and near-identical measurement performance
Differences
Only the DSC (card) is available with digital Input & output.
Special Aspects To Consider
The DCell fits neatly into a strain gauge pocket
The DSC lends itself to PCB mounting
Additional DCell & DSC Variants Available
A separate variant is available with RS232 or RS485 output. Refer to DCell & DSC CAN - 2nd Generation - Manual.
(These variants are sufficiently different to require their own manuals)
The following order codes are supported by an earlier version manual ‘DCell & DSC Version 2’
DLCPKASC, DLCPKMAN, DLCPKMOD, DSC2AS, DSC2MA, DSC2MB, DSC4AS, DSC4MA, DSC4MB
The DCell (puck) products consist of a Digital Strain Gauge Signal
Conditioner with CAN bus output in double sided component
population format.
This is suitable for installation in very small spaces, including load
cell pockets.
External connections are made by wiring to through hole pads.
Mounting is via a 2mm mounting hole to accept M2 screw or American
equivalent #0-80. Important Note: DO NOT USE #2 screw size.
The DSC (card) products are very similar to the DCell but in a
different physical form for mounting stand-alone or on a board.
External connections are via header pins which can plug into
connectors, or be soldered to wires or into a host PCB. DSC has an
open collector output and volt free digital input.
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Some Application Examples
Simple Distributed Measurement
Pressure loads are taken at a number of keys points in a manufacturing process, distributed over a large area.
Each pressure sensor contains a DCell unit, and all the sensors are connected by a single cable carrying power and
CAN communications. A central PC allows continuous display, monitoring and logging of all values from a central
control room. This displays a control-panel and current display window, and logs information to an Excel
spreadsheet for future analysis.
Further monitoring checks and displayed information can easily be added when required to the system where up to
127 ‘nodes’ can be installed.
Low Cost Dedicated Weighing Station
A basic load cell weighing-pad device has a cable leading to a wall mounted weight display.
Digital Load Cell
Load cell products are offered with a high-precision digital communications option.
A DCell is fitted into the gauge pocket of each load cell in manufacture. During product testing, each unit undergoes
a combined load test and temperature cycle. Each unit is then programmed with individually calculated gain, offset,
linearity and temperature compensation tables. All units perform to a very tight specification without the use of any
trimming components.
High Reliability Load sensing
A road bridge has a dedicated load monitoring and active control computer system. System calibration adjustments
are only established during construction, so sensors must be replaceable without recalibration.
Each load monitoring point has a digital load cell fitted, with calibration values set during construction. Selfdiagnostics aid detection of failures.
When a failed load cell is replaced it will produce identical force measurements. The old load cell set-up data
values are programmed into the separate user-level calibration store in the unit, to produce an identically
performing replacement.
Load Balance Monitor
A lorry loading weighpoint monitors left/right load balance and sounds a warning if loading is too uneven for safety.
A drive-on weighing platform is provided with load cells at each of four corners. Each cell is wired to a DSC unit, and
these are cabled to a 3rd party LCD display and control unit, producing a complete turnkey system. A digital I/O card
is wired to the same bus to control the warning alarm. Application software running on the control unit provides a %
left/right balance readout with a graphical tipping display, and a total weight indication.
The balance indication is calculated by comparing the different corner readings. If it exceeds a programmed limit, a
command to the I/O card turns the relay on.
Total weight is calculated by summing the individual results mathematically.
Automatic re-zeroing occurs when the total is near zero for more than a few seconds.
A control button enables a set-up mode for recalibration (protected by operator password), which displays individual
readings and total. Corner compensation can be checked by observing the changing total as a weight is moved
around. Simple button presses control two point recalibration for any cell.
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Chapter 2 Getting Started with the Evaluation Kit
This chapter explains how to connect up a DCell/DSC for the first time and how to get it working. For simplicity,
this chapter is based on the standard DCell/DSC Evaluation Kit, which contains everything needed to communicate
with a puck or card from your PC.
It is advised that first time users wishing to familiarise themselves with the product use the Mantracourt Evaluation
Kit. This provides a low cost, easy way to get started.
If you do not have an Evaluation Kit, the instructions in this chapter mostly still apply, but you will need to wire up
the device (and possible bus-converter) and have some means of communicating with it.
The Evaluation Kit
Contents
• An Evaluation PCB (DSJ1) which comprises of
• A 8 way screw connector for the strain gauge & Temperature sensor
• A 5 way screw connector for power & CAN comms
• A 9 way ‘D’Type for direct CAN (limited to 500Kbps)
• Link headers for CAN, RS232 or RS485 comms selection
• Terminating resistor for CAN & RS485
• LED for power indication
• LED for digital output (DSC only)
• Push Switch for digital input (DSC only)
• An Evaluation DCell or DSC of your choice
• A CD ROM containing Instrument Explorer software
• A 9 way ‘D’Type extension lead
• A USB-CAN converter
• DTEMP temperature sensor for temperature compensation evaluation
Other Things you will need
• A regulated power supply, capable of providing 5.6 –18V at 100mA
• A PC running Windows 98 or above, with a spare USB port and 45Mb free disk space
and, ideally
• A strain gauge, load cell or simulator, 350-5000 ohms impedance
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Checking the Device Type
For a DCell, the Product Code is one of the following 2 types
DLCSMCAN
DLCHMCAN
Industrial Stability MantraCAN output
High Stability MantraCAN output
For a DSC card, the Product Code is one of the following 2 types
DSCSMCAN
DSCHMCAN
Industrial Stability MantraCAN output
High Stability MantraCAN output
The CAN bus Identifier ID of a New DCell/DSC device is factory set to 1
This can be changed if required but for ease of evaluating it is suggested that you use this default value.
Connecting Up The Evaluation Kit
Power is supplied to the DSJ1 via the 5 way connector (J1). This is connected to a supply set between 5.6v and 18v
DC. The red wire being positive and the black negative. The CAN is connected using the 9 way D-type extension lead
to J3 and to the USB-CAN converter.
Ensure LK1 & LK5 are set to “CAN/RS485”. Fit LK2 which terminates the CAN bus.
Switch on, the Green Power LED of the DSJ1 should be on.
Initial Checks
With no load cell connected The LED of the DCell or DSC should flash OFF for 100ms every 0.5s.
Note: If a Load cell is connected and there are no errors then the LED will Flash ON for 100mS then Off for the
above period. This being the normal healthy state.
Another check that the device is working okay is by noting the current drawn from the supply, this should be about
40mA.
Instrument Explorer
Instrument Explorer is Mantracourts own communication interface for our range of standard products. It provides
communications drivers for the DCell/DSC products. A complimentary copy is provided on CD-ROM with the
DCell/DSC Evaluation Kit. Instrument Explorer can also be downloaded from Mantracourts website.
http://www.mantracourt.co.uk/software/Instrument_Exp
lorer
Instrument Explorer is a software application that enables communication with Mantracourt Electronics
instrumentation for configuration, calibration, acquisition and testing purposes.
The clean, contemporary interface allows full customisation to enable your Instrument Explorer to be moulded to
your individual requirements.
What Can Instrument Explorer Do?
• Save and restore customisable user workspace
• Read and Write individual instrument parameters
• Save and restore parameter configurations
• Log data to a window or file
• Perform calibration and compensation
•
Installing Instrument Explorer
Install the Instrument Explorer software by inserting the CD in the CD ROM drive. This should start the ‘AutoRun’
process, unless this is disabled on your computer.
(If the install program does not start of its own accord, run SETUP.EXE on the CD by selecting ‘Run’ from the ‘Start
Menu’ and then entering D:\SETUP, where D is the drive letter of your CD-ROM drive).
The install program provides step-by-step instructio
ns. The software will install into a folder called
InstrumentExplorer inside the Program Files folder. You may change this destination if required.
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Shortcut icons can be created on your desktop and shortcut bar. After installation you may be asked to restart the
computer. This should be done before proceeding with communications.
When given the option to install IXXAT CAN drivers ensure these are selected, which is the default.
Running the Instrument Explorer Software
Having installed Instrument Explorer you can now run the application, which the rest of this chapter is based
around.
From the Windows ‘Start’ button, select Programs, then Instrument Explorer or click on the shortcut on your
desktop.
Instrument Explorer Icon
The application should open and look like the following screen shot. Instrument Explorer Window
T
he layout of Instrument Explorers Window and child windows allows the user full customisation to their
requirements. If the application show a different arrangement of child windows than the above screen shot then
using then load one of the default workspaces as follows:
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Click File on the menu and select Open Workspace. From the file dialogue window select Layout – Standard.iew.
This will ensure your application layout matches this document.
A list of available instruments is displayed in the Select Instrument pane of Instrument Explorer. Select the relevant
device by clicking on the required device icon under the MantraCAN heading.
Instrument Settings
MantraCAN
• Select the ID. The factory default is 1
• Select the baud rate to which the device is set. The factory default is 500KB
• Select the ID type. Default is 11Bit (standard)
• Now click the ‘OK’ button…
The above assumes factory defaults. If your device is known to have different settings use these instead of the ones
stated above.
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Viewing Device Data
The following main parameter list should now appear in the central pane.
Instrument Explorer Parameter List
When an instrument has been selected from the Select Instrument Window this Parameter List window will become
populated.
The parameters and commands which are available for the selected device will appear in this list in a structured
hierarchic manner enabling the user to expand or contract categories by clicking the and buttons on the left of
the list.
There are four types of parameters and commands:
Read/write Numeric – These parameter values are displayed in the right
hand column and can be edited by clicking the value.
The value can then be changed and pressing the Enter key or moving away
from the edited value will cause the new value to be written to the
device. There are no checks on the data entered and it is up to the user
to enter the correct data.
Read-Only – These parameter values are displayed ‘greyed out’ and
cannot be changed.
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Read/write Enumerated – These parameters can only be changed by
selecting the new value from a drop down list.
Clicking in the right hand column will display a down arrow button which
when clicked will display the parameter value options in a list.
Note that all enumerated data (apart from on/off) will be displayed with
a numeric value, hyphen then the description of the value.
The numeric value is the value of the parameter and the description is
just there to help.
Commands – These commands have ‘Click to execute…’ displayed in the
right hand column. Clicking here will display a button. Click this to
issue the command to the device.
As parameters are changed the communications traffic is displayed in the Traffic Pane.
If any errors occur these will be shown in red in the Error Pane. Once an error occurs it will need to be reset before
any more communications can take place. Reset errors by either right-clicking the Error Pane and selecting Reset
Errors from the pop-up menu or select the Communications menu and click the Reset Errors item.
To manually refresh the parameter list click the button on the toolbar or select Sync Now from the Parameters
menu.
Now you have successfully established communications with your evaluation device the next step is to perform a
simple calibration.
Connecting a Load Cell
You can now connect a strain gauge bridge, load cell or simulator to the DCell/DSC.
A suitable strain gauge should have an impedance of 350-5000ohms and (at least for now) a nominal output of
around 2.5mV/V.
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DSJ1 Evaluation Board Sensor Connections
Next Instrument Explorer will set to automatically update dynamic parameters from the device so that
we can see values as SYS changing on the screen. To do this either click the button on the toolbar or
click on the Parameters menu and select the Auto Sync item. Note that these options toggle so be sure
to leave your selection in the active state.
From the Parameter List click the next to the System heading to expand this level. The Parameter List should look
as follows:
This now exposes more levels that can be expanded as
required by clicking the next to the heading name.
Dynamic values (such as SYS and SRAW) will now be updating in real-time from the device.
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Once you have connected the load cell, you should see ‘believable’ output values, in the “SYS” parameter displayed
in the parameter list pane. These values should correspond to mV/V assuming the device is in it’s factory default
state.
For diagnostics the device has two sets of flags. One being latched and held within the devices non volatile memory
(FLAG parameter), the other being dynamic and volatile (STAT parameter).
Instrument Explorer provides a simple method of displaying and resetting of individual flags although these are held
within the device in FLAG and STAT parameters.
To quickly clear all the flags simply write zero to the FLAG parameter. Now if no problems exist all flags should in
their off state.
If any flags remain on then refer to Chapter 3 for flag definitions.
Performing A System Calibration
The values obtained so far are in mV/V units, these are factory calibrated and fixed to within about 0.1% accuracy.
The device also contains two separate user-adjustable calibration parameter groups, these are termed Cell and
System. Cell being used to convert from mV/V to a force and System to convert this force to required engineering
units. We shall being using System for the following exercise where we rescale the output value to read in units of
your choice, and to calibrate precisely to your load cell / system hardware.
Instrument Explorer provide ‘Wizards’ to allow quick and simple calibration operations to be undertaken without the
use of a calculator. Wizards can be activated by simply selecting the required item from the Wizard menu.
Since we are now calibrating at system level we have a choice of two calibration methods:
Sys Calibration Table – This technique is used when a manufacturers calibration document is available for the
connected strain gauge. This normally gives mV/V to engineering unit values.
Sys Calibration Auto – This technique is used when the input can be stimulated with real input values. For example
you have access to test weight / forces.
We will now describe each of these techniques with an example.
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Sys Calibration Table
A 10 tonne load cell manufacturer gives the following data:
mV/V output Force
2.19053 10 tonne
-0.01573 0 tonne
Start the wizard by selecting Sys Calibration Table from the Wizard menu
Click the Next button and enter the low values as shown below
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Click the Next button and enter the high values as shown below
Click Next the following window will be displayed showing the calibrated SYS value which is dependent on the
current input values
The device is now calibrated. However you may find SYS has been ‘clamped’ if the resultant SYS is greater than
SMAX or less than SMIN. If this is the case then change these values to suitable limits. In this example we may set
SMIN to –0.5 (tonne) and SMAX to 12.0 (tonne). This would then provide clamping of SYS to these values and also a
flags being set in FLAG and STAT.
Sys Calibration Auto
Assume we require to calibrate for Kg output and we have available a known accurate 10 Kg and 100 Kg test
weights.
Start the wizard by selecting Sys Calibration Auto from the Wizard menu
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Click Next
Apply the low known test weight and enter the required SYS value for this weight. In this case it will be 10 as we
want the units of SYS to be Kg. Click Next to continue
Apply the high known test weight and enter the required SYS value for this weight. In this case it will be 100. Click
Next to continue
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The device is now calibrated. However you may find SYS has been ‘clamped’ if the resultant SYS is greater than
SMAX or less than SMIN. If this is the case then change these values to suitable limits. In this example we may set
SMIN to –0.5 (Kg) and SMAX to 110.0 (Kg). This would then provide clamping of SYS to these values and also a flags
being set in FLAG and STAT.
For detailed information about calibration calculations please refer to chapter 3.
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Chapter 3 Explanation of Category Items
Instrument Explorer shows the categories to which parameters and generated variables belong. This provides a
convenient method for describing the functionality and purpose of each. The categories can be seen from
Instrument Explorers Parameter List pane and are as follows.
Communications
This category deals with the setting of the CAN ID, the bit rate and the ID size. Care must be taken when changing
any of these parameters otherwise communications can be lost.
Defaults are:
ID = 1
Identifier length = 11Bits (standard)
Bit Rate = 500Kbps
ID, NODEIDL, NODEIDH
Each device has a singe base ID to enable configuration and is factory set to 1, this base ID can be changed. All data
sent to the device will be sent to this ID. All data returned from the device will be on the base ID + 1.
Because the device ID is set via CAN, the device should be the only device connected to the CAN bus while
configuring from factory settings.
Where the DSC parameters are used to define CAN identifiers the following format is used. The packet identifier is
set using a HI and LO parameter. Each of these parameters represents 2 bytes (1 X 16 bit word) that are used to
create the identifier.
MSByte Byte Byte LSByte
HI LO
Although 16 bits are available to be set using these two parameters the value entered will depend on whether the
DSC is set for 11 bit or 29 bit identifiers.
11 bit allows a range of 0 to 3FF
HI is never used on 11 bit so LO would be set to a value from 0 to 3FF
29 bit allows a range of 0 to 1FFFFFFF
HI can range from 0 to 1FFF and LO can range from 0 to FFFF
Example
If the identifier 1ABCDEFF is to be specified:
MSByte Byte Byte LSByte
1A BC DE FF
Hexadecimal
value
NODEIDH = 0x1ABC NODEIDL = 0xDEFF
Decimal value NODEIDH = 6844 NODEIDL = 57087
The above values are sent in the floating point IEEE standard
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If the identifier 1ABCD is to be specified:
MSByte Byte Byte LSByte
00 01 AB CD
Hexadecimal
value
NODEIDH = 0x1 NODEIDL = 0xABCD
Decimal value NODEIDH = 1 NODEIDL = 43981
The above values are sent in the floating point IEEE standard
To connect multiple devices on the same bus, it is first vital to set all the ID’s to different values.
This is because if two devices with the same ID are connected to the same bus, it is not possible to talk to them
individually: So in particular, you cannot correct the problem by changing the ID of one of them!
If a bus connects to two devices with the same ID, the only solution is to remove one of them and connect it to a
one-to-one link to change its station number.
The new value of NODEIDL or NODEIDH does not take effect until the RST command is issued or the device is
power cycled.
To Change the ID of your Device
1. First set NODEIDL and NODEIDH to a suitable new value (making sure that no other device of the same number is
also connected!)
2. Send a RST command or power cycle the device.
3. Change the device settings in Instrument Explorer by selecting Change Settings from the Communications menu.
CAN Bit Rate, BPS
The BPS parameter is a read/write byte value specifying a standard communications bit rate according to the
following table –
BPS value 0 1 2 3 4 5 6 7
Bit rate
(bps)
20K 50K 100K 125K 250K 500K 800K 1M
Warning: When changing this setting it is possible to lose communication with the device. As well as keeping
track of the correct bit rate, it is also essential in this case to be sure that your hardware supports the rate you
are changing to.
The evaluation kit supports all possible DCell/DSC baud rate settings UPTO 1Mbps
The new value of BPS does not take effect until the RST command is issued or the device is power cycled.
To Change The BPS, follow a similar sequence to changing the STN value
1. First set BPS to the new value
2. Send a RST command or power cycle the device.
3. Change the device settings in Instrument Explorer by selecting Change Settings from the Communications menu.
Select new bit rate.
Identifier Size, IDSIZE
Determines if the identifier is 11bit, standard, or 29bit extended. A 0 in IDSIZE selects 11bit (standard) and a 1
selects 29bit (extended).
CAN Bus, CANTXERR, CANRXERR, CANSTATUS
These parameters provide diagnostic data for the CAN bus.
CANTXERR
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