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DCell & DSC Strain Gauge or Load Cell Embedded Digitiser Module

1. DSC DCell amp DSC Strain Gauge or Load Cell Embedded Digitiser Module 2 Generation Software Version 3 onwards User Manual www mantracourt co uk FOR ENTERPRISE ME mantracourt Contents Chapter 1 INtFOUCtION ccivecisucsscsvives iones daa asus A cds vevseec cutscene s vewa seca ese as 4 OVERVIEW da rE E EEEE de Ti 4 Key Feature id A AA E EEE E EA E OERE ATAA EE is de 4 Special Facilities A AA A A A E AA Ai Oh 5 Version 3 Additions and Enhancements ooooooconccnccnncncccncnncnncnnconnrnnonnrn non eee eee eeeeeseeeeeneeeeeeeeeseeseeseeaeeeees 5 Version 4 Additions and Enhancements cecceceecc eee eneeec eee e conc on nono nn nono n eee eeseeseeneeneeeseesenseeseeaeeeees 6 THE PrOdUCt RANGE wicca isd sscw wade dade ae A delet ald A 050 sin sled tle en e A A A AS ti 6 Which Device To USe scusciscesn rata nai oc or cos aldeas Hus aa alo RES AAA 6 Additional DCell DSC Variants Available 0 cece sce eee eee ee cece nce ne ence ee eneeeeeee eee eeseeseeneeeeeeeeesenseeeeeeeeeees 7 Some Application EXAMples s csicc cde ese eea NE oe pantie edie eke v aged a AA A EE AV aa 8 Chapter 2 Getting Started with the Evaluation Kit oooococccccncconcnnccnccncnoconccnronncncccccccconconccnccncccnononss 9 The Evaluation Kits stan cian nad 9 COMES esserne donna ov cov NEEE EEO EEEE te LI AAA vies unused AA A E EE 9 Checking the Device Protocol Type and Station Number sssssssssssss
2. Ak SYS Calibration Table Result Instrument calibration complete The new calibration values have been calculated and the instrument updated Click Finish to complete this Wizard The display below shows the value of SYS You can now apply the low and high inputs to check that the calibration was successful You can press the Back button to return to a previous calibration stage to repeat it SYS 5 514293 NOTE Some instruments have parameters that clamp the output values If the SYS output seems incorrect you should first check the instrument manual to see if there are any parameters that can clamp this output 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 Method Assume we require to calibrate for Kg output and we have available a known accurate 10 Kg and 100 Kg test weights 19 Mantracourt Electronics Limited DCell amp DSC User Manual Start the wizard by selecting Sys Calibration Auto from the Wizard menu SYS Calibration Auto Instructions This Wizard will allow you to calibrate your instrument by applying 4 known low input followed by a known high input Y
3. Bus Standards Serial Data Format Serial data formatting is the same for all the protocols and is fixed to e one start bit e one stop bit e 8 data bits e no parity Communications Flow Control Bus flow control is managed as part of the protocol managed differently by each No hardware or software flow control signals are to be used for any of the bus standards Communications Errors Serial data which does not conform to the expected format causes a serial framing error to be registered which increments the Communication Failure Counter CFCT What this actually means is that following a starting 1 to 0 transition a stop 1 bit was not seen in the expected place This is obviously baud rate dependent the commonest cause being data transmitted at a lower baud rate than the unit was configured for Choice of Bus Formats Essentially the RS232 bus is only suitable where the application will only ever need a single DCell DSC device The only real advantage of RS232 output is that no data converter is required to connect the device to a PC The RS485 bus is the simplest and most flexible choice from the wiring point of view It enables multi drop operation and much longer cable lengths However it usually requires a bus converter which must be chosen to suit the equipment in use The RS232 Bus Standard RS232 has separate dedicated transmit Tx and receive RX wires Each wire is permanently driven by the s
4. If all is healthy the LED should flash ON for a period of 100mS The rate at which the LED flashes is used to indicate the protocol as indicated in the table below Protocol LED Flash Period ASCII 0 5 seconds MODBUS 1 second MANTRABUS II 2 seconds If an error conditions occurs which is based on any of the following error flags being set then the operation of the LED will invert IE the LED will flash off for 100mS at the rate set in the table above These flags Being TEMPUR TEMPOR ECOMUR ECOMOR CRAWUR CRAWOR SYSUR SYSOR amp LCINTEG Mantracourt Electronics Limited DCell amp DSC User Manual 44 Chapter 8 Communication Protocols This chapter gives details of communication protocols and bus connections There are effectively three layers to DCell DSC communications 1 Internally all devices support the same command set as described in earlier sections 2 Command accesses are coded into actual byte sequences according to a communications protocol Several different protocols are available 3 Serial communications are carried out over a bus which operates according to the usual RS232 or RS485 standards The bus standard and protocol type are fixed for a given device during production The communications baud rate and station number the bus address are configured for each device by the ordinary control parameters STN and BAUD see Chapter 2 Getting Started with the Evaluation Kit
5. c cceccsscsscscccsccscescesnsscescesscenssnsssessesccecssassasseseeseeeeeees 22 COMMUNICATIONS v s couse cocyesa uscd ea ceba dus A cape sed A sued eb Os dda deeb A oper dunes ete 22 Station Number Ni a a Sena cb dented eveedan secre doesn 22 Batid rate Control BAUD 0 00 weed dts ease ounce A wenden PON oes SACRE TG Neha wa La bce ns Os VEN Rea ES ei See 23 New For Version 4 DSC Only wc cc seieeevescvessesceeve conectara cacao nia AAA IA ii 23 DSC Issu 3 DED Or HiGher ii ici seais 23 Communications Failure Count CFCT oocoocccccnnnccccnnncnonnncconnnc ono nesses eee esse ee eee esses AEE AEE EEE A EAE 24 Output Format Controls DP and DPB ASCII ONLY cccesccesceencceneeeeeeeeeeeeeeeenseenseeseeeneeeeeseeeseeeseeseeees 24 nformati ON A A OAT TOE EEN E E st daced daw AE 24 Software Version VER enoia rae vb tnd Baers a A E OAA A OTE RE We SAMEEREN 24 Serial Number SERL and SERM ee 3 5005 circa ein cea be dia ias siii aia 24 SIAMNEGAUME A A a late 25 MVV output MVV ociosa nilo enel dani TERES EEEE TOER A TOE E PEER e TSERE S 25 Nominal MV V level NMVYV a A AA A A E E ER ees 25 mV V Output In Percentage Terms ELEC c ccccccccesesccesesccsecscessescceesccceseeceessseseessscsereseseseseossnsuees 25 Lempe rature Valuie TEMP A oy ooo SES Gh A A Pade 25 Output Rate Control RATE cscs savvesecsedvsnscetcedecy veces A E dae EEES EIEEE EEEE ieee Ai 25 Dynamic Filtering FEST and RELV stccec ces echi deel ssact
6. or the sensor cable 63 Mantracourt Electronics Limited DCell DSC User Manual Suitable Cable Types DCell DSC4 RS485 Versions RS485 Bus Cable Requires e 2 x twisted pair with independent shields e Characteristic impedance 50 150 ohms e Core to core and core to shield capacitance below 300pF m A suitable type is BICC Brand Rex BE56723 also equivalent to Belden type 8723 In the UK this is available from Farnell part number 118 2117 DSC Sensor Cable and DSC2 RS232 Versions RS232 Cable Both of these require 3 x twisted pair version otherwise similar to the above A suitable type is BICC Brand Rex PD3003 also equivalent to Belden type 8777 In the UK this is available from Farnell part number 148 540 Warning Special Problems with Portable Computers Many portables use double insulated power supplies with no ground connection and in this case a considerable voltage can appear on the port pins chassis when the PC is powered off the mains When such a system hosts a DCell DSC bus the whole arrangement may be connected to the mains ground only via the external power supply or the ground connections to the data converter or the DCell DSC units Electrical damage due to the brief presence of high voltages can easily occur when such a system is connected up Permanent harm can easily be done to the PC serial port the data converter and or DCell DSC devices This is not simply a theoretical risk We have seen several conver
7. 0 Mantissa 23 bit fraction with implicit 1 Mantracourt Electronics Limited DCell amp DSC User Manual 52 The value of the number is thus 1 pe 2 Exponent 127 4 Mantissa i Note the assumed 1 before the mantissa The exception to this is the special value 0 0 which is represented as 4 zeroes eg a floating point number of 12345 678 is represented as hex C6 40 E6 B6 This is transmitted in nibble format as hex OC 06 04 00 OE 06 OB 06 End of Data Identifier As the protocol has no fixed length or length identifiers the last nibble of data sent to the device has its MS nibble set This indicates to the device that all data has been received amp the next two bytes will be checksum data ACK amp NAK Mantrabus II supports ACK amp NAK sending ACK 06h at the end of a successful operation and NAK 15h for an unknown command or failed operation These are always preceded by the station number see examples below N B Mantrabus ll will not transmit a NAK for invalid checksum data but instead remains silent This is different from the behaviour of the older Mantrabus 1 Writing to Variables Station number and command number are followed by 8 bytes of nibble data the last having its MS bit set followed by the two checksum nibbles eg To write the value 100 0 Floating point 100 0 42h C8h 00h 00h to variable CGAI command number 40 at station 20 send the following FEh 14h 28h 04h
8. 02h OCh 08h 00h 00h 00h 80h OBh OEh DATA EXOR CS Frame Station Cmd MS bit char number number of last Byte set the response is then 14h 06h i e station number ACK Reading of Variables To read an individual variable the command number is sent with the MS bit set i e no data following eg To read CGAI command number 40 from station number 20 send the following FEh 14h A8h OBh OCh I 1 EXOR CS Frame Station Cmd with char number MS bit set of last byte Assuming the value was 12345 678 coded as C640E6B6h representing 1 2 12345 678 8192 the response will be 14h OCh 06h 04h 00h OEh 06h OBh 06h 01h OFh DATA EXOR CS Station number 53 Mantracourt Electronics Limited DCell DSC User Manual Action Commands These are transmitted like read commands i e no data sent The response is as for write commands Mantracourt Electronics Limited DCell amp DSC User Manual 54 Chapter 9 Software Command Reference This chapter contains tables of all DCell DSC commands with brief details of each Commands in Access Order ASCII name CMVV Temp Compensated mV V float Ro ft STAT Status int RO 13 MVV Filtered amp factory calibrated float RO 17 mV V SOUT selected output float Ro b 9 SYS main output ffloae SRO tft TEMP temperature float RO 11 23 SRAW raw system output float RO 12 25 C
9. DPB values The response consists of a sign character DPB decimal digits before a decimal point DP digits after the point and a terminating lt CR gt The length of the response is thus fixed at DP DPB 3 characters Example A command to read the SOUT output could look like this 1001 SOUT lt CR gt if the value 32 1 and format settings are DP 3 and DPB 5 the response string will be 00032 100 lt CR gt Action Command If the device accepts the command then a lt CR gt is transmitted Example A command to reset device 14 would look like 1014 RST lt CR gt the response string will be just lt CR gt Broadcast Commands If the station address in a command message is 000 this means a broadcast command All slaves act as normal on a broadcast command but do not respond Example A command to all devices on the bus to sample their inputs would look like this 1000 SNAP lt CR gt there is no response Bad Commands If any command is not understood by the device then a is transmitted followed by a lt CR gt Example A unrecognised command correctly addressed to station 173 1173 XYWR lt CR gt 49 Mantracourt Electronics Limited DCell DSC User Manual produces the general error response lt CR gt Continuous Output Stream ASCII ONLY For the ASCII protocol only there is a continuous output mode The SOUT value is continually broadcast at the output rate The max
10. DSC must always be as near as possible to the exact conditions of the eventual in system use Parameter Calculations Instrument Explorer provides a Wizard for the calculation of the parameters required by the DSC DCell This is based on Method 3 where data is collected The wizard allows for small changes in the sampled temperature point that may occur when taking a set of results for gain and offset Also taken into account is any variation in the test weights at different temperatures This is a complex mathematical procedure which is best solved by a PC programme such as the wizard Mantracourt Electronics Limited DCell amp DSC User Manual 40 Chapter 6 Linearity Compensation This chapter describes the Linearity Compensation features and how to use them Purpose and Method of Linearisation Load cell sensor outputs are never precisely proportional to the input applied load If the graph of the measurement output against the true value shows slight deviations from the ideal straight line then slight errors remain even when the basic calibration offset and gain is as good as possible Linearity compensation adjusts the raw measurement by a small amount that is calculated as a function of the raw measurement value itself Ideally this will adjust the output response for any given input load by exactly the right amount to place the final result onto the ideal straight line The DCell DSC non linearity compensation uses a sin
11. DSC products from Mantracourt Electronics Ltd Mantracourt are warranted against defective material and workmanship for a period of 3 three years from the date of dispatch If the Mantracourt product you purchase appears to have a defect in material or workmanship or fails during normal use within the period please contact your Distributor who will assist you in resolving the problem If it is necessary to return the product to Mantracourt please include a note stating name company address phone number and a detailed description of the problem Also please indicate if it is a warranty repair The sender is responsible for shipping charges freight insurance and proper packaging to prevent breakage in transit Mantracourt warranty does not apply to defects resulting from action of the buyer such as mishandling improper interfacing operation outside of design limits improper repair or unauthorised modification No other warranties are expressed or implied Mantracourt specifically disclaims any implied warranties of merchantability or fitness for a specific purpose The remedies outlined above are the buyer s only remedies Mantracourt will not be liable for direct indirect special incidental or consequential damages whether based on the contract tort or other legal theory Any corrective maintenance required after the warranty period should be performed by Mantracourt approved personnel only gt Y ISO 9001 RE
12. Modbus accesses are in register pairs Modbus addresses are just 2 MANTRABUS 1 Mantracourt Electronics Limited DCell amp DSC User Manual 56 Chapter 10 Installation This chapter gives detailed information on integrating DCell and DSC devices into a production system including mounting protection adjustments wiring and electrical requirements Before Installation Carefully remove the DCell DSC device from its shipment box Check that the device is complete and undamaged Check the Product Type Code on the product label is that which you ordered The DCell DSC can operate in any industrial environment providing the following limits are not exceeded Operating Temperature 40 C to 85 C Humidity 95 non condensing Storage temperature 40 C to 85 C For precise details of Environmental Approvals see chapter 15 It Is Advisable To Follow The Following Installation Practice Where Possible e Minimise vibration e Do not mount next to strong electrical or magnetic fields transformers power cables e Install electrical protection device as the unit is not internally fused e Always ensure the package is secure and protected Physical Mounting DCell is normally sealed in the pocket of the load cell which provides mechanical and moisture protection and electrical shielding The DCell should be mounted using a 2mm screw to the body of the load cell This should be a Good electrical connection to obtain max
13. Resolution 100Hz readings Noise stable over 1005 50 000 Counts divs Saris 500Hz readings NEE E over100s 18 000 Counts divs na iter auu u Signal Filter O OS recursive zo pas user Temperature Resolution Temperature Measurement Resolution A ae Deg C Temperature Temperature Measurement Accuracy 10 to 85 Temperature Measurement Accuracy 10 to 85 10 to 85 DegC DegC Temperature Measurement Accuracy 55 to 125 A Temperature update Speed q ea Electrical A OM E DR PA Power Supply ripple 100 mV ac pk pk Power Supply current 350R Bridge Seep Bridge po 45 60 m Power 10v 350R Bridge ________________ __ _ 450 w Pe Sees Output Data terminal __ Output Data terminal RS485 DSC offers RS232 Data transmission rate Output cable length speed dependant 1000 Operating temperature range 85 Storage temperature 85 95 Humidity PCB Dimensions DSC 87 4 x 20 x 8 5mm PCB Dimensions DCell Diameter 20mm Height 5 3mm Notes 1 From original offset at any time 2 1st Year 3 Dependent on cable type and is for RS485 For RS232 max length is 20m The DSC digital output is an open collector transistor rated at 100mA 40v 71 Mantracourt Electronics Limited DCell DSC User Manual Technical Specifications DSC DCELL Industrial Stability DSC Conditioner is nominally set for 2 5mV V sensitivity 4 Wire S
14. Stability RS232 output card with ASCII protocol DSCS2MAN Industrial Stability RS232 output card with MANTRABUS protocol DSCS2MOD Industrial Stability RS232 output card with MODBUS protocol DSCH4ASC High Stability RS485 output card with ASCII protocol DSCH4MAN High Stability RS485 output card with MANTRABUS protocol DSCH4MOD High Stability RS485 output card with MODBUS protocol DSCH2ASC High Stability RS232 output card with ASCII protocol DSCH2MAN High Stability RS232 output card with MANTRABUS protocol DSCH2MOD High Stability RS232 output card with MODBUS protocol NOTE For evaluation purposes the electrical output standard RS485 or RS232 is not important Your kit should contain the correct equipment to connect the device to a PC The product code should match your original order The serial number of the device is also shown The station number 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 For RS485 Connect the PC using the 9 way D Type to the RS232 RS485 converter Plug the cable provided into the converter and connect the other end to the 5 way connector marked J1 on the DSJ1 PCB Ensure LK1 amp LK5 are set to CAN RS485 Fit LK2 which terminates the RS485 comms Connect the power cable Red amp Black twisted to your power supply which has been set to deliver between 10 amp 18 vo
15. a CLKi of 1 0 actually adds 0 001 to the CELL output This due to a limitation in the ASCII conversion to floating point numbers Internal Calculation This uses the same basic interpolated table lookup method as for temperature compensation First a working table index i is derived from the current raw input CRAW x as follows n number of points used as set by CLN When x lt CLX1 then i 1 When x gt CLXp 1 then i n 1 Otherwise i is chosen so that CLXj lt x lt CLXj 4 The resulting interpolated adjustment value is then calculated as ofs CLKj CLKj 4 CLKj x x CLXi CLX 4 CLXj Then the compensated cell value is calculated as CELL CRAW ofs 41 Mantracourt Electronics Limited DCell DSC User Manual How to Set Up Linearity Compensation A linearity correction can be set up either from sensor specification calibration data or more commonly from in system testing results Assuming we do not have any prior information on linearity errors the usual approach is to do a series of controlled tests with accurately known test loads Just as with temperature compensation it is possible to obtain a detailed graph of linearity error and then choose a best fit piecewise linear curve for the compensation table However it is generally good enough and much simpler to simply test at several different points and then apply an exact correction at those points If the error curve is
16. data value irrelevant AO B4 checksum hi lo The Acknowledge Response Is Then hex 11 station response 10 info copied from command 00 64 00 02 02 87 checksum hi lo The Mantrabus ll Protocol Mantrabus ll is a two wire system where data is transmitted amp received over a common pair of wires For this reason the framing character must not be sent in a reply from the responding DCell The protocol ensures this does not occur by splitting byte data into nibbles with the exception of the framing character amp station number Framing Character The framing character for Mantrabus ll is FEh this being different from the older Mantrabus FFh to allow the two protocols to be mixed on one bus Checksum Both Host amp Device send their EXOR checksum of all data sent excluding framing character in nibble format the MS nibble being first eg EXOR Checksum of data is A7h Checksum characters sent OAh 07h Data Transfer Data is both sent and received as 4 bytes split into 8 nibbles following the station number plus two nibbles of checksum Floating Point Data Format All data sent amp received in Mantrabus ll is in the IEEE floating point format this being a 4 byte floating point number The byte containing the sign amp exponent is sent first with the LS byte of the mantissa being last The Memory Layout Of The 4 Byte Floating Point Numbers Is MSB 31 Sign bit 1 negate 30 23 Exponent 7 bit excess 127 LSB 22
17. data back lt CR gt i e nothing more before end means the command is an action type execute e Data An ASCII decimal formatted number can include 0 9 and spaces This field can have a maximum length of 15 characters e End of frame A lt CR gt is always present to indicate the end of the message Summary e Acommand message begins with followed by a three digit station address then a and finishes with a lt CR gt e The and lt CR gt only appear at the beginning and end of commands respectively e From the to the final lt CR gt is the command instruction of read write or execute type e All instructions begin with an alphanumeric command identifier of up to 4 characters and end with a non alphanumeric which may be the final lt CR gt Slave Response Message Formats Each slave monitors the bus for command messages It responds to any message that is addressed to it by sending a response message To be accepted by a slave device a message must start with the correct three digit slave address and and end with lt CR gt with no intervening extra The slave will then always respond There are Three Possible Types of Response acknowledge ACK acknowledge with data for a read and not acknowledge NAK ACK is a single lt CR gt character This confirms an execute or write command ACK with data is a decimal number followed by l
18. gauge sensitivity adjustment please consult factory If your strain gauge does not deliver a 2 5mV V full scale output you may want to adjust the sensitivity of the electronics hardware and or the software gain controls If you want to test with an input of more than 2 5mV V you will have to adjust the hardware sensitivity to avoid saturating the input If it is less you can correct in software alone but increasing sensitivity will generally improve accuracy To adjust the mV V for DSC an extra resistor Rg is fitted across the pads RG as shown above in Identifying the DSC Rg Resistor Identifying Sensor End Connections The link across TC can be cut to disconnect the internal 100R gain resistor This is needed for lowering the sensitivity The resistor is 0805 size surface mount chip A 0 1 5ppm Deg C resistor for the high stability version 25ppm Deg C for the Industrial must be used to maintain performance Reducing Sensitivity To accommodate a maximum sensor output larger than 2 5mV V it is necessary to reduce the electrical sensitivity of the input circuitry To decrease sensitivity the link TC is cut and the value of the resistor fitted in Q should be Rg required mV V x 40 Example For 10mV V Rg 10 x 40 4000 Increasing Sensitivity When the full scale output is smaller than 2 5 mV V it may be desired to increase sensitivity However it is often possible instead to compensate partly or e
19. groups or using other addresses i e even numbered registers cannot be addressed directly Parameter Addresses All MODBUS parameter addresses are derived from the equivalent MANTRABUS register number by a simple times 2 plus 1 calculation For example the FLAG parameter is Mantrabus register 14 so this occupies MODBUS holding registers 29 and 30 because 2x14 1 29 See the command table in for the starting register numbers Parameter Values All exchanged values read and write parameters are in the standard IEEE 4 byte floating point format The 32 Bits Of The Number Are Distributed As Follows MSB 31 Sign bit 1 negate 30 23 Exponent 7 bit excess 127 LSB 22 0 Mantissa 23 bit fraction with implicit 1 The value of the number is thus 1 sign 2 Exponent 127 4 Mantissa i Note the assumed 1 before the mantissa The exception to this is the special value 0 0 which is represented as 4 zeroes eg a floating point number of 12345 678 is represented as hex C6 40 E6 B6 These 32 bits are mapped onto a register pair in the following way The lower register holds bits 15 0 and the upper register bits 31 16 These values are coded according to normal Modbus conventions so the actual byte sequence in a read write message is thus Rihi Rito R2pi R210 Which in terms of bits is 15 8 7 0 31 24 23 16 Error Codes Only Three Modbus Error Codes Are Supported Which Are Used As Follows 01 Il
20. 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 See Communications Protocols in chapter 10 as appropriate to the protocol type The Evaluation Kit Contents e An Evaluation PCB DSJ1 which comprises of A 8 way screw connector for the strain gauge amp Temperature sensor A 5 way screw connector for power amp RS485 comms A 9 way D Type for direct RS232 connection to PC CAN amp RS485 Link headers for RS232 or RS485 comms selection Terminating resistor for CAN amp RS485 ON board Temperature Sensor for easy evaluation of Temperature compensation 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 A9 to 25 way D Type adaptor for the PC comms port A 9 way D Type extension lead For RS485 ONLY an RS232 to RS485 converter and connecting cable For RS232 ONLY a power connection cable Other Things you will need e A regulated power suppl
21. output CELL to be in force units which can be used by System to convert to units of weight Temperature compensation and Linearisation are covered in detail in their own chapters Temperature Compensation In Brief When the optional temperature hardware module DTEMP is connected the temperature compensation is available The temperature compensation facility can remove the need for the fitting of compensation resistors to the strain gauges This compensation can apply for gain and offset with up to 5 temperature points The input for the temperature compensation is MVV and the output from the process is CMVV If not temperature compensation is invoked the CMVV is equal to MVV A Detailed explanation is given in chapter 5 Cell Scaling CGAI COFS The temperature compensated value CMVV is scaled with gain and offset using CGAI and COFS respectively The gain is applied first and the offset then subtracted This would be used to give a force output in the chosen units this output being termed CRAW CRAW CMVV X CGAI COFS Two Point Calibration Calculations and Examples Examples are given here for two point calibration as this is by far the most common method Cell Calibration The scaling parameters are CGAI and COFS CGAI is in cell units per mV V COFS is in cell units The cell output calculation is in the absence of temperature and linearity corrections CRAW CMVV x CGAI COFS If we have two electrical output M
22. to test weight forces We will now describe each of these techniques with an example Sys Calibration Table method 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 SYS Calibration Table Instructions This Wizard will allow you to calibrate your instrument by entering input values and required values which can be based on manufacturers tables You will need to know two CELL levels and the required SYS values at these points The two levels of input should be around 25 or below of full scale for the lower value and a high level at around 75 or higher of full scale Press NEXT to continue with the calibration Cancel A SYS Calibration Table Enter Low Data Enter the low level input value and required output value Enter value for CELL at this low input level Enter required value for SYS 0 01573 a Mantracourt Electronics Limited DCell amp DSC User Manual 18 Click the Next button and enter the high values as shown below SYS Calibration Table Enter High Data Enter the high level input value and required output value Enter value for CELL at this high input level Enter required value for SYS 2 19053 fo Click Next the following window will be displayed showing the calibrated SYS value which is dependent on the current input values
23. will be equal to the new input reading If the difference is less than FFLV then the fractional amount added is 25 Mantracourt Electronics Limited DCell DSC User Manual incremented until it reaches the maximum level set by FFST IE if FFST 10 then after a step change the fractional part of a new reading is incremented as follows 1 1 1 2 1 3 1 4 1 5 1 6 1 10 1 10 1 10 This allows the Filter to respond rapidly to a fast moving input signal With a step change which does not exceed FFLV the calculated new filtered value can be calculated as follows New Filter Output value Current Filter Output Value Input Value Current Filter Output Value FFST The time taken to reach 63 of a step change input which is less than FFLV is the frequency at which values are passed to the dynamic filter set in RATE multiplied by FFST The table below gives an indication of the response to a step input less than FFLV Update Rate is 1 table value of RATE see Chapter 3 Output Rate Control Of Final Value Time To settle 63 Update Rate FFST 1 Update Rate FFST 5 0 1 Update Rate FFST 7 For example If RATE is set to 7 100Hz 0 01s and FFST is set to 30 then the time taken to reach a of step change value is as follows Of Final Value Time To settle 63 0 01 x 30 0 3 seconds 1 0 01 x 30 x 5 1 5 seconds 0 1 0 01 x 30 x 7 2 1 seconds The following t
24. ELL celloutput float SRO 27 FLAG int CRAW raw cell output ffloat Ro 5 Bt ELEC float Ro t B3 SZ system zero float RW 22 45 SYSN snapshot result float RO 23 47 PEAK Peak value ffoat Ro h4 49 TROF Float Ro hs o CFCT VER software version byte Ro bo fi SERL serial number low int RO 31 63 SERH serial number high int RO 32 65 STN int BAUD byte Rw Ba fo OPCL RATE DP digits after point byte RW 37 75 DPB digits before point byte RW 38 77 NMVV CGAI float COFS CMIN float Rw M s9 CLN lin n points byte RW 50 101 CLX1 7 CLK1 7 flin corrections float RW l61 67 SGAI SOFS float SMAX system range max float RW 75 151 USR1 9 FFLV Float FFST RST b X 100 SNAP X 103 RSPT X 104 SCON ShuntcalON Eo K dha n O SCOF Shunt cat oFF F K h n O OPON Digital Outputon p K hoy 215 O OPOF Digital output off X 108 217 55 Mantracourt Electronics Limited DCell amp DSC User Manual CTN tempco n points byte RW 110 221 CT1 5 CTG1 5 tempco gain adjust float RW 116 120 233 241 CTO1 5 tempco offset adjust float RW 121 125 243 251 Table Key Denotes a range e g CLK1 7 means CLK1 to CLK7 Access RW RO WO X read write read only write only execute Datatype float int byte 4 byte real two byte integer 1 byte integer none MB reg register number for MANTRABUS protocol MD reg start register address always odd for MODBUS protocol NOTES All
25. GISTERED FIRM THE QUEEN S AWARDS l Fa FOR ENTERPRISE 200 AMS CE In the interests of continued product development Mantracourt Electronics Limited reserves the right to alter product specifications without prior notice DESIGNED amp MANUFACTURED IN THE UK Code No 517 153 Issue 3 0 11 06 12 Mantracourt Electronics Limited DCell amp DSC User Manual 74
26. Mantracourt Electronics Limited DCell DSC User Manual If required the entire unit can be embedded in a potting compound A two part epoxy compound can be used but bubbles and gaps must be avoided to prevent mechanical stresses which could break the device The compound used must be specified for electrical use and have sufficient thermal conductivity to cope with the heat given off up to 1W on a 15V supply DSC no additional electrical shielding is required but moisture and or mechanical protection are often required Any simple box or enclosure can be used If metal the enclosure should be grounded to the SH connection see Communications Cabling and Grounding Requirements below Soldering Methods Take care soldering cables to the pads Use a temperature controlled soldering iron set to a maximum 330 C for no longer than 2 seconds per pad Excessive heat or increased soldering time may result in damage to the PCB NOTES 1 Solder with water soluble flux should not be used even low residue as this can leave a surface film which attracts atmospheric moisture degrading measurement performance AN 2 DCell units can be damaged by poor soldering due to the small nature of the circuit boards Overheating or applying any pressure to a pad can de solder components on the other side of the board or cause the pad itself to become detached Power Supply Requirements The power supply needed is nominally 5 6 to 18V DC but any po
27. S232 RS485 Bus Converters Typical DCell DSC applications use a PC or PLC host connecting via an RS232 port This then requires an RS232 to RS485 bus converter to communicate with the bus The following features are of importance Two Wire RS485 Connection Baud rate Support Must support at least the rates to be used Driver enable Control Can be either hardware control line driven normally via DTR or automatic host transmitting enables driver For Automatic Control The converter detects host transmissions It usually needs to be set to the correct baud rate and may only support certain specific baud rates Power Options Can be self powered i e from the RS232 port maybe RTS DTR or TX data pin or require an external power supply Although a self powered converter seems attractive it will usually have a limited drive capability It will thus only drive a reasonably short bus with a few devices on it The RS232 amp RS485 bus converter Mantracourt supplies as standard is an externally powered device supporting all the DCell DSC data rates up to 115200 It features completely automatic data rate detection no set up switches and automatic enable control switching with opto isolation ZN GND PSU must be connected to GND of the RS485 device Mantracourt Electronics Limited DCell amp DSC User Manual 66 Strain Gauge Sensitivity Adjustment DSC ONLY Standard unit suitable for inputs up to 3m V Beyond this strain
28. T ETER E e ESEE 47 Data Type Conversions and Rounding ssseesesoossssssssessssssssssssssseeeeseseessseseseseseeeeeeeceesccceeeeeeeeeeoeseeeee 47 THE ASCIMPROCOCOL iienaa A E E ved EN A aaa 48 Continuous Output Stream ASCI ONLY ooooooocccccocccccnccnccconononoonnoc orzan nuie aer esaer ipee 50 NEW TOP Versio A reinate rare a a od deeded a duane e aa E aeaa 50 The MODBUS RTU Protocol cti E A A dire a aad 50 The Mantrabus ll Prot cOlr eiris esene nnn A as da 52 Mantracourt Electronics Limited DCell amp DSC User Manual 2 Chapter 9 Software Command Reference csscsscsccsscsncscccsccsccscesnessessesscensensssessesceesseesseessscesensenees 55 Commands in Access Order usss reirs atena iE EEEE EE O AA Ad 55 Chapter 10 Installations sssini ianei enr ria EEE EEE EEEE EEEE EAE EN 57 Before Installation A ENEE ERAEN SETE EES 57 Physical MOUNCING es 57 Electrical Protection siers si deiris conocido EEEE A EEEREN EEEE E AAEE EEE TVER ENEE EEA 57 Moisture Protectio ita de it a EE dere agate id 57 Soldering MENOS rsson eret AA A A a dt aaa 58 Power Supply Requirements ooocooccccnconnconccconcoconooon ron ron nro rro t tE nsin EEEE EEE EEES Ni EEE S EE 58 Cable Requirements a ds 58 Stralm Gauge Input DS Chia A A A E AA A ies 58 Power and COMMUNICATION i 65ce55 cei o iai seeded aE EEE EEEE NEE E EEAS ETEENI ESTEVE EA EEE EE 58 Temperat re SENSO aerie Eana A A A a E O anaes caer EENE EEEn 59 Identifying Strain Gauge Conne
29. VV readings for two known force loads we can convert the output to the required range So if test load fA gt CMVV reading cA test load fB gt CMVV reading cB then calculate the following gain value CGAI fB fA cB cA and the offset is COFS cA x CGAI fA The outputs should then be CELL fA fB true force values as required Calibration Methods There are a number of ways of establishing the correct control values Method 1 Nominal data sheet Performance Values 27 Mantracourt Electronics Limited DCell DSC User Manual This is the simplest method where the given nominal mV V sensor output is used to calculate an approximate value for CGAI Example A 50 kN load cell has nominal sensitivity of 2 2mV V full scale So to get 50 0 for an input of 2 2mV V we set CGAI to 50 2 2 22 7273 This assumes the output for OKN is OmV V Method 2 Device Standard Calibration Values With some load cells you may have a manufacturer s calibration document This gives precise cell output gain and offset specifications for the individual cell These values can be used to set the SGAI and SOFS values to be used Example A 10 tonne load cell has a calibration sheet specifying 2 19053mV V full scale output and 0 01573mV V output offset CGAI is set to 10 2 19053 0 01573 4 532557 COFS is set to 0 01573 x 4 532557 0 0071297 NOTE Methods 1 and 2 require no load tests This means that sy
30. able shows the number of updates x FFST and the error New Filter Output value will differ from a constant Input Value x FFST Error 1 36 78794412 2 13 53352832 3 4 97870684 4 1 83156389 5 0 67379470 6 0 24787522 7 0 09118820 8 0 03354626 9 0 01234098 10 0 00453999 11 0 00167017 12 0 00061442 13 0 00022603 14 0 00008315 15 0 00003059 16 0 00001125 17 0 00000414 18 0 00000152 19 0 00000056 20 0 00000021 Remember that if the step change in mV V is greater than the value set in FFLV then New Filter Output value New Input Value Mantracourt Electronics Limited DCell amp DSC User Manual 26 And the internal working value of FFST is reset to 1 being incremented each update set by RATE until it reaches the user set value of FFST Cell Provides the level where the integration between the DCell DSC and the strain gauge bridge takes place Features include when the optional temperature module is fitted 5 point temperature compensation to produce a temperature compensated value CMVV Scaling using a gain and offset CGAI and COFS respectively producing a value known as CRAW Linearisation using up to 7 points producing the final output from this section known as CELL Over load and under load values can be set in CMIN amp CMAX to alert the user of forces less or greater than the integrator has intended the unit to be operated These features allow the
31. able type and is for RS485 For RS232 max length is 20m The DSC digital output is an open collector transistor rated at 100mA 40v Mantracourt Electronics Limited DCell DSC User Manual 72 Mechanical Specification for DSC Note Viewed from top side CAN label as photo on front cover of manual 87 4mm gt lt 80 9mm gt HOLES D0 Imm x15 0 pean gt an x3 AS fs a aa tH f P 3 2 54mm E E E l 5 e 3 CL 2 5mm f E d e a amp Ext E POR 7 0 5 E RO 8 aia E LA R3 0 A P R3 0 3 4mm 7 3mm fe 7B 4mm gt wc 84 1mm al Mechanical Specification for DCell DCell Diameter 20mm Height 5 3mm and has an 2mm mounting hole to accept M2 screw or American equivalent 0 80 Important Note DO NOT USE 2 screw size DCell Viewed from LED side Mounting Hole V X RS485 B RS485 A Temp Sensor DQ Y CE Approvals European EMC Directive 2004 108 EC BS EN 61326 1 2006 BS EN 61326 2 3 2006 Hole centre positions taken from pcb centre All dimensions are in mm x y Hole diameter Mounting hole 0 0 7 9 2 0 V 6 2 6 1 1 0 V 7 9 3 8 1 0 RS485 B 5 8 6 6 1 0 RS485 A 3 6 8 1 1 0 Temp sensor DQ 1 3 8 8 1 0 EXC 7 5 4 9 0 7 SIG 8 8 1 5 0 7 SIG 8 0 3 9 0 7 EXC 6 3 6 1 0 7 73 Mantracourt Electronics Limited DCell amp DSC User Manual Warranty All DCell amp
32. ads Xj give readings of CRAW Cj for i 1 n Then calculate the errors that need to be removed at these points Ej Xj Cj Now just enter these values into the correction table remembering to scale the errors CLN n CLX X CLKj 1000 e Ej Example Suppose we have a load cell and Cell calibration giving a result in the range 0 500 KgF The following test results were obtained using a series of known test loads For test load of x1 OKg 8 CELL reading c1 0 0010 For test load of x2 100 13Kg CELL reading c2 100 44 For test load of x3 199 72Kg CELL reading c3 200 57 For test load of x4 349 97Kg CELL reading c4 349 75 For test load of x5 450 03Kg CELL reading c5 449 98 We choose these precise test points as our linearisation reference points so CLN 5 CLX1 0 0010 CLX2 100 44 CLX3 200 57 CLX4 349 75 Mantracourt Electronics Limited DCell amp DSC User Manual 42 Note on the Example If you graph the errors from the above example the results look like this 0 4 0 2 0 0 2 0 4 This doesn t show any very definite linear trend so the calibration is okay However there is a big jump between points 3 and 4 which might be worth a more detailed investigation Some important features of the error curve could have been missed by the test 43 Mantracourt Electronics Limited DCell DSC User Manual Chapter 7 Self Diagnostics Diagnostics Flags The main diagnos
33. btracted from the above gain adjusted value The output from the temperature compensation CMVV is then calculated as CMVV MVV x 1 CALC_CTGO x 10 CALC_CTO x 10 The Temperature Measurement The temperature sensor used is a Dallas MAXIM DS18S20 Digital Thermometer using the 1 Wire bus technology This gives a temperature measurement accuracy of 0 5 Degree C over the temperature range 10 to 85 degree C and 2 0 Degree C over temp range 55 to 125 Degree C The resolution of the measurement is 0 0625 Degree C The temperature is sampled and the TEMP variable updated every 5 seconds How to Set Up a Temperature Compensation There are a number of ways of obtaining a temperature compensation curve The best possible compensation for a given piece of physical hardware can only be achieved by performing experiments on that particular unit DCell DSC and associated strain gauges to characterise the measurement output at a variety of different stable temperatures in the required operating range The basic choice of methods depends on trading off ideal accuracy against the complexity of the calibration procedure Method 1 Apply a simple linear drift correction i e for known constant gain and offset changes per degree by specifying zero correction at the calibration temperature and appropriately adjusted correction values at extreme temperatures above and below this This can be used when the measurement or sensor has
34. cable terminated at either end Each end connects to a communicating device while other devices are connected as near as possible directly to the main bus as it passes them i e not on long side branches The bus must be terminated at both ends to avoid reflections Connecting a 120 Ohm resistor between the A and B lines does this Loading In addition to reflections each connected device places a load on the bus According to the RS485 standard a maximum of 32 standard load devices can be simultaneously connected The DCell DSC devices are each one quarter standard load so a maximum of 128 devices may be connected at once to a single length of bus It is possible to increase this with bus repeaters but the bi directional nature of RS485 means it is usually simpler to add extra communications ports at the host driving completely separate busses Grounding The RS485 standard does not specify any particular ground connection If two external devices are both externally grounded i e not floating the grounds must be within the bus common mode range 7 volts to connect safely and communicate Beyond this an isolating converter may be needed 2 Wire amp 4 Wire Connections DCell DSC devices only use two wire RS485 connections A 2 wire RS485 connection uses the same pair for transmit and receive so the master has no special rights to the bus and only the rules of the protocol used prevent two devices transmitting at once R
35. ch as For test load of xA 99 88Kg CELL reading cA 100 0112 For test load of xB 500 07Kg CELL reading cB 498 7735 Calculate gain value In this case put SGAI xB xA cB cA 0 50007 0 09988 498 7735 100 0112 0 001003580 1 003580x10 29 Mantracourt Electronics Limited DCell DSC User Manual Calculate offset value In this case SOFS cA x SGAI xA 100 0112 x 1 003580x10 0 09988 0 00048924 Check Putting the values back into the equation results for the two test loads should then be For x 99 88Kg CELL 100 0112 so SRAW 100 0112 x 1 003580x10 0 00048924 0 09988 For x 500 07Kg CELL 498 7735 so SRAW 498 7735 x 1 003580x10 0 00048924 0 5006987 The remaining errors are due to rounding the parameters to 7 figures Internal parameter storage is only accurate to about 7 figures so errors of about this size can be expected in practice System Limits SMIN SMAX These are used to indicate that the desired maximum and minimum value of SRAW have been exceeded They are set in weight units On SRAW being greater than the value set in SMAX the SRAWOR flag is set in both FLAG and STAT the value of SRAW is also clamped to this value On SRAW being less than the value set in SMIN the SRAWUR flag is set in both FLAG and STAT the value of SRAW is also clamped to this value System Zero SZ SZ provides a means of applying a zero to SYS and SOUT This could be use
36. ctions sssessssossseosesessssssesssssesseseesesssssseseseseseeeeeseceesoceeeooeeeeeeseseeeee 59 DCell Input Connections 25 sonere reini tai A eae bo od EE Ai 59 DSC Input CONNECtIONS sica A EE EE E EA EE A E E 59 ld ntifyingB s E nd Coniectionss rsr neee a n a EE E e a SALATA E Na Saaai 60 DCell Bus CONNECTIONS assetti osain to se iat cose EE EEEE AEE ERREEN EEO EAEE ETEA AREEN EEEE EEEN 60 DSC4 R5485 Versions Bus Connections esos ei aineen VEEE lides 60 DSC2 RS232 Bus CONNECTIONS ssnst a a e i E a A o Sheba tine 60 Strain Gauge Cabling and Grounding Requirements oooccooccccncconnconcconncconcconcnonnoonnno no ronn oro nc conan cnnnonnnons 61 DCell Strain Gauge Wining avi A A A A a a 61 DCell Strain Gauge Wiring ArrangeMent ocooocooccccnncnnnconnconnconncoo nono cnn on ron eeee sense eeeeeeeseeeeeeeeeenseeeeeeeaees 61 DSC Strain Gauge Cabling Arrangement cccce cece ence ence nee e eee ence eee eenee eee ron sense eneeeeeseeneeeeeeenseeeeeeeaees 62 Communications Cabling and Grounding REqUIrFeEMENts ceecceecceecceeee ence cence enceenseeseeeneeeeeeeeeseeeseeseeens 62 DCell Power and Communications Wiring cece eee e sees eee e eect eee e eee e eee e eee e eee eeee sense eeeeeeeeeenseeeeeenseeseeeeaees 62 DSC4 RS485 Versions Power and Communications Wiring ccceece cnc eenceeeceeneeeneeeneeesesenneeesseeeseeeeeeeaees 63 DSC2 RS232 Versions Bus End ArrangeMent cceeccesccencc
37. d to generate an Net value making SRAW in effect a gross value SYS SRAW SZ Care should be taken on how often SZ is written to see WARNING Finite Non Volatile Memory Life later in this chapter System Outputs SYS SOUT SYS is considered to be the main output value and it is this value that would be mainly used by the master SOUT is for backwards compatibility with Version 2 Reading Snapshot SNAP SYSN The action command SNAP samples the selected output by copying SYS to the special result parameter SYSN The main use of this is where a number of different inputs need to be sampled at the same instant Normally multiple readings are staggered in time because of the need to read back results from separate devices in sequence By broadcasting a SNAP command at the required time all devices on the bus will sample their inputs within a few milliseconds The resulting values can then be read back in the normal way from all the devices SYSN parameters Note Instrument Explorer provides wizards for easy calibration of the System stage There are two wizards Sys Calibration Auto and Sys Calibration Table these can be found under the menu item Wizards Mantracourt Electronics Limited DCell amp DSC User Manual 30 Control Shunt Calibration Commands SCON and SCOF The Device is fitted with a Shunt calibration resistor whose value is 100K This can be switched across the bridge using SCON givi
38. e this can remove the need for the usual electrical compensation components altogether Note that the temperature compensation will also remove the temperature drift of the DCell DSC itself if the temperature compensation data is collected when the DCell DSC and strain gauges are tested together as a system Temperature Module Connections and Mounting DTEMP The temperature module is a connected using only two wires The temperature sensor is the Dallas 1 Wire digital device DS18520 DCELL connections to DTEMP EXE SIG SIG EXE Temp sensor DQ One connection is ground for which EXC is used and the other is the 1 wire DQ connection which provides the bi directional data line DSC connections to DTEMP For the DSC TS on the I O connector is connected to DQ of the DTEMP module and GND of the DSC is connected to EXC 37 Mantracourt Electronics Limited DCell amp DSC User Manual The temperature module is a small double sided PCB with an 8 pin SOIC integrated circuit mounted to it The dimensions are 10 5 x 7 6 x 2 5mm There are two solder pads for connection to the DSC or DCell A 2mm hole is used for fixing the temperature module to the body of the load cell The module should ideally be positioned as close as possible to the strain gauges The IC on the temperature module must also be in good thermal contact to the load cell body so the strain gauges and temperature sensor
39. e 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 Weighing Subsystem For Process Control Several strain gauge loads are monitored as part of a larger data acquisition monitoring system based around a high speed Profibus network The load measurements occur in groups of physically related signals which relate to specific area modules along with a number of other measurements and control outputs The strain gauges are wired to DSC cards controlled and interrogated via MODBUS protocol commands on an RS485 bus The DSCs and other 3 party MODBUS compliant devices which govern the area module are all connected to a single RS485 spur The devices in each area module spur are controlled from the main Profibus backbone using an off the shelf bus gateway unit Mantracourt Electronics Limited DCell amp DSC User Manual 8 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
40. e 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 amp 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 15 Mantracourt Electronics Limited DCell amp DSC User Manual DSJ1 Evaluation Board Sensor Connections SH EXC SIG SIG EXC SH EXC Optional Temperature Sensor DTemp DQ See Chapter 10 for Connection Method to Strain Gauge See Chapter 5 for Connections to Temperature Sensor Module Next we will set Instrument Explorer to automatically update dynamic parameters from the device so that we can see values such as SYS changing on the screen To do this either click the 2 button on the toolbar or click on the Parameters menu and select the Auto Sync item Note t
41. e the base measurement is in mV V and is factory calibrated to within 0 1 the of FS output ELEC is still available e Extreme Noise Immunity 5 x heavy industrial level e 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 e Remote shunt cal A 100K 1 50ppm Deg C resistor can be switched across the bridge to allow load cell integrity to be established e Peak amp 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 5 Mantracourt Electronics Limited DCell DSC User Manual e 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 e Wide Operating Voltage The operating voltage is now 5 6 to 18V allowing the device to be powered from a wider range of available system supplies e 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 e Defaults have been changed so that the device is shipped with a baud rate of 115200 and station number of 1 e Scaling implementation has been changed for both CELL and SYS The gain is applied before the offset thus following the more standard approach T
42. ed when writing to integral values data read from a device is not rounded off The ASCII Protocol The ASCII protocol uses only printable characters and carriage return lt CR gt which allows a dumb terminal device or a PC programme like Hyper Terminal to interrogate the device Host Command Message Format The basic command request structure is shown in the following example illustrating the message 1001 SGAI 123 456 lt CR gt meaning write 123 456 to parameter SGAI on station 1 Framing Station Separator Command Access End of Character Address Identifier Code frame oo dori Gar e 999 lt crR gt An Explanation of Each Field is as Follows e Framing Character A character is used to signal the start of a new message This character is only ever transmitted by the host for framing purposes e Station Address A three digit ASCII decimal number 0 999 determining which slave device s the command is intended for All three digits must be sent Address 000 is reserved for broadcast addressing e Separator always present As no checksum or message verification technique is used slaves use this as an extra check on message validity e Command Identifier Up to 4 alpha numeric characters case insensitive giving the name of the required command e Access Code Defines what sort of response is expected means write data is expected to follow means the host is expecting to receive read
43. elect 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 and protocol to match the device you are working with by clicking on the required device icon Mantracourt Electronics Limited DCell amp DSC User Manual 12 Instrument Settings One of the following dialogue windows will be displayed Modbus Instrument Settings Modbus RTU DSC v3 Serial Port Settings Port 1 x Baudrate 115200 v Parity None Data Bits 8 v Stop Bits 1 Handshaking ORTS cTs 12 Wire RTS CI DTR DSR CI Xon xoff Line Control CIRTS Line Hi CI DTR Line Hi MantraASCll 2 Instrument Settings MantraASCll 2 DSC v3 Station No 1 Serial Port Settings Port 1 v Baudrate 115200 v Handshaking ATSACTS C 2 Wie RTS R DSF on off Line Control RTS Line Hi CI DTA Line Hi e Select the serial port to which the device is connected e Select the baud rate to which the device is set The factory default is 115200 e Select the Station No Node The factory default is 1 e Now click the OK button MantraBus i Instrument Settings Mantrabus 2 DSC v3 Station No 1 Serial Port Settings Pot 1 Baudrate 115200 Handshaking CTS 2 Wire RTS DTR DSR on off Line Contr
44. emperature Compensation and Linearity Compensation Note Instrument Explorer provides wizards for easy calibration of the Cell stage There are two wizards Cell Calibration Auto and Cell Calibration Table these can be found under the menu item Wizards Cell Limits CMIN CMAX These are used to indicate that the desired maximum and minimum value of CRAW have been exceeded They are set in Force units On CRAW being greater than the value set in CMAX the CRAWOR flag is set in both FLAG and STAT the value of CRAW is also clamped to this value On CRAW being less than the value set in CMIN the CRAWUR flag is set in both FLAG and STAT the value of CRAW is also clamped to this value Mantracourt Electronics Limited DCell amp DSC User Manual 28 Linearisation In Brief Linearisation allows for any non linearity in the strain gauge measurement to be removed Up to 7 points can be set using CLN The principle of operation is that the table holds a value at which an offset is added The point in the table that refer to CRAW are named CLX1 CLX7 The offsets added at these point are named CLK1 CLK7 and are set in thousandths of a cell unit The output from the Linearisation function is CELL If no Linearisation is used CLN lt 2 the CELL is equal to CRAW A Detailed explanation is given in chapter 6 System System is where the Force output CELL is converted to weight when installed into a system Other featu
45. enables multi drop operation i e a single master can control any number of slave devices at a time In practice the master usually polls the attached slaves interrogating them in a fixed rotation Command Types A single command sent to a device can instruct it to read from or write to an internal parameter value or to execute a Control Action The device responds by returning data for a parameter read or a simple acknowledge for write or action Precise details depend on the protocol in use Each Command Message Contains the Following Information 1 The intended slave address or broadcast 2 The command to access 3 The access type one of read write execute 4 For write accesses only the write value The Command Response will then be one of the Following Three Types 1 An error indication 2 Asimple acknowledge 3 A read data value implicit acknowledge The various protocols differ quite a lot in the available types of error and acknowledgements The distinction between different access types is also protocol dependent in that some use a dummy read or write command for execute access Slave Addressing and Broadcast Every slave device on the bus is identified by a unique address value known variously as its station number node id etc depending on the protocol Each command message contains an address specifying to which slave device it is directed A slave will ignore all communica
46. ending end with no transmit enable disable controls so RS232 is only suitable for one to one communications The connection is basically three wire in that the Tx and RX signals are related to a common ground potential For DCell DSC connections this ground is shared with the power return VIN It is therefore especially important for RS232 devices to connect the ground at the device end to avoid noise from communications degrading the reading accuracy The RS232 standard specifies operation over line lengths of 15M 50 ft or less more or less independent of baud rate The drive capability of RS232 compatible hardware varies a great deal but most exceed this comfortably at least at the baud rates used by DCell DSC devices 45 Mantracourt Electronics Limited DCell DSC User Manual The RS485 Bus Standard RS485 differs from RS232 in two important respects 1 It uses differential signalling on pairs of signal wires With small voltage detection thresholds and a large amount of common mode rejection this improves performance over longer distances 2 It uses driver enable disable controls to allow the same wires to be shared between several devices This enables multi drop operation The RS485 standard is a two wire bus For good noise immunity the two wires are normally twisted together and shielded There is no defined ground connection All attached devices load the A and B lines so as to normally pull the grounds of fl
47. eneeeneeeeeeeene eens eens eeeeeeneeeneeeeeseenseeeeeeeseeeeeeeaees 63 Suitable Cable Types ii caus inne deve Veto biededaaheee lay A ay Se AAA A AAA een 64 DCell DSC4 RS485 Versions RS485 Bus Cable ccc ce ece cece esc e cee ec ence eee ne ence nee ne ones ee eeeeeeeeeeensensenseeeeeeeees 64 Warning Special Problems with Portable Computers ccceecceseceecceeeeeeneeeeeeenceeneeeneeeeeeeeeseenseenseeseeens 64 TO Avoid These Problems vicios a a E edge sdeima en EREE DERE 64 RS232 BUS LAYVOUE sossen sises tAn EE VEETEE oo n cede EEEREN an EA e A AR 64 RS485 Bus La yut sissors oird abana cas valving ERE NE EEE A a E EVERE iio Rea 64 RS485 Bus Connections for Multiple DCells cece cece cece nce e eee eect enc ee nee eee eens eenseeneeeenseenseeeeeenseeeeeeeaees 65 RS485 Bus Connections for Multiple DSC RS485 Versions cceeccesceeeceenceeneeeneeeneeeneeeseceenseeeeeenseeneeeeaees 65 RSZ32 4 RS485 BUS CONVEFtELS skorer os ue cias caus ees Foswe cones Gad sieved OA e ba woesacewasneedneaedies a ina 66 Strain Gauge Sensitivity Adjustment DSC ONLY cc ccc eec cence ence ence ence sees eeeeeeneeenseeeeeeneeeeeseeeseeeseeneeees 67 Identifying the DSC Rg Resistor cecccescccence eee ee scenes eens eens eee eens en eseeeeeees sense eeaseeeseeeseeeeeseeesseeaees 67 Chapter 1T Troubleshooting essensen cavs dni AAA AAA cess cceeseeesed cowecevenea 68 LED Indicators vested ees canis EI O vate sack
48. eter Now if no problems exist all flags should in their off state If any flags remain on then refer to Chapter 8 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 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 calibration value and System to convert this calibration value to the required engineering units The use of CELL is optional We shall be 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 provides 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 17 Mantracourt Electronics Limited DCell amp DSC User Manual Sys Calibration Auto This technique is used when the input can be stimulated with real input values For example you have access
49. evice wiring station number baud rate protocol working A quick checklist elaborates on these requirements in the case that you are using the Instrument Explorer evaluation software other software may have different requirements at the PC end Check that PC End 1 PC software settings right serial port baud rate and protocol standard data setup is 1 start bit 1 stop bit no flow control 2 PC serial port okay check with other serial device e g wire 2 PCs together with Hyperterminal running on both RS232 Versions RS232 Evaluation Cable 3 Evaluation Kit cable on right serial port end without power supply wires connects to PC RS485 Versions Cable Data Converter 4 Cable to data converter right serial port standard 9 pin straight through cable not null modem type with Tx Rx crossed 5 Power connected to data converter Mantracourt Electronics Limited DCell amp DSC User Manual 68 6 Data converter baud rate setting if not Evaluation Kit type DIL switches for this may be essential for automatic enable switching 7 Data converter enable switching if not Evaluation Kit type If done by control line check the serial port connects this correctly If by transmission detect how is baud rate set Evaluation Board or Device 8 Power reaches the device 9 RS485 connections the right way round With comms idle B should be a few tenths of a volt higher than A 10 Device settings correct s
50. ger parameters returning the device serial number This is decoded as 65536 SERH SERL Mantracourt Electronics Limited DCell amp DSC User Manual 24 Strain Gauge This is where the measurement process starts If the optional temperature module is fitted then TEMP will display actual temperature in Degree C Otherwise TEMP will display 125 Degree C RATE is the parameter that selects measurement cycle update rate mV V output MVV MVV is the factory calibrated mV V output and it is this value that all other measurement output values are derived from Factory calibration is within 0 05 Nominal mV V level NMVV This is used to represent the nominal mV V value representing 100 of full scale This value is used solely for the generation of ELEC It is factory set for 2 5mV V If the electronic gain is adjusted by changing the gain resistor then if ELEC is used NMVV value must be changed to represent the new nominal mV V mV V Output In Percentage Terms ELEC This is mainly for backwards compatibility with Version 2 It is the mV V value represented in percentage terms 100 being the value set by NMVV Temperature Value TEMP If the optional temperature module is fitted DTEMP then TEMP will display actual temperature in Degree C Otherwise TEMP will display 125 Degree C TEMP is used by the temperature compensation See chapter 5 Output Rate Control RATE The RATE parameter is used to select the output update rate accord
51. ges 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 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 Multiple output options Choice of two communications standards RS232 DSC only or RS485 Choice of three different protocols ASCII MODBUS or MANTRABUS for ease of integration All variants provide identical features and performance Mantracourt Electronics Limited DCell amp DSC User Manual 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 Device Identifier Every unit carries a unique serial number tag readable over the communications link Communications Error Detection An inte
52. gle lookup table similar to those used for temperature compensation see previous chapter This provides a linearly interpolated compensating value with up to 7 control points which is then added to the output result Generally linearisation is a finer level of compensation than temperature compensation It should only be applied after the basic Cell calibration and temperature compensation if any have been set up Although the tests are generally simpler than testing over temperature the accuracy requirement is often greater See below for notes of possible difficulties to be avoided Control Parameters Refer to Chapter 9 for command numbers The lookup table based on parameters CLXi CLKi defines an offset adjustment based on the CRAW value which is then added in to give the final CELL output So linearity correction is applied after any temperature compensation The Parameters Involved Are CLN Sets the number of linearisation points from 2 up to 7 CLX1 7 Raw input CRAW value points CLK1 7 Output CELL adjustments to apply at these points They are used like this e The number of calibration points is set by CLN from 2 up to 7 e Raw input value points are set by CLX1 CLX2 CLX7 or up to the number set by CLN These must be arranged in order of increasing input value e The output corrections at these points are set by CLK1 CLK2 CLK7 e Corrections are specified in thousandths of a cell unit So
53. h Device To Use It is important to select the correct product for your application e First choose DCell or DSC based on your physical installation needs e Choose the communications protocol depending on performance integration requirements e the RS232 output option may be simpler if your system only uses a single DSC card Common Features Both physical formats offer identical control and near identical measurement performance Both are available in all three output protocols MODBUS ASCII or MANTRABUS Mantracourt Electronics Limited DCell amp DSC User Manual 6 Differences Only the DSC card is available with the RS232 output option and has the digital Input amp output Special Aspects To Consider The DCell fits neatly into a strain gauge pocket The DSC lends itself to PCB mounting The RS485 output version must be used for multiple devices on the same bus Additional DCell amp DSC Variants Available A separate variant is available with CANbus output Refer to DCell amp DSC CAN 2 Generation Manual These variants are sufficiently different to require their own manuals The following order codes are supported by an earlier version manual DCell amp DSC Version 2 DLCPKASC DLCPKMAN DLCPKMOD DSC2AS DSC2MA DSC2MB DSC4AS DSC4MA DSC4MB 7 Mantracourt Electronics Limited DCell DSC User Manual Some Application Examples Simple Distributed Measurement Pressure loads are taken at a number of keys
54. has already been sampled It is reset when a new result has been made available Output Update Tracking The OLDVAL flag can be used for output update tracking This allows sampling each result exactly once To achieve this poll the STAT value until OLDVAL is cleared to indicate a new output is ready then read SYS this reading will set the OLDVAL flag in STAT This scheme works as long as the communications speed is fast enough to keep up With faster update rates and slower baud rates it may not be possible to read out the data fast enough User Storage USR1 USR9 There are nine storage locations USR1 to USR9 These are floating point numbers which can be used for storage of data This data could be calibration time and date operator number customer number etc This data is not used in anyway by the DCell or DSC Reset The Reset command RST This command is used to reset the device This command MUST be issued if the following parameters are changed before the change will take effect Alternatively the power maybe cycled RATE STN BAUD DP amp DPB The reset action may take up to about a second to take effect followed by the normal start up pause of 1 second WARNING Finite Non Volatile Memory Life The DCell and DSC use EEPROM type memory as the storage for non volatile controls i e all the settings that are retained even when powered down The device EEPROM itself is specified for 100 000 write cycles for any one sto
55. hat these options toggle ae 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 of Systen ii This now exposes more levels that can be expanded as Scaling required by clicking the next to the heading name Limits SZ 0 0 SNAP Click to execute Peak Trough SGAI 1 0 SOFS 0 0 Limits SMIN 100 0 SMAX 100 0 SZ 0 0 SNAP Click to execute Peak Trough RSPT Click to execute Dynamic values such as SYS and SRAW will now be updating in real time from the device Mantracourt Electronics Limited DCell amp DSC User Manual 16 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 Latched Dynamic 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 Flags A Latched FLAG 0 0 Reset E To quickly clear all the flags simply write zero to the FLAG param
56. he host both signals that it has seen the warning and readies the system to detect any re occurrence i e it resets the latch What the host should actually do with warnings depends on the type and the application Sometimes a complete log is kept sometimes no checking at all is needed Often some warnings can be ignored unless they recur within a short time Warning flags survive power down i e they are backed up in non volatile EEPROM storage Though useful this means that repeatedly cancelling errors which then shortly recur can wear out the device non volatile storage see Chapter 3 Basic Set up and Calibration Meaning and Operation of Flags The various bits in the FLAG value are as follows Bit Value Description Name po 1 unused reserved Unused Temperature over range TEMP TEMPOR 6 Strain gauge input under range ECOMUR 64 512 System over range SRAW SYSOR 1024 unused reserved Unused 31 Mantracourt Electronics Limited DCell DSC User Manual N AJ KR wiry gt oojK COIN 8192 unused reserved Unused 11 16384 BRWNOUT 32768 Reboot warning Normal Power up REBOOT NOTE The mnemonic names are used by convenience properties in Instrument Explorer but are otherwise for reference only the flags can only be accessed via the FLAG parameter The various warning flags have the following meanings TEMPUR and TEMPOR indicate temperature under and over range The tem
57. here 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 NMVV 0 0 Read Only These parameter values are displayed greyed out and cannot be changed Mantracourt Electronics Limited DCell amp DSC User Manual 14 Read write Enumerated These parameters can only be changed by BAUD 0 selecting the new value from a drop down list Clicking in the right hand column will display a down arrow button which BAUD 0 5 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 Lakh mo Y The numeric value is the value of the parameter and the description is Only 1 4800 7 just there to help aa 2 9600 3 19200 4 38400 5 57600 6 76800 7 115200 8 230400 9 460800 Commands These commands have Click to execute displayed in the RSTEMPUR Click to execute right hand column Clicking here will display a L J button Click this to issue the command to the device Click to exeaute ly As parameters are changed th
58. his allows for an offset change to be made easily as the offset is not a component of gain Version 4 Additions and Enhancements DSC e Reset to default communication parameters A pair of pads on the underside of the DSC when shorted together at power up will reset Station no to 1 and baudrate to 115200 Note This is only for issue 3 pcb and higher Please refer to underside for issue marking DCell amp DSC e For ASCII versions Setting Station No to 998 gives continuous output streaming as version 3 except that on powering on streaming starts without requiring an XON character The Product Range Devices are available in two physical formats The DCell puck products consist of a Digital Strain Gauge Signal Conditioner with RS485 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 The DSC is also available with an RS232 output 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 Whic
59. i e it keeps happening again This can be immediate regular every few seconds or irregular occasional See Self Diagnosis for precise details of how the individual warnings operate Bear In Mind The Following Possible Problems 1 REBOOT or an increasing CFCT may indicate intermittent connections 2 Where ECOMUR OR or EXCUR EXCOR are triggered suspect input wiring 3 Various range errors CRAWUR OR SRAWUR OR are also likely to be set if the excitation was interrupted EXCUR OR 4 For range errors check the associated limit parameters CMIN MAX SMIN MAX 5 Problems are likely if any calibration MIN MAX parameters are set the wrong side of zero i e MIN gt 0 or MAX lt 0 69 Mantracourt Electronics Limited DCell DSC User Manual Problems With Bus Baud Rate There are a number of special difficulties to be considered here e Systems with very long cabling may not work with higher baud rates e When using an RS232 RS485 converter it may be necessary to change some converter settings when changing baud rate Certain converters may not support some baud rates e Always remember you need to reboot devices before the change takes effect e A bus with two devices talking at different baud rates may become unusable So always change all at once by powering down or issuing a broadcast reset command RST Difficult problems can always be overcome if necessary by isolating individual devices and trying the different ba
60. imum output rate is 300Hz with minimum baudrate of 115200 The output is switched on and off by sending the standard ASCII XON XOFF control bytes ctrl Q 0x11 and ctrl S 0x13 This feature is intended for output to a single simple serial display devices and printers It Has Certain Special Limitations As Follows e It can only be used in one to one operation i e only one unit on a bus otherwise collisions will occur e Ona RS485 bus it is not always easy to switch off as the stop instruction must be transmitted when the device itself is not transmitting If the output rate is limited by communications speed then output is virtually continuous and may be impossible to stop N B this does not apply to RS232 which has separate transmit and receive connections e The operation does not start automatically i e an initial Ctrl Q must be sent This means that if there is for instance a brief power interruption output will stop To avoid possible problems continuous output operation is only enabled when the station number STN is set to the special value of 999 New for Version 4 e When Station No is set for 998 the continuous output streams starts automatically from power up The MODBUS RTU Protocol MODBUS is a proprietary standard of Modicom Inc The full specification is quite complex including a timeout based framing strategy and polynomial CRC calculation so full details are not given here Refer to Modicom doc
61. imum performance Connecting wires are soldered directly to the pads on the top and or bottom of the PCB Care must be taken to electrically insulate the connection pads from the surrounding metal DSC is normally installed in a protective enclosure such as a metal box The pins can be plugged into standard 0 1 pitch PCB header sockets or soldered directly into a host board or to connecting wires It can be mounted either way up Unwanted pins projecting on one side may be cropped off For extra vibration resistance the 3 mounting holes provided can be used If not required the protruding end with the single hole can be cut off to make the board smaller Electrical Protection No additional electrical shielding is normally needed Electrostatic protection is sufficient for installation purposes only Devices are protected against shorting of communications lines to power supply and shorting of sensor inputs No over current protection is provided in case of faults so the supply arrangements should ensure adequate power limiting or fusing NOT PROTECTED AGAINST REVERSE POLARITY OF SUPPLY Moisture Protection Both DCell and DSC must only be operated in a dry environment as moisture can dramatically degrade the measurement performance DCell Will normally be sealed into a load cell pocket While flexible silicone sealant can be used to completely embed the unit this is not adequate moisture protection in itself 57
62. ing at high baud rate on longer distances a triple twisted pair cable is recommended A suitable type is BICC Brand Rex PD3003 also equivalent to Belden type 8777 In the UK this is available from Farnell enter Belden 8777 for real length options Mantracourt Electronics Limited DCell amp DSC User Manual 58 Temperature Sensor A shielded twisted pair is recommended with a maximum length of 10m the shield being connected to the load cell body or SH if DSC For short lengths lt 2m in a low noise environment inside load cell body for example then normal cable can be used Identifying Strain Gauge Connections DCell Input Connections EXE SIG SIG EXE Temp sensor DQ The Optional Temperature sensor has two connections DQ which provides the bi directional data line and EXC which provides the Ov connection Care must be taken with connections to the temperature sensor as erroneous values typically 85 C can occur if the cables are too long or in noisy electrical environments Please ensure if using own supplied temperature sensor is either DS18S20Z or BS18S20 DS18B20 MUST NOT be used DSC Input Connections Strain Gauge Bridge Connections Are As Follows e EXC positive negative excitation supply e SIG positive negative output signal e SH Shield connection for shield of strain gauge cable e GND can be used as the ground connection for the temperature sensor O
63. ing to the following table of values RATE value 0 1 2 3 4 5 6 7 8 9 10 update rate readings per 1 2 5 10 20 50 60 100 200 300 500 second The default rate is 10Hz RATE 3 The other settings give a different speed accuracy trade off Invalid RATE values are treated as if it was set to 3 The underlying analogue to digital conversion rate is 4 8Khz These results are block averaged to produce the required output rate To Change The Output Rate 1 Set RATE to the new value 2 Click on the RST button to reboot the device 3 Wait for one second for the reset procedure to complete and measure cycle to start With RATE set to 0 you should be able to see the SYS update rate slow to once a second and the noise level should also noticeably decrease All the main reading output values are updated at this rate Rate does not change the rate at which temperature output TEMP is updated Dynamic Filtering FFST and FFLV The Dynamic filter is basically a recursive filter and therefore behaves like an RC circuit It has two user settings a level set in mV V by FFLV and a maximum number of steps set by FFST maximum value FFST can be is 255 If a difference between a new input value RMVV and the current filtered value MVV is greater than FFLV then the fractional amount of the new reading added to the current reading is reset to 1 that is to say that output of the filter
64. inputs to check that the calibration was successful You can press the Back button to return to a previous calibration stage to repeat it SYS 99 99995 NOTE Some instruments have parameters that clamp the output values If the SYS output seems incorrect you should first check the instrument manual to see if there are any parameters that can clamp this output 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 21 Mantracourt Electronics Limited DCell DSC User Manual 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 allows the devices station number node and baud rate to be changed and also to monitor and reset the communications failure counter CFCT For the ASCII protocol there are DP and DPB controls which set the format of the ASCII string ret
65. 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 www mantracourt co uk products_software html 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 e Save and restore customisable user workspace e Read and Write individual instrument parameters e Save and restore parameter configurations e Log data to a window or file e 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 instructions The software will install into a folder called InstrumentExplorer inside the Program Fi
66. is section DCell Power and Communications Wiring The following diagram illustrates how to connect a puck to the communications and power supply bus cable DCell Bus End Arrangement M2 screw to metal body EMC Gland 2 x Twisted Pair NI zez S8 Note shield terminated at EMC gland using 360 termination Body is Grounded Note The specified cable above shows a yellow wire this will be replaced with a white wire Key Requirements The cable must enter the load cell via an EMC cable gland which connects the cable shield to the load cell body This must be a 360 Degree connection The cable should be a twin twisted pair with independent shields with one pair used for the communications and the other for the power wires There MUST be a common connection from the PSU and the RS485 ground to ensure the RS485 stays within the required common mode voltage of 7v The shield should be connected to the grounded enclosure of the power supply Mantracourt Electronics Limited DCell amp DSC User Manual 62 DSC4 RS485 Versions Power and Communications Wiring The following diagram illustrates how to connect a DSC4 card to the communications and power supply bus cable DSC4 RS485 Versions Bus End Arrangement cae m a SE cc et a e e lE Note The specified cable above shows a yellow wire this will be replaced with a white wire Key Requirements The cable should be a twin twisted pair with i
67. known temperature coefficients Method 2 Where the temperature characteristics of the measurement are known but not linear a similar scheme to Method 1 can be used with a multi point table defining an approximation to the known ideal temperature curves of offset and gain variations NOTE Both of the above methods are based on known characteristics which could come from datasheets but these methods would not compensate for the DCell DSC Method 3 Do a series of measurements at different temperatures and install the appropriate correction values to give exactly correct results at those same temperatures i e calculate ideal gain and offset corrections at the tested temperatures This method is the most common There is a wizard available in Instrument Explorer which will enable this method to be easily completed by calculating the gain and offset corrections for you Method 4 Use a set of test results to plan a best correction curve not necessarily perfect at test temperatures but slightly better overall 39 Mantracourt Electronics Limited DCell DSC User Manual NOTES All of these methods can be applied either to data from individual devices or to an average correction for a particular type of sensor hardware During testing temperatures should be measured using the internal TEMP measurement as this is the measurement used to do the corrections For in system tests the environment of the DCell
68. l fitted with calibration values set during construction Self diagnostics 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 Remote Radio Weigher A variety of lifting machines in a loading yard can be used with a weighing link to display weight in tonnes on a remote hand held readout A heavy duty strain gauge load link is fitted with a battery powered radio modem and DCell The independent handheld display unit communicates with the DCell over a transparent radio link providing a simple LCD readout and tare button operation 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 3 party LCD display and control unit producing a complete turnkey system A digital 1 0 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 th
69. legal Function request for function other than 3 16 02 Illegal Data Address attempt to read an unsupported register address 03 Illegal Data Value attempt to write a read only parameter or message too long for buffer valid messages have a known maximum length Write Command Example Write value 1 23 represents as hex 3F9D70A4 to registers 57 58 on slave 4 by sending hex 04 station address 10 function code 00 38 start reg hi lo NB h38 56 addresses register 57 00 02 quantity 2 registers 04 byte count 4 70 AZ first lower register 17 value hi lo 3F 9D second upper register 18 value hi lo 6B AB checksum hi lo A Correct Response Would Then Be hex 04 station address 10 info copied from command 00 38 00 02 co 50 checksum hi lo 51 Mantracourt Electronics Limited DCell DSC User Manual Read Command Example Read a value from registers 13 14 on slave 52 by sending hex 34 station address 03 function code 00 OC start reg hi lo NB h14 20 addresses register 21 00 02 quantity 2 registers 01 AD checksum hi lo A Correct Response With A Value 55 2317 Hex C25CED51 Would Then Be hex 34 station response 03 function 04 byte count ED 51 C2 5C data AA D4 checksum hi lo Execute Command Example Execute command 101 on slave 17 by sending hex 11 station address 10 function code 00 64 start addr h64 100 register 101 00 02 quantity 2 registers 04 byte count 00 00 00 00
70. les folder You may change this destination if required 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 Note about CAN drivers It is not necessary to install the optional CAN drivers which are selected by 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 11 Mantracourt Electronics Limited DCell DSC User Manual Instrument Explorer Icon la r i W Shortcut to Instrumente The application should open and look like the following screen shot Instrument Explorer Window YE Instrument Explorer AE Mantrabus 1 ADP15 standard ADW15 standard Su LCAIS Fal standard mma UAB15 Fal standard MantraASCIH 2 E v3 e DSC v3 Mantrabus 2 DCell v3 a DSC v3 MantraCAN ak DCell v3 Not Logging Not Watching No Errors The 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 load one of the default workspaces as follows Click File on the menu and s
71. lts Switch on the Green Power LED should be on Connecting Up The Evaluation Kit For RS232 Connect the supplied power cable Red amp Black twisted to the 5 way connector marked J1 Connect the 9 way D Type extension lead to the 9 way D Type socket marked J3 of the DSJ1 and the other end to the comms port of the PC Ensure LK1 amp LK5 are set to RS232 see PCB ident for the markings of these links Now connect power cable to your power supply which has been set to deliver between 10 amp 18 volts Switch on the Green Power LED should be on Note that if your PC serial port has a 25 way serial port connector you should use the 9 to 25 way D type adaptor provided to connect to the evaluation hardware Mantracourt Electronics Limited DCell amp DSC User Manual 10 Initial Checks With no load cell connected The LED of the DCell or DSC should flash OFF for 100ms every 0 5 1 or 2 seconds depending on protocol See following table Protocol LED Flash Period ASCII 0 5 seconds MODBUS 1 second MANTRABUS II 2 seconds 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 For RS232 variants this should be about 33mA for RS485 Variant about 30mA Instrument Explorer Instrument Explorer
72. luding any troughs should be above 5 6V and less than 18V If the supply polarity and voltage is correct then switch off remove the strain gauge from circuit and switch on If the LED is still off check the current drawn by the device With no strain gauges should be approx 30mA If the LED is permanently ON then contact factory If The LED is ON for the majority of time then Flashes OFF for 100mS then a fault exists This Fault can be read back using the communications Likely causes of this are Strain Gauge Integrity error or Limits reached for MVV CRAW SRAW or TEMP First check the connections to the strain gauge are correct Next check the input is not over range or the limits set for CMIN CMAX SMIN or SMAX have not been exceeded No Communications The majority of problems involve a failure to communicate as there are a fair number of optional settings that must be set the same at both ends of the link For this reason any communications application should always check command responses and flag a problem when there these responses are not activated Possible problems can be categorised according to where in the chain of communication the problem may be The typical chain runs as follows e PC software port connection baud rate station number protocol e PC serial port working e Serial lead to converter e RS232 RS485 data converter power supply PC port wiring transmit enable baud rate setting e Bus wiring e D
73. ly 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 STN does not take effect until the RST command is issued or the device is power cycled To Change the Station Number of your Device 1 First set STN 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 NOTES e The valid range of STN depends on the protocol but it is always at least 1 253 e All the protocol types have a bus address type device identifier which is known as the station number for MANTRABUS address for ASCII and node id for MODBUS e The valid ranges for different protocols are 1 253 for MANTRABUS 1 999 for ASCII and 1 255 for MODBUS e Inall cases if STN is set outside the valid range it behaves as if set to a default of 1 Baud rate Control BAUD The BAUD parameter is a read write byte value specifying a standard communications baud rate according to the following table BAUD 1 2 3 4 5 7 value 2400 4800 57K6 76K8 115K2 230K4 460K8 bps BAUD can only take the values shown above If set lt 0 or gt 9 the baud rate defaults to 9600 Warning When changing this setting it is possible to lose communication with the device As well as keeping track of the c
74. 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 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 amp 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 Serial output Lower cost cabling improved noise immunity and longer cable runs with no accuracy penalty Device addressing allows up to 253 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 sta
75. ndependent shields with one pair used for the communications and the other for the power wires The cable shield must be grounded to the SH pin at the DSC end and not at the host end Any further metal housing should also be grounded to the DSC SH pin and should not be connected to the bus cable shield or the sensor cable There MUST be a common connection from the PSU and the RS485 ground to ensure the RS485 stays within the required common mode voltage of 7v DSC2 RS232 Versions RS232 output Power and Communications Wiring The following diagram illustrates how to connect a DSC2 card to the communications and power supply bus cable DSC2 RS232 Versions Bus End Arrangement 3 x Twisted Pair Tx Rx RS232 GND Power 1 PSU Ground Note The specified cable above shows a yellow wire this will be replaced with a white wire Key Requirements The cable should be a triple twisted pair with independent shields Each of the Rx Tx and VIN wires is paired with a VIN wire For short cable lengths at low baud rates in a low noise environment then 4 core shielded cable can be used with the RS232 GND and PSU V being common The cable shield should also be connected to the grounded enclosure of the power supply The cable shield must be grounded to the SH pin at the DSC end and not at the host end Any further metal housing should also be grounded to the DSC CH pin and should not be connected to the bus cable shield
76. neeeeeeeeeeeeeseeeeeeeees 39 Parameter Calculations A A a tas 40 Chapter 6 Linearity Compensation sisser idilio RITA inicias 41 Purpose and Method of Linearisation ocooooooccccncconnconnconncnnncnonono nro rro n ron eeneeeneeeenseeeseeeeeeeseeeeeeeaees 41 Control PAM ii A A A A AA 41 Internal CalCulation occ wseehaa ss tenesedacaded E etwas sew saanse tabs dasa cbene cddemngnesdeseees isGdeus diria 41 How to Set Up Linearity COMPENSATION cece eee cece eee e eee e eee teen eee e neces eee e eee ne eens eneeeeeeeeeeeeeeeeeeeneeees 42 Parameter Calculations and Example ccceccecsccecceeneeesseeeeeeenseeeseessees esse eesseeeeeeeeseeseeeeeeesseeeseeeaees 42 Chapter 7 Self DiaGmOstics ii A AAA AAA AAA AAA AA 44 DiAaSNOStics a A A a a is ee 44 Diagnostics LED 00 A A A A abeuendeaeeteds 44 Chapter 8 Communication Protocol we cnn rne e dai E a iras 45 Bus AU A e ent 45 Sefial iData EM A A A A a ERS 45 Communications FOW Control onteien doc a a a ds dete e ado 45 Communications ErroFS cas 0 A A A A A it eens 45 Choice of Bus Eds A ia 45 The RS232 BUS S tada oir A AR dende 45 The RS485 BUS Cada deci A A A A ae 46 Communications Prot A A 9 Savy A A A A AA AAA OLE ERED EL Og AA IOANE 46 Ghoosing a Protocol sc vnc asado 46 Communications Software for the Different Protocols cccecceeccencceseeeeeeeeeeeeneeenseeeeeeeeeeeeseeeseeeseeseeens 46 Common Features of All Protocols seernes iseasi a Eo E EEEIEE EE
77. ng an approximate change of 0 8mV V at nominal 2 5mV V The command SCOF removes the resistor from across the bridge It is important for the user to remember to switch out the shunt calibration resistor after calibration has been confirmed Digital Output OPON and OPOF For DSC ONLY an open collector output is available This can be switched on using OPON and off by the command OPOF This output is capable of switching 100mA at 30v TBC Flags Diagnostics Flags FLAG and STAT All the self diagnostics rely on the FLAG amp STAT parameters which are 16 bit integer register in which different bits of the value represent different diagnostic warnings FLAG is stored in EEPROM and is therefore non volatile STAT is stored in RAM and reset on power up to 0 FLAG is latching requiring reset by the user where as STAT is non latching showing current error status Latched Warning Flags FLAG The flags are normally used as follows FLAG is read at regular intervals by the host like the main output value but generally at longer intervals If some warnings are active i e FLAG is non zero then the host tries to cancel the warnings found by writing FLAG 0 The host then notes whether the error then either remains i e couldn t be cancelled or if it disappears or if it re occurs within a short time and will take action accordingly The warning flags are generally latched indicators of transient error events By resetting the register t
78. nter compatible with other devices such as PCBs MANTRABUS II efficient binary protocol checksums give better security than ASCII Communications Software for the Different Protocols To access a DCell DSC you will need a communications application running on your PC or PLC in addition to the appropriate hardware connections The simplest approach for initial experiments is to use the Instrument Explorer evaluation application Other Simple Ways Of Using The Different Protocols Are As Follows 1 The ASCII protocol only uses basic printable characters and so can be accessed with a simple terminal program like Windows HyperTerminal 2 The MODBUS protocol can be accessed via a proprietary generic MODBUS application For evaluation purposes we suggest the free shareware demo of ModScan32 from Win Tech software visit www win tech com Mantracourt Electronics Limited DCell amp DSC User Manual 46 Common Features of All Protocols The communications protocols are all of the master slave type A central host device normally a PC or PLC acts as a bus master in control of all communications Communications consist of the master transmitting command messages addressed to particular DCell DSC slave devices The target slave may then transmit a response message back to the master Because there is only one bus master and slaves never initiate communications the master is in control of all communications This
79. ntirely in software by increasing a software gain control CGAI or SGAI To increase sensitivity TC is left in place so that the fitted Rg appears in parallel this gives better temperature stability Its value should then be RG 1 0 025 rad m V V 0 01 Two effects should be noted 1 The purpose of increasing sensitivity is to reduce reading noise which governs the effective resolution Using software gain alone obviously gives reduced performance 2 The sensitivity should however not be set greater than typically 1mV V Beyond this input noise usually dominates and no extra benefit can be achieved 67 Mantracourt Electronics Limited DCell DSC User Manual Chapter 11 Troubleshooting This chapter gives a quick guide to problem solving for DCell DSC devices Bear in mind that the quickest way to pin down problems is to usually replace items with known good alternatives This also applies to cables power supplies devices etc LED Indicator The LED is used to indicate the protocol selection the device is powered and the Device is Operating For correct operation the LED should Flash ON for 100mS then repeat at a rate depending on the protocol See table below If this is not the case then follow the instructions below Protocol LED Flash Period ASCII 0 5 seconds MODBUS 1 second MANTRABUS II 2 seconds If the LED is OFF check the power supply polarity amp voltage The voltage inc
80. o device Dynamic Status Flags STAT Status are live flags indicating current status of the device Some of these flags have the same bit value amp description from FLAG Meaning and Operation of Flags The various bits in the STAT value are as follows Bit Value Description Name o 1 Setpoint output status SPSTAT 1 2 Digital Input status DSC ONLY IPSTAT_ 2 4 Temperature under range TEMP TEMPUR 3 8 Temperature over range TEMP TEMPOR 32 Strain gauge input over range ECOMOR Cell under range CRAW CRAWUR 128 11 2048 Load Cell Integrity Error LCINTEG LCINTEG 4096 Shunt Calibration Resistor ON SCALON Ah w nj i 00 Mantracourt Electronics Limited DCell DSC User Manual 32 8192 e output value previously read OLDVAL 16384 32768 SPSTAT indicates the state of the Open collector output 1 being output on 0 being output off IPSTAT indicates the state of the digital input Only available on DSC model Bit set indicates input is closed to Ov V or GND SCALON Used to indicate that the Shunt Calibration command SCON has been issued amp therefore the shuntcal resistor is now in circuit with the strain gauge bridge SCOF command resets this bit Note that when Shunt Calibration is active the Load Cell Integrity Error will also be generated OLDVAL is set when the device is read via the communications Thus indicating this value
81. oating devices to within a few volts of each other The common mode tolerance effectively about 7 Volts then allows communications without any further grounding provision An RS485 bus of any length also behaves like a transmission line and so must be terminated to avoid reflections This is done by connecting a 120 Ohm resistor between the A and B lines at each end of the bus The RS485 standard is specified for operation up to 4000 feet 1200 metres at any rate below 9600 baud and proportionately less at higher rates However this assumes an ideal straight cable run with termination at both ends In practice a bus with many devices along its length can fall short of this especially if any connected devices are on long stubs leading off the main bus This may mean that the bus has to run at a slower speed than expected for reliable communications Communications Protocols All communications take place according to a specific protocol All devices on a bus must use the same protocol to avoid confusion The protocol specifies the structure and meaning of data exchanged and how access is controlled so as to avoid collisions The various DCell DSC variants support a variety of different protocols allowing integration with various other types of devices on a network Choosing a Protocol The current choices are ASCII printable characters easy to drive direct output to printers displays MODBUS RTU binary industry standard i
82. ol CI DTR Line Hi OK Cancel The above assumes factory defaults If your device is known to have different settings use these instead of the ones stated above 13 Mantracourt Electronics Limited DCell amp DSC User Manual Viewing Device Data The following main parameter list should now appear in the central pane Instrument Explorer Parameter List YE Instrument Explorer File Communications Parameters Watch Logging Wizards Macros View Help 16 35 58 01 03 00 B2 00 02 64 2C aed 16 35 58 USR9 E 16 35 58 01 03 04 00 00 00 00 FA 33 16 35 58 01 03 00 80 00 02 C5 EC a DSC v3 213 16 35 58 USR8 1116 35 58 01 03 04 00 00 00 00 FA 33 1116 ES E 01 a AE 00 02 A5 EA 1116 35 58 U Mantrabus 2 16 35 58 01 03 04 00 00 00 00 FA 33 16 35 58 01 03 00 AC 00 02 04 24 bd DCell v3 16 35 58 USRE 16 35 58 01 03 04 00 00 00 00 FA 33 a DSC v3 16 35 58 01 03 00 AA 00 02 E4 28 16 35 58 USR5 116 35 58_01 03 04 00 00 00 00 F 33 MantraCAN e DCell v3 c a DSC v3 Modbus RTU E DCell v3 mma DSC v3 Not Logging Not Watching No Errors 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 amp buttons on the left of the list T
83. orrect baud 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 115200 New For Version 4 DSC Only e With version 3 pcb and higher A reset to comms defaults is available This will return Station No to 1 and baudrate to 115200 This is achieved by powering off the DSC shorting the 2 pads together whilst powering on DSC Issue 3 pcb or Higher 000909 Ensure issue 3 or Higher 2 unmasked pads The new value of BAUD does not take effect until the RST command is issued or the device is power cycled To Change The Baud Rate follow a similar sequence to changing the STN value 1 First set BAUD to the new value 23 Mantracourt Electronics Limited DCell DSC User Manual 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 baud rate Communications Failure Count CFCT The Communications Failure Count CFCT can be used to indicate the quality off the communications bus Each time there is a UART framing error or a data overrun error the count is incremented This is a read Write parameter so resetting is by writing the value 0 This value is not saved on power fail and is reset to zero on power up Output Format Controls DP and DPB ASCII ONLY The parameters DP and DPB are
84. ou will need two levels of input at around 25 or below of full scale and a high level input at around 75 or higher of full scale You will also need to know the required value of SYS for both of these input levels Press NEXT to continue with the calibration Cancel Click Next Ak SYS Calibration Auto Acquire Low Input Apply the low level input and enter the value required in the text box below Ensure that the low input is still applied when the Next button is clicked Enter required value for SYS at this low input level g 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 A SYS Calibration Auto Acquire High Input Apply the high level input and enter the value required in the text box below Ensure that the high input is still applied when the Next button is clicked Enter required value for SYS at this high input level hog 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 Mantracourt Electronics Limited DCell amp DSC User Manual 20 A SYS Calibration Auto Result Instrument calibration complete The new calibration values have been calculated and the instrument updated Click Finish to complete this Wizard The display below shows the value of SYS You can now apply the low and high
85. ounded Key Requirements All the load cell wires should be kept as short as feasible at most 20cm The EXC wires should be twisted together also the SIG pair and the two pairs kept apart It is also recommended to secure the wires from moving due to shock or vibration If the DCell is mounted outside the body of the load cell then for optimal performance twin twisted cable should be used although standard 4 core shielded cable can be used in low noise environments The M2 mounting hole must be grounded via an M2 screw to the load cell body for specified performance to be met The 2mm mounting hole to accept M2 screw or American equivalent 40 80 Important Note DO NOT USE 2 screw size 61 Mantracourt Electronics Limited DCell DSC User Manual DSC Strain Gauge Cabling Arrangement Shield EMC Gland Note shield terminated at EMC gland using 360 termination Tail length must be kept to a mimimum Note The specified cable above shows a yellow wire this will be replaced with a white wire Key Requirements The Strain Gauge cable should be a twin twisted pair with independent shields with the two pairs used for the EXC and SIG signal pairs For specified performance the load cell must be grounded to the SH Communications Cabling and Grounding Requirements To achieve full performance specifications and conform to environmental approvals it is important to follow the wiring procedures outlined in th
86. ourt Electronics Limited DCell amp DSC User Manual 64 RS485 Bus Connections for Multiple DCells EMC Gland wv 360 Terminating 1 120R i Terminating 1 Resistor A A AA A E A A i i Twisted 120R Terminating Pair Resistor l Me a e j 1 RS485 4 i Device GND I Note The specified cable above shows a yellow wire this will be replaced with a white wire PSU ihs RS485 Bus Connections for Multiple DSC RS485 Versions AA Twisted Pair al 120R Terminating Resistor Twisted 120R Terminating Pair Resistor Note The specified cable above shows a yellow wire this will be replaced with a white wire RS485 At B Device GND 65 Mantracourt Electronics Limited DCell DSC User Manual Key Requirements e The main bus cable must be terminated at either end e Where the bus does not go directly to each attached device each stub cable connecting to the bus should have just one device on it e Stub branches should be kept as short as possible less than 10m at most e The stub cables should be grounded at each device and the main cable grounded at the data converter end None of these should connect e Stubs are not terminated Bus Layout and Termination The ideal bus is a single length of
87. perature minimum and maximum settings are part of the temperature calibration fixed at 50 0 and 90 0 C Only active when optional Temperature module fitted ECOMUR and ECOMOR are the basic electrical output range warnings These are tripped when the electrical reading goes outside fixed 120 limits This indicates a possible overload of the input circuitry i e the input is too big to measure The tested value ECOM is an un filtered precursor of ELEC CRAWUR and CRAWOR are the cell output range warnings These are tripped when the cell value goes outside programmable limits CMIN or CMAX The tested value CRAW is the cell output prior to linearity compensation SYSUR and SYSOR are the system output range warnings These are triggered if the SYS value goes outside the SMIN or SMAX limits LCINTEG indicates a missing or a problem with the Load cell It is based on the common mode of the SIG being correct NOTE This flag will also be set when the shunt calibration has been switched on WDRST indicates that the Watchdog has caused the device to re boot If this error continually occurs consult factory BRWNOUT indicates that the device has re booted due to the supply voltage falling below 4 1V the minimum spec for supply voltage is 5 6V and this must include any troughs in the AC element of this supply REBOOT is set whenever the DCell DSC is powered up and is normal for a power up condition This flag can be used to warn of power loss t
88. 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 RS485 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 253 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 cel
89. rage location although typically this is 1 000 000 Therefore When automatic procedures may write to stored control parameters it is important to make sure this does not happen too frequently So you should not for example on a regular basis adjust an offset calibration parameter to zero the output value However it is reasonable to use this if the zeroing process is initiated by the operator and won t normally be used repeatedly For the same reason automatically cancelling warning flags must also be implemented with caution It is okay as long as you are not getting an error recurring repeatedly and resetting it every few seconds 33 Mantracourt Electronics Limited DCell DSC User Manual Chapter 4 The Readings Process This chapter gives an account of the reading process except for the linearity and temperature compensation processes which have their own chapters later on Flow diagram Electrical mmv MMV NMVV x 100 CTGx Ctx CTOx Ctx 1 F CLKx CLXx The underlying analogue to digital conversion rate is 4 8Khz These results are block averaged to produce the required output rate set by the RATE control This block averaged result is then passed through the dynamic filter at the same rate and then into the chain of above calculations The named values shown in the boxes are all output parameters which can be read back over the comms link The diagram shows three separate calib
90. ration stages called the Electrical Cell and System This allows independent calibrations to be stored for the device itself the load cell and the installed system characteristics Electrical The Electrical calibration produces corrected electrical readings from the internal measurements This is factory set by Mantracourt during the production process The main outputs from this are e MVV is the factory calibrated output in mV V units e ELEC is the mV V in terms Where the 100 value is set using NMMV This is for backwards compatibility only e TEMP is a device temperature measurement in C and requires an optional module There are also two flags ECOMUR and ECOMOR not shown on the diagram which indicate an input electrical under or over range Mantracourt Electronics Limited DCell amp DSC User Manual 34 Cell The Cell calibration converts the mV V output into a cell force reading This can be used by an OEM sensor manufacturer to provide a standard calibrated output in force units which could be based on either typical or device specific calibration data This stage also includes the temperature and linearity corrections not covered here The outputs from this are e CMVV is the temperature compensated mV V MVV e CRAW is the scaled temperature compensated value CMVV e CELL is a load cell force reading in Force units e g kN e CRAWUR and CRAWOR are two flags indicating
91. reasonably smooth this should give exact results at the test points and reasonably accurate values in between NOTES Linearisation tests should only be done after the cell calibration is set because the correction values are dependent on the cell calibration Similarly linearisation testing should only be done at the calibration reference temperature or after temperature compensation is installed to avoid temperature effects from distorting the results The linearisation tests should not reveal any significant remaining linear trend in the errors If errors do appear to lie on a definite line this could drastically reduce the accuracy of the correction If this does happen it shows that the cell calibration is wrong and should be redone The table points must always cover more or less the whole range of output values to be used because corrections are extrapolated outward beyond the first and last points It is always worthwhile including more test points than will be used in the correction table because this gives confidence that no regions of rapidly changing error have been missed Tests should be done both with steadily increasing and decreasing load values as hysteresis effects for load cells are often of a similar size to non linearities Parameter Calculations and Example Based on the simple method outlined above we suppose that we have obtained test results for a series of precisely known load values test lo
92. res such as SZ offers a means of zeroing the system output SYS Peak and Trough values are also recorded against the value of SYS these are volatile and reset on power up A command SNAP records the next SYS value and stores in SYSN this is useful where more than 1 device in a system and to prevent measurement skew across the system the SNAP command can be broadcast to all devices ready for polling of their individual SYSN values System Scaling SGAI SOFS The cell output value CELL is scaled with gain and offset using SGAI and SOFS respectively The gain is applied first and the offset the subtracted This would be used to give a force output in the chosen units this output being termed SRAW SRAW CELL X SGAI SOFS If we have two cell output CELL readings for two known test loads we can convert the output to the required range So if Test load xA gt CELL reading cA Test load xB gt CELL reading cB Then we calculate the following gain value SGAI xB xA cB cA And then the offset SOFS cA x SGAI xA The outputs should now be SRAW xA xB true load values as required Example of calculations for SGAI and SOFS Example A 2500Kgf load cell installation is to be calibrated by means of test weights The cell calibration gives an output in Kgf ranging 0 2000 A system calibration is required to give an output reading in the range 0 1 0 tonnes Calculations Take readings with two known applied loads su
93. rruption of normal communications due to drop outs or noise is detected as badly formatted receive data which triggers a communications failure counter to be incremented 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 Easy mounting via a 2mm screw e Connection via solder holes to either side of PCB e Lower profile single PCB construction e Additional I O e Easier shielding connection at load cell connector end DCell amp DSC e Baud Rates to 230400 Higher baud rate allow faster polling of groups of devices on a single bus also faster measurement sampling requires faster communications for individual devices allowing the higher sampling to be realised over the communications link e Higher sampling rates Sampling to 500Hz can now be achieved Also more sampling rates are available as follows 1 2 5 10 20 50 60 100 200 300 500Hz e Lower cost With new technology and further use of miniaturisation the cost is now lower e ESD protection to 15KV RS485 version Higher ESD voltage rating reduces the possibility of damage by static e Real mV V calibration Instead of full scal
94. s AAA E enh dha deeds A ete bem aaes 68 NO COMMUNICATIONS a a A a E a 68 Bad Readings A A A A AA A A AS o 69 Unexpected Waring Flags 7 ani a a a dida 69 Problems With Bus Baud Rate cui A A A ov evoked td bi 70 Recovering a lost Deel DSG A A id 70 Chapter A2 Specifications iS AA AS AA wecdosedees 71 Technical Specifications DSC DCELL High Stability ccc cece ccc e esc e eee eee eeeeeenceeneeeseeeeeeeeeseenseeeseeseeees 71 Technical Specifications DSC DCELL Industrial Stability c cece cece cece ence ence eeceeneeeeaeeseeeeeseeeseeeseeseeens 72 M chanical Specificationfor DSG 2 cece vd tug oe co scdoednwnidvndena tegen ceseamecdevesawetsebnugee caste 73 Mechanical Specification for Dell A ind 73 CE ADD al ceci A A sede tee nee wees Pea 73 WATTS A A sae stupas A a A an 74 3 Mantracourt Electronics Limited DCell DSC User Manual 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 digital serial output They allow multiple high precision measurements to be made over a low cost serial link Outputs can be accessed directly by PLCs or computers or connected via various types of network telephone or radio modem all without compromising accuracy Key Features Ultra
95. see the same temperature EXE DO Se Control Parameters The temperature compensation parameters define a pair of lookup tables that contain adjustments to the cell calibration gain and offset over temperature The parameters concerned are the following CTN Number of temperature table points CT1 CT5 C Indicated TEMP value at table point CTO1 CTO5 mV V MV V x10 Offset adjustment at Offset table point CTG1 CTG5 ppm Gain x10 at Gain table point CTN sets the number of points in the gain amp offset table s A CTN value of less than two effectively switches off temperature compensation The maximum number of point is 5 values greater than 5 reset CTN to 0 switching off temperature compensation CT1 to CT5 sets the temperature in degree C of the correction points The table must be filled from CT1 up to amp including CT CTN and must be entered in order of increasing temperature value CTO1 to CTO5 provide the offset adjustment in mV V x10 The reason for the multiplication is due to the limitation set by the ASCII protocol of only being able to enter up to 6 decimal places The CTOx value is subtracted from the uncompensated value CTG1 to CTG5 provide the gain adjustment in ppm terms The actual gain value used is calculated as 1 CTGn x 10 Internal Calculation The temperature compensation calculation is described as follows The GAIN correction is applied first The current meas
96. ssible droop or ripple must be included The devices contain brown out detection which may trigger if the supply voltage at the device drops below the 5 6 volts A single device consumes typically 40mA with a 3500 gauge connected except RS232 output units which use about 10mA more An installation should therefore assume at least 60mA per unit and allow for extra current being taken at power on though supply voltage can safely drop temporarily and for possible voltage drops in long cables Any power supply ripple should be below 100mV and supply arrangements should provide current limiting for fault conditions see Electrical Protection above Cable Requirements Strain Gauge Input DSC For optimal performance twin twisted pair with individual shields is recommended this gives good noise immunity Maximum length should not exceed 20m Normal 4 core shielded cable can be used in areas of low electromagnetic noise Power and Communication Again twin twisted pair cable is recommended for this The cable should have the following characteristics e Twisted pair with independent shields e Characteristic impedance 50 150 ohms e Core to core and core to shield capacitance below 300pF m A suitable type is BICC Brand Rex BE56723 also equivalent to Belden type 8723 In the UK this is available from Farnell part number 118 2117 Normal 4 core shielded cable can be used in areas of low electromagnetic noise For RS232 operat
97. ssssesssssssssssssssssssessssseeesesseeeeeessseseee 10 Connecting Up The Evaluation Kit For RS485 ooooccncccnccconcccnnconnconcconnconn conc cnc rro nro rro ona ro nc conan cnn nonanons 10 Connecting Up The Evaluation Kit For RS232 oooocooccccncconcncnnconnconcconnccnn cnn nono nn oo or ron crono ro nc conan cnn nona nono 10 Initial CHECKS LA a A A A A 11 Instrument EXP T ricota cai die eii Eaa a AaS 11 What Gan Instrument EXplorer Dot a A E Oti aa 11 Installing Instrument Explorer ci eevee cs bacnalwens sen s nee din Cole dae donee a Nees EEE nas ds 11 Running the Instrument Explorer SOfFtWArEC ccc ece ence eee ence ence eeeeeee eens sees eeneeenseeneeeenseeeeeeeeeeeseeeeeeeaees 11 Instrument Explorer Icon a A A de dane A A Ain 12 Instrument Explorer WidOW pci a A A AS Daven dee A AS wae 12 INSEFUMENESECEINGS ii lin a aaa ivan 13 Viewing Device Data A A A cds ea A ita ados 14 Instrument Explorer Parameter List esescesooossssoossososssssssssseosssesoesecossssessecceseeeeessseesssssocecesosssseosss 14 Connecting Load Callao A vehi vbes ad A ira danes 15 DSJ1 Evaluation Board Sensor Connections e essesssssesecsssssssessoosssnesssossessvesrsosseseserosssscereesoseesesessssese 16 Performing A System Calibration s a sc ce os AAA ic 17 Sys Calibration Table method we ccc e ana i chase deencn taaan dad 18 Sys Calibration Auto Method ii a ento 19 Chapter 3 Explanation of Category Items
98. stematic installation errors cannot be removed such as cells not being mounted exactly vertical The accuracy is also limited by the DCell DSC electrical calibration accuracy which is about 0 1 The remaining methods require testing with known loads but are therefore inherently more reliable in practice as they can remove unexpected complicating factors relating to installation Method 3 Two Point Calibration Method This is a simple in system calibration procedure and probably the commonest method in practice as in the previous example Two known loads are applied to the system and reading results noted then calibration parameters are set to provide exactly correct readings for these two conditions eg a 10KN 1 tonne load cell has a CELL reading of 0 120721mV V with no load and 2 21854mV V with a known 100Kg test weight To calibrate this to read in a 1 0 to 1 0 tonne range Calculate CGAl as 0 1 2 21854 0 120721 0 047669 Set COFS 0 120721 x 0 047669 0 005755 Method 4 Multi point Calibration Test For ultimate accuracy to a whole series of point measurements may be taken to determine the best linear scaling of input output Effectively a best line through the data is then chosen and the calibration is set up to follow the line Testing of this sort is also used to establish linearity corrections and similar tests at different temperatures are used to set up temperature compensation see Chapters on T
99. suddaweeees 33 The Reset Command ia bdo 33 WARNING Finite Non Volatile Memory Life cece cece sce e nce e eee e ence nee e eee eeeeeeeeeenseenseeneeeeeeeeeseenseeeseeeeeens 33 Chapt r 4 The Readings Process iccsscasscacedecedacieevdeduadedecedncedndievineievas a Uacedeies ddmiewwdenwaeeanee dade ds 34 Flow dia Sramsccks cece eisensev sais tE E ARA ias 34 Celtand SyStem ScCalinigs cssansesccue hes dcest se Veamalesh fe A ctanste depa laa 35 Calibration Parameters Summary and Defaults cccccc esc e cece ence ence ence eee eee eeenseeeseeeeeeneeeeeseeeeeenseeeeeens 36 Chapter 5 Temperature Compensation cecccecccccccesccssccesccecccesscessseescesscessscesssesssseesesssessseesseeees 37 Purpose and Method of Temperature Compensation ccecceeeceeeceenceenceeneeeeeeenseeneeeeeeeenseeseeeeseeneeeeaees 37 Temperature Module Connections and Mounting DTEMP ccccecessceecceenccenceeeseenseeseeesseeeeseeeseeeseeseeens 37 DCELL connections to DIEMP oreesa devas oe cease eave oe es Soules Sa ose lt bvebscadaudeteagneaawouoredeaeedesdadepeveene a 37 DSC connections to DTEMP acarrea tad ce eeaubeeteccsueeveGssdaunduen 37 Control PAM A A Ate 38 Internal Calculation is A TEEN a ETE S 38 The Temperature Measurement oooooccocnconcconocononnnoncnnn eens eee ee ease nesses eeee sees a e aaa i a e e aa 39 How to Set Up a Temperature Compensation cece cece cence tence eee ence eee ee eee eneeeeen
100. t CR gt This confirms a read and returns the data value NAK is an lt CR gt sequence The device rejected the command There Are Several Possible Reasons For A NAK Response Command identifier not recognised Badly formatted command Missing command identifier unrecognised access code character or unexpected character somewhere else Access attempted not supported by this command Mantracourt Electronics Limited DCell amp DSC User Manual 48 NOTES e From receipt of the host s terminating lt CR gt to a response from the device if any will be at most 50mS After this it can be assumed there is no response e There is no value checking A slave can not NAK a command because a write data value is unsuitable in some way only if write access itself is disallowed For the Ack with data i e a successful read command the returned value consists of printable ASCII characters finishing with a lt CR gt formatted according to the DP and DPB settings as follows Write Command If the device accepts the command then a lt CR gt is transmitted There is no error checking on the data received by the device Example A command to set the BAUD parameter to three on station 1 could look like this 1001 BAUD 3 lt CR gt assuming a device with STN 1 is present it will respond with lt CR gt Read Command Returns the requested value specified by the command The returned value is formatted according to the DP and
101. t in output units The units and functions of the main scaling controls can thus be summarised as Cell Calibration CGAI Force mV V mV V gain factor COFS Force CELL Offset Value CMIN Force Minimum value for CRAW CMAX Force Maximum value for CRAW System Calibration SGAI Eng Force SYS CELL gain factor SOFS Eng SRAW value offset SMIN Eng Minimum value for SRAW SMAX Eng Maximum value for SRAW SZ Eng SYS value offset MVV is mV V force is force units and eng is engineering units 35 Mantracourt Electronics Limited DCell DSC User Manual Calibration Parameters Summary and Defaults The various control parameters are listed for each stage This also includes the compensation parameters not covered in this chapter but shown in the flow diagram The default values shown set the device back to its nominal default calibration mV V Cell Control Defaults Command Action Default Values FFLV Filter dynamic level 0 001 FFST Filter Steps max 100 NMMV Nominal 2 5mV V 2 5 RATE Rate 10Hz 3 CGAI basic cell gain 1 0 COFS basic cell offset 0 0 CTN number of temp points 0 CT1 5 temp points Deg C 0 0 0 0 0 0 CTO1 5 offset adjusts 0 0 0 0 0 0 CTG1 5 gain adjusts 1 0 1 0 1 0 1 0 CMIN CRAW min limit 3 0 CMAX CRAW max limit 3 0 CLN number of linearity points 0 CLX1 7 linearity raw value points 0 0 0 0 0 0 CLK1 7 linearity adjusts 0 0 0 0 0 0 System Con
102. tatesetadebeh A pias se Semi 25 Cells ie Sirus A A Seadu ence A AS cece desea a debe elebeta eee 27 Temperature Compensation In Brief ccce cece cece ence ence ence ence eee e nee e eee cono e sees enseeneeeneeeeeeeeeseeeseeeseeseeens 27 Cell Sealing CGAI COPS rr r a A A A A A a 27 Cell Limits CMN CMAX 6 cota RA A OEE ERES 28 LinCarisation In Brie esoo secano liinda une dns ete da EE ONAE aan ne aaa adidas 29 Mi A di adios 29 System Sc aling SGAl SOS usos aia a 29 1 Mantracourt Electronics Limited DCell DSC User Manual System Limits SMIN SMA v3 ccoo essen cases cade esni A a A Ad 30 Syster O A A A tata 30 System Outputs SYS SOUT e ccwssccs cece cease oea ipi ad de sveees coved ii Ai ad EAR 30 Reading Snapshot SNAP SYSN cuasi in a A A A EEE 30 COMO o A A A A A a 31 Shunt Calibration Commands SCON and SCOF cccccescceeene cece nese eens cece ese eeeneeeeeeeeseeenaeeeeenseeessaeeeeeas 31 Digital Output OPON and OPROP ccc ene toed be A tet A cede esi claude a A bi Meee 31 Flags soe i ess vietewes ce uenteet A OEE E Te 31 Diagnostics Flags FLAG ANG STAT 8s csieescessdesaecebnws sieved cesses ances a auue Viwee swede Sete a it 31 Latched Warning Flags FLAG hirsinen cited seacdteten pita se Aaa 31 Dyhamic Status Flags STA Th A AA Aa bovekdawsedeesdaedans 32 Output Update Tracking iii AAA AA A AAA A A An 33 User Storage A Rata A A A A A 33 USA TAUS O aa aaa N E A oetende as 33 dr A A A A AA A A
103. tation number baud rate How do you know these are correct A substitute device is very useful here 11 Device protocol double check product label 12 Device running okay LED is flashing devices take 20 30mA supply current without sensor attached 30 50 with Bad Readings The cause can be either hardware or software related Software 1 Check the MVV reading first and ensure it is correct This figure is the RAW input and is not affected by the user configurable calibration settings 2 If MVV looks correct check the calibration settings step by step Consider resetting all the calibration controls to default values see Chapter 4 The Readings Process This should make SOUT MVV at all times Hardware 3 Load Cell problem should be indicated by flags in STAT LCINTEG 4 Genuine hardware problems usual show up as total failure i e no reading always unchanging usually near zero sometimes always full scale Check wiring take voltage level readings and again if possible use a known good device and set up 5 Check the sensor is connected properly and has some resistance across excitation wires and around 350 Ohms across output wires when disconnected from device 6 Check for damaged DCell DSC device by replacement Unexpected Warning Flags Remember that all warning flags in FLAG must be explicitly reset they do not clear themselves when a problem is resolved If a flag cannot be cleared the cause must be persistent
104. ters and some DCell devices destroyed in this way Also note that this kind of damage may often not be immediately obvious appearing as erratic operation rather than outright failure To Avoid These Problems 1 Any portable should be separately grounded e g via the converter supply before connecting it to the mains supply or to a DCell DSC bus 2 We always recommend the use of externally powered rather than port powered data converters see below for details of suitable converters RS232 Bus Layout Essentially the only limitation here is on the cable length As described in The RS232 Bus Standard in chapter 8 this is supposedly up to 15m independent of baud rate This is not a very realistic figure for typical modern hardware For genuine RS232 compatible hardware the length might be at least twice this at 9600 baud and perhaps more at lower speeds However some PCs have serial ports that are not truly RS232 hardware compatible and may not have sufficient drive for specified operation In these cases the port will probably still be usable with a short enough cable It would be far safer though to replace the suspect hardware with something more suitable RS485 Bus Layout See also the general discussion of RS485 characteristics The RS485 Bus Standard in chapter 8 Multiple devices are connected in parallel to the communications and power supply wire pairs as shown in the following diagrams Mantrac
105. ther Connections DSC ONLY Resistor RG and track cut TC are used to adjust the mV V sensitivity see Strain Gauge Sensitivity Adjustment next page 59 Mantracourt Electronics Limited DCell DSC User Manual Identifying Bus End Connections DCell Bus Connections V V RS485 B RS485 A DSC4 RS485 Versions Bus Connections e V and V are the DC power supply and return connections e RS485 A and RS485 B are RS485 communications connections e GND is a communications ground connection e SH is the shield connection e OP is the open collector digital output e IP is the volt free digital input e TS connects to DQ of the optional temperature sensor DSC2 RS232 Bus Connections e V and V are the DC power supply and return connections e RX and TX are RS232 communications connections RX being the DSC s receive e GND is a communications ground connection e SH is the shield connection Mantracourt Electronics Limited DCell DSC User Manual 60 Strain Gauge Cabling and Grounding Requirements To achieve full performance specifications and conform to environmental approvals it is important to follow the wiring procedures outlined in this section DCell Strain Gauge Wiring The following diagram illustrates how to wire up a DCell to a strain gauge DCell Strain Gauge Wiring Arrangement M2 Screw to Metal Body eg Load Cell Body 177 Load Cell Body is Gr
106. tics facilities are by means of the flags See chapter 3 Flags for a full description of the flags and their meaning The flags are normally used something like this FLAG is read at regular intervals by the host like the main output value but generally at longer intervals If some warnings are active i e FLAG is non zero then the host tries to cancel the warnings found by writing FLAG 0 The host then notes whether the error then either remains i e couldn t be cancelled or if it disappears or if it re occurs within a short time and will take action accordingly The warning flags are latched indicators of transient error events By resetting the register the host both signals that it has seen the warning and readies the system to detect any re occurrence i e it resets the latch What the host should actually do with warnings depends on the type and the application Sometimes a complete log is kept sometimes no checking at all is needed Often some warnings can be ignored unless they recur within a short time Warning flags survive power down i e they are backed up in non volatile EEPROM storage Though useful this means that repeatedly cancelling errors which then shortly recur can wear out the device non volatile storage see WARNING Finite Non Volatile Memory Life in chapter 3 Diagnostics LED A new feature for Version 3 is the addition of an LED to indicate the current status of the device and also it s protocol
107. tions that are not addressed to it All the protocols also define a special address value normally 0 which is reserved for broadcast commands which all slaves act on No response is allowed to broadcast commands as multiple replies would collide with one another Parameters Parameters are the values used for all control settings and output values They have an associated storage type byte integer or real value and may be either read write read only or write only Output or result values are mostly read only Configurable parameters are held in non volatile storage so control settings are retained permanently even when power is removed Data Type Conversions and Rounding Type Conversion Depending on the protocol an integer byte parameter may need to be converted to or from a floating point representation for reading or writing The rules are as follows For reading integer and byte parameters are treated as unsigned and never read negative i e read value ranges are 0 to 65535 0 and O to 255 0 For writing values written to integer and byte parameters are truncated to the nearest integer and negative or positive values are acceptable NOTE Floating point data is not always exact even when reading integral data 47 Mantracourt Electronics Limited DCell DSC User Manual E G could get 3 999974 instead of 4 eg for a byte write 240 240 1 and 239 66 are all the same value Rounding Although rounding is appli
108. train Gauge Drive Capability 320 500 Ohms Offset Temperature Stability 5 10 ppm C Gain Temperature Stability_________________ _ 30 f 50 ppmc Offset Stability with Time TT 35 160 ppmofFR 1 25 Gain Stability with Time A Non Linearity before Linearization pl R z E Internal Resolution f mMillion Counts divs Resolution 1Hz readings Noise stable over 100s 66 000 Counts divs Resolution 10Hz readings Noise stable over 100s 40 000 Counts divs Resolution 100Hz readings Noise stable over 100s 10 000 Counts divs Resolution 500Hz readings Noise stable over 100s 5 000 Counts divs Signal Filter Dynamic recursive type user programmable AA AA ES EIA Optional Temperature Resolution _____ ___ Temperature Measurement Resolution Deg C Temperature Measurement Accuracy 10 to 85 Deg C Temperature Measurement Accuracy 55 to 125 i Deg C Temperature update Speed __ d O Seconds C al V de Power Supply ripple mV ac pk pk Power Supply current 350R Bridge mA Power 10v 350R Bridge 450 mW Environmental R5485 DSC offers RS232 Datatransmissionrate 240 230 400 bps Output cable length speed dependant Note3 10 m Operating temperature range 40 85 C Storage temperature 40 85 C Humidity RH AAA AS 87 4 x 20 x 8 5mm Diameter 20mm Height 5 3mm Notes 1 From original offset at any time 2 1st Year 3 Dependent on c
109. trol Defaults Command Action Default Values SGAI basic gain 1 0 SOFS basic offset 0 0 SMIN SRAW min limit 100 0 SMAX SRAW max limit 100 0 SZ output zero offset 0 0 Mantracourt Electronics Limited DCell amp DSC User Manual 36 Chapter 5 Temperature Compensation This chapter explains how to use the Temperature Compensation facilities to compensate for changes in the measurement with ambient temperature Temperature compensation is only provided when an optional module consisting of a digital temperature sensor is wired to the DCell or DSC Purpose and Method of Temperature Compensation Most measurement methods are affected by changes in temperature and uncompensated load cells are especially sensitive having a large overall temperature coefficient Temperature compensation adjusts the measured value in a way that depends on a temperature measurement so that ideally the output does not depend on the current temperature In practice it is usual to refer to a calibration reference temperature The ideal output value is then what the reading would have been if made at the reference temperature The DCell DSC temperature compensation facilities make adjustments to the Cell calibration parameters i e gain and offset which depend on temperature according to a digitally programmed curve These adjustments are automatically applied based on the current device temperature measurement With some car
110. ud rates in turn This deals with all possible problems as long as your hardware can deliver all the supported baud rates Recovering a lost DCell DSC For baud rate problems see previous section You can try all 3 protocols if confused but this should be indicated by the product code on the product label if it has not been removed If a station number is unknown it can be reset via broadcast command as long as the device is the only one on the bus If two devices on the same bus end up set to the same bus address they can no longer be commanded separately The only solution is to remove one device from the bus and connect it exclusively to a PC to change its STN Always remember that a reboot power off or RST command is needed to change STN and BAUD settings Mantracourt Electronics Limited DCell amp DSC User Manual 70 Chapter 12 Specifications Technical Specifications DSC DCELL High Stability Set for 2 5mV V sensitivity Strain Gauge Excitation System 4 Wire arrain Gauge Excitation Voltage 5 25 VDC stain Gauge Drive Capability 320 o om Strain Gauge Sensitivity 5 3 mw o Temperature Stability ee ppm C Gain Temperature Stability A ppm C_ Offset Stability with Time ppm of FR 1 Gain Stability with Time ppm of FR 2 5 25 ppmofFR O e E Resolution 1Hz readings Noise stable over 100s 200 000 Counts divs Reso ution 10Hz readings NOR over 100s 120 000 Counts divs
111. umentation Knowledge of the MODBUS protocol is therefore assumed The MODBUS protocol is a partial implementation of the RTU binary form of the MODBUS standard sufficient to allow DCell DSC units to coexist on a serial bus with other MODBUS compliant devices NOTE Third party applications for MODBUS communications are readily available e g ModScan from Win Tech software www win tech com who offer a free trial version Modbus Messages All messages and responses are formatted and checksummed according to the normal RTU rules The slave number is the device station number Slave 0 may also be used for broadcast writes The device command set is mapped into the MODBUS Output or Holding Registers Parameters read or write are mapped onto a pair of registers containing a 4 byte floating point value Action Commands are implemented as dummy parameters Writing activates the command and reading returns a dummy value with no action Only Two Valid Message Function Codes Are Supported Function 03 Read Holding Registers to read a register pair Function 16 Preset Multiple Registers to write a register pair Mantracourt Electronics Limited DCell amp DSC User Manual 50 The start address must always be a valid parameter address which is always an odd number see the following The only permitted data length is two registers i e 4 bytes Registers cannot be read or written singularly in larger
112. under or over range for the force measurement System The System calibration converts the Cell output into a final output value in the required engineering units This is normally be set up by a systems installer or end user to provide whatever kind of output is needed independently of device specific information in the Cell calibration Making this split allows in service replacement without re calibration The Outputs From This Are e SRAW is a re scaled and offset adjusted output derived from CELL e SYS is the final output value after removing a final user output offset value SZ from SRAW e SRAWUR and SRAWOR are output warning limit flags In practice SRAW and SYS can be used to represent something like gross and net values Cell and System Scaling Both the Cell and System calibrations are simply linear rescaling calculations i e they apply a gain and offset In both cases four parameters define the scaling offset and min and max limit values These calculations are applied in the following way Output Input x GAI OFS Output min output MAX Output max output MIN In addition if the value exceeds either limit one of two dedicated error flags is set The control parameters thus have the following characteristics e GAI is the multiplying factor set in output units per input unit e OFS is the value that gives zero output set in output units e MAX and MIN are output limit values se
113. ured temperature is checked against the table values CT1 to CT CTN to establish an index value if the measured temperature is below that of CT1 then CT1 is used as the index If the temperature is above CT CTN 1 then CT CTN 1 is used This can be represented as follows A working table index i is derived from the current measured temperature T as follows n number of points used as set by CTN When T lt CT1 then i 1 When T gt CTn 1 then i n 1 Otherwise i is chosen so that Ti lt T lt Ti 1 Once an index into the table has been established the gain value to be used is extrapolated between the index value and the value above If the temperature is above CT CTN or below CT1 then the calculated temperature gain value is extrapolated from CT CTN 1 to CT CTN or CT1 to CT2 respectively Mantracourt Electronics Limited DCell amp DSC User Manual 38 This can be represented mathematically as follows CALC_CTG CTGi CTGi 1 CTGi x T CTi CTi 1 CTi The actual gain value used is 1 CALC_CTGO x 10 6 and is multiplied by the uncompensated value MVV The offset correction is then applied Using the same temperature index i as found for the GAIN index above The Offset value is extrapolated between the same two temperature points This can be represented mathematically as follows CALC_CTO CTOj CTOj44 CTO x T CTi CTj 4 CTi The actual offset value used is CALC_CTO x 10 and is su
114. urned by the device See Chapter 12 Care should be taken when changing the station number or baud rate as communications can be lost with the host Also note that some commands require the reset RST command to be sent or a power cycle before the new values take effect STN BAUD DP and DPB are such commands When using Instrument Explorer to change either the STN or BAUD parameter communications with the device will be lost after the RST command has been issued as the software will be using the previous settings In this case you need to change the device settings in Instrument Explorer by selecting Change Settings from the Communications menu Station Number STN The STN parameter controls the station number which specifies the device address for bus communications As supplied devices have the station number factory set to 1 as described previously in Version 3 Additions and Enhancements Chapter 1 Mantracourt Electronics Limited DCell amp DSC User Manual 22 Checking the Device Protocol Type and Station Number To connect multiple devices on the same bus it is first vital to set all the station numbers to different values This is because if two devices with the same station number 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 station number of one of them If a bus connects to two devices with the same station number the on
115. used to control the formatting of floating point values in the ASCII protocol DP controls the number of decimal places after the point and DPB controls the number of decimal places before the point Values of 1 8 are appropriate in both cases All output values are then transmitted in this same format As values are limited to a normal 4 byte accuracy about 7 digits it may sometimes be necessary to alter the formatting for best accuracy in reading writing values eg if DP 5 and DPB 2 the value 1 257 is output as 01 25700 The new value of DP and DPB does not take effect until the RST command is issued or the device is power cycled It is important to ensure that when settings DpB the maximum number expected to be formatted does not exceed the number of integer digits i e DpB 3 cannot display numbers greater than or equal to 1000 Failure to observe this will lead to non numeric ASDCII codes after the polarity character Information Reports the current version of the devices software and the devices unique serial number Note that VERSION is the read able item derived from the devices internal value of VER and SerialNumber is derived from SERL and SERH Software Version VER The VER parameter read only byte returns a value identifying the software release number coded as 256 major release minor release eg current version 3 1 returns VER 769 Serial Number SERL and SERH SERL and SERH are read only inte
116. y capable of providing 10 18V at 100mA 10V is minimum requirement for RS485 converter e APC running Windows 98 or above with a spare RS232 communications port and 45Mb free disk space and ideally e A strain gauge load cell or simulator typically 350 5000 ohms impedance Refer to specifications Chapter 12 9 Mantracourt Electronics Limited DCell DSC User Manual Checking the Device Protocol Type and Station Number Before running the communications application you will need to know both the protocol to use and the station number of the device For DSC the product label shows the product code which determines the protocol and its serial number For the DCell the serial number is it s only means of identification The serial number must be used to cross reference the dispatch note to identify the protocol of the device For a DCell the Product Code is one of the following 6 types DLCSASC Industrial Stability ASCII output DLCSMAN Industrial Stability MANTRABUS output DLCSMOD Industrial Stability MODBUS output DLCHASC High Stability ASCII output DLCHMAN High Stability MANTRABUS output DLCHMOD High Stability MODBUS output For a DSC card the Product Code is one of the following 12 types DSCS4ASC Industrial Stability RS485 output card with ASCII protocol DSCS4MAN Industrial Stability RS485 output card with MANTRABUS protocol DSCS4MOD Industrial Stability RS485 output card with MODBUS protocol DSCS2ASC Industrial

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DCell & DSC Strain Gauge or Load Cell Embedded Digitiser Module