H-4191 User Manual
Contents
1. Z2 0 lt cr gt lt lf gt Retries 0 no retries WAT ERLO G H 4191 SDI 12 Command and Response Protocol 2 11 2 12 Extended XHELP This command is used for installation and testing This command causes the H 4911 to display a listing of the supported SDI 12 commands This is not compliant with the SDI 12 specification and is not used with data loggers 2 12 SDI 12 Command and Response Protocol IATER L G H 4 1 9 1 2 SERIES Chapter 3 Auto Scan Mode 3 0 Auto Scan Mode The Auto Scan mode described in this chapter provides support for a simplex telemetry architecture for collecting data from remote SDI 12 sensors via a wireless link Wireless applications often arise where a SDI 12 sensor must be physically located hundreds or thousands of feet from the data logger Normal communications with SDI 12 sensors requires up to five transmissions to complete a measurement sequence e Master transmits the SDI 12 command e Slave transmits its response e Slave transmits a service request e Master transmits a SDI 12 data command e Slave transmits its data buffer If any of these transmissions are corrupted or lost the sequence must be repeated or re tried This sequence must be repeated for every SDI 12 sensor attached to the H 4191 Most telemetry architectures require the radios to be setup with either a sleep amp sniff configuration or setup with the receivers continually powered With the Auto S2. it will be assumed to be after the last digit For example 3 29 23 5 25 45 300 If one or more values were specified and a aDO returns no data lt CR gt lt LF gt only it means that the measurement was aborted and a new M command must be sent Example of a H 4191 aDO command Previous Command Response TZM IN ZOO2L lt er gt lt LtS Subsequent Command Response ZDO Z 12 01 lt cr gt lt lf gt Where 12 01 is the battery voltage War ERLOG H 4191 SDI 12 Command and Response Protocol 2 5 2 5 Continuous Measurements This is anew command for the Version 1 2 SDI 12 Specification Sensors that are able to continuously monitor the phenomena to be measured such as a cable position do not require a start measurement command They can be read directly with the R commands RO R9 The R commands work exactly like the D DO D9 commands The only difference is that the R commands do not need to be preceded with an M command Example of a H 4191 aRO command Previous Command Response ZRO Z 12 01 lt cr gt lt lf gt Where 12 01 is the battery voltage 2 6 Send Acknowledge Command The Send Acknowledge Command returns a simple status response which includes the address of the sensor Any measurement data in the sensor s buffer is not disturbed Command Response a a lt cr gt lt lf gt Where a Is the sensor address 0 9 A Z a z 2 6 SDI 12 Command and Response
3. 4191 Operation 1 5 When monitoring traffic between a data recorder and its SDI 12 sensors the display may sometimes have spurious characters which prefix the command For example pOM 00153 p0D0 0 4 56 0 0000 50 0 The lower case p in this example was caused by the break pulse generated by the data recorder A break is a 12mS or longer pulse on the data line which wakes the sensors from their low power sleep mode The serial asynchronous receiver transmitter UART in the H 4191 misinterprets the break as a random character 1 5 Low Power Operation The H 4191 normally reverts to a low power or sleep mode If either the DSR or CTS RS 232 inputs are active asserted the H 4191 awakens powers up its RS 232 transceiver and is available for full operation The red LED on the side of the enclosure is illuminated when the H 4191 is awake Most PC terminal programs automatically assert both DSR and CTS by default When the H 4191 is connected to a PC the H 4191 will normally awaken and remain awake as long as it is connected 1 6 Operation with a Radio Applications often arise where a SDI 12 sensor must be physically located hundreds or thousands of feet from the data logger Transparent wireless SDI 12 bridges are available for these applications Unfortunately transparent bridges can miss or drop measurements because of corrupted radio packet transmissions Wireless bridges are problematic because the SDI 12 protocol provides
4. 5 OxFF characters The OxFF characters are automatically discarded by the H 4191 When the remote H 4191 module s are awakened by the radio asserting RTS or CTS the H 4191 may miss the first few characters while completing its power up housekeeping The OxFF preamble characters allow time for the H 4191 to power up and be ready to input and process the command payload The H 4191 also supports a very low power simplex mode for use with telemetry radios where the H 4191 initiates SDI 12 measurements itself and pushes the data to the data logger or host See the Chapter 3 Auto Scan for further details 1 7 Sensor Z When implementing a wireless SDI 12 bridge as described in the previous section it is useful for the data logger to be capable of monitoring the battery voltage in the remote station In addition to functioning as a RS 232 to SDI 12 gateway the H 4191 has a built in sensor which responds to SDI 12 address Z The Z sensor can measure the H 4191 s 12V input voltage is used to facilitate turning flow control On or Off and is useful for testing and maintenance The Z sensor responds to all SDI 12 compliant commands however it is only accessible via the RS 232 port The built in sensor will not respond to a data logger connected to the SDI 12 port The sensor address can be changed from Z to another value if needed with the extended Change_Address_Command See Section 2 for further details WarerL
5. Protocol VATER L G H 4191 SERIES 2 7 Initiate Verify Command The Verify Command causes a verify sequence to be performed The result of this command is similar to the aM command except that the values generated are fixed test data and the results of diagnostic checksum tests The data generated in response to this command is placed in the sensor s buffer for subsequent collection using D commands The data will be retained in the sensor until another M C or V command is executed Command Response Description av atttn lt cr gt lt l1f gt Initiate verify sequence Where a is the sensor address 0 9 A Z a z V is an upper case ASCII character ttt is a three digit integer 000 999 specifying the maximum time in seconds the sensor will take to complete the command and have data available in its buffer n is a single digit integer 0 9 specifying the number of values that will be placed in the data buffer If n is zero 0 no data will be available using subsequent D commands Example of a aV command Command Response Time Values Description wa 40013 lt cr gt lt 1f gt _ 1 sec 3 Return fixed data and diagnostic data for testing purposes Subsequent Command Response WZDO Z2 123 456 78 9 y lt cr gt lt lf gt Key Description Units 123 456 Fixed test data 78 9 Fixed test data y FLASH checksum test 0 Failed 1 Passed War ERLOG H 4191 SDI 12 Command and Response Pr
6. d6 H 4191 Operation 1 7 1 8 RS 232 Hardware Flow Control The RS 232 port of the H 4191 supports optional RTS CTS hardware flow control for slow PLC s or RTU s which cannot input or receive the entire SDI 12 response message The H 4191 monitors its CTS input and transmits RS 232 characters only if CTS is asserted The H 4191 can buffer up to 128 SDI 12 response characters any additional input characters will be lost While the H 4191 is busy sending a SDI 12 command or doing retries it can buffer up to 128 characters from the RS 232 port The H 4191 de asserts the RTS output when the buffer is within 4 characters of becoming full The H 4191 comes from the factory with the RTS CTS hardware flow control set to Off An extended SDI 12 command allows the hardware flow control feature to be turned On or Off The On Off setting is stored in Flash memory internal to the H 4191 and remains in effect even if the power is lost See Chapter 2 for details 1 8 Operation WATERLOG H 4191 Chapter 2 SDI 12 Command and Response Protocol 2 0 SDI 12 Command and Response Protocol This is a brief description of the Serial Digital Interface SDI 12 Command and Response Protocol used by the WATERLOG Series Model H 4191 sensor Included is a description of the commands and data format supported by the H 4191 Refer to the document A SERIAL DIGITAL INTERFACE STANDARD FOR HYDROLOGIC AND ENVIRONMENTAL SENSORS Version 1 2 April 12 1996 Coordina
7. will be retained in the sensor until another M C or V command is executed Command Response Description aci Watttinn lt cre lt ifa Initiate measurement Where a is the sensor address 0 9 A Z a z 2 C is an upper case ASCII character ttt is a three digit integer 000 999 specifying the maximum time in seconds the sensor will take to complete the command and have measurement data available in its buffer nn is a two digit integer 00 99 specifying the number of values that will be placed in the data buffer If n is zero 0 no data will be available using subsequent D commands The data recorder may wake the sensor with a break and collect the data anytime after the specified processing time has elapsed 2 4 SDI 12 Command and Response Protocol VATER LOG H 4191 mS E RIES 2 4 Send Data Command The Send Data command returns sensor data generated as the result of previous aM aC or aV commands Values returned will be sent in 33 characters or less The sensor s data buffer will not be altered by this command Command Response aDO through aD9 apd d res pd d lt cr gt lt lf gt Where a is the sensor address 0 9 A Z a z 2 D0 D9 are upper case ASCII characters p Is a polarity sign or d d represents numeric digits before and or after the decimal A decimal may be used in any position in the value after the polarity sign If a decimal is not used
8. H 4191 will not respond if the command was invalid the address was out of range or the Flash memory programming operation failed Command Response Description aAn n lt cr gt lt l1f gt Change sensor address Where a is the current old sensor address 0 9 A Z a z 2 An ASCII may be used as a wild card address if the current address is unknown and only one sensor is connected to the bus A is an upper case ASCII character n is the new sensor address to be programmed 0 9 A Z NOTE To verify the new address use the Identify Command Example of a Change Sensor Address command Command Response Description ZA9 Men a Change sensor address to 9 War ERLOG H 4191 SDI 12 Command and Response Protocol 2 9 2 10 Extended Read Flow_Mode and Write Flow_Mode The RS 232 port of the H 4191 supports optional RTS CTS hardware flow control for slow host devices which cannot input or receive the entire SDI 12 response message The H 419 monitors it s CTS input signal and transmits RS 232 characters only if CTS is asserted The H 4191 comes from the factory with the RTS CTS hardware flow control set to OFF These two commands allow the hardware flow control feature to be checked or turned ON or OFF The On Off setting is stored in flash memory internal to the H 4191 and remains in effect even if the power is lost Once a new setting is written a copy is sent to the sensor data buffer for verificat
9. Model H 4191 RS 232 to SDI 12 Interface Module WATERLOG Owner s Manual Version 1 1 for Revision C or greater us DESIGN ANALYSIS ASSOCIATES INC 75 West 100 South Logan Utah 84321 Phone 435 753 2212 Fax 435 753 7669 Web http www waterlog com E mail waterlog waterlog com DESIGN ANALYSIS ASSOCIATES INC 75 West 100 South Logan Utah 84321 Phone 435 753 2212 Fax 435 753 7669 Web http www waterlog com E mail waterlog waterlog com Chapter 1 Operation 1 0 Introduction The WATERLOG H 4191 is a RS 232 to SDI 12 gateway interface module When connected to a personal computer or RS 232 terminal the H 4191 can be used to test and monitor SDI 12 sensors and data recorders The H 4191 allows a programable logic controller PLC remote terminal unit RTU or other data collection device with a RS 232 interface to access SDI 12 sensors The H 4191 provides the RS 232 to SDI 12 electrical interface generates the critical bus timing parity and command retries needed for the SDI 12 bus protocol The SDI 12 Serial Digital Interface is ideal for data logging applications with the following requirements Battery powered operation with minimal current drain Low system cost e Digital sensors output data directly in user units Sensors are interoperable and available from many different manufacturers The H 4191 has the following features Provides both electrical and protocol interface
10. Voltage Input 9 to 16 0 Volts DC Supply Current Sleep Mode 200A typ Active 25mA typ Surge Protection Built in 1 5 KVA Environmental Operating Temperature 40 C to 50 C Storage Temperature 50 C to 70 C Mechanical Material ABS plastic Size 3 75 Long x 2 65 Wide x 1 25 Deep Connectors RS 232 9 Pin female D sub DCE connections SDI 12 4 position terminal strip pluggable Phoenix Combicon WATERLOG H 4191 SERIES Appendix A Specifications Warranty The WATERLOG H 4191 is warranted against defects in materials and workmanship for two years from date of shipment Notes Specifications subject to change without prior notice due to ongoing commitment to product testing and improvement Specifications A 1
11. ands Standard Commands aM Make battery voltage measurement aRO Make battery voltage measurement aD0 Send Data aV Verify al Send Identification a Send Acknowledge aAn Change Address Extended Commands aXHELP Display the supported commands aXRFM Read hardware flow control mode O no I yes aXWFMn Write hardware flow control mode O no 1 yes aXRRT Read max retries O no retries aXWRTn Write max retries O no retries aXRASM Read AutoScan mode O off 1 on aXWASMn Write AutoScan mode O off 1 on aXRASI Read AutoScan interval 0 to 65535 seconds aXWASIn Write AutoScan interval 0 to 65535 seconds aXFAS Force AutoScan sequence aXRTL Read AutoScan task list aXWTL Write AutoScan task list aXTCOP Test the COP timer 2 2 SDI 12 Command and Response Protocol VATER L G H 4191 a SERIES 2 2 Measure Command The Measure Command causes a measurement sequence to be performed Data values generated in response to this command are stored in the sensor s buffer for subsequent collection using D commands The data will be retained in the sensor until another M C or V command is executed Command Response Description aM atttn lt cr gt lt lf gt Initiate measurement Where a is the sensor address 0 9 A Z a z 2 M is an upper case ASCII character ttt is a three digit integer 000 999 specifying the maximum time in seconds the sensor will take to comp
12. can mode the H 4191 is configured to periodically scan the sensors attached to its SDI 12 port and transmit push the data to the remote host With this architecture the receivers in the remote telemetry radios are not used and can be shut off to save power This scheme provides for very low power operation with a solar panel In addition only one transmission is needed for each sensor scan The data from all of the sensors attached to the SDI 12 port of a H 4191 is concatenated and sent in one transmission The pros and cons of the simplex telemetry architecture are as follows The H 4191 is programmed to transmit data on a fixed schedule such as every 15 minutes The H 4191 does not have a real time clock and has no knowledge of time of day The data logger or host must accept and parse asynchronous data from the remote site s e The data logger cannot schedule or synchronize the measurements A data transmission includes the concatenated data from all of the SDI 12 sensors attached to the SDI 12 port The remote telemetry radios can be configured with their receivers powered off WarerL d6 H 4191 Auto Scan Mode 3 1 With this telemetry architecture it is recommended the telemetry radios be configured for Acknowledged service With acknowledged service the transmitting module listens for an ACK acknowledgment If the transmitting module does not receive the ACK within the allotted time it will retransmit the packet The retrans
13. cated by the need to embed one or more SDI 12 end of command characters within the message string Without special care the first character encountered will be interpreted as a command delimiter To overcome this problem use the colon character as a place holder for the characters When writing the task list the H 4191 will automatically substitute the 6699 character when a character is encountered Command Description aXRTL Read TaskList axwTLdddddd Write TaskList Where a is the sensor address 0 9 A Z a z 2 XRTL are upper case characters XWTL are upper case characters ddddd is the ASCII task list string Example of a H 4191 Extended Read TaskList command Command Response ZXRTL Z TaskList ZM 1 0M 1 1M 2 lt cr gt lt lf gt Example of a H 4191 Extended Write TaskList command Command Response ZXWTLZM 1 OM 1 1M 2 7 TaskList ZM 1 0M 1 1M 2 lt cr gt lt 1lf gt 3 6 Auto Scan Mode WATERL G j H 4191 RS 232 Port Type Asynchronous 9600 baud 8 bit no parity fixed Flow Control RTS CTS optional Command Buffer 60 characters SDI 12 Port Baud Rate 1200 Protocol SDI 12 7 bit even parity 1 stop bit Output Voltage Levels Minimum high level 3 5 volts Maximum low level 0 8 volts Internal Voltage Monitor Address Z Range 6 18V Resolution 12 bit 004V Accuracy 1 Power Requirements
14. collect and view the current value Example of a H 4191 Extended Read AutoScanMode command Command Response Time Values Description ZXRASM Z700ll lt cr gt lt lf gt 1 sec 1 Read AutoScanMode Command Response Description ZDO Z2 0 lt cr gt lt lf gt AutoScanMode OFF Example of a H 4191 Extended Write AutoScanMode command Command Response Time Values Description ZXWASM1 Z700ll lt cr gt lt lf gt 1 sec 1 Write AutoScanMode Command Response Description ZD0 Z 1 lt cr gt lt lf gt AutoScanMode ON 3 4 Auto Scan Mode WATERL G j H 4191 3 4 Extended Read AutoScanInterval and Write AutoScanInterval The H 4191 comes from the factory with AutoScanInterval set to 900 seconds 15 minutes These two commands allow the scan interval to be examined or changed The setting is stored in Flash memory internal to the H 4191 and remains in effect even if the power is lost Once a new setting is written a copy is sent to the sensor data buffer for verification This data can be viewed by using a subsequent D command To read or verify the value any other time use the XRASI command Command Response Description AXRASI a0011 lt cr gt lt lf gt Read AutoScanInterval aXWASIn a0011 lt cr gt lt 1f gt Write AutoScanInterval Where a is the sensor address 0 9 A Z a z XRASI are upper case characters XWASI are upper case characters n 0 to 65535 seconds This comma
15. equence specified by the SDI 12 protocol The H 4191 generates up to four breaks with up to four retries per break 16 retries total The number of retries can be examined or changed using these two commands In some cases where a wild card address is employed with multiple sensors on a bus MaxRetry should be set to 0 no retries Once a new setting is written a copy is sent to the sensor data buffer for verification This data can be viewed by using a subsequent D command To read or verify the value any other time use the XRRT command Command Response Description aXRRT a0011 lt cr gt lt 1f gt Read MaxRetry aXWRTn a0011l lt cr gt lt lf gt Write MaxRetry Where a is the sensor address 0 9 A Z a z XRRT are upper case characters XWRT are upper case characters n number of retries This command takes 001 seconds to complete and places 1 value in the data buffer Use the aDO command to collect and view the current value Example of a H 4191 Extended Read MaxRetry command Command Response Time Values Description ZXRRT z70011 lt cr gt lt lf gt 1 sec 1 Read MaxRetry Command Response Description 2D ON Z 4 lt cr gt lt 1f gt Do up to 4 retries Example of a H 4191 Extended Write Flow_Control_Mode command Command Response Time Values Description ZXWRTO Z0011 lt cr gt lt lf gt 1 sec 1 Write MaxRetry Command Response Description ZD0
16. eter 3 is extracted The data from all three measurements is concatenated into one message and sent to the telemetry radio Each transmission is prefixed by a character and ends in a lt CR gt lt LF gt sequence The measurement fields are separated by a comma Each measurement field includes the sensor wow number a character and the measurement data For example 0 12 3 1 4 5 2 4 99 3 1 2 lt CR gt lt LF gt The data logger or telemetry host can use the character to frame the message and discard stray packets It must parse the message and extract the data fields 3 2 Auto Scan Mode WATERL G H 4191 3 2 Operation The Auto Scan mode is controlled by three settings AutoScanMode ScanInterval and the Task List These settings are made with extended commands to sensor address Z and are described in the following sections The Auto Scan mode is enabled by setting AutoScanMode 1 When activated the H 4191 will awaken from low power sleep and perform a sensor scan at the interval determined by the Scan Interval setting The H 4191 has no knowledge of time of day and employs a non temperature compensated time clock such that the scan time may drift a few seconds each day With this data acquisition architecture the data logger will normally time stamp the data however the measurement scans cannot be synchronized with other stations or aligned to fixed points of the clock 3 3 Extended Force Auto Scan Comma
17. functions between RS 232 amp SDI 12 Works with any sensor command response message including vendor specific extended commands Buffers the command so no special timing is required Generates proper parity for the SDI 12 bus Automatically sends SDI 12 retries Passes the sensor service request to the host Supports optional CTS RTS hardware flow control for a slow host device Low power mode facilitates use with a RS 232 data radio LED shows when the H 4191 is awake Built in sensor can measure the battery voltage Auto Scan feature supports low power operation with telemetry radios The H 4191 is packaged in a rugged plastic enclosure with screw mount ears Connectors located on each end provide easy hookup WarerL d6 H 4191 Operation 1 1 1 1 Applications Figure 1 shows a monitoring application where a laptop computer is used to monitor the SDI 12 communication between a data recorder and two SDI 12 sensors Figure 2 shows the connections when using the H 4191 as a gateway between a PLC and two SDI 12 sensors Laptop Computer Data Recorder E el 5 H 4191 Interface RS 232 v z ke a gt N SDI 12 Sensors SDI 12 Bus Figure 3 Interface between a PLC and Figure 4 Monitor a data recorder two SDI 12 Sensors 1 2 Operation The H 4191 has a microprocessor with both RS 232 and SDI 12 interface ports The H 4191 normally ope
18. insufficient time to make retries or other recovery When coupled with a data radio the H 4191 can be used to construct a non transparent wireless SDI 12 link With this architecture the H 4191 is permanently connected to one or more sensors at the remote site A pair of RS 232 data radios are installed between the data logger and the remote H 4191 The radios are normally programmed for sleep amp sniff low power operation When properly configured the data logger radios and H 4191 module can provide a low power wireless SDI 12 bridge capable of performing retries The data logger must be setup to initiate and collect SDI 12 commands responses from a RS 232 port instead of its normal SDI 12 port SDI 12 commands from the data logger are forwarded via the radios to the remote H 4191 When the remote data radio receives an inbound data packet it pulses the CTS input which awakens the H 4191 in preparation to receive the inbound message When the H 4191 detects the character it transmits the contents of its buffer to the remote SDI 12 bus in a contiguous frame with proper parity and bus timing The H 4191 waits for and collects any sensor response and forwards it to the radio The sensor response is sent over the radios back to the data logger If one or more of the radio transmissions is lost or corrupted the data logger can retry the entire sequence as needed The H 4191 has an internal inactivity timer which keeps the module a
19. ion This data can be viewed by using a subsequent D command To read or verify the value any other time use the XRFM command Command Response Description aXRFM a0011l lt cr gt lt 1lf gt Read Flow_Mode aXWFMn a0011 lt cr gt lt 1f gt Write Flow_Mode Where a is the sensor address 0 9 A Z a z XRFM are upper case characters XWFM are upper case characters n 0 flow control OFF 1 flow control ON This command takes 001 seconds to complete and places 1 value in the data buffer Use the aDO command to collect and view the current value Example of a H 4191 Extended Read Flow Control Mode command Command Response Time Values Description ZXRFM Z700ll lt cr gt lt lf gt 1sec 1 Read Flow Mode Command Response Description ZDO Z2 0 lt cr gt lt 1lf gt Flow Mode OFF Example of a H 4191 Extended Write Flow_Control_Mode command Command Response Time Values Description ZXWFM1 Z700ll lt cr gt lt lf gt 1sec 1 Write Flow Mode Command Response Description ZD0 Z4 1 lt cr gt lt lf gt Flow Mode ON 2 10 SDI 12 Command and Response Protocol IATER LOG H 4 1 9 1 SERIES 2 11 Extended Read MaxRetry and Write MaxRetry The H 4191 automatically generates SDI 12 compliant parity and timing After transmitting the command the H 4191 waits for up to 40mS for a sensor response If the sensor response fails to arrive the H 4191 performs a retry s
20. lete the command and have measurement data available in its buffer n is a single digit integer 0 9 specifying the number of values that will be placed in the data buffer If n is zero 0 no data will be available using subsequent D commands Upon completion of the measurement a service request a lt cr gt lt If gt is sent to the data recorder indicating the sensor data is ready The data recorder may wake the sensor with a break and collect the data any time after the service request is received or the specified processing time has elapsed Example of a H 4191 aM command Command Response Time Values Description Z7MI Z70021 lt cr gt lt lf gt 2 sec 1 Make measurement Subsequent Command Response TADOT Z 12 01 lt cr gt lt lf gt Where 12 01 is the battery voltage War ERLOG H 4191 SDI 12 Command and Response Protocol 2 3 2 3 Concurrent Measurement Command This is anew command for the Version 1 2 SDI 12 Specification A concurrent measurement is one which occurs while other SDI 12 sensors on the bus are also taking measurements This command is similar to the aM command however the nn field has an extra digit and the sensor does not issue a service request when it has completed the measurement Communicating with other sensors will NOT abort a concurrent measurement Data values generated in response to this command are stored in the sensor s buffer for subsequent collection using D commands The data
21. mission is made after a random delay slot to help avoid collisions With this scheme reliable transmission and retries are made by the telemetry radios not the data logger The 10 second inactivity timer in the H 4191 allows time for the radio the perform acknowledged service transmissions at the completion of a scan The Auto Scan mode is configured with extended SDI 12 commands to the H 4191 s built in SDI 12 sensor address Z The Z sensor is only accessible via the RS 232 port The built in sensor will not respond to a data logger connected to the SDI 12 port The sensor address can be changed from Z to another value if needed with the extended ChangeAddressCommand described in Section 2 3 1 Task List When the Auto Scan mode is activate the sensor scan is controlled by a Task List programmed into H 4191 The Task List is a simple ASCII string with SDI 12 commands in a comma separated variable CSV format Depending on the task list any SDI 12 address and any command can be generated 1 woe The format is as follows lt cmd gt lt gt lt parameter gt lt gt For example 0M 1 1M 2 5M 3 In this example a OM command is first sent to the SDI 12 port The response is collected from sensor O and the measurement data from parameter 1 is extracted Next the command 1M is sent to sensor 1 and the data from parameter 2 is extracted Finally the command 5M is transmitted and the data from param
22. nd This command is used for setup and testing and causes the H 4191 to immediately perform an Auto Scan sequence This command works regardless of the AutoScanMode setting Command Response Description aXFAS a0011 lt cr gt lt 1f gt Force an Auto Scan sequence Where a is the sensor address 0 9 A Z a z XFAS are upper case characters Example of a H 4191 Extended Force Auto Scan command Command Response ZXFAS None WATERLOG H 4191 Auto Scan Mode 3 3 3 3 Extended Read AutoScanMode and Write AutoScanMode The H 4191 comes from the factory with Auto Scan set to OFF These two commands allow the Auto Scan feature to be checked or turned ON or OFF The setting is stored in Flash memory internal to the H 4191 and remains in effect even if the power is lost Once a new setting is written a copy is sent to the sensor data buffer for verification This data can be viewed by using a subsequent D command To read or verify the value any other time use the XRASM command Command Response Description AXRASM a0011 lt cr gt lt lf gt Read AutoScanMode aXWASMn a001l1l lt cr gt lt 1f gt Write AutoScanMode Where a is the sensor address 0 9 A Z a z XRASM are upper case characters XWASM are upper case characters n 0 AutoScan Off 1 AutoScan On This command takes 001 seconds to complete and places 1 value in the data buffer Use the aDO command to
23. nd takes 001 seconds to complete and places 1 value in the data buffer Use the aDO command to collect and view the current value Example of a H 4191 Extended Read AutoScanInterval command Command Response Time Values Description ZXRASI Z700ll lt cr gt lt lf gt 1 sec 1 Read AutoScanInterval Command Response Description ZD0 7 900 lt cr gt lt lf gt AutoScanInterval 900 seconds Example of a H 4191 Extended Write AutoScanInterval command Command Response Time Values Description ZXWASI60 Z700ll lt cr gt lt lf gt 1 sec 1 Write AutoScanInterval Command Response Description ZD0 Z2 60 lt cr gt lt lf gt AutoScanInterval 60 seconds WATERLOG H 4191 Auto Scan Mode 3 5 3 5 Extended Read TaskList and Write TaskList The Task List is a simple ASCII string with SDI 12 commands in a comma separated variable CSV format These two commands allow the Task List to be observed or programmed The task list can be up to 32 characters Note in the example below that a measurement sequence in the task list can include the battery voltage measurement made by the H 4191 itself ZM The aXRTL Command works somewhat like a continuous measurement aRO command where the data is sent directly in the response No subsequent aDO command is needed The response message includes the sensor address usually Z a TaskList header and then the task list characters Writing a new task list is compli
24. ommonly complete a message with the ENTER Key If you use the ENTER Key to terminate the message do not type the character The H 4191 automatically generates SDI 12 compliant parity and timing After transmitting the command the H 4191 waits for up to 40mS for a sensor response If the sensor response fails to arrive the H 4191 performs a retry sequence specified by the SDI 12 protocol The H 4191 generates up to four breaks with up to four retries per break 16 retries total The number of retries can be programmed see Chapter 2 1 2 2 Sensor Response The response from a SDI 12 sensor is input by the H 4191 at 1200 baud and output to the RS 232 port at 9600 baud Any sensor service requests or other SDI 12 bus traffic are also forwarded from the SDI 12 port to the RS 232 port This feature allows the H 4191 to be used to passively monitor the activity on a SDI 12 bus between a data recorder and its sensors WarerL d6 H 4191 Operation 1 3 1 3 Making Connections Connect the RS 232 port of the H 4191 to the serial port of your personal computer or other host device with a standard 9 pin RS 232 cable provided The H 4191 has a female connector and is a DCE modem device The cable has 9 pin RS 232 connectors which can be plugged directly into a PC serial port without the use of gender or null modem adapters Program your host device for 9600 baud 8 bit no parity full duplex communication The host device must assert either CTS o
25. otocol 2 7 2 8 Send Identification Command The Send Identification Command responds with sensor vendor model and version data Any measurement data in the sensor s buffer is not disturbed Command Response nat allccccccccmmmmmmvvvxx xx lt cr gt lt lf gt Where a is the sensor address 0 9 A Z a z 2 I is an upper case ASCII character 1 is the SDI 12 version compatibility level e g version 1 2 is represented as 12 cccccccc is an 8 character vendor identification to be specified by the vendor and usually in the form of a company name or its abbreviation mmmmmm is a 6 character field specifying the sensor model number vyv is a 3 character field specifying the sensor version number XX XX is an optional field of up to a maximum of 13 characters to be used for serial number or other specific sensor information not relevant to operation of the data recorder Example of a aI command a12 DAA H 4191lvvvS nnnnnnVvkkk lt cr gt lt lf gt H 4191 implementation of the optional 13 character field S nnnnnnvkkk 12 bytes total Where nnnnnn is a Six character sensor serial number kkk is a three digit sensor firmware revision level 2 8 SDI 12 Command and Response Protocol IATER Lb G H 4191 a SERIES 2 9 Change Sensor Address Command The Change Sensor Address Command allows the sensor address to be changed The address is stored in non volatile Flash memory within the sensor The
26. r DSR to awaken the H 4191 from it s low power sleep mode RS 232 Connector Transmit Data Receive Data Data Set Ready Ground not used Input Clear To Send Awakens the H 4191 when asserted Controls TxD if RTS CTS flow control is on RTS Output Request To Send Asserted when awake and output buffer is not full The H 4191 has a 4 position terminal strip for making connections to the SDI 12 bus The H 4191 is powered Ok a from the 12V power G S N 100 Rev A terminal Input 9 to 16 Volts 9600 Baud RS 232 DCE 1 4 Operation WATERLOG H 4191 1 4 Testing the Interface You can test the H 4191 with a simple RS 232 terminal or computer using a terminal program such as SimpleTerm Xtalk or Hyperterminal The terminal program must assert either the CTS or DSR or both input signals to the H 4191 to awaken it from sleep The red LED on the H 4191 will be illuminated when it is awake and ready to communicate The interface is a full duplex connection depending on the settings of your terminal program you may or may not be able to see what you are typing on your screen If you make a mistake while typing the command use backspace key to delete the previous keystroke If you make a mistake and are not sure what is in the H 4191 s buffer press the or ENTER Keys to flush the buffer and start over When the H 4191 is first powered up it transmits a H 4191 Initialized debugging message to the RS 232 por
27. rates as a SDI 12 master device it issues SDI 12 commands and collects responses Under certain conditions the H 4191 can respond to host commands itself as a pseudo SDI 12 sensor see Section 1 7 The RS 232 interface port is connected to a personal computer or other host device The H 4191 provides two way communication between the RS 232 host and the SDI 12 bus During normal operation the host device sends an address together with a command to a SDI 12 sensor The sensor then replies with a response 1 2 Operation WATERLOG H 4191 1 2 1 Commands The RS 232 host interface is fixed at 9600 baud The H 4191 inputs SDI 12 commands ASCII characters from the host and places the character string in a buffer Up to 128 characters can be buffered The command can be sent at any speed even hand typed commands will work The backspace character 08h is supported and deletes the previous character in the buffer Note the SDI 12 protocol requires upper case characters When the H 4191 detects the SDI 12 command terminator character the H 4191 generates a SDI 12 break and transmits the contents of the buffer to the SDI 12 port in a contiguous burst with the proper parity and bus timing The H 4191 also accepts the lt CR gt character ENTER Key as a command terminator and substitutes the lt CR gt character with the required SDI 12 command terminator This makes the H 4191 easier to use for computer users who more c
28. t 1 4 1 H 4191 Initiates the Commands Try the following commands The sensor address in these examples is O and the sensor is a Design Analysis H 350 pressure sensor If your sensor has a different address use the appropriate address 1 Check to see if you can communicate with the sensor Issue a OI Identify command The sensor should respond with 012 DAA H 350001S 000000V 10 lt CR gt lt LF gt 2 Make a measurement Issue a OM command The sensor should respond with 00153 lt CR gt lt LF gt After 14 seconds the sensor will send a service request O lt CR gt lt LF gt Issue a ODO command to collect the data The sensor should respond with 0 4 56 0 0000 0 2 lt CR gt lt LF gt 1 4 2 H 4191 Monitors the SDI 12 Bus The H 4191 can be used to passively monitor the activity on a SDI 12 bus You can observe both the commands from the data recorder and the responses from the sensors The communications between a data recorder and a Model H 350 pressure sensor would appear as follows OM 00153 0D0 0 4 56 0 0000 50 0 In this example the data recorder issued a OM command the sensor responded with 00153 lt CR gt lt LF gt sensor 0 measurement time 015 sec 3 parameters will be returned Next the data recorder issued a ODO command and the sensor responded with 0 4 56 0 0000 50 0 lt CR gt lt LF gt sensor 0 stage 4 56 PSI 0 0 temperature 50 0 WarerL d6 H
29. ted by the SDI 12 Support Group 135 East Center Logan Utah During normal communication the data recorder sends an address together with a command to the H 4191 SDI 12 sensor The H 4191 then replies with a response In the following descriptions SDI 12 commands and responses are enclosed in quotes The SDI 12 address and the command response terminators are defined as follows a Is the sensor address The following ASCII Characters are valid addresses 0 9 A Z a z 2 Sensors will be initially programmed at the factory with the address of 0 for use in single sensor systems Addresses 1 to 9 and A to Z or a to z can be used for additional sensors connected to the same SDI 12 bus Address and are wild card addresses which select any sensor regardless of its actual address n Is the last character of a command block lt cr gt lt lf gt Are carriage return OD hex and line feed OA hex characters They are the last two characters of a response block Notes e All commands responses are upper case printable ASCII characters e Commands must be terminated with a character e Responses are terminated with lt cr gt lt If gt characters The command string must be transmitted in a contiguous block with no gaps of more than 1 66 milliseconds between characters WAT ERLOG H 4191 SDI 12 Command and Response Protocol 2 1 2 1 Command Summary The H 4191 supports the following SDI 12 comm
30. wake to process the service request and receive subsequent radio packets If both the RS 232 and SDI 12 ports become 1 6 Operation WATERLOG H 4191 inactive and both CTS and RTS are not asserted for longer than 10 seconds the timer expires and the H 4191 enters its low power sleep mode The H 4191 examines the aTTTN lt CR gt lt LF gt sensor response initiated by an aM measure command and initializes a second keep awake timer to TTT 3 seconds This ensures the H 4191 will remain awake to process the service request When the service request actually arrives the keep awake timer is zeroed While the keep awake timer is running the H 4191 sends a null 00h to the radio once second to keep the radio link awake while waiting for the service request Be aware that with a point to multipoint telemetry architecture the data logger must take care to not generate excessive retries when attempting to recover a missed measurement During a retry the transmissions are seen by all of the remote stations in the system and will cause them to stay awake to process the communications If one remote station were to quit working for some reason the extra retry communications causes stress on the batteries of the remaining stations If excessive retries are done the remote stations can fail one by one in a cascade of increasing retries When sleep amp sniff radios are employed the host data logger should prefix outbound commands with 4 or
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