WTTCP-M - Weeder Technologies
Contents
1. RB4 L 4 7K O 5 5 is 3 x 1ce E 5 R3 REF osc2 RA4 T raz LZ VOD INA128 vs in et Ral T 2 eee a vee Lt JZ Wk Elyss ras Li 7d cs 3l REF E im T vss al 1N 2 Q D4 C18 C11 TT d E 81 MAE INL O Power LM4848 2 5 zn ifuF MSE OUT vss L4 BOUES CR1 1 18 IC5 R6 D O HE iez 28nHz LH74 4 7K Di 78LB85 iR C 4 7 1c9 1N4HB1 Eg a INA128 2E 1 3 REF Min Vout J3 gt LSB il vcc Lt o g Address R2 jl REF aces a z 7 398K E ci c2 ca Aras ate our IS U C 47uF A 1uF B 1uF ae e quls J y R6 C vss cis 3 s 4 7K 1HBuF ano DEL a 4 5 ul ke a EM OUT gt k D C17 RS IC18 p iBuF 18K T6562 Thermocouple Input Channels Rev B Page 8 Copyright 2012 2013 by Weeder Technologies2. eeder Technologies 90 A Beal Pkwy NW Fort Walton Beach FL 32548 Thermocouple Input Module WTTCP M www weedtech com This product is a direct replacement for the WTTCI M FEATURES 4 thermocouple input channels DIP switch addressable stack up to 32 modules on the same port for 128 inputs Accepts J K T E isolated thermocouples Each channel individually selectable to read temperature in Fahrenheit or Celsius Temperature conversions use high order polynomial equations eliminating look up table interpolation errors Incorporates on board temperature sensor no ice point reference necessary Thermocouple inputs protected to 40 volts Software calibrated no trim pots to adjust All user configuration and calibration data stored in non volatile memory Industry standard RS 232 interface Meets all EIA TIA 232E and V 28 specifications Wide power supply range 8 to 30 VDC Screw terminal connectors used on all inputs DESCRIPTION Connects to the RS 232 serial port of a PC laptop or other host Attach up to four separate thermocouples of various types and use the host to read the temperatures of each Simple command strings sent from the host will initiate a conversion on an input channel which in turn will read the thermocouple voltage in QV convert it to temperature then add the cold junction reference temperature The results returned to th
3. and can B 42 00001 be left open or connected to another module s C 43 00010 host port Up to 32 modules can be chained together in this fashion to form a network Either D 44 00011 plugged together end to end or separated by a E 45 00100 cable Because a module contains two individual bi directional ports which pass data through it F 46 00101 also acts as a repeater extending the total G 47 00110 OMS length of the RS 232 communications ine H 48 00111 A modem can serve as the host for remote 49 01000 operation but since a modem uses a DCE port J 4A 01001 a nul modem adapter must be placed between the modem and the data module s host K 4B 01010 port A gender changer may also be required In L 4C 01011 addition any hardware software flow control M 4D VOU must be disabled in the terminal program N 4E 01101 Each module in a network should be set to a different address using the on board 32 position O 4F 01110 DIP switch A module will only respond to data packets that begin with its own unique header P 50 01111 character which is determined by this DIP a 61 10000 Switch setting See Table 1 Data packets transmitted by a module will also begin with this b 62 10001 header character The host PC can use the c 63 10010 header character to address each individual module in a network and to identify a module d 64 10011 which is tal
4. attached to the input terminals of that channel The temperature will be displayed in the degree units Fahrenheit or Celsius which had previously been selected by using the UNITS command TYPE Sets the thermocouple type for a specific input channel Each channel must be set to the same type as the thermocouple which is attached to its inputs Choices are J K T or E and is determined by the types of metals which are used to construct the thermocouple sensor Those metals consist of the following TABLE 2 COMMAND SET WTTCP M J Iron Constantan K Chromel Alumel T Copper Constantan E Chromel Constantan Consult the thermocouple manufacturer to determine which type or types you are using It is perfectly acceptable to mix different thermocouple types on the same WTTCP board provided that each channel has its type value set accordingly UNITS Sets the degree units for a specific thermocouple input channel Choices are Fahrenheit or Celsius and will determine the format of the temperature data which is returned to the host when issuing the READ command for that channel Note this also sets the degree units used in the CALIBRATE command string CALIBRATE Takes the actual measured values of two temperature points and computes the calibration coefficients for a specific thermocouple input channel To calibrate apply a precision 1000 calibration signal to the input channel
5. a module to a host PC use a standard RS 232 cable with male and female DB9 connectors on opposite ends This cable should be wired straight through pin to pin with no crossover of the data lines In other words not a null modem cable Connect a suitable DC power source to the and terminals of the data module It is highly recommended to use an ungrounded AC adapter such as that which is available from Weeder Technologies This will provide isolation and prevent ground loops which are commonly created if the power supply and computer are grounded at different points When the data module is first powered up the red LED will flash briefly This indicates that the on board microcontroller has booted up successfully completed its internal diagnostic test and has transmitted the reset character to the host to signal that it is up and running The red LED will also flash anytime the module receives or transmits any data packet thus making it a valuable diagnostic tool when troubleshooting communications problems An easy to use Windows software package called ModCom is available and can be downloaded from Weeder Technologies web site This program will allow the user to quickly set up custom buttons which transmit Copyright O 2012 2013 by Weeder Technologies Rev B Weeder Technologies commands custom windows that poll for data and a variety of other screen objects such as slider controls event counters amp timer
6. e host will be equal to the absolute temperature of the thermocouple tip and can be listed in degrees Celsius or Fahrenheit This module is ideal for wide range temperature measurement in harsh industrial environments using a PC or laptop for data collection 850 863 5723 SPECIFICATIONS Thermocouple Inputs Temperature Range Resolution Accuracy Over Voltage Range Calibration Processor Clock Communications Power Requirements Current Draw Operating Temperature Board Dimensions Weight 4 differential channels 210 C to 1372 C 346 F to 2502 F see Table 4 1 C or 1 F selectable 0 1 2 degrees Each input protected from 40V to 40V Gain and zero offset corrected in firmware PIC16F648 20 MHz 9600 Baud N 8 1 8 to 30 VDC 28 to 32 mA 10 C to 80 C 3 5 x 2 0 x 0 7 1 9 oz Copyright 2012 2013 by Weeder Technologies Rev B Weeder Technologies WTTCP M TABLE 1 ADDRESS SETTING STACKABLE DATA MODULES All modules in this series incorporate two EIA TIA 232E serial ports which communicate at HEADER DIP SWITCH 9600 baud no parity 8 data bits and 1 stop bit CHARACTER SETTING DB9 connectors are jumpered to satisfy ASCII HEX 1 on 0 off hardware handshaking The port labeled 12345 HOST is configured as a DCE device and A 41 00000 should be connected to a PC s serial port The port labeled SLAVE is a DTE device
7. en objectto edit its properties Change the polling command change the text set up alarm trips for the Data Windows which cause them to switch colors when the temperature goes above or below a pre defined limit etc Deg For Help press ri EditMode Unlocked nits Log 0 Seq i Cond 24 Page 1 user For more details read through the help files which can be accessed by clicking on the lt Help gt menu item at the top of the screen The temperature shown in each Data Window can also be logged to a file Go to the lt Run Loop gt menu item at the top of the screen and click on lt Data Logging gt Within this dialog box you can specify the data log file name set the time interval between log events and select those screen objects that you wish to log to file The contents of the file can be viewed or printed by clicking on the corresponding button shown in this dialog box or by clicking on a toolbar button at the top of the main screen TEMPERATURE CONVERSIONS The temperature versus voltage relationship of the output of a typical thermocouple is not linear Therefore simply reading the voltage and multiplying it by a scaling factor will not convert it to temperature or at least not with any degree of accuracy over a broad range Because of this a very common design approach for converting the voltage to temperature is to use a lookup table of known voltages that represent various temperatures and t
8. ere the thermocouple sensor is enclosed in a metal tube for instance most are offered in a choice of configurations grounded ungrounded or exposed junctions Avoid those which are listed as grounded unless of course you plan on mounting the probe to a structure or framework which is either non conductive or in itself electrically isolated Consult the probe manufacturer for details on how to identify those units which are grounded and which are not Note some thermocouple probes have a metal shield or braid covering the length of wires and if this probe uses a grounded junction configuration the metal braid will also be grounded to the thermocouple tip and may cause problems if it comes into contact with any metal structure or framework If wishing to use an existing thermocouple mounted in the field which you are uncertain of its grounding state perform the following steps to determine if it is isolated or at least within the common mode range of the WTTCP Attach the thermocouple wires to an input channel of the WTTCP and apply power to the module Using a voltmeter connect the black probe to power supply ground and the red probe directly to the screw terminals which are holding the thermocouple wires You should read a voltage between 3V and 3V If not the thermocouple tip is grounded and the voltage potential of that ground is outside the range of the WTTCP s inputs In this case the thermocouple must be rem
9. he physical limitations of the thermocouple itself and the mathematical boundaries inherent to the polynomial equation that is used to calculate the temperature The former specifications can be obtained from the thermocouple manufacturer and will vary depending on the form of weld used to make the junction and the type of insulating material used to cover the wires As for the limits of the polynomial equation used for temperature conversions refer to Table 4 THERMOCOUPLE GROUNDING Although the WTTCP benefits from a wide range of input voltages that it can safely handle before damage results 40 volts the common mode voltage range is much smaller When attached to a thermocouple that is electrically isolated this poses no problem because the wires of the thermocouple will float to the bias point which is midway in the common mode region However if the thermocouple tip or junction is grounded whether accidentally or intentionally to the housing which it is mounted to and that housing has a voltage potential beyond the common mode range of the WTTCP s inputs errors in temperature readings will result In addition this condition may create a ground loop and any electrical noise induced by the ground loop will also cause errors Care must be observed to be certain that the thermocouple tip does not make electrical contact with any conductive surfaces it may be mounted to When using a prefabricated temperature probe one wh
10. hen use interpolation for those voltages that fall in between the table listings This is fine for low precision applications but because of the gaps in the lookup table interpolation errors can not be avoided and thus limits the reliability of the system The WTTCP however uses a different approach The signal from the thermocouple is amplified converted to a digital format and then subjected to a high order polynomial equation using 32 bit floating point math The result is a voltage to temperature conversion with an accuracy of Copyright 2012 2013 by Weeder Technologies Rev B Weeder Technologies TABLE 4 TEMPERATURE RANGE WTTCP M TYPE CELSIUS FAHRENHEIT J 210 to 1200 346 to 2192 K 200 to 1372 328 to 2502 T 200 to 400 328 to 752 E 200 to 1000 328 to 1832 0 1 C across the entire range of temperatures Built in to the WTTCP s firmware is the polynomial coefficients published by the United States National Institute of Standards NIST which are needed for voltage to temperature conversions for each of the four thermocouple types that the module supports When a READ command is issued by the host the appropriate NIST coefficients are extracted and plugged into the mathematical equation mentioned above TEMPERATURE RANGE The range of temperatures which can be measured by the WTTCP and its thermocouple sensors is dependant on two factors t
11. hnologies DCE PORT DTE PORT TO SLAVE 8 to 38 VDC TO HOST THERHOCOUPLE INPUT MODULE UTTCP H C12 E i uF R7 ym 10K il TT ae J1 C6 5 C13 1C6 i 1uF R4 R5 aaas THE nee INA128 IE 3 ves 758 758 vcc Lt ots Z c4 cs As iT c Com mit Rec g yss veo amp 3l RER 2 1uF 1uF i3 ADRA REF IN Ici iuF Zit c9 ADRI ns L3 EE m co gt 1 l3 Haxz3z d CHi OuT oe a n T a 1uF 8 1uF E CHE T RG A vss L o riv vec ie i jt Ana ci w te 3l LED1 s CH4 4 7K J4 aE o t i L H son 1c 3 cz ano Lis SCK CH4 HH n 14 T iu 13 Eha dE INaiz0 4 o Rsexe TTL 1N4148 228 PICi6F648 PASS M pep Yen 13 12 izups neni il in L2 Q oL DZ MCLR RBS E ci4 oF REZ fiada o 8 3 M REL ix Boe OUT F O Se Rs232 TTL RRE LI Kt RG B Was 5 1a 184148 amp kes LIT vs H REG
12. king e 65 10100 f 66 CERT COLLISION CONTENTION g 67 10110 The utilization of the communications line can be thought of more as a single bi directional data h 68 10111 bus operated in a multi drop mode rather then a i 69 11000 standard RS 232 data link A transmission from a a data module travels in both directions j 6A 11001 upstream to the host and downstream to signal k 6B 141010 other modules that it has seized the line Before transmitting a module will listen to the I 6C 11011 communications line and wait for quiescence m 6D 11100 After a silent period equal to the length of one byte the waiting module will send its data packet n 6E 11101 using a Carrier Sense Multiple Access with o 6F 11110 Collision Detection communications protocol See the application note AN100 at the back of p 70 11111 this manual for more details T Copyright 2012 2013 by Weeder Technologies Page 2 Rev B Weeder Technologies COMMAND SET The host PC communicates with the Thermocouple Input Module using a command set comprised of standard ASCII character strings as depicted in Table 2 Some commands are used to setup and configure the individual channels while others are used to poll for data A detailed description of each command follows READ Reads the current value of the specified input channel The results returned to the host will be equal to the absolute temperature of the thermocouple sensor which is
13. of the WTTCP Use the READ TITLE COMMAND DESCRIPTION Read the current value of a thermocouple input channel chn A D READ R chn Returns the thermocouple temperature listed in the degree units which has been selected by UNITS Sets the thermocouple type for a specific input channel chn A D TYPE T chn value value J K T or listed in accordance with ANSI conventions Default J If value omitted reads the current setting Note 3 Sets the degree units for a specific thermocouple input channel UNITS U chn value chn A D value F or C F Fahrenheit C Celsius default F If value omitted reads the current setting Note 3 Takes the actual measured values of two temperature points and computes the calibration coefficients for a given thermocouple input CALIBRATE C chn t1 t2 channel chn A D t1 is the measured temperature when a 1000 calibration signal is applied to the input t2 is the measured temp when a 100 calibration signal is applied to the input Note 3 4 5 ERROR This character will be returned after an invalid command or variable RESET This character will be returned after a power on reset or brownout Note 1 All command strings sent to the data module should be preceded with the header character see Table 1 and terminated with a carriage return All responses from the data module will also appear in this format Note 2 Any spaces shown above in the listing of
14. oved from its original mounting and re mounted in a way which keeps it electrically isolated from the frame that it is attached to or replaced with a thermocouple which uses an ungrounded configuration Copyright 2012 2013 by Weeder Technologies Rev B Weeder Technologies WTTCP M Address Setting Trans Rec Indicator LED This DIP switch sets the Flashes whenever there is address of the Data Module communications between and determines the header host PC and Data Module character of its data packets RS 232 E RS 232 Slave Port lt Host Port Connects to Connects to the Host port O the serial of another port of the Data Module host PC CJ LEN A B C D LEES A QOOOOOO D Ley Power Source Jumper Power Supply Inputs Thermocouple Input Channels Draw power from external input Will accept any voltage Each channel can be set up for terminals or from an upstream between 8 and 30 VDC types J K T or E ungrounded Data Module via the host port thermocouples Each Input protected from 40V to 40V A 0 5 Holes will accept size 4 40 screws 1 0 2 0 Y 0 375 j 275 0 375 3 5 BEL M ee Copyright 2012 2013 by Weeder Technologies Page 7 Rev B WTTCP M Weeder Tec
15. rt of a PC or laptop does not supply enough current to serve as the power supply source command to measure the temperature and record the average reading of multiple samples Then repeat this process using a 100 calibration signal Include the results in the CALIBRATE command string using a hyphen to separate the two numbers The WTTCP will use this data to calculate the gain and offset coefficients particular to that channel and store it in non volatile memory If necessary repeating this process will zero in the calibration accuracy and a deviation of 1 degree or less across the full temperature range can be achieved IMPORTANT be sure to set the TYPE and UNITS for the channel appropriately before calibrating Both should be set to the same as the calibration signal source Once calibrated the TYPE and UNITS can then be changed to any of the other choices without having to recalibrate Note the module has been calibrated at the factory it is not necessary to perform this operation prior to use ERROR Any data string sent from the host containing the correct header character but an invalid command or variable will be responded to with this error indicator RESET Upon power up or any other reset condition this indicator is transmitted to the host Note all user configuration and calibration data is stored in non volatile memory A reset or loss of power will not corrupt these settings OPERATION To hook the dat
16. s bar graph level indicators button selection arrays signal lamps and more In addition conditional statements can be set up to take action when specific events or conditions are met sequences can be written and then called by other screen objects during run time and data can be logged to a file automatically at user defined intervals Once ModCom is installed and running go to the Communicate menu item at the top of the screen and click on lt Send Receive gt A dialog box will pop up which you can use to type in the commands from Table 2 transmit them directly to the data module and see the response coming back Use this dialog box to familiarize yourself with the command set and to experiment with the various features supported by the module The experience gained here is significant since these are the same command strings you will use when setting up the other objects in ModCom To read thermocouple temperatures start with the sample application WTTCP mod which can be found in the ModCom subfolder called Samples After this file is opened it will appear as shown in Figure 1 To start the main run loop click on the green toolbar button at the top of the screen At this time the Data Windows will begin polling for data and show the temperature readings of the thermocouples which are attached to each input channel of the WTTCP Note any input channels which are left open will show the temperature of the WTTCP circ
17. the command strings are for clarity only They should not be included in the actual transmission from the host nor expected in a response from the data module Note 3 After successful execution this command will be echoed back to the host in the same format as received Note 4 The data module has been calibrated at the factory it is not necessary to perform this operation prior to use Note 5 If t1 t2 is omitted the factory calibration coefficients for this particular channel will be restored Copyright O 2012 2013 by Weeder Technologies Page 3 Rev B Weeder Technologies WTTCP M TABLE 3 TERMINAL CONNECTOR DESCRIPTION NAME TYPE ELECTRICAL SPECS COMMENTS DB9 RS 232 serial port configured as DCE HOST EIA TIA 232E Standard Connects to host PC Hardware handshake female jumpered DB9 RS 232 serial port configured as DTE Can SLAVE EEG EIA TIA 232E Standard be connected to another data module s HOST port for networking Power tise N A Power source selection jumper Selects Source P either external or port powered Note 1 T Screw Term 8 to 30 VDC External unregulated power supply input Screw Term GND External power supply ground A D Screw Tenn Range 3V to 3V Input channels which can accept isolated Max input 40V to 40V or ungrounded thermocouples only Note 1 Selecting port powered will draw from the power supply source of an upstream data module Caution the COM po
18. uit board including any heat generated by the on board components You can use the buttons to the right of each Data Window to change the display format from Fahrenheit to Celsius or vice versa and to select the thermocouple types The selections you make with these buttons will be stored in the WTTCP s memory and remain there even if power is cycled Each Data Window can be customized by the user for appearance or even set up to signal an alarm condition by changing colors if the temperature exceeds a predefined high or low limit To do this first halt the run loop by clicking on the red toolbar button at the top of the screen Then right click on the object to pull up its properties dialog box Within this box are a number of options which can be modified by the WTTCP M FIGURE 1 MODCOM APPLICATION z Wiima Modtom BA Fie Edt View Page Communicate Runioop Place Object Security Help DG Bat Thermocouple Input Module A Sequence is used to read the configuration of the Thermocouple input channels al start up These values are sent to the Conditional statements which choose the appropriate messages to display in the status windows Deg ia Ld A m 4 tal d m The buttons transmit a TIKITE command to the Thermocouple Input H HENI JaN configuration The data returned is sent on to the Conditionals to J K T E update the window Right click on any scre
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