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M1000/M2000 User Guide - Ocean Networks Canada

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1. o o Setup Hints Until you become completely familiar with the SetUp command the best method of changing setups is to change one parameter at a time and to verity that the change has been made correctly Attempting to modify all the setups at once can often lead to confusion If you reach a state of total confusion the best recourse is to reload the factory setup as shown in Table 5 5 and try again changing one parameter at a time Use the Read Setup RS command to examine the setup information currently in the module as a basis for creating a new setup For example Assume you have a M1111 unit and you wish to set the unit to echo so that it may be used in a daisy chain See Communications Read out the current setup with the Read Setup command Command 1RS Response 310701C2 By referring to Table 5 3 we find that the echo is controlled by bit 2 of byte 3 From the RS command we see that byte 3 is currently set to 01 This is the hexadecimal representation of binary 0000 0001 To set echo bit 2 must be set 1 This results in binary 0000 0101 The new hexadecimal value of byte 3 is 05 To perform the SU command use the data read out with the RS command changing only byte 3 Command 1WE SU is write protected Response Command 150310705 2 Response Verify that the module is echoing characters and the setup is correct By using the RS command and changing one setup parame
2. ND command is especially usefu with computers that handle communications on an interrupt basis The ND command may be used to get the maximum possible throughput without producing redundant data Command 1ND Response 00072 00 Command 1ND Response 1ND 00072 009F A special condition exists when using the ND command with the M1600 frequency pulse modules These modules differ from the other sensor input modules in that they require an input trigger signal to obtain new data If signal exists on the input of the M1600 an ND command will wait indefinitely for new data and the module will not respond In order to escape this condition a single contro C 03 may be issued by the host to abort the ND command The aborted ND command will respond with the data value currently stored in the output buffer Be aware that on an RS 485 system the control C character may interfere with the ND output data causing a communica tions collision Read Data RD The read daia command is the basic command used to read the buffered sensor data The output buffer Figure 2 1 allows the data to be read immediately without waiting for an input A D conversion For example Command 1RD Response 00072 00 Command 1RD Response tRD 00072 10A4 Since the RD command is the most frequently used command in normal operation a special shortened version of the command is available If a module is addressed without a two letter com
3. Step 2 The breakpointtable should be cleared by using the Erase Breakpoints EB command This command will completely erase the breakpoint table Any previous breakpoint information will be permanently lost MetraByte M2000 Programming Manual 5 3 Command 1WE Response Command 1EB Response Step 3 Clear any data stored in the output offset register by using the Clear Zero CZ command Command 1WE Response Command 1CZ Response Step 4 Use the SetUp SU command to program the correct number of displayed digits Command 1WE Response Command 515031070182 typical Response Step 5 Start the function programming by setting the minimum point using the MiNimum command as described in the linear scaling section Step 6 Set the maximum function point with the MaXimum command as described in the linear scaling section Step 7 Use the BreakPoint BP command to program the nonlinear function into memory Apply the proper excitation to the module for Breakpoint 00 Use the BreakPoint command to enter the data into memory Command 1WE Response Command 1BP00 00100 00 Response At this point it may be useful to verify that the breakpoint data has indeed been recorded in memory Without changing the excitation read the output data Command 1 Response 00100 00 5 4 MetraByte M2000 Programming Manual The output data should match the data programmed with the
4. Command 1BP00 00031 62 Response Apply 2 voits to the input Command 1BP01 00044 72 Response Continue until all breakpoints are programmed 8 Verify the transfer function To get better conformity more breakpoints may be programmed especially near the minimum end of the scale where the function curvature is greatest There is no particular requirement to have breakpoints at regular intervals The breakpoint intervals may be varied to achieve the best overall conformity Small breakpoint intervals assure better conformity in areas where the function curvature is the greatest Example N 5 Breakpoints may be used to improve the linearity of a module in linear output applications The M2141 module programmed in Example N 4 is to be programmed back to its original 10 V input output transfer function 1 Define function data Analog Input Data Output Minimum 10V 10000 00 Maximum 10 V 410000 00 No Breakpoints MetraByte M2000 Programming Manual 5 13 2 Erase breakpoints 3 Clear zero 4 Setup the displayed output for five digits Command 15031070142 typical Response 5 Program minimum by applying exactly 10 V to the input Command 1MN 10000 00 Response 6 Program maximum by applying 10 V to the input Command 1MX 10000 00 Response 7 There are no breakpoints to be programmed 8 Verify the function scaling Analog Input Data Output 5V 05010 00 OV 00020 00 5V
5. command also specifies whether the high alarm is momentary or latching A letter indicating the alarm type L for latching or M for momentary must follow the alarm value For example Command 1HI 00100 00M Response Command 1HI 00100 00M Response 1HI 00100 00ME3 The alarm limit should be set within the output range of the module If the alarm limit is set beyond the output range the alarm will be activated only on an overload condition The high alarm value may be read back with the Read High Alarm RH command A latched alarm may be cleared with the Clear Alarms CA command More information on alarms may be found in the Digital I O section Low Alarm Limit LO The low alarm command sets the value and type of the low alarm The data specified with the LO command is stored in nonvolatile memory and compared with the sensor data after every A D conversion If the input data is less than the low limit the low alarm is activated The low alarm status may be read using the Digital Input command The alarm may be used to activate a digital output by using the Enable Alarms EA command A letter indicating the alarm type L for latching or M for momentary must follow the alarm value For example Command 1L0 00000 00M Response Command 1L0 00000 00M Response 1L0 00000 00MEC The alarm limit should be set within the output range ofthe module If the alarm limit is set beyond the output range the
6. prompt precedes an error message All response messages are terminated with a CR Many commands simply return a single character to acknowledge that the command has been executed by the module Other commands send data information following the prompt The response format of all commands may be found in the detailed command description The maximum response message length is 20 characters command response sequence is not complete until valid response is received The host may not initiate a new command until the response from a previous command is complete Failure to observe this rule will result in communications collisions A valid response can be in one of three forms 1 a normal response indicated by a prompt 2 an error message indicated by a prompt 3 a communications time out error When a module receives a valid command it must interpret the command perform the desired function and the communicate the response back to the host Each command has an associated delay time in which the module is busy calculating the response lf the host does not receive a response in an appropriate amount of time specified in Table 4 1 a communications time out error has occured After the communications time out it is assumed that no response data is forthcoming This error usually results when an improper command prompt or address is transmitted Long Form Responses When the pound sign command prompt is use
7. warranties on behalf of the customer On those other manufacturers products that Keithley purchases for resale Keithley shall have no duty of obligation to enforce any manufacturers warranties on behalf of the customer Software Keithley warrants that for a period of one 1 year from date of shipment the Keithley produced portion of the software or firmware Keithley Software will conform in all material respects with the published specifications provided such Keithley Software is used on the product for which it is intended and other wise in accordance with the instructions therefore Keithley does not warrant that operation of the Keithley Software will be uninterrupted or error free and or that the Keithley Software will be adequate for the customer s intended application and or use This warranty shall be null and void upon any modification of the Keithley Software that is made by other than Keithley and not approved in writing by Keithley If Keithley receives notification of a Keithley Software nonconformity that is covered by this warranty during the warranty period Keithley will review the conditions described in such notice Such notice must state the published specification s to which the Keithley Software fails to conform and the manner in which the Keithley Software fails to conform to such published specification s with sufficient specificity to permit Keithley to correct such nonconfor mity If Keithley determines that the Keith
8. 1 5 2 When using the SU command to change the address of a module be sure to record the new address in a place that is easily retrievable The only way to communicate with a module with an unknown address is with the Default Mode The most significant bit of byte 1 bit 7 must be set to 0 In addition there four ASCII codes that are illegal for use as an address These codes are 00 0D 24 23 which are ASCII codes for the characters NUL CR and Using these codes for an address will cause an ADDRESS ERROR and the setup data will remain unchanged This leaves a total of 124 possible addresses that can be loaded with the SU command It is highly recommended that only ASCII codes for printable characters be used 21 to 7E which greatly simplifies system debugging with a dumb terminal Refer to Appendix A for a list of ASCII codes Table 5 1 lists the printable ASCII codes that may used as addresses Table 5 1 Byte 1 ASCII Printable Characters HEX ASCII HEX ASCII HEX ASCII ASCII gt lt lt lt lt 3 7 5 lt gt B C D E F G H 1 J K L M N Dah 5 3 Byte 2 Byte 2 is used to configure some of the characteristics of the communications channel linefeeds parity and baud rate Linefeeds The most significant bit of byte 2 bit 7 controls linefeed generation by the m
9. 10100011 5 36 24 00100100 164 4 10100100 37 25 00100101 165 10100101 amp 38 26 00100110 166 10100110 27 00100111 167 A7 10100111 40 28 00101000 168 8 10101000 Rot lt lt gt gt 00101001 00101010 00101011 00101100 00101101 00101110 00101111 00710000 00110001 00110010 00110011 00110100 00110101 00110110 00110111 00111000 00111001 00111010 00111011 00111100 00111101 00111110 00111111 01000000 01000001 01000010 01000011 01000100 01000101 01000110 01000111 01001000 01001001 01001010 01001011 01001100 01001101 01001110 01001111 01010000 01010001 01010010 01010011 01010100 01010101 01010110 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 10101001 10101010 10101011 10101100 10101101 10101110 10101111 10110000 10110001 10110010 10110011 10110100 10110101 10110110 10110111 10111000 10111001 10111010 10111011 10111100 10111101 10111110 10111111 11000000 11000001 11000010 11000011 11000100 11000101 11000110 11000111 11001000 11001001 11001010 11001011 11001100 11001101 11001110 11001111 11010000 11010001 11010010 11010011 11010100 11010101 11010110 gt 177 KX SCOT 01010111 01011000 01011001 01011010 01011011 01011100 01011101 01011110 01011111 01100000
10. 30 374 32 2 31 30 2 4 two lowest order hex digits of the sum 4 which agrees with the transmitted checksum Note that the transmitted checksum is the character string equivalent to the calculated hex integer The variables must be converted to like types in the host software to determine equivalency If checksums do not agree a communications error has occurred If a module is setup to provide linefeeds the linefeed characters not included in the checksum calculation Parity bits are never included in the checksum calculation Table 4 1 M1000 Command Set Command and Definition Read Alarms Digital inputs Set Digital Outputs New Data Read Data Read Event Counter Read Low Alarm Value Read High Alarm Value Read Setup Read Zero Write Enable Write Protected Commands CA CE CZ DA EA Hi LO RR SU SP TS TZ Clear Alarms Clear Events Clear Zero Disable Alarms Enable Alarms Set High Alarm Limit Set Low Alarm Limit Remote Reset Setup Module Set Setpoint Trim Span Trim Zero Typical Command Message prompt 1DI 1DOFF 1ND 1RD 1RE 1RL 1RH 1RS 1RZ 1WE 1CA 1CE 1CZ 1DA 1EA 1Hl 12345 67L 1LO412345 67L 1RR 1SU31070142 1SP 00600 00 175 00600 00 172 00000 00 Typical Response Message 0003 00072 00 4 00072 00 0000107 00000 00 L 00510 00 L 31070142 00000 00 4
11. Figures 1 1 or 1 2 Put the module in the default mode by grounding the Default terminal Initialize the terminal communications package on your computer to put it into the terminal mode Since this step varies from computer to computer refer to your computer manual for instructions Begin by typing 1RD and pressing the Enter or Return key The module will respond with an followed by the data reading at the input The data includes sign seven digits and a decimal point For example if you are using a thermocouple module and measuring room temperature your reading might be 400025 00 The temperature reading will initially be in which has been preset at the factory Once you have a response from the module you can turn to the section on commands and get familiar with the command set All modules are shipped from the factory with a setup that includes a channel address of 1 300 baud rate no linefeeds no parity alarms off no echo and 2 character delay Refer to the setup section to configure the module to your application 10 to 30 Ydc Power Supply 0 O e e e e e e Q EEA Q Figure 1 1 RS 232C Quick Hook up 1 2 N IN DO1 HI DIA EV poe flo 1 DEFAULTS FOL TAGE 8 495 Figure 1 2 5 485 Quick Hook Up RS 485 Quick Hook up to a RS 232 port An RS 485 module may be easily interfaced to an RS 232C terminal for evaluation purpos
12. RS command to determine all of the setups stored in the module In Default Mode all commands are available as usual A module in Default Mode will respond to any address except the four identified illegal values NULL CR A dummy address must be included in every command for proper responses The ASCII value of the module address may be read back with the RS command An easy way to determine the address character is to deliberately generate an error message The error message outputs the module s address directly after the prompt Setup information in a module may be changed at will with the SetUp SU command Baud rate and parity setups may be changed without affecting the Default values of 300 baud and no parity When the DEFAULT pin is released the module automatically performs a program reset and configures itself to the baud rate and parity stored in the setup information The Default Mode is intended to be used with a single module connected to a terminal or computer for the purpose of identifying and modifying setup values In most cases a module in Default Mode may not be used in a string with other modules RS 232 5 485 Quick Hook Up Software is not required to begin using your M1000 module We recommend that you begin to get familiar with the module by setting it up on the bench Start by using a dumb terminal or a computer that acts like a dumb terminal Make the connections shown in the quick hook up drawings
13. The isolation allows up to 500V of common mode voltage between the input ground and the power connections The input comparator employs hysteresis to provide reliable readings with noisy or slow input signals The amount of hysteresis may be controlled by connecting the hysteresis control line HYSTR to ground or the 2 5V terminal through an external resistor Fig 2 shows the most frequently used connection Figure 2 Controlling Hysteresis For Positive Going Signals Vswitching Vhysteresis 2 5V 40 5 2 5V 50 For Vhysteresis gt 5mV and lt 0 5 R 34 Vhysteresis 0 5 Vhusteresis SOGGSSSSS SSgg This connection is used for unipolar positive going frequency signals hysteresis is centered around a 2 5V switching level If R is left open the switching levels and 42V 2 5V 0 5V If R is shorted the hysteresis decreases with resulting switching levels of 2 5V 5mV Any hysteresis value from 5mV to 0 5V may be obtained by selecting an appropriate value for R Fig 2 shows the relationship between the hysteresis and R 959695990009 The input comparator may be setup for comparisons around zero volts by using the connections in Fig 3 This connection is useful for AC or bipolar signals Since the input section is isolated the 2 5V pin may be connected to any signal with a common mode voltage up to 500V With the hysteresis control con nected as in Fig 3 the s
14. Wild AGN 23 431113 19 015 i dS TIAS S1Nv 18N02 138440 21 NOY 81192 inaano Ze 5 6 10 Ob Yiya 2 1 1 A aic 1 201 1 lt Wav IH NC 08320119 3311 3 WNOSIS 358491 4 Wesberg y901g 12 1 2 3 COMMUNICATIONS Introduction The M1000 series of interface modules has been carefully designed to be easy to interface to all popular computers and terminals All communications to and from the modules are performed with printable ASCI characters This allows the information to be processed with string functions common to most high level languages such as BASIC For computers that support standard interfaces such as RS 232C no special machine language software drivers are necessary for operation The modules can also be connected to auto answer modems for long distance operation without the need for a supervisory computer The ASCII format also makes system debugging easy with a dumb terminal The MetraByte system is designed to allow multiple modules to be connected to a communications port with a single 4 wire cable Up to 32 RS 485 modules may be strung together on one cable 124 with repeaters A practical limit tor RS 232C units is about ten although a string of 124 units is possible The modules communicate with the host on a polling system that is each module responds to its own unique address and must be interrogated by the host A module can
15. user option See Checksum section below All commands must be terminated by a Carriage Return character ASCH 0D all command examoles in this text the Carriage Return is either implied or denoted by the symbol CR Data Structure Many commands require additional data values to complete the command definition as shown in the example commands in Table 4 1 The particular data necessary for these commands is described in full in the complete command descriptions most common type of data used commands responses is analog data Analog data is always represented in the same format for all models in the M1000 series Analog data is represented as a nine character string consisting of a sign five digits decimal point and two additional digits The string represents a decimal value in engineering units Examples 12345 68 00100 00 00072 10 00000 00 When using commands that require analog data as an argument the full nine character string must be specified even though some digits may not be significant Failure to do this will result ina SYNTAX ERROR Analog data responses from the module will always be transmitted in the nine character format This greatly simplifies software parsing routines since all analog data is in the same format for ail module types In many cases some of the digits in the analog data may not be signiticant For instance the M1300 thermocouple input modules feature 1 de
16. you This warranty is void if the product has been repaired or altered except by MetraByte or has been subjected to misuse negligence or accident no case shali MetraByte s liability exceed the original purchase price The aforementioned provisions do not extend the original warranty period of any product which has been repaired or replaced by MetraByte WARNING The circuits and software contained in the M1000 Series modules are proprietary to MetraByte Corporation Purchase of these products does not transfer any rights or grant any license to the circuits or software used in these products Disassembling or decompiling of the software program 5 explicitly prohibited Reproduction of the software program by any means is illegal As explained in the setup section all setups are performed entirely from the outside of the M1000 module There is no need to open the module because there are user serviceable parts inside Removing the cover or tampering with modifying or repairing by unauthorized personnel will automatically void the warranty MetraByte is not responsible for any consequential damages RETURNS When returning products for any reason contact the factory and request a Return Authorization Number and shipping instructions Write the Return Authorization Number on the outside of the shipping box MetraByte strongly recommends that you insure the product for value prior to shipping tems should not be returned col
17. 00 01036 40 01017 70 9 3 APPENDIX ASCII TABLES Table of ASCII characters and their equivalent values Decimal Hexadecimal Hex and Binary Claret represents Control function A D Hex Binary D Hex Binary 0 00 00000000 128 80 10000000 A 1 01 00000001 129 81 10000001 B 2 02 00000010 130 82 10000010 3 03 00000011 131 83 10000011 D 4 04 00000100 132 84 10000100 AE 5 05 00000101 133 85 10000101 F 6 06 00000110 134 86 10000110 G 7 07 00000111 135 87 10000111 M 28 08 00001000 136 88 10001000 9 09 00001001 137 89 10001001 AJ 10 OA 00001010 138 8A 10001010 K 11 OB 00001011 139 8B 10001011 L 12 OC 00001100 140 8C 10001100 M 13 OD 00001101 141 8D 10001101 N 14 OE 00001110 142 8E 10001110 O 15 OF 00001111 143 8 10001111 P 16 10 00010000 144 90 10010000 Q 17 11 00010001 145 91 10010001 18 12 00010010 146 92 10010010 S 19 13 00010011 147 93 10010011 520 14 00010100 148 94 10010100 U 21 15 00010101 149 95 10010101 V 22 16 00010110 150 96 10010110 N 23 17 00010111 151 97 10010111 X 24 18 00011000 152 98 10011000 Y 25 19 00011001 153 99 10011001 7 26 00011010 154 9A 10011010 27 1 00011011 155 9B 10011011 28 1 00011100 156 9C 10011100 29 1D 00011101 157 9D 10011101 30 1E 00011110 1588 9E 10011110 31 1F 00011111 159 9F 10011111 32 20 90100000 160 0 10100000 33 21 00100001 181 1 10100001 34 22 00100010 162 2 10100010 35 23 00100011 163
18. 01100001 01100010 01100011 01100100 01100101 01100110 01100111 01101000 01101001 01101010 01101011 01101100 01101101 01101110 01101111 01110000 01110001 01110010 01110011 01110100 01110101 01110110 01110111 01111000 01111001 01111010 01111011 01111100 01111101 01111110 01111111 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 11010111 11011000 11011001 11011010 11011011 11011100 11011101 11011110 11011111 11100000 11100001 11100010 11100011 11100100 11100101 11100110 11100111 11101000 11101001 11101010 11101011 11101100 11101101 11101110 11101111 11110000 11110001 11110010 11110011 11110100 11110101 11110110 11110111 11111000 11111001 11111010 11111011 11111100 11111101 11111110 11111111 3 APPENDIX M1400 DATA SHEET SPECIFICATIONS Typical 25 C V 15V RTD Types 00385 00392 100 9 0 C Resolution 0 1 Accuracy 0 3 Input connections 2 3 or 4 wire Excitation current 0 25 mA Max Lead resistance 650 Input protection to 120 Vac Automatic linearization and lead compensation User selectable C or F Lead resistance effect 3 wire 2 5 C per Q of imbalance 4wire Negligible SENSOR HOOKUPS The RTD sensor must be connected as shown in the accompaning diagrams to insure proper operation
19. 2 MetraByte M2000 Programming Manual used to simplify software in host computers Despite the fixed format the programmer has a certain amount of flexibility to structure the output data for the best compromise between resolution and readability For example an output indication of 05 volts could be structured in three different output formats 00000 05 05 volts 00050 00 50 millivolts 50000 00 50 000 microvolts The first consideration must be the resolution or the number of output counts available in the output structure If the overall function span is 0 to 50 millivolts the first example would only yield 5 counts from 00000 00 to 00000 05 In most applications this resolution would not be acceptable The next obvious output structure is to output the data in units of millivolts as shown in the second example This format would give us 5 000 counts of resolution Finally the third example expresses the output data in units of microvolts to give a possible resolution of five million counts The second factor that must be considered is the performance limitations of the A D converter The best resolution of the ADC is 50 000 counts Resolution is degraded by round oif errors noise etc so that a practical expectation for usable resolution would be in the range of 5 000 to 20 000 counts Output resolution may be limited by picking a suitable output format or by using the appropriate displayed digits setup as described in t
20. 3 WIRE The M1400 modules are shipped from the factory configured for 3 wire operation Connect the RTD sensor as shown in the diagram The wires coonected to the and I terminals should be matched in length and gauged for proper lead compensation and SENSE terminals must be tied together at the connector with a short wire jumper For proper 3 wire lead compensation the 3 4 wire set up bit must be 0 see Set Up SU command A typical set up for 3 wire operation would be 31070182 llead 500096099099 J3 WIRE JUMPER Figure 1 Three Wire RTD Connection 4 WIRE For 4 wire operation connect the sensor as shown in the diagram If the RTD is equipped with heavy excitation wires they should be connected to the I and I terminals For proper 4 wire operation the RTD set up bit must be set to 1 see Set Up SU command A typical set up for 4 wire operation would be 31071182 e e e e e e e e e Figure 2 Four Wire RTD Connection 2 WIRE The 2 wire connection requires two jumpers on the connector as shown in the diagram This connection provides no lead compensation The RTD set up bit can be set to either 0 or 1 for this connection SIS 69699 sg Ji J2 WIRE JUMPER Figure 3 Two Wire RTD Connection START UP During normal operation the RTD lead resistance is periodically scanned and filtered by the M1400 module This may result in large initial errors if the RTD senso
21. Breakpoint command Once Breakpoint 00 has been entered proceed to Breakpoint 01 Set the analog excitation for the correct value for Breakpoint 01 Load ihe breakpoint into memory using the BreakPoint command Be sure to specify 01 in the BreakPoint command Command 1WE Response Command 1BP01 00200 00 Response Verify that the data has been entered properly Command 1 Response 00200 00 Continue this process until all breakpoints have been programmed Step 8 Test the input output transfer function of the module to verify that the breakpoint data has been entered properly Large errors in the output data are generally caused by improper breakpoint programming In most cases it is not necessary to repeat the whole breakpoint sequence if the error is confined to one portion of the curve Breakpoints may be re programmed individually to correct any errors However it is not possible to insert extra breakpoints in the middle of the table to correct for a poor initial function approximation Example N 1 A voltage output pressure sensor produces 0 V 100 psi and 5 V 600 psi Its output characteristic is nonlinear and may be described by the equation P 100 80V 4 V2 where V p sensor output in volts pressure in psi A simple linear equation may be derived by using the endpoint data 100 100V MetraByte M2000 Programming Manual 5 5 Unfortunately describing the sensor output with this eq
22. LED display panels to provide a continuous visual output To specify continuous output add a C suffix to the model number 1511 for example Programmable Scaling The Metrabyte 02500 series of interface modules are bridge units similar to the M1500 series except that the input output transfer function may be programmed by the user Output data may be scaled to any desired engineering units such as pounds psi Newtons etc Non linear functions may also be programmed into the module All scaling data is stored in non volatile memory and may be re programmed any number of times Call factory for details Bridge Completion Resistors For convenience standard bridge completion resistors may be obtained from Metrabyte Standard values available are 120 and 350 Q C 8 APPENDIX D M1600 DATA SHEET The M1601 2 Frequency Input modules feature a versatile input stage that can be used in a variety of applications Fig 1 is a block diagram of the input signal conditioning i Protection Comparato A Output to uP Hysteresis Figure 1 M1601 2 Input Signal Conditioning Block Diagram The input signal is applied to a precision comparator through the input Input protection is provided to withstand inputs up to 230Vac The comparator output is then fed through an opto isolator to the module s microprocessor for scaling and formatting The input section is completely isolated from the power and communications lines
23. Zero CZ command The SP command will write over any data written into the Output Offset Register by the Trim Zero TZ command If the Output Offset Register is used as a trim value this must be accounted for by the host before using the SP command The value stored in the offset register may be read back using the Read Zero RZ command The setpoint data or trim data in the Output Offset Register is saved in nonvolatile memory Setup Command SU Each M1000 module contains an EEPROM Electrically Erasable Programmable Read Only Memory which is used to store module setup information such as address baud rate parity etc The EEPROM is a special type of memory that will retain information even if power is removed from the module The EEPROM is used to replace the usual array of DIP switches normally used to configure electronic equipment The SetUp command is used to modify the user specified parameters contained in the EEPROM to taylor the module to your application Since the SetUp command is so important to the proper operation of a module a whole section of this manual has been devoted to its description See Section 5 4 17 SU command requires an argument of eight hexadecimal digits to describe four bytes of setup information Command 1SU31070182 Response Command 1SU31070182 Response 151 3107018299 Trim Span TS The trim span command is the basic means of trimming the accuracy of a M1000 se
24. baud rate is correct 2 If daisy chaining RS 232C modules be sure that the echo bit is set to 1 3 If using byte time delay make sure that the proper delay is set The above procedure basically makes sure that the module and the system are speaking the same language Reinstall module in the system and try again Events counter not counting properly 1 Check that the frequency of the signal being counted is less than 60Hz Error in displayed value 1 Make sure that the C F bit is set to a 0 Otherwise the values will be scaled by the F equation 9 CALIBRATION The M1000 module is initially calibrated at the factory and has a recommended calibration interval of one year Calibration constants are stored in the EEPROM and may be trimmed using the Trim Span TS and Trim Zero TZ commands There are no pots to adjust Calibration procedure is as follows Voltage and current inputs clear the output offset register using the Clear Zero CZ command Zero trims are not neccessary due to the built in auto zero function Apply a known calibrated voltage or current to the input of the module The calibrated stimulus should be adjusted to be near 90 of the full scale output of the modules for best results Obviously the accuracy of the calibrated voltage or current must be better than the rated accuracy of the module which in most cases is 0 02 of full scale Use the Read Data RD command to obtain an ou
25. because that was the original baud rate of the module The module remains in 300 baud after this sequence We can use the Read Setup RS command to check the setup data Command 1 5 Response 31020080 Notice that although the module is communicating in 300 baud the setup data indicates a baud rate of 9600 byte 2 02 To actually change the baud rate to 9600 send a Remote Reset RR command RR is write protected Command 1 Response Command 1RR Hesponse Up to this point all communications have been sent at 300 baud The module will not respond to any further communications at 300 baud because it is now running at 9600 baud At this point the host computer or terminal must be set to 9600 baud to continue operation 5 5 If the module does not respond to the new baud rate most likely the setup data is incorrect Try various baud rates from the host until the module responds The last resort is to set the module to Default Mode where the baud rate is always 300 Setting a string of RS 232C modules to a new baud rate requires special consideration Refer to the Communications section for instructions Bits 3 and 4 These two bits of byte 2 are not used by the M1000 series and should be set to 9 Table 5 2 Byte 2 Linefeed Parity and Baud Rate BYTE2 FUNCTION DATA BIT 7 6 5 43210 LINEFEED NO LINEFEED NO PARITY NO PARITY EVEN PARITY ODD PARITY NOT USED 38400 BAUD 19200 BAUD 9600 BAUD 4800
26. by the pressure sensor does not have to be known to program the M2131 However it is wise to record the voltages produced by the sensor at each breakpoint With this information replacement M2131 s may be programmed with a voltage source to avoid repeating the tank filling exercise MetraByte M2000 Programming Manual 5 11 Example N 4 Program a M2141 10 V input module to calculate the square root of the input signal from 0 to 10 V We ll keep the units in terms of millivolts so that the square root of 10 000 millivolts 10 V is 100 To keep things simple for this example we will create a function with nine breakpoints at even 1 V intervals 1 Construct the function table Analog input Data Output Minimum OV 00000 00 Maximum 10V 00100 00 Breakpoint 00 1 00031 62 Breakpoint 01 2V 00044 72 Breakpoint 02 00054 77 Breakpoint 03 4V 00063 25 Breakpoint 04 5V 00070 71 Breakpoint 05 6V 00077 46 Breakpoint 06 7 00083 67 Breakpoint 07 BV 00089 44 Breakpoint 08 9v 00094 87 2 Erase breakpoints Command 1EB Response 3 Clear zero Command 1CZ Response 4 Display all digits Command 150310701 2 typical Response 5 Program minimum by applying 0 V short to input Command 1MN 00000 00 Response 5 12 MetraByte M2000 Programming Manual 6 Program maximum by applying exactly 10 volts to the input Command 1MX 00100 00 Response 7 Program breakpoints Apply 1 volt to the input
27. commands and a sample format for each command is listed in Table 4 1 Command Structure Each command message from the host must begin with a command prompt character to signal to the modules that a command message is to follow There are two valid prompt characters a dollar sign character is used to generate a short response message from the module A short response is the minimum amount of data necessary to complete the command The second prompt character is the pound sign character which generates long responses the long response format will be covered a little later The prompt character must be followed by a single address character identifying the module to which the command is directed Each module attached to a common communications port must be setup with its own unique address so that commands may be directed to the proper unit Module addresses are assigned by the user with the SetUp SU command For best results use printable ASCII characters such as 1 ASCII 31 or A ASCII 41 are the best choices for address characters The address character is followed by a two character command which identifies the function to be performed by the module All of the available commands are listed in Table 4 1 along with a shert function definition All commands are described in full later in this section Commands must be transmitted as upper case characters A two character checksum may be appended to any command message as a
28. cools to 95 C the LO alarm is again turned on and the control process repeats indefinitely The control signals are shown in Figure 6 6 6 7 Ys 49 04 40 J8j 04 u0 7 adug Amjua uo 00 S6000 IH rejuauJ0 00 65000 z 1H Dun 211 00 S01 004 07 Ayaw OO 700100 91 440 NO 056 LA AR A ARAL A AN 9 modes 9901 anya dws SUMO JIABM 1 D JJO UO 21441 9 9 5582044 M 6 8 In this case the high alarm was set to momentary mode The high alarm could have been set to the latching mode without affecting the LO alarm output However the output at the HI alarm terminal would change If the high alarm is set to Latching the alarm output is simply the complement of the LO alarm Either alarm output may be used for control depending on which one will result in negative feedback For example in a refrigeration system the HI output may be used to control the refrigeration compressor and the low alarm value is used only to set the desired hysteresis value SETPOINT In the preceding example the low and high alarm limits are used to specify a hysteresis value around a desired setpoint To change the desired setpoint both the low and high alarm values must be changed In this type of controller operation the Read Data RD or New Data commands will read out the actual value of the process variable The M1000 modules provide a means of downloadin
29. is very useful in on off controllers as described in the digital section of this manual The value stored in the offset register may be read back using the Read Zero RZ command Data loaded in with the SP command will be read back with the sign changed The output register may be reset to zero with the Clear Zero CZ command The output data may be read with the Read Data RD command some cases when a computer is used as a host it may be possible to read back the same data value several times before it is updated with a new A D conversion To guarantee that the same data is not read more than once the New Data ND command may be used Each time an RD or ND command is performed the New Data Flag is cleared The flag is set each time the output data register is loaded as the result of a new A D conversion The ND command will wait until the flag is set before it outputs the data reading The remainder of Figure 2 1 depicts several functions known collectively as the Digital section It consist of a versatile alarm function an event counter and general purpose digital inputs and outputs These functions are described in detail in the Digital I O section The heart of the alarm section consists of two registers that are used to store high and low alarm limit values These registers may be down loaded with data values by using the and LO alarm commands The alarm values are loaded with the same data format that is used wi
30. never initiate a communications sequence simple command response protocol must be strictly observed to avoid communications collisions and data errors Communications to the M1000 modules is performed with two character ASCII command codes such as RD to Read Data from the analog input A complete description of all commands is given in the Command Set section typical command response sequence would look like this Command 1RD Response 00123 00 A command response sequence is not complete until a valid response is received The host may not initiate a new command until the response from a previous command is complete Failure to observe this rule will result in communications collisions A valid response can be in one of three forms 1 a normal response indicated by a prompt 2 an error message indicated by a prompt 3 a communications time out error When a module receives a valid command it must interpret the command perform the desired function and then communicate the response back to the host Each command has an associated delay time in which the module is busy calculating the response If the host does not receive a response in an appropriate amount of time specified in Table 3 1 a communications time out error has occurred the communications time out it is assumed that response data is forthcoming This error usually results when an improper command prompt or address is transmitted The fo
31. random Breakpoints must be entered in sequence starting at the minimum value and progress in ever increasing values of the X variable To obtain better conformity a new function table must be started from the beginning Therefore to avoid needless trial and error it is best to test the breakpoint table on paper to determine if the conformity error is acceptable Another approach is to simply use all 23 breakpoints available for the best conformity For this example we may improve the conformity error by using nine breakpoints Input Output Minimum o V 00000 00 1 00200 00 Breakpoint 00 082 V 00020 00 Breakpoint 01 168 V 00040 00 Breakpoint 02 258 V 00060 00 Breakpoint 03 352 V 00080 00 Breakpoint 04 45 V 00100 00 Breakpoint 05 552 V 00120 00 Breakpoint 06 658 V 001 40 00 Breakpoint 07 768 V 00160 00 Breakpoint 08 882 V 400180 00 MetraByte M2000 Programming Manual 5 9 Example N 3 In many cases the system transfer function may not be known In these situations a M2000 may be programmed empirically using test inputs derived by the sysiem itself A standpipe in a municipal water system has an irregular shape as shown in Figure 14 It is desirable to obtain a direct reading of the volume of water contained in the standpipe Because of the shape a simple water height measurement would give grossly inaccurate readings of volume Also the actual relationship of volume to height is complex and unkno
32. repairs of products Only properly trained ser vice personnel may perform installation and service procedures Keithley products are designed for use with electrical signals that are rated Installation Category I and Installation Category II as de scribed in the International Electrotechnical Commission IEC Standard IEC 60664 Most measurement control and data I O sig nals are Installation Category I and must not be directly connected to mains voltage or to voltage sources with high transient over volt ages Installation Category II connections require protection for high transient over voltages often associated with local AC mains connections Assume all measurement control and data I O con nections are for connection to Category I sources unless otherwise marked or described in the Manual Exercise extreme caution when a shock hazard is present Lethal voltage may be present on cable connector jacks or test fixtures The American National Standards Institute ANST states that a shock hazard exists when voltage levels greater than 30V RMS 42 4V peak or 60VDC are present A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring Operators of this product must be protected from electric shock at all times The responsible body must ensure that operators are pre vented access and or insulated from every connection point In some cases connections must be exposed to potential huma
33. resistance in the GND lead to be within the 5V common mode condition is 66 7 ohms For 20 gauge wire this results in a maximum bus length of 6670 feet for a single module These calculations can be reduced to a general rule of thumb by taking the number of modules on the bus and multiplying it by the bus length in feet The resultant number must be less than the number given in the following Table Wire Gauge Maximum modules X feet 22 4000 20 6000 18 10000 Communications Delay All M1000 modules with RS 485 outputs are setup at the factory to provide two units of communications delay after a command has been received see Setup section This delay is necessary when using host computers that transmit a carriage return as a carriage return linefeed string Without the delay the linefeed character may collide with the first transmitted character from the module resulting in garbled data If the host computer transmits a carriage return as a single character the delay may be set to zero to improve communications response time 3 8 4 COMMAND SET The M1000 modules operate with a simple command response protocol to control all module functions A command must be transmitted to the module by the host computer or terminal before the module will respond with useful data A module can never initiate a communications sequence A variety of com mands exists to exploit the full functionality of the modules A list of available
34. the dumb terminal will be echoed by the daisy chain To avoid double characters when typing commands set ihe terminal to full duplex mode or turn off the local echo The daisy chain will provide the input command echo RS 485 RS 485 is a recently developed communications standard to satisfy the need for multidropped systems that can communicate at high data rates over long distances RS 485 is similar to RS 422 in that it uses a balanced differential pair of wires switching from 0 to 5 volts to communicate data RS 485 receivers can handle common mode voltages from 7V to 12V without loss of data making them ideal for transmission over great distances RS 485 differs from RS 422 by using one balanced pair of wires for both transmitting and receiving Since an RS 485 system cannot transmit and receive at the same time it is inherently a half duplex system RS 485 offers many advantages over RS 232C 1 balanced line gives excellent noise immunity 2 can be used to to communicate with M1000 modules at 38400 baud 3 communications distances up to 10 000 feet 4 true multidrop modules are connected in parallel 5 modules can be disconnected without breaking communications 6 up to 32 modules on one line 124 with repeaters 7 no communications delay due to multiple modules 8 simplified wiring using standard telephone cable Of course RS 485 does have its disadvantages Very few computers or terminals have built in support for this ne
35. the external trim CA After the external trim has been performed check the offset Command 1RD Response 00022 22 This value is within the 30 mV offset necessary to provide enough headroom for the strain gage bridge The remaining offset may be trimmed out with the Trim Zero TZ command Command 1WE Response Command 1TZ 00000 00 Response The bridge is now trimmed to zero Verify Command 1RD Response 00000 00 The Trim Zero TZ command may be used at any time to balance out offsets due to temperature residual stress tare etc Excitation M1500 modules may be ordered with either 5 V or 10 V excitation Maximum excitation current available is 60 mA Modules with 10 V excitation may be used with bridges that have input impedances of 166 ohms or greater Half bridges of 120 strain gages may be used with 10 V excitation if the bridge is completed with 350 resistors Modules with 5 V excitation will source bridges of 85 and up The actual excitation voltage may vary 0 5 V from the nominal values of 10 V and 5 V However the module s internal microprocessor constantly monitors the actual excitation voltage and provides compensation for any deviation from the nominal value This results in a constant data output for a constant bridge load even if the excitation changes From a user s point of view the excitation voltage will appear to be exactly 10 V or 5 V C 5 CALI
36. which has no meaningful data In some cases the user may want to limit the output resolution to 1 degree To do this select bits 6 and 7 to display 5 digits With this selection the rightmost two digits will always be set to O The number of displayed digits affects only data received from an RD or ND command Large Signal Filter Bits 3 4 5 Small Signal Filter Bits 0 1 2 The M1000 series modules contain a versatile single pole low pass digital filter to smooth out unwanted noise caused by interference or small signal variations The digital filter offers many advantages over traditional analog filters The filtering action is done completely in firmware and is not affected by component drifts offsets and circuit noise typically found in analog filters The filter time constant is programmable through the SetUp SU command and can be changed at any time even if the module is remote from the host The digital filter features separate time constants for large and small signal variations The Large Signal Filter time constant is controlled by bits 3 4 5 This time constant is used when large signal variations are present on the input The 5 10 Small Signal Filter time constant is controlled by bits 0 1 2 This filter time constant is automatically selected when input signal variations are small The microprocessor in the MetraByte module automatically selects the correct filter constant after every A D conversion The constant select
37. with components of a level of reliability suitable for use in life support or critical applications Disclaimer Information furnished by Keithley MetraByte is believed to be accurate and reliable However the Keithley MetraByte Corporation assumes no responsibility for the use of such information nor for any infringements of patents or other rights of third parties that may result from its use No license is granted by implication or otherwise under any patent rights of Keithley MetraByte Corporation Notes Keithley MetraByte Asyst DAC is also referred to here in as Keithley MetraByte Basic a trademark of Dartmouth College IBM is a registered trademark of International Business Machines Corporation PC XT AT PS 2 and Micro Channel Architecture MCA are trademarks of International Business Machines Corporation Microsoft is a registered trademark of Microsoft Corporation Turbo C is a registered trademark of Borland International 10 New Contact Information Keithley Instruments Inc 28775 Aurora Road Cleveland OH 44139 Technical Support 1 888 KEITHLEY Monday Friday 8 00 a m to 5 00 p m EST Fax 440 248 6168 Visit our website at http www keithley com Safety Precautions The following safety precautions should be observed before using this product and any associated instrumentation Although some in struments and accessories would normally be used with non haz ardous vol
38. 000 Programming Manual number 03 is being specified Breakpoint numbers are expressed in two digit hexadecimal notation ranging from OO to 16 for a total of 23 decimal points During a normal programming operation breakpoints are entered in sequence in progessively increasing X values starting from the minimum value see Minimum MN command Breakpoint programming must start with Breakpoint 007 Itis not necessary to specify all the breakpoints any number up to 23 may be used However a breakpoint sequence must start at 00 and be entered sequentially Any remaining breakpoints may be left unspecified Following the breakpoint number the output Y axis data must be specified The data must be in standard M1000 format sign five digits decimal point 2 digits The output data specifies the module s output response for the test stimulus applied to the modute input Before setting the breakpoints with the BreakPoint BP Command the overall function span must be specified by the MiNimum MN and MaXimum MX commands See Chapter 5 for programming instructions Erase Breakpoints EB The EB command erases all previously entered breakpoints from the module s EEPROM Erased data cannot be recovered Therefore before using the EB command be prepared to re program all of the breakpoints in the unit The EB command is used to provide a clean slate before entering abreakpoint sequence Previous end point data entered by th
39. 000 model number Most sensor modules contain two digital outputs and the M1701 2 has eight digital outputs open collector configuration is used to provide maximum versatility in interfacing to solid state relays SSR s or to standard logic levels such as TTL or CMOS Each digital output can sink up to 30mA and can withstand up to 30V Power in the transistor must be limited to 300 mW The emitter of each transistor is tied to the GND terminal on the input connector R1 amp R2 Limit Current to 30mAMax Figure 6 1 Digital Outputs Used With Relays A typical connection of a digital output is shown in Figure 6 1 In this case a solid state relay is controlled by the M1000 module The SSR can then be used to control AC power to alarms heaters pumps etc A typical connection to a logic input is shown in Figure 6 2 In some cases the common mode voltage of the GND terminal may be significantly different from the ground potential of the logic input to be interfaced This may occur when the module is powered remotely In this case an opto isolator may be used to eliminate the common mode voltage See Figure 6 2 all cases the current switched by the transistor may not be more than 30 mA Limit current ta 30m Max Figure 6 2 Digital Outputs Used with Logic Only three commands can effect the Digital Output The Enable Alarms EA and Disable Alarms DA commands select the function of the DO LO and DO1 HI pin outpu
40. 04990 00 During the verification process we find that the module exhibits some errors This is due to the 1 typical error inherent in the analog to digital converter The nonlinearity may be corrected by using breakpoints In this case instead of using the breakpoints to create a nonlinear function they will be used to straighten the nonlinearity of the ADC Only a few breakpoints 5 14 MetraByte M2000 Programming Manual are necessary to reduce the linearity error to 02 or less In this case we will use three breakpoints to linearize the module Minimum Maximum Breakpoint 00 Breakpoint 01 Breakpoint 02 Analog Input 10V 4 10V 5V 0 45V Data Output 10000 00 10000 00 05000 00 00000 00 05000 00 Since the minimum and maximum data have already been programmed only Step 7 is necessary to program in the breakpoints After the breakpoints have been entered verify the module transfer function Analog Input 7 5 0 7 5 V Data Output 07502 00 00000 00 07498 00 This time the module output is in eror by 02 or less due to linearizing effect of the breakpoints Example N 6 2141 module may be programmed to create an absolute value function as shown in Figure 15 However this function violates the rectangular area rule To overcome this limitation the function may be re drawn as shown in Figure 16 This curve satisfies the rectangular area rule The funct
41. 34 Unit 2 Commerce Park Brunel Road Theale Berkshire RG7 4AB 0118 929 7500 Fax 0118 929 7519 Flat 2B Willocrissa 14 Rest House Crescent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 Viale San Gimignano 38 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 New Pier Takeshiba North Tower 13F 11 1 Kaigan 1 Minato ku Tokyo 105 0022 81 3 5733 7555 Fax 81 3 5733 7556 2FL URI Building 2 14 Yangjae Dong Seocho Gu Seoul 137 888 82 2 574 7778 Fax 82 2 574 7838 Postbus 559 4200 AN Gorinchem 0183 635333 Fax 0183 630821 c o Regus Business Centre Frosundaviks All 15 4tr 169 70 Solna 08 509 04 679 Fax 08 655 26 10 Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 1FL 85 Po Ai Street Hsinchu Taiwan R O C 886 3 572 9077 Fax 886 3 572 9031 Copyright 2001 Keithley Instruments Inc Printed in the U S A 4 02
42. 7 M1000 User Commands Note that in all command and response examples given below a carriage return is implied after every character string Clear Alarms CA The clear alarms command turns both the HI and LO alarms OFF This com mand does not affect the enable disable or momentary latching alarm con ditions The alarms will continue to be compared to the input data after the CA command is given In cases where the alarm condition persists the alarms will be set at the end of the next input data conversion The primary purpose of the CA command is to clear latching alarms See the Alarms section for more information Command 1CA Response Command 1CA Response 1CADF Clear Events CE The Clear Events command clears the events counter to 0000000 Command 1CE Response Command 1 Response 1CEE3 Note When the events counter reaches 9999999 it stops counting A CE com mand must be sent to resume counting Clear Zero CZ The Clear Zero command clears the output offset register value to 00000 00 This command clears any data resulting from a Trim Zero TZ or SetPoint SP command Command 1CZ Response Command 1 2 Response 1CZF8 Disable Alarms DA Most models in the M1000 series feature LO DOO and HI DO1 pins on the module connector These pins serve a dual function and can be used to output either the alarm outputs or digital outputs 0 and 1 The Disable Alarms command i
43. Alarm EA command is used The connector pins may be switched back to the general purpose digital outputs using the Disable Alarms DA command The EA DA selection is nonvolatile The general purpose digital outputs are open collecior transistor switches that may be controlled by the host with the Digital Output DO command They are designed to activate external solid state relays to control AC or DC power circuits The output may also be used to interface to other logic level devices The number of digital outputs available depends on the module type with eight being the maximum The Digital Input DI command is used to sense the logic levels on the digital input pins DIO DI7 The digital inputs are used to read logic levels generated by other devices They are also useful to sense the state of electro mechanical limit switches The number of digital inputs varies with the modute type The DIO input is shared with the input to the Event Counter The Event Counter is used to accumulate the number of positive transitions that have occurred on the DIO EV connector pin The counter can accumulate up to 9999999 decimal events and may be read with the Read Events RE command The counter input is filtered and uses a Schmitt trigger input to provide a bounce free input for mechanical switches The counter value may be zeroed with the Clear Events CE command H31Nn03 iMana Way 071 2 32 40108 310N 9v 14
44. Alarms DA command is used to configure these pins as digital outputs Digital output settings are not stored in nonvolatile memory If a power failure occurs all digital outputs will be set to 0 upon power up The DO command is the only means of changing digital outputs There is no software provision to read the state of the digital outputs 4 10 Enable Alarms EA Digital outputs DOO LO and DO1 HI serve a dual purpose as digital outputs and alarms Digital output 0 is shared with the LO alarm and digital output 1 is shared with the HI alarm The Enable Alarms EA command configures the shared outputs to indicate alarm conditions and disconnects digital outputs 0 and 1 The EA command only affects the electrical output of the alarms to the pins The alarm status can be read at any time with the Digital Input DI command The complement to the EA command is the Disable Alarms DA command Command 1EA Hesponse Command 1 Response 1EAE1 High Alarm Limit HI The high alarm command sets the value and type of the high alarm The data specified by the HI command is stored in nonvolatile memory and compared with the sensor data after every A D conversion The high alarm is activated if the input data is greater than the value stored by the HI command The high alarm status may be read using the Digital Input DI command The alarm may be used to activate a digital output by using the Enable Alarms EA command
45. BAUD 2400 BAUD 1200 BAUD 600 BAUD 300 BAUD O ok wh O 5 6 Byte 3 This byte contains the setup information for several seldom used options The default value for this byte is 01 Alarm Enable Bit 7 determines if the outputs from the LO and alarms are connected to module terminal block If the value is 0 the alarms are not connected to the terminal block this condition the outputs are controlled by the Digital Output DO command If bit 7 is 1 the alarms are connected to the terminal block This bit is also controlled by the Enable Alarms EA command which sets the bit to 1 The Disable Alarms DA command clears the bit to 0 Low Alarm Latch Bit 6 determines whether the LO Alarm is latching or momentary A 1 indicates that the alarm is latching 0 indicates a momentary alarm Bit 6 is also controlled by the LO Alarm LO command High Alarm Latch Bit 5 determines whether the HI Alarm is latching or momentary 1 indicates latching Bit 5 is also controlled individually by the HI Alarm HI command Disable CJC RTD 3 4 Wire Trigger Edge Select The setup information stored in bit 4 has different meanings depending on the M1000 model number Disable CJC this functions pertains only to the M1300 series of thermocouple input modules If the bit is set to 1 the Cold Junction Compensation is disabled module calculates the tempe
46. BRATION Since the M1500 modules use a ratiometric technique to compensate for variances in the excitation voltage special consideration is required to properly calibrate the unit Figure 3 shows the calibration setup The Digital Voltmeter DVM must be capable of measuring the excitation voltage to 4 digit accuracy The voltage source must be able to provide millivolt signals accurate to 5 microvolts The resistive divider may be constructed from 1 resistors of equal value from 100 to 1000 The resistor divider places the voltage source in the center of the common mode range of the input amplifier for best accuracy Yoltage Source e e e e e e Figure 3 M1500 Calibration Step 1 power up the unit under test and let it warm up for at least two minutes Step 2 set the voltage source to 0 volts short Perform a TZ 00000 00 Trim Zero command to eliminate any common mode offset errors Step 3 measure the excitation voltage with the DVM Divide the result by the nominal excitation voltage either 10 V or 5 V to obtain compensation factor CF Step 4 calculate the correct calibration voltage to apply to the unit For 30 mV units the voltage is V 50 mV X CF For 100 mV units the voltage is V 100 mV X CF Set the voltage source to the calculated voltage V Step 5 trim the unit with the Trim Span TS command C 6 30 mV modules the command is 1TS 00050 00 For 100 mV modules t
47. ECT TO THE OTHER HARDWARE AND OTHER SOFTWARE Limitation of Liability KEITHLEY INSTRUMENTS SHALL IN NO EVENT REGARDLESS OF CAUSE ASSUME RESPONSIBILITY FOR OR BE LIABLE FOR 1 ECONOMICAL INCIDENTAL CONSEQUENTIAL INDIRECT SPECIAL PUNITIVE OR EXEMPLARY DAMAGES WHETHER CLAIMED UNDER CONTRACT TORT OR ANY OTHER LEGAL THEORY 2 LOSS OF OR DAMAGE TO THE CUSTOMER S DATA OR PROGRAM MING OR 3 PENALTIES OR PENALTY CLAUSES OF ANY DESCRIPTION OR INDEMNIFICATION OF THE CUSTOMER OR OTHERS FOR COSTS DAMAGES OR EXPENSES RELATED TO THE GOODS OR SERVICES PROVIDED UNDER THIS WARRANTY KEITHLEY Keithley Instruments Inc 28775 Aurora Road Cleveland Ohio 44139 440 248 0400 Fax 440 248 6168 1 888 KEITHLEY 534 8453 www keithley com Sales Offices BELGIUM Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 CHINA Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 8610 6202 2886 Fax 8610 6202 2892 FINLAND Tiet j ntie 2 02130 Espoo Phone 09 54 75 08 10 Fax 09 25 10 51 00 FRANCE 3 all e des Garays 91127 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 GERMANY Landsberger Strasse 65 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 GREAT BRITAIN Unit 2 Commerce Park Brunel Road Theale Berkshire RG7 0118 929 7500 Fax 0118 929 7519 INDIA Flat 2B Willocrissa 14 Rest House Crescent Bangalor
48. FUNCTION DATA BIT ee eae Mamor TALARMSON 1 HGHALARMWOMENTARY o _ THIGH ALARMLATCHNG Tow ALARM MOMENTARY 9 estos oo awae oaos STARTING EDGE 01909 o C STARTING EDGE D16008 1 esws 9 Fannen moemoe 9 DELAYS 2 BYTE TIME DELAYS 5 9 Byte 4 This setup byte specifies the number of displayed digits and the digital filter time constants Number of displayed digits For ease of use the data outputs of all M1000 modules are standardized to a common 7 digit output consisting of sign 5 digits decimal point and two more digits Typical output data looks like 00100 00 However best case resolu tion of the A D converter is 1 part in 50 000 or about 4 1 2 digits In some cases the resolution of the output format is much greater than the resolution of the measurement system In such cases the trailing digits of the response would display meaningless information Bits 6 and 7 are used to insert trailing zeros into the output data to limit the output resolution and mask otf meaningless digits Bit7 0 0 XXXX0 00 4 displayed digits 0 1 XXXXX 00 5 displayed digits 1 0 XXXXX XO 6 displayed digits 1 1 XXXXX XX 7 displayed digits For example the M1411 model for RTD s has 1 degree output resolution The appropriate number of digits for this module is 6 to mask off the 01 digit
49. KEITHLEY M1000 M2000 User Guide A 07 ONFIDENCE WARRANTY Hardware Keithley Instruments Inc warrants that for a period of one 1 year from the date of shipment 3 years for Models 2000 2001 2002 2010 and 2700 the Keithley Hardware product will be free from defects in materials or workmanship This warranty will be honored provided the defect has not been caused by use of the Keithley Hardware not in accordance with the instructions for the product This warranty shall be null and void upon 1 any modification of Keithley Hardware that is made by other than Keithley and not approved in writing by Keithley or 2 operation of the Keithley Hardware outside of the environmental specifications therefore Upon receiving notification of a defect in the Keithley Hardware during the warranty period Keithley will at its option either repair or replace such Keithley Hard ware During the first ninety days of the warranty period Keithley will at its option supply the necessary on site labor to return the product to the condition prior to the notification of a defect Failure to notify Keithley of a defect during the warranty shall relieve Keithley of its obligations and liabilities under this warranty Other Hardware The portion of the product that is not manufactured by Keithley Other Hardware shall not be covered by this warranty and Keithley shall have no duty of obligation to enforce any manufacturers
50. Program the endpoint with the MiNimum command Command 1 WE Response Command 1 00000 00 Response 5 Apply exactly 20 mAto the module input and store the maximum endpoint with the MaXimum MX command Command 1 WE Hesponse Command 1 00100 00 Response 4 6 MetraByte M2000 Programming Manual 6 Verify the module response by testing it with various inputs within its range Input Current Output Data 8 mA 00025 00 12 00050 00 16 mA 00075 00 Rescaling is now complete Example L 2 A paddle wheel flow sensor will be used to monitor the flow of water in a pipe characteristics of the sensor and the size of the pipe results in an output frequency of 10 Hz per gallon per minute The operating range is from 1 to 20 gallons per minute We would like to scale a M2000 module to output data in units of 1 gatlons The logical module choice in this application is the M2601 frequency input module The frequency output of the flow sensor will range from 10 Hz to 200 Hz easily within the 5 Hz to 20 kHz range of the M2601 1 Erase Breakpoints Command 1WE Response Command 1EB Response 2 Clear Zero Command 1WE Response Command 1CZ Response 3 The minimum endpoint in this case is 10 Hz corresponding to an output of 00001 00 gpm The maximum frequency at 20 gpm is 200 Hz The maximum output data is 00020 00 To get 1 gpm resolution set up the
51. a 0011 0001 31 hex The SU command is write protected to guard against erroneous changes in the setup data therefore each SU command must be preceded by a Write Enable WE command To abort an SU command in progress simply send a non hex character an X for example to generate a SYNTAX ERROR and try again caution Care must be exercised in using the SU command improper use may result in changing communications parameters address baud rate parity which will result in a loss of communications between the host and the module In some cases the user may have to resort to using Default Mode to restore the proper setups The recommended procedure is to first use the Read Setup RS command to to examine the existing setup data before proceeding with the SU command Byte 1 Byte 1 contains the module channel address The address is stored as the ASCII code for the string character used to address the module In our example command 1SU31070080 the first byte 31 is the ASCII code for the character 1 If our sample command is sent to module the EEPROM will be loaded with the address 1 which in this particular case remains unchanged change the module address to 2 byte 1 of the SetUp command becomes 32 which is the ASCII code for the character 2 Now the command will look like this 1SU32070080 When this command is sent the module address is changed from 1 to 2 The module will no longer respond to address
52. a dual function is both a digital input and the Event Counter input When reading digital inputs with a checksum be sure not to confuse the checksum with the data Digital Output DO The DO command controls eight bits of digital outputs on the module connector The number of digital outputs implemented depends on the model used The digital outputs allow the module to control external circuits under host command The DO command requires an argument of two hex characters specifying the eight bits of output data Digital DO7 D 004 D DQ1 D Data Bits 7 6 5 4 3 2 1 0 The electrical implementation of the digital output consists of open collector transistors wired to the module connector If a digital output is set to 1 the corresponding transistor is turned on and sinks current Note that when a digital output bit is set to 1 the electrical output is near 0 volts If a digital output is set to 0 the corresponding transistor is turned off and sinks no current Assume a module has two digital outputs and you wish to turn both outputs on sinking current Set data bit 0 and data bit 1 to 1 Since the module has only two digital outputs the other bits are don t cares For example this command will turn both outputs Command 1DOFF Response To turn both outputs off you could use the command Command 10000 Response Digital outputs 0 and 1 share connector pins with the and LO alarms The Disable
53. ad an illegal address into a module with the SetUp SU command An attempt to load an address greater than 7F will also produce an error BAD CHECKSUM This error is caused by an incorrect checksum included in the command string The module recognizes any two hex characters appended to a command string as a checksum Usually a BAD CHECKSUM error occurs due to noise or interference on the communications line many cases repeating the command will solve the problem If the error persists either the checksum is being calculated incorrectly or 4 20 there is a problem with the communications channel In some cases more reliable transmissions may be obtained by using a lower baud rate COMMAND ERROR This error occurs when the two character command is not recognized by the module Often this error results when the command is sent with lower case letters All valid commands are upper case NOT READY If a module is reset it performs a self calibration routine which takes 2 3 seconds to complete Any commands sent to the module during the self calibration pericd will result ina NOT READY error When this occurs simply wait a couple seconds and repeat the command The module may be reset in four ways a power up reset a Remote Reset RR command a line break or an internal reset All modules contain watchdog timer to ensure proper operation of the microprocessor The timer may be tripped if the microprocessor is executin
54. again using the Setpoint command The desired oven temperature is 100 C This time we ll use the SP command to load the 100 C value into the temperature module As before we would like a hysteresis band of 5 from the nominal temperature of 100 C In this case set the low limit to 00005 00 latching and the high limit to 00005 00 The high and low limits are now used solely to define the hysteresis band If the oven temperature is low say 90 C the resulting deviation from the setpoint of 100 C is 10 C This value exceeds the low limit and the LO alarm control output is 6 9 turned to activate the heater The latched LO alarm will stay on until the measured temperature exceeds 105 C At this point the deviation from the setpoint is greater than 5 C the value loaded into the high limit When the high limit is exceeded the latched LO alarm output is turned off turning off the heater The control action is identical to the controller described in Figure 6 6 The benefit of using SP command is that only one command is necessary to change the setpoint value The hysteresis is stored in the HI and LO alarm registers and does not have to be changed when a new setpoint is used The SP command makes it particularly easy to construct a controller whose setpoint is a time varying function downloaded from a host computer The SP command can also be used without control functions whenever a deviation output is desired The setpoint valu
55. alarm will be activated only on an overload condition The low limit value may be read back with the Read Low Limit RL command More information on alarms may be found in the Digital I O section New Data Command ND The New Data ND command is a variation of the Read Data RD command used to read sensor data from the module The ND command guarantees that the output data has not been previously read The M1000 module acquires analog input data eight times a second and stores the result in the output buffer see Figure 2 1 The Read Data RD command simply reads the results stored in the output buffer A fast host communicating at a high baud rate could possibly read the output buffer several times before the information is updated with a new A D conversion This results in redundant information which may be confusing or may be a waste of host processor time Associated with the output buffer is the New Data Flag see Figure 2 1 This flag is cleared each time an RD or ND command is performed The flag is set when the module s microprocessor loads the output buffer with the result of the most recent A D conversion The ND command will output data only when the New Data Flag is set If the flag is cleared when an ND command is received the module will wait until new data is present in the output buffer before responding to the command Thus the output data obtained with an ND command is always the result of a new A D conversion 4 12
56. ansfer function is the easiest and most common way to reprogram the module The linear scale function is defined by specifying the two endpoints of the linear function as shown in Figure 7 Any linear function within the analog input range of the module may be defined Custom scaling requires a calibrated analog input signal to define the end points of the linear transfer function The signal could be a voltage current or frequency depending on the specific model type The MiNimum and MaXimum commands are used to program the end point data into the modules s memory Programming procedures 1 Make sure the module has not been previously programmed with Break Point BP Commands If it has clear the breakpoints with the Erase Breakpoints EB command 2 Clear any data in the output offset register with the Clear Zero CZ command 3 Determine the endpoints which will be used to define the linear function The analog input values must lie within the operating range of the module The analog inputs used to determine the endpoints will also define the overload outputs of the module Construct an output data format that is best suited for your application 4 Apply acalibrated analog signalto the module input corresponding to the most negative input ofthe desired linear scale Perform a Minimum MN command to store the function endpoint into the modules s memory 5 Apply a calibrated analog signal to the module input corresponding to the m
57. anual The SU data may vary depending on your particular module setup See the Setup section in the M1000 manual 5 Apply 0 volts short to the input of the M2131 to enter the minimum point of 100 psi Command 1MN 00100 00 Response 6 To set the maximum point apply 5 V to the input and program the maximum point to be 600 psi Command 1MX 00600 00 Response 7 Program the first breakpoint Apply 1 volt to the input and perform the BreakPoint command Command 1BP00 00184 00 Response Verify the breakpoint data Command 1 Response 00184 00 Repeat the procedure for the remaining breakpoints Apply 2 volts to the input Command 1BP01 00276 00 Response Command 1 Response 00276 00 Apply 3 volts to the input Command 1BP02 00376 00 Response MetraByte M2000 Programming Manual 5 7 Command 1 Response 00376 00 Apply 4 volts to the input Command 1BP03 00484 00 Response Command 1 Response 00484 00 The function programming is now compiete 8 The transfer function may be verified by applying test inputs to the module and obtaining output data The data can then be compared to the original quadratic equation to check for conformity error Example Apply 5 volts to the M2131 input and read data Command 1 Response 00142 00 To check plug 5 volts into the quadratic equation 100 80 5 4 5 141 conformity error at thi
58. at write data into nonvolatile memory are write protected to prevent accidental erasures These commands must be preceded with a Write Enable WE command or else a WRITE PROTECTED error will result 4 22 CHAPTER 5 SETUP INFORMATION amp COMMAND The MetraByte M1000 modules feature a wide choice of user configurable options which gives them the flexibility to operate on virtually any computer or terminal based system The user options include a choice of baud rate parity address and many other parameters particular choice of options for module is referred to as the setup information The setup information is loaded into the module using the SetUp SU command The SU command stores 4 bytes 32 bits of setup information into a nonvolatile memory contained in the MetraByte module Once the information is stored the module can be powered down indefinitely 10 years minimum without losing the setup data The nonvolatile memory is implemented with EEPROM so there are no batteries to replace The EEPROM has many advantages over DIP switches or jumpers normally used for option selection The module never has to be opened because all of the options are selected through the communications port This allows the setup to be changed at any time even though the module may be located thousands of feet away from the host computer or terminal The setup information stored in a module may be read back at any time using the Read Setup com
59. ched Command 1RD Read Data Response 00002 34 The initial offset is 2 34 mV The M1521 has a useful input range of 60 mV After subtracting the offset the input overhead is 62 34 mV and 57 66 mV C3 expected 0 to 30 mV output of the load cell easily falls within the overhead range and no external trimming is necessary To Trim Zero Command 1WE TZ is write protected Response Command 1TZ 00000 00 zero is the desired output Response Now read the data output to verify the trim Command 1RD Read Data Response 00000 00 The load cell system has been trimmed to zero Example 2 A strain gage bridge will be used to measure both compression and tensile strains on a structural member The bridge is attached to a M1521 module and the ideal output from the bridge is 30 mV full scale Clear the Zero Trim Command 1WE Response Command 1CZ Clear Zero Response Measure the initial offset from the bridge Command 1RD Response 00043 21 In this case the bridge exhibits a large initial offset of 43 21mV Subtract this value from the 60 mV useful range of the M1521 to obtain and input overhead value of 16 79 mV to 103 21 mV this case the 16 79 mV overhead is not large enough to cover the 30 mV that may be obtained from the bridge The bridge must be trimmed externally to bring the offset to within 30 It is not necessary to obtain an exact zero with
60. curate check can be made by filling the tank with known amounts of water and verifying the output readings Example L 4 A M2251 4 20 mA module will be used to provide a computer interface to an existing process 4 20 mA signal The loop transmitter produces a linear 4 20 mA signal corresponding to a sensor temperature of 0 200 degrees C In this case we d like to take advantage of the factory linearity correction inthe M2251 for greater accuracy To do this we must use the same analog input minimum and maximum points as programmed at the factory The M2251 minimum and maximum points are 0 mA and 25 mA The 4 20 mA span of the process transmitter must be extrapolated to 0 25 mA to provide the correct data when using the MN and MX commands The transfer relationship of the 4 20 mA transmitter can be described by the equation T2 125 X mA 50 Plug values of 0 mA and 25 mA into the equation to derive extrapolated values of T T 50 12 5 X 0 50 T 12 5 X 25 50 262 5 These values will be used in the MN and MX instructions Program the module 1 In this case it is assumed that the M2251 is fresh from the factory it still contains linearity correction in the breakpoint table In order to take advantage of the linearity correction the breakpoints will not be erased 2 Clear zero Command 1WE Response Command 1CZ Response 4 10 MetraByte M2000 Programming Manual 3 The minimum endpoint has bee
61. d the module will respond with a long form response This type of response will echo the command message supply the necessary response data and will add a two character checksum to the end of the message Long form responses are used in cases where the host wishes to verify the command received by the module The checksum is included to verify the integrity of the response data The command prompt may be used with any command For example Command 1RD short form Response 00072 10 Command 1RD long form Response 1RD400072 10A4 A4 checksum Checksum Checksum a two character hexadecimal value added to the end of a message verifies that the message received is exactly the same as the message sent The checksum ensures the integrity of the information communicated Command Checksum two character checksum may be appended to any command to the M1000 module as a user option When a module interprets a command it looks for the two extra characters and assumes that it is checksum If the checksum is not present the module will perform the command normally If the two extra characters are present the module will calculate the checksum for the 4 4 message If the calculated checksum does not agree with the transmitted checksum the module will respond with a BAD CHECKSUM error message and the command will be aborted If the checksums agree the command will be executed If the module receives a single extra c
62. ding in a manual explains dangers that might result in personal injury or death Always read the associated infor mation very carefully before performing the indicated procedure The CAUTION heading in a manual explains hazards that could damage the instrument Such damage may invalidate the warranty Instrumentation and accessories shall not be connected to humans Before performing any maintenance disconnect the line cord and all test cables To maintain protection from electric shock and fire replacement components in mains circuits including the power transformer test leads and input jacks must be purchased from Keithley Instru ments Standard fuses with applicable national safety approvals may be used if the rating and type are the same Other components that are not safety related may be purchased from other suppliers as long as they are equivalent to the original component Note that se lected parts should be purchased only through Keithley Instruments to maintain accuracy and functionality of the product If you are unsure about the applicability of a replacement component call a Keithley Instruments office for information To clean an instrument use a damp cloth or mild water based cleaner Clean the exterior of the instrument only Do not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument Products that consist of a circuit board with no case or chassis e g data acquisitio
63. e 560 001 91 80 509 1320 21 Fax 91 80 509 1322 ITALY Viale San Gimignano 38 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 JAPAN New Pier Takeshiba North Tower 13F 11 1 Kaigan 1 chome Minato ku Tokyo 105 0022 81 3 5733 7555 Fax 81 3 5733 7556 KOREA 2FL URI Building 2 14 Yangjae Dong Seocho Gu Seoul 137 888 82 2 574 7778 Fax 82 2 574 7838 NETHERLANDS Postbus 559 4200 AN Gorinchem 0183 635333 Fax 0183 630821 SWEDEN c o Regus Business Centre Frosundaviks All 15 4tr 169 70 Solna 08 509 04 679 Fax 08 655 26 10 SWITZERLAND Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 TAIWAN 1FL 85 Po Ai Street Hsinchu Taiwan R O C 886 3 572 9077 Fax 886 3 572 9031 4 02 M1000 M2000 User Guide Revision A May 1988 Copyright 9 Keithley MetraByte Corp 1988 Part Number 24744 iii Warranty Information All products manufactured by Keithley MetraByte are warranted against defective materials and worksmanship for a period of one year from the date of delivery to the original purchaser Any product that is found to be defective within the warranty period will at the option of Keithley MetraByte be repaired or replaced This warranty does not apply to products damaged by improper use Warning Keithley MetraByte assumes no liability for damages consequent to the use of this product This product is not designed
64. e MiNimum MN and MaXimum MX commands are not affected Command 1EB Response Command 1 Response 1EBE2 E2 is the checksum MiNimum MN The MiNimum MN command is used to define an endpoint of a transfer function programmed into a M2000 module The minimum endpoint defines the most negative value allowed on the analog input before an overload will occur In effect the minimum value is the starting breakpoint in a programmed transfer function To use the MiNimum MN command a known analog test stimulus must be applied to the analog input of the module The test stimulus must correspond to the most negative value of the desired analog input range The analog input stimulus specifies the starting input value X axis of the transfer function The test input must lie within the specified full scale input range of the module MetraByte M2000 Programming Manual 3 3 The argument of the MN command specifies the starting output value Y axis of the transfer function Command 1MN 00100 00 Response Command 1MN 00100 00 Response 1 00100 00 2 215 the checksum The argument of the MN function must be in standard analog data format MaXimum MX The MaXimum MX command specifies the most positive analog input allowed before an overload indication will occur The MaXimum command also defines the positive end point of a transfer function programmed into the M2000 To perform MaXimum command a
65. e may be read back by using the Read Zero RZ command The RZ simply reads back the contents of the output offset register The RZ command will always read back the setpoint value with the sign changed The setpoint value is stored in the same register as the output offset trim see TZ command n cases where the output offset register is used to hold a calibration trim value the SP command will erase the trim In most cases an offset calibration trim is not necessary and the trim value would read back as 00000 00 using the Read Zero RZ command If the trim is non zero it must be read and stored by the host before the SP command is executed To download setpoint values the host must then subtract the trim value from the desired setpoint to derive the proper data for the SP command To restore the trim use the SP command to download the negative of the trim that was previously read back with the RZ command 6 10 7 POWER SUPPLY MetraByte modules may be powered with an unregulated 10 to 30V dc Power supply ripple must be limited to 5V peak to peak and the instantaneous ripple voltage must be maintained between the 10 and 30 volt limits at all times All power supply specifications are referred to the module connector the effects of line voltage drops must be considered when the module is powered remotely All M1000 modules employ an on board switching regulator to maintain good efficiency over the 10 to 30 volt input
66. ed depends on the magnitude of the change of the input signal and the setup for the number of digits displayed The microprocessor always keeps the value of the last calculated output to compare to a new data conversion If the new data differs from the last output by more than ten counts of the last displayed digit the large signal time constant is used in the digital filter 1f the result of the most recent A D conversion differs from the last output value by less than ten counts the last displayed digit the small signal time constant is used Let s look at an example The M1411 module for RTD s has a standard output resolution of 1 degrees The standard number of displayed digits setup for this module is 6 digits specified by byte 4 of the setup data Therefore the large signal filter will be selected if new input conversion differs from the previous value by more than 1 0 degree Previous data New data Filter selected large small 00100 00 00100 50 small 00100 00 00101 50 large 00100 00 00099 90 small 00100 00 00098 90 large 00050 50 00050 00 small 00050 50 00060 00 small If the number of displayed digits is changed to reduce output resolution the filter selection is also affected If the number of displayed digits in the previous example is changed to 5 the output resolution becomes 1 0 degree n this case the large signal time constant is used if the new reading differs from the old by more than 10 0 de
67. eeds the second alarm value At this point the control output is turned off typical example of a controller with hysteresis is illustrated in Figure 6 5 temperature sensor module such as a M1311 J Thermocouple model maybe used to regulate the temperature of an oven The thermocouple is used to sense the oven temperature The LO alarm output controls a solid state relay SSR which in turn controls the oven heater Enable Alarms EA command must be used to activate the alarm outputs In this case the desired regulated temperature is 100 C Lo alarm is set to 95 C in the latching mode with the LO command The HI alarm command is used to set the upper limit to 1059 in the momentary mode total hysteresis is the difference between the two alarm values or 10 C In the steady state condition the oven temperature will oscillate between 95 C and 100 C ideally Assume the oven temperature is below 95 C This value is less than the value loaded into the low limit therefore the LO alarm output is turned on Since the low alarm is set for latching mode the controi output stays on even as the oven temperature goes above the 95 C low limit The control output will stay on until the temperature reaches the value loaded into the high limit in this case 105 C At this point the latched LO alarm is turned off turning off the heater The control output will remain off as the oven cools down through heat losses When the oven
68. er function curve For instance a M2121 has a range of 1V and the standard table values are Analog Input Data Output Minimum 1V 01000 00 Maximum 1 401000 00 Plotted on a graph Figure 5 these two points specify the endpoints of the transfer curve In this case the analog input variable X is in terms of voltage The X values in the table specify the minimum and maximum voltages that may be applied to the analog input that will result in alinearized output The X voltage values are actually stored in memory in terms of ADC binary data Voltage values applied to the analog input that are more negative than Xmin will result an overload output of 99999 99 Similarly voltage values greater than Xmax will result in 99999 99 MAXIMUM 01000 00 00500 00 MINIMUM Figure 5 Function Endpoints The corresponding Y values in the table specify the output data of the minimum and maximum points In this case a 1V input corresponds to an output of 01000 00 millivolts The Y values are always stored in the standard data format of sign 5 digits decimal point and two additional digits 2 4 MetraByte M2000 Programming Manual The minimum and maximum points are the only table values necessary to specify a linear transfer function For analog input values between Xmin and Xmax the output values determined by linearly interpolating between the minimum and maximum points Forinstance in the case of the M2121 a
69. es This connection is only suitable for benchtop operation and should never be used for a permanent installation Figure 1 3 shows the hook up This connection will work provided the RS 232C transmit output is current limited to less than 50 ma and the RS 232C receive threshold is greater than OV Ali terminals that use 1488 and 1489 style interface IC s will satisfy this requirement With this connection characters generated by the terminal will be echoed back To avoid double characters the local echo on the terminal should be turned off If the current limiting capability of the RS 232C output is uncertain insert a 100Q to1kQ resistor in series with the RS 232 output In some rare cases it may be necessary to connect the module s DATA pin to ground through 1000 to 1kQ resistor 10 to 30 de Power Supply M1122 Dag to DEFAULTE A e e e e 2 2 e Figure 1 3 RS 465 Quick Hook Up with RS 232C Port 1 4 2 FUNCTIONAL DESCRIPTION A functional diagram of a typical MetraByte sensor module is shown in Figure 2 1 It is a useful reference designed to illustrate the data path in the module and to explain the function of many of the module s commands The first step is to acquire the sensor signal and convert it to digital data Figure 2 1 all the signal conditioning circuitry has been lumped into one block the analog to digital converter A D Autozero and autocalibration is pe
70. es recommended calibration points Due to the nonlinear nature of thermocouples it may be necessary to repeat the TS command to obtain the desired output After calibration is complete be sure to enable the cold junction compensation by clearing bit 4 in byte 3 of the setup data RTD Use a calibrated resistor mounted directly on the module connector to avoid lead resistance errors The resistor must be accurate to 0 01 for proper calibration Recommended calibration points are listed in Table 9 1 Follow the command sequence described for voltage inputs to calibrate the module Due to the nonlinear nature of RTD s it may be necessary to repeat the TS command to obtain the desired output 9 2 Table 9 1 Calibration Values Model M111X M112X M113X 114 121 123 M124X M125X M131X M132X M133X M134X M135X M136X M137X M138X M141X M142X M151X M152X M160X M161X Input Stimulus 90mV 4900mV 4 5V 9V 9000LA 90 900 20 39 13 41 269mV 417 816mV 68 783 17 445 15 576 10 094mV 33 442 300 000 300 000 25 90mV 18KHZ 25 Sec Output Data 00090 00 00900 00 04500 00 09000 00 09000 00 00090 00 00900 00 00020 00 00700 00 01000 00 00350 00 01000 00 01500 00 01500 00 01500 00 01982 00 00558 00 00547 60 00025 00 00090 00 18000 00 25000 00 OF 01292 00 01832 00 00662 00 01832 00 02732 00 02732 00 02732 00 03600
71. es 4 1 Function Programming 4 3 Linear Scaling 4 4 Programming Steps 5 2 Examples 5 4 Chapter 1 introduction The MetraByte M2000 series of intelligent analog to computer interfaces are designed to solve many difficult interfacing problems that cannot be performed with existing standard interfaces The M2000 series may be programmed to create custom transfer functions to interface to non standard sensors or to scale the outputs to any engineering units desired The M2000 series is an enhancement of ihe MetraByte M1000 series cf standard interfaces The M2000 series is similar to the M1000 series in every respect except that the M2000 interfaces allow custom input to output transfer functions As shipped from the factory the M2000 modules operate in the same manner as their M1000 counterparts For example a M2111 shipped from the factory contains the same transfer function as a M1111 module in this case they are both 3 100 mV inputs and communicate with RS 232C Before any attempt is made to program a M2000 you must first be familiar with the operation of a M1000 module as described in the M1000 manual The M2000 contains buiit in commands to create custom functions All programming is performed through the communications port of the M2000 module There is never any need to open the module case Modules may be re ranged remotely as many times as desired Function data is stored in nonvolatile memory to retain the scaling even if power is
72. for one character time This results in a delay of two character periods For longer delay times specified in the setup data this sequence is repeated Programmed communications delay is seldom necessary in an RS 232C daisy chain since each module in the chain adds one character of communications delay Changing Baud Rate It is possible to change the baud rate of an RS 232C daisy chain on line This process must be done carefully to avoid breaking the communications link 1 Use the SetUp SU command to change the baud rate setup on eac module in the chain Be careful not to generate a reset during this process reset can be caused by the Remote Reset RH command a line break or power interruptions 2 Verify that all the modules in the chain contain the new baud rate setup using the Read Setup RS command Every module in the chain must be setup for the same baud rate 3 Remove power from all the modules for at least 10 seconds Restore power to the modules This generates a power up reset in each module and loads in the new baud rate 4 Change the host baud rate to the new value and check communications 5 Be sure to compensate for a different communications delay as a result of the new baud rate 3 5 Using Daisy Chain With A Dumb Terminal A dumb terminal can be used to communicate to a daisy chained system The terminal is connected in the same manner as when using a compuier as a host Any commands typed into
73. g a setpoint value without affecting the desired hysteresis by using the Setpoint SP command Setpoint command is used to load the desired control value into the output offset register see Figure 2 1 The value in the output offset register is always added to the data derived from the sensor input For instance if the sensor data is 00100 00 and the output offset register contains 00050 00 a Read Data command will yield an output of 00150 00 The Setpoint command loads a value into the offset register to null out the sensor data If the command 15 00100 00 is given to a module with address 1 the effect of the command is to load the output offset register with 00100 00 An RD command will now result in the deviation of the input data from the downloaded setpoint value A careful look at Figure 2 1 will reveal that the alarm limits are checked after the output offset is added the input data To construct a controller using the SP com mand the high and low alarms must be loaded with the hysteresis values referred to the deviation from the setpoint value In the oven controller example the hysteresis was set to 5 C from the desired contro temperature of 100 C When using the SP command the high limit would be set to 00005 00 and the low limit would be set to 00005 00 to get the same hysteresis affect The Latching modes of the alarm limits are used in the same manner as previously described Let s look at the oven controller
74. g its program improperly due to power transients or static discharge Ifthe NOT READY error persists for more than 30 seconds check the power supply to be sure it is within specifications PARITY ERROR A parity error can only occur if the module is setup with parity on see Setup Usually a parity error results from a bit error caused by interference on the communications line Random parity errors are usually overcome by simply repeating the command If too many errors occur the communications channel may have to be improved or a slower baud rate may be used A consistent parity error will resutt ifthe host parity does not match ihe module parity In this situation the easiest solution may be to change the parity in the hostto obtain communication Atthis pointthe parity in the module may be changed to the desired value with the SetUp SU command The parity may also be changed or turned off by using the Default Mode SYNTAX ERROR A SYNTAX ERROR will result if the structure of the command is not correct This is caused by having too few or too many characters signs or decimal points missing or in the wrong place Table 4 1 lists the correct syntax for all the commands 4 21 VALUE ERROR This error results when an incorrect character is used as a numerical value Data values can only contain decimal digits 0 9 Hex values used in the SetUp SU and Digital Output DO commands can range from 0 F WRITE PROTECTED All commands th
75. gree output resolution typical analog data value from this type of module could be 00123 00 The two digits to the right of the decimal point have no sig nificance in this particular model However the data format is always adhered to in order to maintain compatability with other module types The maximum computational resolution of the module is 16 bits which is less than the resolution that may be represented by an analog data variable This may lead to round off errors in some cases For example an alarm value may be stored in a 1002 module using the H command Command 1HI 12345 67M Response The alarm value may then be read back with the Read High RH command Command 1RH Response 12345 60 It appears that the data read back does not match the value that was originally saved The error is caused by the fact that the value saved exceeds the computational resolution of the module This type of round off error only appears when large data values saved in the module s EEPROM are read back In most practical applications the problem is nonexistent Overload values of analog data are represented by 99999 99 and 99999 99 4 2 Data read back from the Event Counter with the Read Events RE command is in the form of a seven digit decimal number with no sign or decimal point Round off errors do not occur on the event counter For example Command 1RE Response 0000123 The Digital input Digital Outpu
76. grees Previous data New data Filter selected large small 00100 00 00105 00 small 00100 00 400111 00 large 00100 00 00091 00 small 00100 00 00085 00 large 00050 00 00045 00 small 00050 00 00039 00 large Large Signal Time Constant The large signal filter time constant is specified by bits 3 4 5 of byte 4 It may be specified from 0 no filter to 16 seconds The time constant for a first order filter is the time required for the output to reach 63 of its final value for a step input Small Signal Time Constant Bits 0 1 2 specify the filter time constant for small signals values are similar to the ones for the large signal filter Most sensors can benefit from a small amount of small signal filtering such as T 0 5 sec In most applications the small signal time constant should be larger than the large signal time constant This gives stable readings for steady state inputs while providing fast response to large signal changes Table 5 4 Byte 4 Displayed Digits and Filter Time Constants BYTE 4 DATA BIT 7 6648210 XXXX0 00 DISPLAYED DIGITS 00 _ 00 DISPLAYED DIGITS 0 1 XXXXXXODISPLAYED DIGITS 70 _ DISPLAYED DIGITS 141 000 t pog O 0 5 SECOND TIME CONSTANT 0 19 10SECONDTMECONSTANT 0 11 20SECONDTIMECONSTANT 1 0 0 1 19 NO SMALL SIGNAL FILTERING 0 0 0 O25 SECOND TIME CONSTANT 0 0 1 0
77. haracter it will respond with a SYNTAX and the command will be aborted For example Command 1RD no checksum Response 00072 10 Command 1RDEB with checksum Response 00072 10 Command 1RDAB incorrect checksum Response 1 BAD CHECKSUM Command 1RDE one extra character Response 21 SYNTAX ERROR Response Checksums If the long form version of command is transmitted to a module a checksum will be appended to the end of the response For example Command 1RD short form Response 00072 10 Command 1RD long form Response 1RD 00072 10A4 A4zchecksum Checksum Calculation The checksum is calculated by summing the hexadecimal values of all the ASCII characters in the message The lowest order two hex digits of the sum are used as the checksum These two digits are then converted to their ASCII character equivalents and appended to the message This ensures that the checksum is in the form of printable characters Example Append a checksum to the command 1DOFF Characters 1 DO F ASCII hex values 23 31 44 4F 46 46 Sum hex addition 23 31 44 4F 46 46 173 The checksum is 73 hex Append the characters 7 and 3 to the end of the message 1DOFF73 Example Verify the checksum of a module response 1RD 00072 10A4 The checksum is the two characters preceding the CR A4 Add the remaining character vatues n 1 R D 0 0 0 7 2 1 0 2 314 52 44 2B 30 30
78. he M1000 Setup section In the present example of the 0 to 50 mV output probably the best compromise is to use the millivolt form to represent the data This gives 5 000 count resolution in easy to interpret units of millivolts In this case the displayed digits setup should be programmed to display all digits It may be tempting to use the microvolt output format in an effort to extract 50 000 counts of resolution but the units digit will tend to be noisy The uncertainty of the units digit may be counteracted somewhat by using large amounts of digital filtering in the module setup In this case the setup data should specify a displayed digits setting of the first five digits only since the digits to the right of the decimal point have no meaning Also the microvolt format is a bit more awkward to interpret than the millivolt format In some cases it may require bit of creative thinking to develop a suitable output format For example a M2000 module may be requiredto output data in units of specific gravity In a typical application the specific gravity output may range between 5 and 2 The most obvious output format would have the output data ranging from 00000 50 to 00002 00 This format gives only 150 counts of resolution between the minimum and maximum outputs However since the specific gravity o wateris defined to be 1 the output may be scaled in units of percent of water The specific gravity of water would then be 100 perce
79. he command is 1TS 00100 00 Step 6 verify the trim using the 1RD command The result should be either 00050 00 or 00100 00 Calibration Example We wish to calibrate a M1511 module This unit contains 5 V excitation and 30 mV input Step 1 is straightforward and needs no further explanation Step 2 set the voltage source to O volts Trim zero Command 1WE Response Command 1TZ 00000 00 Response Step 3 measure the excitation voltage with the DVM In this example the measured voltage is 4 954 V Calculate the compensation factor CF 4 954 5 9908 Step 4 calculate the calibration voltage V 50mV X 9908 49 54 mV Set the voltage standard to 49 54 mV Step 5 perform the Trim Span command Command 1WE Response Command 1TS 00050 00 Response Step 6 verify the calibration continuing to apply 49 54 mV to the input Command 1RD Response 00050 00 C 7 The span trim is now complete The Trim Zero TZ command used to trim sensor offsets without affecting the span trim OPTIONS Digital Output All M1500 units come standard with a Digital Input Event Counter input This connector pin may be factory configured for a Digital Output Low Alarm output Consult factory Continuous Output Any of the D1000 sensor input modules may be factory configured to provide continuous output data without interrogation from the host This option is ideal for use with
80. he notation on the label DATA is simply used to indicate the complement of DATA negative true To minimize unwanted reflections on the transmission line the bus should be arranged as a line going from one module io the next Tree or random structures of the transmission line should be avoided For wire runs greater than 500 feet total the end of the line should be terminated with a 100 ohm resistor connected between DATA and DATA 3 7 Special care must be taken with very long busses greater than 1000 feet to ensure error free operation Long busses must be terminated as described above The use of twisted cable for the DATA and lines will greatly enhance signal fidelity Use parity and checksums along with the form of all commands to detect transmission errors In situations where many modules are used on a long line voltage drops in the power leads becomes an important consideration The GND wire is used both as a power connection and the common reference for the transmission line receivers in the modules Voltage drops in the GND leads appear as a common mode voltage to the receivers The receivers are rated for a maximum of 7V of common mode voltage For reliable operation the common mode voltage should be kept below 5V The resistance of 20 gauge wire commonly used in telephone cable is about 10 ohms per 1000 feet The maximum current draw from a single module is 75 ma Using Ohm s Law the maximum allowable
81. hosi Use the Default Mode to enter the desired address baud rate and other setups see Setups The use of echo is not necessary when using a single module on the communications line Multi party Connection RS 232C is not designed be used a multiparty system however the M1000 modules can be daisy chained to allow many modules to be connected to a single communications port The wiring necessary to create the daisy chain is shown in Figure 3 1 Notice that starting with the host each Transmit output is wired to the Receive input of the next module in the daisy chain This wiring sequence must followed until the output of the last module in the chain is wired to the Receive input of the host All modules in the chain must be setup to the same baud rate and must echo all received data see Setups Each module must be setup with its own unique address to avoid communications collisions see Setups In this network any characters transmitted by the host are received by each module in the chain and passed on to the next station until the information is echoed back to the Receive input of the host In this manner all the commands given by the host are examined by every module If a module in the chain is correctly addressed and receives a valid command it will respond by transmitting the response on the daisy chain network The response data will be ripple through any other modules in the chain until it reaches its final destination
82. ied we would like to trim the output to read zero To trim the system use the TZ command and specify the desired output reading Command 172 00000 00 zero output Response The TZ command will load a data value into the Output Offset Register to force the output to read zero The module will compensate for any previous value loaded into the Output Offset Register If another output reading is taken it will show that the offset has been eliminated Command 1RD Response 00000 00 Although the TZ command is most commonly used to null an output to zero it may be used to offset the output to any specified value Assume thatwith the previously nulled load cell system we performed this command Command 1TZ 000100 00 Response The new data output with no load applied would be Command 1RD Response 000100 00 The load cell output is now offset by 100 The offset value stored by the TZ commandis stored in nonvolatile memory may be read back with the Read Zero RZ command and cleared with the Clear Zero CZ command The SetPoint SP command will write over any value loaded by the TZ command Write Enable WE Each MetraByte module is write protected against accidental changing of alarms limits setup or span and zero trims To change any of these write protected parameters the WE command must precede the write protected command The response to the WE command is an asterisk indicating that the module i
83. if the cylinder reads 750 psi it is 100 fuil Pressure Volts Output 96 0 1 00000 00 375 2 5 00050 00 750 4 00100 00 Nonlinear Functions As we have shown with the linear pressure sensor example the output may be scaled to any units we desire However the real power of the M2000 series is that they may be programmed to provide a nonlinear transfer function This capability may be used to provide outputs in engineering units for nonlinear sensors The M2000 uses a linear piece wise approximation technique to describe nonlinear functions Up to 24 linear segments may be used to approximate a function as shown in Figure 1 Figure 2 shows some of the variety of curves that may be programmed into the M2000 Pd Figure 1 Linear piece wise approximation MetraByte M2000 Programming Manual 1 3 Linear Scaling Absolute Value s Square Square Root Polynomial Figure 2 Typical curves that can be programmed by the M2000 The M2000 modules may also be programmed in the field to specific test inputs where the actual nonlinearity is not known Chapter 2 Theory of Operation The M2000 performs all scaling functions in firmware using the module s interna microproces sor All scaling and nonlinear function data is stored in a table contained in EEPROM nonvolatile memory Scaling data stored in the memory will remain intact indefinitely even if power is removed M2000 modules may be re scaled up to 10 000 times All re
84. ilable to activate an alarm or shut down the system if the temperature goes out of limit Oven Chamber Limit current ES to 3 m OF auras SAt 3 13138 3650 N 3 ULISNBAL 0422 59 178430 giaz LOQ IH Ha 200 10ta 30 de Power Supply 00000646 0004 44 Due 9090000000000 ON OFF CONTROLLER WITH HYSTERESIS The simple single value controller by its very nature suffers from erratic output that may not be acceptable particularly when high power equipment is being controlled To lengthen the control cycle and to make the control action smoother hysteresis also known as dead band is often used in on off controllers With hysteresis the process variable is controlled between the two setpoints in order to lengthen the duty cycle of the control output To increase the control duty cycle the hysteresis or difference between the setpoints must be increased Figure 6 6 shows the effect of hysteresis on the control output The high and low alarm limits on the M1000 sensor modules may be set to provide on off control with hysteresis The two limits specify the two control setpoints The difference between the high limit and the low limit is the hysteresis value The high limit must be greater than the low limit for proper operation The alarm output used to control the process must be set to the Latching mode 1f the control output is turned on it will remain on until the input data exc
85. ing change see Figure 2 1 Echo When bit 2 is set to 1 the M1000 module will retransmit any characters it has received on the communications line This option is necessary to daisy chain multiple RS 232C modules Echo is optional for systems with a single RS 232C module Bit 2 must be cleared to 0 on RS 485 models See the Communications section for a more complete description Delay Bits 0 and 1 specify a minimum turn around delay between a command and the module response This delay time is useful on host systems that are not fast enough to capture data from quick responding commands such as RD This is particularly true for systems that use software UART s The specified delay is added to the typical command delays listed in the Communications section Each unit of delay specified by bits 0 and 1 is equal to time required to transmit one character with the baud rate specified in byte 2 For example one unit of delay at 300 baud is 33 3 ms for 38 4 kilobaud the delay is 0 26 ms The number of delay units is selectable from 0 to 6 as shown in Table 5 3 In some systems such as IBM BASIC a carriage return CR is always followed by a linefeed LF The 1000 modules will respond immediately after command terminated by a CR and will ignore the linefeed To avoid a communications collision between the linefeed and the module response the module should be setup to delay by 2 units 5 8 Table 5 3 Byte 3 Options BYTE 3
86. ion along with fast response to step inputs The MetraByte modules allow for user selectable output scaling in C or F on temperature data This selection is depicted in Figure 2 1 as a switch following the digital filters default scaling in the modules is C but this may be converted to F by feeding the data through a conversion routine The switch position is controlled by a bit in the setup data and may be changed with the SetUp SU command scaling selection is nonvolatile For non temperature applications the C position should always be selected The scaled data is summed with data stored in the Output Offset Register to obtain the final output value The output offset is controlled by the user and serves many useful purposes The data in the Output Offset Register may be used to trim any offsets caused by the input sensor It may be used to null out undesired signal such as a tare weight The Trim Zero TZ command is used to adjust the output to any desired value by loading the appropriate data value in the offset register The data in the offset register is nonvolatile The output offset may also be modified using the Set Point SP command The data value specified by the SP command is multiplied by 1 before being loaded into the register The Set Point command specifies a null value that is subtracted from the input data The output reading becomes a deviation value from the aownloaded setpoint This feature
87. ion table for this curve looks like this Minimum Maximum Breakpoint 00 Breakpoint 01 Analog Input 10 10 V 9 990 V OV Data Out 00010 00 10000 00 09990 00 00000 00 MetraByte M2000 Programming Manual 5 15 Figure 15 Figure 16 The absolute value function will be valid for inputs between 9 990 V and 10 V This technique may be used for other functions that violate the rectangular area rule Specifications are subject to change without notice All Keithley trademarks and trade names are the property of Keithley Instruments Inc All other trademarks and trade names are the property of their respective companies KEITHLEY Keithley Instruments Inc Sales Offices BELGIUM CHINA FINLAND FRANCE GERMANY GREAT BRITAIN INDIA ITALY JAPAN KOREA NETHERLANDS SWEDEN SWITZERLAND TAIWAN 28775 Aurora Road Cleveland Ohio 44139 440 248 0400 Fax 440 248 6168 1 888 KEITHLEY 534 8453 www keithley com Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 8610 6202 2886 Fax 8610 6202 2892 Tiet j ntie 2 02130 Espoo Phone 09 54 75 08 10 Fax 09 25 10 51 00 3 all e des Garays 91127 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 Landsberger Strasse 65 82110 Germering 089 84 93 07 40 Fax 089 84 93 07
88. known analog stimulus must be applied to the sensor input of the M2000 unit This test input must correspond to most positive value ofthe programmed transfer function The analog test signal must remain within the specified input range of the M2000 module The analog input establishes the maximum input value X axis for the transfer function The maximum output value Y axis is specified as the argument of the MaXimum command Command 1MX 00500 00 Response Command 0500 00 Response 1MX 00500 00AE AE is the checksum Chapter 4 Programming This section will cover the mechanics of programming a custom transfer function into the M2000 Ali programming is performed through the communications port of the M2000 using a dumb terminal or a computer operating as a dumb terminal In field installations where AC power is not readily available programming may be accomplished with standard battery operated ASCII terminals Since all programming is accomplished through the communica tions port access to the module is not necessary and ranging may be accomplished remotely Programming Software Although ali programming functions may be accomplished with a dumb terminal the task may be greatly simplified with the use of utility software running on a computer MetraByte offers programming software which will run on many ofthe popular personal computers The software provides many enhancements that are not available through manual prog
89. le s internal receive buffer This character will be echoed after the response string is transmitted by the module This situation will occur if the host computer appends a linefeed character on the command carriage return In this case the linefeed character will be echoed after the response string has been transmitted The daisy chain also affects the command timeout specifications When a module in the chain receives a character it is echoed by retransmitting the character through the module s internal UART This method is used to provide more reliable communications since the UART eliminates any slewing errors caused by the transmission lines However this method creates a delay in 3 4 propagating the character through the chain The delay is equal to the time necessary to retransmit one character using the baud rate setup in the module Baud Rate Delay 300 33 30 ms 600 16 70 ms 1200 8 33 ms 2400 4 17 ms 4800 2 08 ms 9600 1 04 ms One delay time is accumulated for each module in the chain For example if four modules are used in a chain operating at 1200 baud the accumulated delay time is 4 X 8 33 ms 33 3 ms This time must be added to the times listed in Table 3 1 to calculate the correct communications time out error For modules with RS 232C outputs the programmed communications delay specified in the setup data see Setup section is implemented by sending a NULL character 00 followed by an idle line condition
90. lect as they will not be accepted 1 GETTING STARTED Default Mode All M1000 modules contain an EEPROM Electrically Erasable Programmable Read Only Memory to store setup information and calibration constants The EEPROM replaces the usual array of switches and pots necessary to specify baud rate address parity etc The memory is nonvolatile which means that the information is retained even if power is removed No batteries are used so it is never necessary to open the module case The EEPROM provides tremendous system flexibility since all of the module s setup parameters may be configured remotely through the communications port without having to physically change switch and pot settings There is one minor drawback in using EEPROM instead of switches there is no visual indication of the setup information in the module It is impossible to tell just by looking at the module what the baud rate address parity and other settings are It could be very difficult to establish communications with a module whose address and baud rate are unknown To overcome this difficulty each module has an input pin labeled DEFAULT By connecting this pin to Ground the module is placed in a known communications setup called Default Mode The Default Mode setup is 300 baud no parity any address is recognized Grounding the DEFAULT pin does not change of the setups stored in EEPROM The setup may be read back with the Read Setup
91. ley Software does not conform with the published specifications Keithley will at its option provide either the programming services necessary to correct such nonconformity or develop a program change to bypass such nonconformity in the Keithley Software Failure to notify Keithley of a nonconformity during the warranty shall relieve Keithley of its obligations and liabilities under this warranty Other Software OEM software that is not produced by Keithley Other Software shall not be covered by this warranty and Keithley shall have no duty or obligation to enforce any OEM s warranties on behalf of the customer Other Items Keithley warrants the following items for 90 days from the date of shipment probes cables rechargeable batteries diskettes and documentation Items not Covered under Warranty This warranty does not apply to fuses non rechargeable batteries damage from battery leakage or problems arising from normal wear or failure to follow instructions Limitation of Warranty This warranty does not apply to defects resulting from product modification made by Purchaser without Keithley s express written consent or by misuse of any product or part Disclaimer of Warranties EXCEPT FOR THE EXPRESS WARRANTIES ABOVE KEITHLEY DISCLAIMS ALL OTHER WARRANTIES EXPRESS OR IMPLIED INCLUD ING WITHOUT LIMITATION ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE KEI THLEY DISCLAIMS ALL WARRANTIES WITH RESP
92. limits Latching alarm can be turned off with the Clear Alarms CA command alarm output is turned on sinking current when the measured sensor input is greater than the high limit loaded in with the command The LO alarm output is turned on sinking current when the input value is less than the stored low limit The alarm limit values may be read back at any time using the Read Low RL or Read High RH commands ON OFF CONTROLLERS The alarm capabilities of the M1000 sensor input modules may be utilized to construct simple ON OFF controllers that operate without host intervention In fact since all the alarm information is stored in nonvolatile memory the module can act as a stand alone controller with the communications lines disconnected The simplest controller connection is to use a momentary alarm output to control the process typical application would have a temperature input module controlling a heater as shown in Figure 6 5 To maintain a constant temperature set the low limit to the setpoint desired and specify the alarm output to be momentary Use the LO alarm output to contro the heater If the temperature measurement exceeds the low limit the heater will be turned off 6 5 When the temperature goes below the limit the LO alarm output goes on turning on the heater The negative feedback action of the control output will keep the temperature at the desired value The high limit is still ava
93. llowing table lists the timeout specification ior each command Mnemonic Timeout DI DO RD WE 10 ms ND See text All other commands 100 ms Table 3 1 Response Timeout Specifications This timeout specification indicates the turn around time from the receipt of a command to when the module will start to transmit a response RS 232C RS 232C is the most widely used communications standard for information transfer between computing equipment RS 232C versions of the M1000 will interface to virtually all popular computers without any additional hardware Although the RS 232C standard is designed to connect a single piece of equipment to a computer the MetraByte system allows for several modules to be connected in a daisy chain network structure The advantages offered by the RS 232C standard are 1 widely used by all computing equipment 2 no additional interface hardware in most cases 3 separate transmit and receive lines ease debugging 4 compatible with dumb terminals However RS 232C suffers from several disadvantages 1 low noise immunity 2 short usable distance 50 to 200 feet 3 maximum baud rate 19200 4 greater communications delays multiple module systems 5 less reliable loss of one module results in no communications 6 wiring is slightly more complex than RS 485 7 host software must handle echo characters Single Module Connection Figure 1 1 shows the connections necessary to attach one module to a
94. mand RS The following options be specified by the SetUp command Channel address 124 values Linefeeds Parity odd even none Baud rate 300 to 38 400 Alarm enable disable Alarm momentary latching CJC disable M1300 series RTD 3 4 wire M1400 series Positive negative edge trigger M1600 series Fahrenheit Celsius Echo Communication delay 0 6 characters Number of displayed digits Large signal filter constant Small signal filter constant Each of these options will be described in detail below For a quick look up chart on all options refer to Tables 5 1 4 Once you are completely familar with the setups you can refer to Table 5 6 for a summary of all of the setup information Command Syntax The general format for the SetUp SU command is 1SU byte1 byte 2 byte 3 byte 4 A typical SetUp command would look like 815031070182 Notice that each byte is represented by its two character ASCII equivalent In this example byte 1 is described by the ASCII characters 31 which is the equivalent of binary 0011 0001 31 hex The operand of a SU command must contain exactly 8 hex 0 characters Any deviation from this format will result in a SYNTAX ERROR The Appendix contains a convenient hex to binary conversion chart For the purposes of describing the SetUp command bit 7 refers to the highest order bit of a byte of data Bit 0 refers to lowest order bit bit number 7654 3210 binary dat
95. mand the module interprets the string as an RD command Command 1 Response 00072 10 Command 1 Response 1RD 00072 10A4 4 13 READ EVENTS The Read Events command reads the number of events that have been accumu lated in the Events Counter The output is a seven digit decimal number For example Command 1RE Response 0000107 Command 1RE Response 1RE00001074A The maximum accumulated count is 9999999 When this count is reached the Events Counter stops counting The counter may be cleared at any time with the Clear Events CE command The Event Counter count is not stored in nonvolatile memory If power is removed the Event Counter will reset to all 075 upon power up The Remote Reset RR command or a line break does not effect the value of the Event Counter When reading the Event Counter with a checksum be sure not to confuse the checksum with the data Read High Alarm RH The Read High alarm command reads the value and type ofthe high alarm previously loaded by the HI command The alarm type can be either latching or momentary A letter indicating the alarm type L for latching or M for momentary will follow the alarm value For example Command 1RH Response 00510 00L Command 1RH Response 1RH 00510 00LF0 The RH command be used to verify the data loaded into nonvolatile memory by the HI command 4 14 Read Low Alarm RL The Read Low alarm command reads
96. module to display six digits Command 1WE Hesponse MetraByte M2000 Programming Manual 4 7 Command 15031070182 typical Response 4 Using a calibrated frequency generator apply 10 Hz to the module input Set the minimum point Command 1WE Response Command 1MN 00001 00 Response 22 Set the frequency generator to 200 Hz to program the maximum point Command 1WE Response Command 1MX 00020 00 Response 6 Use the frequency generator to verify a few points in the scale Analog Input Data Output 30 Hz 00003 00 100 Hz 00010 00 155 Hz 00015 50 Programming is now complete and the M2601 be attached to the flow sensor Example L 3 many cases the analog calibration values may be produced directly by the sensors to be used inasystem The module may be re ranged in the field to encompass any errors due to sensor inaccuracies In this example we wish to use a pressure sensor to measure the volume of waterin a cylindrical tank that is 10 feet tall with the capacity of 1500 gallons The pressure sensor is mounted at the bottom of the tank so that it will produce an output corresponding to the height of water in the tank The pressure sensor chosen produces 1V 0 psi and 5V 10 psi A full tank with 10 feet of water will produce 4 335 psi 1 ft 4335 psi weli within the range of the pressure sensor A M2131 5 V input module will be used as the interface 4 8 MetraBy
97. n analog input value of 5V is linearly interpolated to an output value of 00500 00 Figure 5 It should be apparent at this point that a M2000 module may be re scaled by modifying the minimum and maximum values in the table This may be accomplished by using the Minimum MN command and the Maximum MX command Using the M2121 1 volt module as an example we may use the MN and MX commands to alter the table to look like this Analog Input Data Output Minimum 0 00100 00 Maximum 41V 400800 00 this case the minimum point is 0 V corresponding to the output data 00100 00 maximum point is 1 V input and 00800 00 output The graph of this equation is shown in Figure 6 00500 00 00100 00 Fig 6 By changing the minimum and maximum values in the table an infinite number of linear functions may be specified bounded by X values 1 and Y values of X99999 99 Figure 7 shows a few possibilities MetraByte M2000 Programming Manual 2 5 t 1 Figure 7 exact procedure necessary to program the maximum and minimum points is described in Chapter 5 Breakpoints Looking back at Figure 4 we can see that most of the transfer function table is reserved for Breakpoints Breakpoints are used to modify the basic linear curve defined by the Minimum and Maximum points to create nonlinear functions Nonlinear functions in the M2000 are approximated by using linear segments which are specified b
98. n board for installation into a computer should never require cleaning if handled according to in structions If the board becomes contaminated and operation is af fected the board should be returned to the factory for proper cleaning servicing M1000 SERIES USERS MANUAL REVISION 3 30 87 The information in this publication has been carefully checked and is believed to be accurate however no responsibility is assumed for possible inaccuracies or omissions Applications information in this manual is intended as suggestions for possible use of the products and not as explicit performance specific application Specifications may be subject to change without notice M1000 modules are not intrinsically safe devices and should not be used in an explosive environment unless enclosed in approved explosion proof housings TABLE CONTENTS Warranty 5 CHAPTER Getting Started Default Mode 1 1 Quick Hook Up 1 2 CHAPTER 2 Functional Description Block Diagram 2 4 CHAPTER 3 Communications RS 232C 3 2 Single Module and Multi party Connection 3 3 Software Considerations 3 4 Changing Baud Rate 3 5 Using a Daisy Chain With a Dumb Terminal 3 6 RS 485 3 6 RS 485 Multidrop System 3 7 CHAPTER 4 Command Set Table of Commands 4 7 UserCommands 4 8 Error Messages 4 16 CHAPTER 5 Setup Information and Command Command Syntax 5 2 Setup Hints 5 13 CHAPTER 6 Digital O Function Digital Outputs 6 1 Digital inputs 6 3 Even
99. n con tact Product operators in these circumstances must be trained to protect themselves from the risk of electric shock If the circuit is capable of operating at or above 1000 volts no conductive part of the circuit may be exposed Do not connect switching cards directly to unlimited power circuits They are intended to be used with impedance limited sources NEVER connect switching cards directly to AC mains When con necting sources to switching cards install protective devices to lim it fault current and voltage to the card Before operating an instrument make sure the line cord is connect ed to a properly grounded power receptacle Inspect the connecting cables test leads and jumpers for possible wear cracks or breaks before each use When installing equipment where access to the main power cord is restricted such as rack mounting a separate main input power dis connect device must be provided in close proximity to the equip ment and within easy reach of the operator For maximum safety do not touch the product test cables or any other instruments while power is applied to the circuit under test ALWAYS remove power from the entire test system and discharge any capacitors before connecting or disconnecting cables or jump ers installing or removing switching cards or making internal changes such as installing or removing jumpers Do not touch any object that could provide a current path to the com mon side of
100. n extrapolated to be 00050 00 0 mA The maximum point is 00262 50 25 mA We ll setup the module to display temperature with 1 degree resoiution Command 1WE Response Command 1SU31070142 typical Response 4 Apply 0 mA open circuit to the current input and program the minimum point Command 1WE Response Command 1MN 00050 00 Response 5 Apply exactly 25 mA to the current input to program the maximum point Command 1WE Response Command 1 00262 50 Response 6 Apply test currents to the module to verify the scaling Appiy 4 mA to the input Command 1 Response 00000 00 Apply 20 mA to the input Command 1 Response 00200 00 5 Nonlinear Programming Nonlinear functions may be created by first specifying a linear function with the MiNimum and MaXimum MX commands The linear function is then modified by using the BreakPoint BP command Almost any practical nonlinear function may be approximated provided it satisfies two rules 1 The nonlinear function must be totally enclosed by the rectangular area defined by the minimum an maximum points Figure 10 gives examples of the rectangular area MAX MAX Figure 10 Figure 11 illustrates function that is not possible since portion of the curve lies outside of the rectangle In most cases this limitation may be overcome by simply re arranging the curve so that the rec
101. nsor module The TS command loads a calibration factor into nonvolatile memory to trim the full scale cutput of the signal conditioning circuitry It is intended only to compensate for long term drifts due to aging of the analog circuits and has a useful trim value of 10 of the nominal calibration set at the factory It is not intended to be used to change the basic transfer function of the module Full information on the use of the TS command may be found in the Calibration section Command 1TS 00500 00 Response Command 1TS 00500 00 Response 1TS 00500 00B0 Caution TS is the only command associated with the span trim There is no provision to read back or clear erroneous information loaded by the TS command Unwarranted use of the TS command may destroy the calibration of the unit which can only be restored by using laboratory calibration instruments in a controlled environment Trim Zero TZ The Trim Zero command is used to load a value into the Output Offset Register Figure 2 1 to null out an undesirable offset in the output data It may be used to trim offsets created by sensors such as strain gages It may also be used to null cut data to create a deviation output Example Assume a M1511 bridge input module is being used with a load dello weight measurement An inital reading of the load cell with no weight applied may reveal an initial offset error Command 1RD Response 00005 00 4 18 With no weight appl
102. nt The output data in percent units would range from 00050 00 to 00200 00 This format allows up to 15 000 counts of resolution and reads out in units that may be easily interpreted MetraByte M2000 Programming Manual 4 3 Linearity The analog to digital converter used in the M2000 has a typical integral nonlinearity of 1 of full scale At the factory the ADC linearity is corrected by using breakpoints to reduce the nonlinearity to 01 If the breakpoint table is erased with the Erase Breakpoints command the linearity correction is lost In some cases when linear re scaling is performed the programmer may take advantage of the factory linearity correction Example L 4 If less than half of the full analog input scale is used the linearity correction should be erased with the EB command Linearity may be improved with the use of breakpoints Example N 5 M2000 FUNCTION PROGRAMMING The M2000 transfer function may be programmed by modifying the function table with the MiNimum MN MaXimum MX and BreakPoint BP commands All three commands operate on the same basic principle Each command is used to specify an input output X Y data pairinthe functiontable To perform a programming command aknown analog excitation must be applied to the analog input of the M2000 module The excitation may be a voltage current frequency orthe output of a resistive bridge depending on the specific M2000 module type The known excitati
103. odule This option can be useful when using the module with a dumb terminal All responses from the M1000 are terminated with a carriage return ASCII 00 Most terminals will generate a automatic linefeed when a carriage return is detected However for terminals that do not have this capability the MetraByte module can generate the linefeed if desired By setting bit 7 to 1 the module will send a linefeed ASCII 0A before and after each response If bit 7 is cleared 0 no linefeeds are transmitted When using the command prompt the linefeed characters are not included in the checksum calculation Parity Bits 5 and 6 select the parity to be used by the module Bit 5 turns the parity on and off If bit 5 is 0 the parity of the command string is ignored and the parity bit of characters transmitted by the module is set 1 If bit 5 is 1 the parity of command strings is checked and the parity of characters output by the module is calculated as specified by bit 6 If bit 6 is O parity is even if bit 6 is 1 parity is odd If a parity error is detected by the module it will respond with a PARITY ERROR message This is usually caused by noise on the communications line If parity setup values are changed with the SU command the response to the SU command will be transmitted with the old parity setup The new parity setup becomes effective immediately after the response message from the SU command Baud Rate Bi
104. on value is used to create the X values in the function table The Y table values are loaded with data specified in the command argument For example suppose we a M2121 1 V module and we d like to program the minimum table value to 5V Ymin 00100 00 Apply 5 volts to the module input with a calibrated voltage source Perform the MiNimum MN command with the Ymin value as the data argument in the MN command Command 1WE MN is write protected Response Command 1MN 00100 00 Response When the module executes the MN command the microprocessor performs two functions First it reads the data produced by the A D converter with the 5V input The A D converter data is stored as Xmin inthe function table The micro then reads the argument of the MN instruction which in this case is 00100 00 and stores this value in the table as Ymin This completes the definition of the new minimum point The module will immediately use this new minimum point data in calculating output data Note that the MN command will write over any previous data in the table The old data is permanently lost This is also true with the MaXimum MX and BreakPoint BP commands 4 4 MetraByte M2000 Programming Manual Since the MN MX and BP commands affect the calibration of the module they must not be used indiscriminately unless you are prepared to re calibrate the unit LINEAR SCALING Rescaling the M2000 to a linear tr
105. onse 1RS3107014292 The response contains the module s channel address baud rate averaging con stanis C F and other parameters Refer to the setup command SU and the Setup section of this manual for a full list of parameters contained within the setup information When reading the setup with a checksum be sure notto confuse the checksum with the setup information Read Zero RZ The Read Zero command reads back the value stored in the Output Offset Register Figure 2 1 Command 1RZ Response 00000 00 Command 1RZ Response 1RZ 00000 00B0 The data read back from the Output Offset Register may be interpreted in several ways The commands that affect this value are the Trim Zero TZ SetPoint SP and Clear Zero CZ 4 16 Setpoint SP The data specified by the setpoint command is multiplied by 1 and loaded into the Output Offset Register Figure 2 1 The SP command is useful in on off controller applications and is described in detail in the Digital V O section of this manual The SP command may be used to null out sensor data to obtain a deviation output when the RD or ND commandas are used Command 1SP 00450 00 Response Command 1SP 00450 00 Response 15 00450 00 0 It is possible to load setpoint data that is beyond the output range of the sensor In this case the setpoint can never be reached by the sensor data unless an overload is present To clear a setpoint use the Clear
106. ost positive analog input value Perform a Maximum MX command to load the endpoint data into the module memory 6 Verify that the transfer function has been correctly loaded into the module by applying test inputs to the module and reading out the data with the Read Data RD command Example L 1 Reprogram M2151 4 20 mA module to output data in terms of percent that is 4 mA will read out to be 0 and 20 mA will read out as 100 1 If the module had been previously programmed with breakpoints erase the function table with the Erase Breakpoints EB command MetraByte M2000 Programming Manual 4 5 Command 1WE Response Command 1EB Response 2 Clear any offset data with the Clear Zero command Command 1WE Response Command 1CZ Response 3 The minimum analog input in this case is 4 mA Any current less than 4 mAwillresuitina negative over range 99999 99 The maximum positive input is 20 mA Since the minimum value of 4 mA corresponds to 0 the appropriate output data would be 00000 00 The output data corresponding to 20 mA is 00100 00 This data format gives us whole units of percent to the left of the decimal point To get the maximum resolution from the module set up the number of displayed digits with the SetUp SU so that all digits are displayed Command 1WE Response Command 150310701 2 typical Response 4 Apply exactly 4 mA to the current input of the module
107. r is connected while the M1400 is powered up To avoid this error wire the sensor should to the connector before power is applied The error may also be eliminated by performing a Remote Reset RR command LEAD RESISTANCE OVERLOAD the lead resistance exceeds 650 the output data is set to 99999 99 SENSOR GROUNDING The sensor input is electrically isolated from the power and communications inputs for common mode voltages up to 500V if the sensor is to be grounded or shielded the ground connection should be made to the I terminal for best performance B 2 gt APPENDIX 1500 5 The M1500 Bridge Sensor Interface Modules contain all of ihe signal conditioning functions necessary to interface Strain Gage and other resisitive bridge devices to an RS 232C or RS 485 computer port Each module contains excitation an instrumentation amplifier and a smart analog to digital converter to convert resistive bridge sensor signals to ASCII data The user should become familiar with the generic D1000 information described in the D1000 Users Manual before attempting any of the procedures outlined below DATA FORMAT The ASCII output data is expressed in millivolts with 10 microvolt resolution For Example Command 1RD Read Data Response 00012 34 In this case the output data is 12 34 millivolts Modules that are configured for 30 mV and have a usable span of 60 mV Modules configured for 100 mV have a
108. ramming In many applications the M2000 modules may be programmed strictly through software methods without the need for external excitation sources Contact MetraByte for availability GENERAL GUIDELINES Input Scaling The analog input characteristics of a M2000 module may not be altered by the user Input scaling is accomplished by selecting the correct M2000 model forthe application Programming a M2000 involves altering the scaling of the unit s A D converter output There is no provision for changing the gain or offset of the analog circuitry Excitation When the M2000 modules are programmed manually with a terminal external excitation sources are necessary to establish calibration points within the module Excitation may be provided by standard voltage current and frequency calibration sources The final absolute accuracy of the module is directly dependent on the accuracy of the excitation sources In some cases the excitation may be generated directly by the system being monitored situations when excitation sources are not available or impractical modules may be programmed with MetraByte programming software without excitation Output Data Format One of the preliminary decisions to be made before programming is how the output data will be structured All MetraByte sensor modules communicate data in a fixed format of sign five digits decimal point and two additional digits 00100 00 is an example The fixed format is 4
109. range therefore the actual current draw is inversely proportional to the line voltage M1000 modules without sensor excitation consume a maximum of 75 watts and this figure should be used in determining the power supply current requirement For example assume a 24 volt power supply will be used to power four modules The total power requirement is 4 X 75 3 watts The power supply must be able to provide 3 24 125 amps For modules with sensor excitation consult individual data sheets for power requirements In some cases a small number of modules may be operated by stealing power from a host computer or terminal Many computers provide a 15 volt output on the RS 232C D25 connector Small systems may be powered by using wall mounted calculator type modular power supplies These units are inexpensive and may be obtained from many retail electronics outlets For best reliability modules operated on long communications lines gt 500 feet should be powered locally using small calculator type power units This eliminates the voltage drops on the Ground lead which may interfere with communications signals In this case the V terminal is connected only to the local power supply The Ground terminal must be connected back to the host to provide a ground return for the communications loop All MetraByte modules are protected against power supply reversals 8 TROUBLESHOOTING Symptom No module response Events coun
110. range cannot be re scaled to 10 V or any other range Analog input scaling is performed by selecting the M2000 model that best matches the sensor signal The ADC data is then manipulated with the function table to provide output data in engineering units 2 2 MetraByte M2000 Programming Manual Programming Table Figure 4 shows a programmer s model of the table used to program the input output trans fer function of the M2000 The table values are intentionally left blank so that it may be copied and used as a worksheet to help program the modules ANALOG DATA OUTP lt 2 MINIMUM MAXIMUM BREAKPOINT 00 BREAKPOINT 1 X BREAKPOINT 22 BREAKPOINT BREAKPOINT O4 BREAKPOINT 05 BREAKPOINT 26 ele ig gt il lt 8 9 lt S 2 lt gt lt lt o lt 9 gt lt lt lt lt BREAKPOINT 07 BREAKPOINT A Y BREAKPOINT B Xa Ys gt lt BREARPONTOE Me Ye o gt x lt lt m BREAKPOINT 19 8 11 X Ys BREAKPOINT 12 Y X lt 12 12 BREAKPOWTIS Xd Ye BREAKPOINT 16 gt lt gt 15 15 Figure 4 Breakpoint Table MetraByte M2000 Programming Manual 2 3 The two most important points in the table are the Minimum and Maximum points These two table entries specify the minimum and maximum endpoints of the transf
111. rature output with a fixed cold junction temperature of O C This setup is useful for calibrating the module or in cases where remote CJC is used Normally this bit is cleared to O RTD 3 4 Wire this functions pertains only to the M1400 series of RTD input modules If the bit is set to 1 the module provides the correct lead compensation calculation for 4 wire RTD s if the bit is cleared to 0 the module calculates the correct lead compensation for 3 wire RTD s Measurement errors may result if the module is not set to the correct sensor type Trigger Edge Select this function pertains only to the M1600 series frequency and pulse modules Bit 4 determines the polarity of the edge used to trigger the measurement cycle If bit 4 is 1 then the measurement cycle is 5 7 started positive going edge measurement cycle is started on the negative going edge if bit 4 is 0 In general this setup has very little effect on frequency inputs is primarily used with pulse inputs where the pulse train deviates from 5095 duty cycle Celsius Fahrenheit The default scaling for temperature output modules is Celsius which is selected by making bit 0 To change the scaling to Fahrenheit set bit to 1 All modules that do not have temperature output must have bit 3 cleared to zero The scaling factors are operative only on the sensor data HI and LO limits and setpoints must be modified by appropriate commands to reflect a scal
112. removed Linear Scaling The basic concept of the M2000 series is to create interfaces which output data in engineering units that may be instantly read and interpreted without any data conversion necessary by a host computer In fact the M2000 interfaces may be used with a dumb terminalto provide data readings in easy to understand engineering units For example a typical pressure sensor might provide a 1 to 5V linear output for pressures of 0 to 1000 psi Using a M1131 module or an unprogrammed M2131 unit the output data would look like this Pressure psi nsor Qutpu M2131 Output mV 0 1V 01000 00 500 3V 03000 00 1000 5V 05000 00 The standard output of the M2131 reads out in units of millivolts Even though the M2131 will faithfully output the sensor voltage the real parameter of interest is pressure not voltage and 1 2 MetraByte M2000 Programming Manual the voltage readings may be difficult to interpret To make the output data more readable the M2131 may be programmed to output the data in units of pressure Pressure psi Sensor Output M2131 Output psi 0 1 00000 00 500 3V 00500 00 1000 5 01000 00 In some cases the desired output may be more specific to a particular application Assume that the same pressure sensor is used to measure the fullness of a pressure vessel such as a cylinder of compressed air The M2131 could be scaled to output in units of percent and in this case we will assume that
113. rformed internally and is transparent to the user The full scale output of the A D converter may be trimmed using the Trim Span TS command The TS command adjusts calibration values stored internally in the EEPROM The TS command should only be used to trim the accuracy of the unit with a laboratory standard reference applied to the sensor input The trimmed data now flows into either of two digital filters The filter selection is performed automatically by the microprocessor after every A D conversion The filter selection depends on the difference of the current A D output data and the previous data stored in the output data register If the least significant decimal digit from the A D differs from the old output data by more than 10 counts the large signal filter is selected if the change is less than 10 counts the smail signal filter is used The two filter system allows for different degrees of filtering depending on the rate of the input change steady state signals the small signal filter averages out noise and small input changes to give a stable steady state output The large signal filter is activated by step changes or very noisy input signals The time constants for the two filters can be specified independently with the SetUp SU command filter values are stored in nonvolatile memory Typically the small signal filter is set to a larger time constant than the large signal filter This gives very good noise reject
114. rotected to guard against accidentally altering data values stored inthe module s EEPROM Therefore all programming commands must be preceded with a Write Enable WE command All of the M1000 command response protocol rules apply to the M2000 This section is intended only to describe the new commands For programming information refer to Chapter 5 BREAK POINT BP Nonlinear functions may be approximated in the M2000 by describing the function curve with a series of line segments see Figure 1 The line segments are programmed into the M2000 using the BreakPoint BP command A breakpoint specifies the intersection between two linear seqments used to approximate the nonlinear transfer function Up to 23 breakpoints may be used to specify 24 linear segments in a curve To program a breakpoint a known analog stimulus must be applied to the sensor input of the M2000 module This specifies the input variable X axis location of the breakpoint The corresponding output data Y axis of the breakpoint is specified as an argument to the BreakPoint command Example Spaces have been added to the command for clarity Command 1 BP 03 00100 00 Response Command 1 BP 03 00100 00 Response 1BP 03 00100 00FA FA is the checksum The first two characters following the BP command specify the breakpoint number Up to 23 breakpoints may be programmed into the M2000 In the sample command above breakpoint 5 2 MetraByte M2
115. s point is 1 psi Example N 2 A pressure sensor rated for 0 200 psi has a nonlinear transfer function described by the relationship V 4x10 P 5 10 V 0101 voits P 010 200 psi Use a M2121 1 V input module to linearize the sensor output and conver the data to engineering units This example differs from Example N 1 because the desired output data in psi 15 the 5 8 MetraByte M2000 Programming Manual independent variabie in the equation One solution to this problem would be to convert the equation to a form of P f V and then proceed as we did Example N 1 However this kind of mathematical rigor is not necessary To program the M2121 we simply need to construct a table of X Y pairs In this case we may choose breakpoints to be in even intervals of psi and then calculate the matching values of V Our table with four breakpoints would look like this Input Output Minimum OV 00000 00 Maximum 00200 00 Breakpoint 00 168 V 00040 00 Breakpoint 01 352 V 00080 00 Breakpoint 02 552 V 00120 00 Breakpoint 03 768 V 00160 00 Notice that in this case the breakpoints were selected by picking even intervals of pressure The pressure values are then plugged into the sensor equaiion to produce the breakpoint voltages The mechanics of entering the breakpoints is the same as in Example 1 If better conformity is required more breakpoints may be used However breakpoints cannot be simply added to the table at
116. s ready to accept a write protected command After the write protected command is success fully completed the module becomes automatically write disabled Each write 4 19 protected command must be preceded individually with a WE command For example Command 1WE Response Command 1WE Response 1WEF7 If a module is write enabled and the execution of a command results in an error message other than WRITE PROTECTED the module remains write enabled until a command is successfully completed resulting in an prompt This lets the user correct the command error without having to execute another WE command ERROR MESSAGES The M1000 modules feature extensive error checking on input commands to avoid erroneous operation Any errors detected will result in an error message and the command will be aborted All error messages begin with followed by the channei address a space and the error description The error messages have the same format for either the or command prompts For example 1 SYNTAX ERROR There are eight possible error messages and each error message description begins with a different character This makes it easy for a computer program to identify the error without having to read the entire string ADDRESS ERROR There are four ASCII values that are illegal for use as a module address NULL 00 CR 00 24 and 23 The ADDRESS ERROR will occur when an attempt is made to lo
117. s used to connect the digital outputs 0 and 1 to the connector pins The alarm settings are not affected in any way except that the alarm outputs are disconnected from the module connector The alarm status can still be read with the Digital Input DI command The complement to the DA command is the Enable Alarms EA command Command 1DA Response Command 1DA Response 1DAEO Digital Input 01 The DI command reads the status of the digital inputs and the alarms The res ponse to the DI command is four hex characters representing two bytes of data The first byte contains the alarm status The second byte contains the digital input data Command 1DI Response 0003 Command 1DI Response 1DIO003AB Listed below are the four possible alarm states in the first digital input byte and their hex values 00 Both HI and LO alarms off 01 Hl alarm off LO alarm 02 Hlalarm on LO alarm off 03 Both HI and LO alarms on The second byte displays the hex value of the digital input status The number of digital inputs varies depending on module type Digital In DI7 016 DIS 014 013 Di2 Di1 D Data Bits f B 5 4 3 2 1 Q For example A typical response from a 101 command could be O1FE This response indicates that the HI alarm is off the LO alarm is on DIO 0 and other digital inputs are 1 4 9 All digital inputs that are not imp emented or left unconnected are read as 1 Digital input 0 serves
118. scaling operations are performed with simple commands given to the module through its communications port The M2000 series command set encompasses all the the M1000 commands plus additional commands to perform function programming There is no need to open or have access to the module to perform re scaling In many cases the modules may be re scaled remotely after they have been installed Detailed descriptions of the M2000 programming commands are given in Chapter 5 Figure 3 is a simplified block diagram of the M2000 showing only the portions related to re scaling The microprocessor reads the raw Analog to Digital Converter ADC data after every conversion The uP takes the raw ADC data and looks it up in a table held in EEPROM The table contains entries which map the raw ADC data to output data in engineering units If an exact match is not found the data is interpolated between the two closest table entries The resulting datain engineering units is stored a memory buffer where it may be read by the Read Data RD or New Data ND Commands Analog Digital Communications Input Data Interface Analog to Digital Converter Micro processor EEPROM TABLE Figure 3 Block Diagram Note that the re scaling operation acts on the output of the analog to digital converter The basicinput to output transfer function of the ADC is fixed and cannot be changed For example a M2131 module with a 5 V input
119. t and Setup commands use hexadecimal representations of data The data structures for these commands are detailed in the command descriptions Write Protection Many of the commands listed in Table 4 1 are under the heading of Write Protected Commands These commands are used to alter setup data in the module s EEPROM These commands are write protected to guard against acc idental loss of setup data All write protected commands must be preceded by a Write Enable WE command before the protected command may be executed Miscellaneous Protocol Notes The address character must transmitted immediately after the command prompt character After the address character the module will ignore any character below ASCII 23 except of course CR This allows the use of spaces ASCII 920 within the command message for better readability if desired The length of a command message is limited to 20 printabie characters If a properly addressed module receives a command message of more than 20 characters the module will abort the whole command sequence and no response will result a properly addressed module receives a second command prompt before it receives a CR the command will be aborted and no response will result Response Structure Response messages from the M1000 module begin with either an asterisk ASCH 2A or a question mark ASCII 3F prompt The prompt indicates acknowledgment of a valid command The
120. tages there are situations where hazardous conditions may be present This product is intended for use by qualified personnel who recog nize shock hazards and are familiar with the safety precautions re quired to avoid possible injury Read and follow all installation operation and maintenance information carefully before using the product Refer to the manual for complete product specifications If the product is used in a manner not specified the protection pro vided by the product may be impaired The types of product users are Responsible body is the individual or group responsible for the use and maintenance of equipment for ensuring that the equipment is operated within its specifications and operating limits and for en suring that operators are adequately trained Operators use the product for its intended function They must be trained in electrical safety procedures and proper use of the instru ment They must be protected from electric shock and contact with hazardous live circuits Maintenance personnel perform routine procedures on the product to keep it operating properly for example setting the line voltage or replacing consumable materials Maintenance procedures are de scribed in the manual The procedures explicitly state if the operator may perform them Otherwise they should be performed only by service personnel Service personnel are trained to work on live circuits and perform safe installations and
121. tangular areais larger Figure 12 showsthe same curve as Figure 11 but slightly modified to allow it to be programmed into the M2000 MAX FIGURE 11 ILLEGAL FUNCTION FIGURE 12 Modified Function 5 2 MetraByte M2000 Programming Manual 2 The nonlinear function must be a single valued function of X That is for each input value there can exist one output value Figure 13 shows two illegal functions This limitation is seldom encountered in natural phenomenon Figure 13 illegal Functions Programming Steps 1 Define the function data to be programmed 2 Erase breakpoints 3 Clear zero 4 Use SetUp SU command to set number of displayed digits 5 Program the minimum endpoint 6 Program the maximum endpoint 7 Program breakpoints 8 Verify the function Step 1 Define the function data to be programmed The ability of the M2000 to simulate a nonlinear transfer function is highly dependent cn the location of the breakpoints seiected by the programmer The ultimate conformity to the desired function is directly dependent on the linear segment approximation loaded into the module The M2000 gives the programmer a great deal of flexibility in how the breakpoints are placed In areas where the function curves sharply or where greater accuracy is desired breakpoints may be placed close together for better conformity to the desired function The chart in Figure 4 is a handy form to help organize the breakpoint data
122. te M2000 Programming Manual 1 Erase Breakpoints Command 1WE Response Command 1EB Response 2 Clear Zero Command 1 WE Response Command 1 CZ Response 3 To produce the analog Xmin and Xmax endpoint values we will use the actual water levels in the tank to produce a calibration pressure The accuracy of the pressure transducer is not important as long as it is stable and linear To set the minimum value we will empty the tank and set the minimum value to 00000 00 The maximum value will be programmed with the tank full and the maximum output data will be set to 01500 00 gallons In this case an output resolution in units of gallons is acceptable and we can set up the module so that 5 digits are displayed The digits to the right of the decimal point will always read out 00 Command 1WE Response Command 1SU31070142 typical Response 4 With the tank empty program the minimum point Command 1 WE Response Command 1 MN 00000 00 Hesponse 5 Fill the tank with water and program the maximum point Command 1 WE Response MetraByte 2000 Programming Manual 4 9 Command 1 MX 01500 00 Response 6 Verify the scaling In this case it is difficult to verify the scaling quickly and accurately A check be made by letting water out of the full tank and checking to see if the module output readings are reasonable A more ac
123. ter at a time any problems associated with incorrect setups may be identified immediately Once a satisfactory setup has been developed record the setup value and use it to configure similar modules If you commit an error in using the SetUp command it is possible to lose communications with the module In this case it may be necessary to use the Default Mode to re establish communications The DA EA and LO commands affect some of the bits of the setup data that are associated with alarms If these commands are performed the setup data read back with the Read Setup RS command may not correspond exactly with the data previously written with the SetUp SU command 5 13 Table 5 5 Factory Setups by Model All modules from the factory are set for address 1 300 baud no parity Model Setup Message M111X M121X M123X M125X 310701C2 M112X M124X 31070182 M113X M114X 31070142 M13XX 31070142 M14XX 31070182 M15XX 310701C2 M16XX 310701 0 170 31070100 6 DIGITAL I O FUNCTION The M1000 series features versatile digital l O capability to interface to auxiliary equipment The functions available are 1 Digital Outputs 2 Digital Inputs 3 Alarm Outputs 4 Events Counter Digital Outputs A digital output consists of an open collector transistor controlled by the host using the Digital Output DO command See Figure 6 1 The number of digital outputs implemented depends on the specific M1
124. ter not counting properly Error in displayed value module response Assuming that the module is in a system complete the following steps before removing it from the system These steps will check the obvious things before removing 1 Using voltmeter measure the power supply voltage at the module Vs and Ground terminals to ensure that the power supplied is between 10 and 30 2 Check to see that the communications lines are connected properly and that there are no breaks in the lines 3 If you are using the RS 232C to RS 485 converter make sure the baud rate switch is sei to the correct position If the above steps do not correct the problem remove the module from the system and return to the bench Complete the following steps 1 Connect a working power supply between 10 and 30 Vdc to the Vs and Ground terminals on the module 2 Connect the module to a dumb terminal as in the Quick Hook Up proceedure Your terminal should be set to 300 baud rate and no parity Also if you are using the RS 485 converter make sure its baud rate is set to 300 baud 3 Connect a jumper wire from the Ground terminal to the Default terminal 4 Turn the power supply on type 1RD on the terminal and press the Return key If the module still does not respond call the factory for assistance If the module responds send a 1RS command to see if the information in the module s setup message is correct 1 Check that the
125. th the output data The high and low alarm registers are nonvolatile so they will not be lost when the unit is powered down The values contained in the alarm registers may be read back at any time with the Read High RH and Read Low RL commands The data held in the alarm registers is continually compared with the calculated output data The result of the comparison is used to trip alarms that may be used as control outputs The high alarm is turned on when the output data exceeds the high limit value The low alarm is activated if the output data is less than the low alarm value Each alarm has two user selectable modes either Momentary M or Latching 1 Momentary alarms are activated only while the alarm condition is met if the output data returns within limits the alarm is turned off Conversely when latching alarms are activated they remain on even if the 2 2 output data returns within limits Latching alarms are turned off with the Clear Alarms CA command or if the opposite alarm limit is exceeded The state of the alarms may be read with the Digital Input DI command Also the alarm outputs may be used to activate digital outputs on the module connector to turn on alarms or to perform simple control functions To help limit the number of terminals required on the module connector the alarm outputs are shared with the general purpose digital output bits DOO and DO1 To connect the alarm outputs to the connector the Enable
126. the Receive input of the host The daisy chain network must be carefully implemented to avoid the pitfalls inherent in its structure The daisy chain is a series connected structure and any break in the communications link will bring down the whole system Several rules must be observed to create a working chain 1 All wiring connections must be secure any break in the wiring power ground or communications will break the chain All modules must be plugged into their respective connectors 2 All modules must be setup for the same baud rate 3 All modules must be setup for echo y 99 Receive O Transmit Figure 3 1 RS 232 Daisy Chain Network Software Considerations If the host device is a computer it must be able to handle the echoed command messages on its Receive input along with the responses from the module This can usually be handled by software string functions by observing that a module response always begins with a or character and ends with a carriage return A properly addressed M1000 module in a daisy chain will echo all of the characters in the command including the terminating carriage return Upon receiving the carriage return the module will immediately calculate and transmit the response to the command During this time the module will not echo any characters that appear on its receive input However if a character is received during this computation period it will be stored the modu
127. the circuit under test or power line earth ground Always make measurements with dry hands while standing on a dry insulated surface capable of withstanding the voltage being measured The instrument and accessories must be used in accordance with its specifications and operating instructions or the safety of the equip ment may be impaired Do not exceed the maximum signal levels of the instruments and ac cessories as defined in the specifications and operating informa tion and as shown on the instrument or test fixture panels or switching card When fuses are used in a product replace with same type and rating for continued protection against fire hazard Chassis connections must only be used as shield connections for measuring circuits NOT as safety earth ground connections If you are using a test fixture keep the lid closed while power is ap plied to the device under test Safe operation requires the use of a lid interlock 5 02 If d is present connect it to safety earth ground using the wire recommended in the user documentation The AN symbol on an instrument indicates that the user should re fer to the operating instructions located in the manual The symbol instrument shows that it can source mea sure 1000 volts or more including the combined effect of normal and common mode voltages Use standard safety precautions to avoid personal contact with these voltages The WARNING hea
128. the value and type of the low alarm The alarm type can be either latching or momentary A letter indicating the alarm type L for latching or M for momentary will follow the alarm value For example Command 1RL Response 00000 00L Command 1RL Response 1RL 00000 00LEE The RLcommand may be used to verify data loaded into the nonvolatile memory with the LO command Remote Reset RR The reset command allows the host to perform a program reset on the module s microprocessor This may be necessary ifthe module s internal program is disrupted by static or other electrical disturbances Once a reset command is received the module wili recalibrate itself The calibration process takes approximately 2 seconds For example Command 1RR Response Command 1RR Response 1RRFF In general the state of the digital outputs and the event counter will not be affected by the RR command However if data in the microprocessors RAM Random Access Memory has been lost the RR command will result in a full power up reset Any commands sent to the module during the self calibration sequence will result in a NOT READY error 4 15 Read Setup RS The read setup command reads back the setup information loaded into the module s nonvolatile memory with the SetUp SU command The response to the RS command is four bytes of information formatted as eight hex characters Command 1RS Response 31070142 Command 1RS Resp
129. tput reading If the output corresponds to the applied input no calibration is necessary If the output is in overload check the circuit connections or use a different input value to obtain an output within the operating range of the module To trim the output use the Trim Span TS command The argument of the TS command should correspond to the desired module output After performing the TS command verify the trim using the RD command For example To trim a M1121 module the following steps should be performed 1 Clear the output offset register Command 1WE Response CZ is write protected Command 1CZ Response 2 Apply an input voltage near 90 of rated full scale In this case we will use a 900 mV input voltage that is accurate to at least 0 02 Obtain an output reading Command 1RD Response 00900 30 In this case the output of the module is off 300 pV To trim Command 1WE Response TS is write protected Command 1TS400900 00 Response This sequence will trim the output to the desired calibrated value of 00900 00 Verity Command 1RD Response 00900 00 The module is calibrated Thermocouples To start the calibration disable the cold junction compensation by setting bit 4 in byte 3 of the setup data with the SetUp SU command The module may now be calibrated using a known input voltage Perform the calibration as described for a voltage input module Table 9 1 giv
130. ts To route digital outputs to these pins use the Disable Alarms DA command Enable Alarms EA command configures these two pins as alarm outputs The Enable Alarms and Disable Alarms commands do not affect the other digital outputs 002 007 The digital outputs are controlled by the host with the Digital Output DO command If the module loses power the digital outputs are turned off The outputs will remain off until switched by a Digital Output DO command The function of the shared pins DOG LO and DO1 Hi is not affected if power is lost since this information is stored in nonvolatile memory The digital outputs are not affected by the Remote Reset RR command or a reset caused by a line break 6 2 DIGITAL INPUTS Digital inputs are used to sense switch closures and the state of digital signals The inputs are protected to voltages up to 30V and are normally pulled up to the logic 1 condition see Figure 6 3 Digital inputs can be read by the Digital Input DI command Voltage inputs less than 1 V are read back as 0 Signals greater than 3 5 V read as 1 No other commands have affect on the inputs Switch closures can be read by the digital input by simply connecting the switch between GND terminal and a digital input Internal pull ups used so additional parts are unnecessary The pull ups supply only 0 5 mA therefore self wiping switches designed for low current operation should be
131. ts 0 2 specify the communications baud rate The baud rate can be selected from eight values between 300 and 38400 baud Refer to Table 5 2 for the desired code The baud rate selection is the only setup data that is not implemented directly after an SU command In order for the baud rate to be actually changed a module reset must occur A reset is performed by sending a Remote Reset RR 5 4 command performing a line break see Communications or powering down This extra level of write protection is necessary to ensure that communications to the module is not accidently lost This is very important when changing the baud rate of an RS 232C string For more information on changing baud rate refer to the Communications section Let s run through an example of changing the baud rate Assume our sample module contains the setup data value of 31070080 Byte 2 is 07 By referring to the SU command chart we can determine that the module is set for no linefeeds no parity and baud rate 300 If we perform the Read Setup command with this module we would get Command 1RS Response 31070080 Let s say we wish to change the baud rate to 9600 baud The code for 9600 baud is 010 from Table 5 2 This would change byte 2 to 02 To perform the SU command we must first send a Write Enable command because SU is write protected Command iWE Response Command 1SU31020080 Response This sequence of messages is done in 300 baud
132. ts Counter 6 4 Alarm Outputs 6 5 On Off Controller 6 5 Setpoint 6 9 CHAPTER 7 Power Supply CHAPTER 8 Troubleshooting CHAPTER 9 Calibration Appendix A ASCII TABLE Appendix B M1400 Data Sheet Appendix C M1500 Data Sheet Appendix D M1600 Data Sheet WARRANTY MetraByte Corp warrants your M1000 series module to be free from defects in parts materials and workmanship under normal use and service for a period of one year from the date of delivery and will repair or replace at its sole option any defective unit brought to its attention during that period MetraByte Corp makes no implied warranty that the M1000 series modules will be suitable to your purpose Some states do not allow the exclusion of implied warranties or limited warran ties so the above may not apply to you In no event will MetraByte Corp be liable to you for any damages including lost profits lost savings or other incidental or consequential damages arising out of the use or inability to use this product even if MetraByte or an authorized MetraByte dealer has been advised of the possibility of such damages or for any claim by any other party MetraByte Corp cannot assume responsibility for infringement of present or future patents or other third party rights resulting from the use of these products Some states do not allow the limitation or exclusion of liability for incidental or consequential damages so the above limitation or exclusion may not apply to
133. ts Counter Circuit 64 ALARM OUTPUTS The M1000 sensor input modules perform limit checking by comparing the sensor input value to downloaded HI LO limit values stored in memory see and LO commands The result of the limit check can be used to control special HI and LO digital outputs The DOM LO and DO1 HI output pins can be configured to be alarm outputs by using the Enable Alarms EA command After performing an EA command the state of the DO LO and DO1 HI pins will be controlled by the alarm settings The EA command does not affect the other digital outputs DO2 DO8 The Disable Alarms DA command is used to disconnect the alarms from the output pins whereupon they are controlled by the Digital Output DO command Since the Alarm Outputs share the same circuits with the Digital Outputs all electrical interfacing considerations are the same Alarm limit values are loaded into the module with the Low limit LO and Hi limit HI commands The limit values are stored in nonvolatile memory so they will not be lost when power is removed The HI and LO commands are also used to specify whether the alarms are momentary or latching If an alarm is specified as momentary the alarm is activated as long as the alarm condition exists The alarm output will turn off when the input is within limits A Latching alarm is activated when the specified limit is exceeded and will remain on even if the input value returns within
134. ttachments that would affect the zero balance Obtain an initial reading using the Read Data RD command The output data will indicate the total offset of the system Subtract the offset value from the usable input range of your module either 60mV or 120mV The result is the maximum usable input overhead If the overhead is not sufficient for your application the bridge must be trimmed externally to lower the offset to an acceptable value The bridge may be trimmed with a small series resistance or a large shunt resistance to the appropriate leg of the bridge as shown is Fig 2 f the initial offset is acceptable the offset may be trimmed with the Trim Zero TZ command Shunt Trim e e e e e e e Figure 2 Bridge Circuit Trim Example 1 A load cell to be used in a weighing application is mated to a M1521 module The load celi is rated for 3 mV V which results in a maximum 30 mV with 10 V excitation However in this particular application the load cell is used only in tension so its ideal output will be from 0 to 30 mV The load cell is mounted in its final position with the weighing attachments Clear any offset data that may be stored in the M1521 module Command 1WE CZ is write protected Response Command 1CZ Clear Zero Response Verify that the Zero Trim is cleared Command 1RZ Read Zero Response 400000 00 Obtain an initial offset reading from the load cell with no weight atta
135. uation results in a 25 psi errorat V 2 5 V To obtain better accuracy we may approximate the quadratic transfer function using breakpoints Since the sensor output range is 0 5 V the M2131 with an input range of 5 V is most suitable for this application For simplicity we will use only four evenly spaced breakpoints to plot the function This will resultin a function approximation with a maximum error of 1 psi For better conformity more breakpoints may be used 1 First construct the function table Analog input Qutput Minimum 0 00100 00 00600 00 Breakpoint 00 00184 00 Breakpoint 01 2V 00276 00 Breakpoint 02 3 V 00376 00 Breakpoint 03 4 V 00484 00 Notice that we ve broken up the curve into five evenly spaced voltage segments by using four breakpoints The breakpoint output values were obtained by plugging the breakpoint voltage values into the quadratic equation that describes the sensor 2 Prepare the M2131 by erasing any stored breakpoints All programming commands must be preceded by a Write Enable WE command the interest of simplicity the Write Enable commands are not shown in this or any of the following examples Command 1EB Response 3 Clear any data in the output offset register Command 1CZ Response 4 We will setup the output data to display psi with 1 resolution Command 1SU31070182 typical Response 5 6 MetraByte M2000 Programming M
136. ure sensor and apply 5 V to the moduie input Command 1MX 35000 00 Response Re connectthe pressure sensor to the M2131 Starting with the standpipe empty we may begin to program the breakpoints We will set a breakpoint every 1500 gallons for a total of 20 breakpoints To set the first breakpoint fill the standpipe with 1500 gallons of water Since we will be using actual volumes of water to calibrate the standpipe the accuracy at which we can measure 1500 gallons will greatly influence the final performance of the system With 1500 gallons in the standpipe used as the input excitation program the first breakpoint Command 1BP00 01500 00 Response Test Command 1 Response 01500 00 Fill the standpipe with an additional 1500 gallons to program the second breakpoint The standpipe now holds 3000 gallons Command 1BP01 03000 00 Response Command 1 Response 03000 00 Repeat these steps until the standpipe is full For each step fili the standpipe with an additional 1500 gallons and program the breakpoint with the accumulated amount of water in the standpipe When the breakpoint programming is complete the M2131 will give a very accurate indication of the volume of water in the standpipe directly in units of gallons In this example the actual transfer function of the system is unknown Instead the function is plotted in the field by applying known inputs to the system Note that the voltage produced
137. usable span of 120 mV The extra Overhead is used to trim any bridge offsets SETUP DATA The factory setup for all versions of M1500 modules is 310701 2 SENSOR CONNECTIONS See Figure 1 for the proper bridge sensor connections Shields or grounds should be connected to the Excitation terminal OFFSET TRIM The M1500 modules do not provide any means of trimming the analog offset of the sensor bridge However sensor of sets may be nulled from the output data with the Trim Zero TZ command This method of trimming is convenient because the offset may be trimmed through the communications port at any time There is no need to have access to the module since the trimming is performed remotely input signal conditioning circuitry of the 1500 modules have wide input range to accommodate large sensor offsets without the need for external trims Modules rated for 30 mV have an input range capability of 60 mV Modules specified for 100 mV have an input range of 120 mV e e 2 e e e Figure 1 Bridge Circuit Wiring To perform an initial offset trim attach the bridge unit to the module as shown in Fig 1 Clear out any previous offset trims with the Clear Zero CZ command Apply the desired zero condition to the bridge sensor For a Strain Gage Bridge this would be the relaxed or unstrained condition For load cells the zero condition could include any tare weight due to a weighing platform or other a
138. use the M2121 module again as an illustrative example to show the effect of a breakpoint Figure 9 shows the M2121 function table with 1 breakpoint programmed Analog Input Data Output Minimum 1V 01000 00 Maximum 1V 01000 00 Breakpoint 00 2V 00800 00 Breakpoint 01 01000 00 00800 00 01000 00 Fig 9 MetraByte M2000 Programming Manual 2 7 Breakpoints 01 through 16 hex are erased and do not enter the function calculation The Minimum and Maximum table entries contain the standard data values of x01000 00 mV The new curve is shown in Figure 9 Notice how the breakpoint has affected the whole curve creating a nonlinear function Here are a few samples of the input output values that may be obtained from this curve nalog In Data Output 8 V 00700 00 6 V 00400 00 4V 00100 00 2 V 00200 00 00500 00 2V 00800 00 4V 00850 00 6V 00900 00 48V 00950 00 The procedure to create a breakpoint table is detailed in Section 4 Chapter 3 Command Set The M2000 module series incorporates the same command Set as the M1000 series with new commands added to facilitate custom range programming The added M2000 commands are used only for programming For normal operational commands refer to the M1000 manual CAUTION THE M2000 PROGRAMMING COMMANDS MUST BE USED WITH CARE EACH OF THE COMMANDS IS CAPABLE OF DESTROYING FACTORY CALIBRATION All of the commands added to the M2000 series are write p
139. used For other types of switches it may be necessary to provide extra pull up current with an external resistor The resistor should be tied between the switch and V Connection to logic outputs is shown in Figure 6 2 Opto isolation is used for isolation and where common mode exists between the M1000 module and the signal being sensed Digital inputs may be used to sense AC voltages by using isolated sensing modules offered by many manufacturers Figure 6 3 Digital Inputs 6 3 EVENT COUNTER The Event Counter input is connected to the Digital Input 0 terminal It can be used to count any low speed event that occurs on the DIG EV input Any of the interfacing techniques described for Digital Inputs may be used The input pulses must meet the specifications in Figure 6 4 to avoid missing counts Switch inputs are filtered to eliminate contact bounce The Event Counter is read by using the Read Events RE command The maximum accumulated count is 9 999 999 If the maximum count is reached counting stops The Event Counter may be cleared to zero with the Clear Events CE command The Event Counter is not nonvolatile and the count will be lost if power to the module goes down Upon power up the counter is cleared to zero The Remote Reset RR command or a line break will not affect the counter EY 5 PEN INPUT MINE E NE US Num 50 Duty Cycle Single Single 60 Hz Pulse Pulse 12ms Min 15ms Min Figure 6 4 Even
140. w standard Interface boards are available for the IBM PC and compatibles and other RS 485 equipment will become available as the standard gains popularity This means that an RS 485 system usually requires the extra expense of an interface MetraByte Corp offers interface converters to convert RS 232C and RS 422 to RS 485 For systems that require more than a few modules iong wiring distances or high speed RS 485 is recommended 3 6 B Black R Red G Green Y Yellow Figure 3 2 5 485 Multidrop Network RS 485 Multidrop System Figure 3 2 illustrates the wiring required for multiple moduie RS 485 system Notice that every module has a direct connection to the host system Any number of modules may be unplugged without affecting the operation of the remaining modules Each module must be setup with a unique address and the addresses be any order All RS 485 modules must be setup for no echo to avoid bus conflicts see Setup Also note that the connector pins on each module are labelled with notations B R G and Y These notations designate the colors used on standard 4 wire telephone cable Label Color B GND Black V Red G DATA Green Y DATA Yellow This convention is used all MetraByte RS 485 equipment to simplify installation If standard 4 wire telephone cable is used it is only necessary 10 match the labeled pins with the wire color to guarantee correct installation T
141. witching points occur symetrically on either side of the 2 5V level Since the low side of the input signal is connected to the 2 5V pin the switching points appear to be symmetrical to zero as referenced to the input signal The hysteresis may be varied from 5mv to 20 5 as shown in Fig 2 Vswitching Vhysteresis 2 5 0 5 1 7 x 5 0 For gt 5mV and lt 0 5 R 34 Vhysteresis 0 5 Vhusteresis Vswitching 25 14 2 e e e Figure 3 Controlling Hysteresis For Bipolar Signals The hysteresis control may aiso be connected to ground which produces another set of switching levels This connection is shown in fig 4 lf the HYSTR terminal is shorted to GND the nominal switching point is 1 6V with 5 of hysteresis To measure AC signals super imposed on a DC value the input may be AC coupled by simply placing a capacitor in series with the IN terminal The module contains an internal 1 resistor connected from the IN to 2 5V for biasing 01 uf cap may be used for frequencies down to 10 HZ M2000 SERIES PROGRAMMING MANUAL TABLE OF CONTENTS CHAPTER 1 CHAPTER 2 CHAPTER 3 CHAPTER 4 CHAPTER 5 Linear Scaling 1 1 Nonlinear Functions 1 2 Block Diagram 2 1 Programming Table 2 2 Breakpoints 2 5 BreakPoint Command 3 1 MiNimum Command 3 2 MaXimum Command 3 3 Programming Software 4 1 General Guidelin
142. wn Gallons d Height Figure 14 Scaling when function is unknown The standpipe is 50 feet tall and has a known capacity of 30 000 gallons A pressure sensor may be used et the base of the standpipe to obtain a reading of the water height Since 1 foot of water produces a pressure of 4335 psi the maximum pressure expected is 50 X 4335 21 7 psi The pressure sensor we willuse produces 0 5 volts for pressures of 0 25 psi A M2131 5 V input module will be used as the interface install the pressure sensor and the M1231 in place at the standpipe Prepare the M2131 by erasing breakpoints and clearing zero as detailed in Example N 1 In this case we will setup the M2131 to display four digits which will result in an output resolution of 10 gallons Start programming with the standpipe empty Enter the minimum value Command 1MN 00000 00 Response In this example the maximum point may be programmed by filling the standpipe to obtain the maximum pressure output However this is awkward and unnecessary Since the standpipe capacity is known to be 30 000 gallons and the pressure can never reach 25 psi we can simulate a maximum that we know can never be attained To do this we may apply 5V to the module input to simulate 25 psi The 5 V source does not have to be accurate We can set the 5 10 MetraByte M2006 Programming Manual maximum value to 35 000 gallons which is more than the standpipe can hold Disconnect the press
143. y the data values held in the Breakpoint Table Up to 23 breakpoints may be programmed to specify up to 24 linear segments Figure 8 illustrates the action of the breakpoints Figure 8a shows a basic linear transfer function described by the Minimum and Maximum points Figure 8b shows the effect of one breakpoint used to modify the linear function Notice that the breakpoint has created a nonlinear function described by two linear segments joined at the breakpoint Figure 8c shows that two breakpoints may be used to specify a nonlinear curve described by three linear segments Up to 23 breakpoints may be used to create complex nonlinear curves Breakpoints are stored in the EEPROM table in the same fashion as the minimum and maximum points Each breakpoint is described by an X Y pair specifying the analog input value at which the breakpoint occurs and the corresponding output data value When the micropro cessor reads the analog X data from the ADC it searches the breakpoint table to find the X value closest to the input data The micro then linearly interpolates between two breakpoints to calculate the resulting output data 2 6 MetraByte M2000 Programming Manual ykp Figure 8 Breakpoint Examples Any number of breakpoints up to 23 values may be specified The breakpoint table must be filled progressively starting with Breakpoint 00 to Breakpoint 16 hex Unused or erased breakpoints are not used in the function calculation Let s

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