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Using a KPSI Transducer Probe

P/N: 500-1CB-0005

By Don Marek

Lab Manager

Texas A&M University-Kingsville

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Table of Contents

I. Install the software. ................................................................................................................. 3 II. Building the Circuit............................................................................................................... 3

Figure 1: Schematic of the circuit........................................................................................... 3 Figure 2: Completed circuit without cover over 9-pin connection. ........................................ 4 Figure 3: Completed circuit connected to a laptop serial interface card................................. 5

III. Reading the probe. ................................................................................................................ 5 Figure 4: Screen for setting the communication parameters. ................................................. 6 Figure 5: Main screen of KITS. .............................................................................................. 6

IV Writing a Script to Test Probe Functions .............................................................................. 6 Figure 6: Screen for executing a script. .................................................................................. 7 Figure 7: Script to get temperature and change units of reported depth................................. 7

VI. Calibrating the probe to Zero................................................................................................ 8 Figure 8: Script to zero probe. ................................................................................................ 8 Figure 9: Script to retrieve a depth. ........................................................................................ 8 Figure 10: Put the probe in a measured amount of water to determine whether it is reading. 9

VII. Care of probe....................................................................................................................... 9 Figure 11: The desiccant inside the plastic tube must be replaced periodically..................... 9

VIII. Using the probe with a Campbell CR205 datalogger. ..................................................... 10 REFERENCES ......................................................................................................................... 11

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Getting Started Guide for Using the KPSI Probe Model 500 The pressure transducer can be used to measure the depth of water whether in a small tank (12 feet or less depth) or in a gully or tributary of a shallow creek. This guide shows how to connect the probe to the computer so it can be determined whether the probe is functional. A section will be added later for using it with a Campbell Scientific CR205 data logger. I. Install the software. Download the files kitsins.exe and kitsuman.exe from http://www.pressuresystems.com/. The first file is the program to contact the probe and should be installed first; in the second file are the manuals in PDF format that are installed under the same location as the kitsin.exe file. Follow the onscreen instructions. SDI-12 is a timing dependent protocol and will not function with a Windows Hyperterminal type communications program. II. Building the Circuit Construct the circuit as shown in the following schematic. The diode can be purchased at Radio Shack and must be that specific part number to function properly. A 9V battery is adequate for an external supply.

Figure 1: Schematic of the circuit.

Parts required:

1. Diode 1N4148 Radio Shack Catalog #: 276-1620 (No substitution!!!) 2. 25-Position D-Sub Metal Hoods for 9-Pin D-Sub Connectors Catalog #: 276-1510 3. 9-Position Female D-Sub-miniature Crimp Type Connect Catalog#: 276-1428 4. Dual-Row Barrier Strips-4 PositionCatalog #: 274-65 5. 9 Volt Snap Connector Catalog #: 270-324 6. 9 Volt alkaline battery 7. Dual-Row Barrier Strips-4 Position Catalog #: 274-658 8. Short length of multi-conductor cable with at least 2 or more wires.

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Tools required: Needle nose pliers, Philips and a flathead screwdriver, wire strippers, soldering iron, solder, voltmeter with DC and diode test options. Construct the circuit so that it looks similar to the one pictured. It may be better to solder some of the connections, particularly on the 9-pin connection side. If a multi-conductor cable is available, try to use the same colored wire for each relevant connection. Red for power to the probe, black for ground/negative connection, white for data so that there is less problems when trying to use the circuit later. Make sure that the diode is connected in the correct direction relative to the female connector. The diode’s purpose is to make sure that an electrical signal is sent in one direction. A voltmeter can be used to check the direction of the diode.

Figure 2: Completed circuit without cover over 9-pin connection.

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Make sure to wire the ground from serial pin 5 to the battery or power supply’s negative connection. The RS232 operates on voltage levels, and the grounding to pin 5 provides a reference voltage to help the port to correctly function. Wrap some electrical tape around the diode before placing the cover on the 9-pin connection. A 6-terminal strip was used in the above circuit, but four terminals are enough to wire everything.

Figure 3: Completed circuit connected to a laptop serial interface card.

III. Reading the probe.

The circuit is constructed and the software installed. Wire the probe as shown to the circuit. Make sure to connect to a “real” serial port such as a 9-pin port on the back of almost any desktop PC. If using a laptop, a single serial PC Card should work. The probe was read successfully with an SIIG, Inc 16550 Serial Port PC Card. An USB to serial interface will probably not work since SDI-12 is based on timing signals that must be precisely processed through a serial port connection. Start the KPSI software. Go to the menu items and select “Configure” and select “Xducer site network Ctrl-F2”. The following window will appear. Set the Protocol, and Serial Port Options as shown in Figure 4. The “Port” can be set for Com 1, Com 2, Com 3, or Com 4. To determine the COM’s available on the computer, go to “Start”->”Settings”->”Control Panel”->”System”->”Hardware” Tab->”Device Manager”. Under the Device Manager window, looks for the “+” with “Ports(COM & LPT)” to identify active COM’s. The COM number can be changed by clicking under “Advanced” and changing the port number.

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Figure 4: Screen for setting the communication parameters.

Initially, a list of 15 transducers will appear; you might reduce this list to only 1 transducer. This can be done by highlighting the columns, pressing right click, and select the option to delete the additional transducers. The software will offer a prompt to make sure you want the additional probe deleted. The new “network” can be saved under a different file name. After setting up for only one transducer and connecting the circuit, press the “QUERY” button. If successful, you should see a number under the ‘ID Response’ and ‘Ser#’ column. A string of digits should match the serial number on the probe. Here is an example:

Figure 5: Main screen of KITS.

The digits “304558” will match the serial number print on the connected probe set to address ‘0’. IV Writing a Script to Test Probe Functions Scripts can be written to identify the probe, read temperature in Celsius or Fahrenheit, and test which units are best to measure the depth of water for an application. To write a script, go to “Test Execute Script”.

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Figure 6: Screen for executing a script.

Use the “Browse” button to select a file. Pressing the “View/Edit” button will automatically enter the Windows Notepad editor. Enter the following script with no Tabs and no empty lines between commands. No exclamation (!) is required at the end of each command. This a good script to try first after connecting the probe. The program below executes commands to identify the probe, get the temperature Celsius, change the output temperature to Fahrenheit, output the depth to millimeters and return a value. The probe must be set to address 0 (zero) for the script in Figure 7 to work. 0I 'Identify 0M2 'Get temp WaitSR 'Service request 0D0 'Get measurement 0XUT+1 'Change temp F 0M2 'Get temp again WaitSR 0D0 0XUP+5+2 'Set output mm to decimal places 0M WaitSR 0D0

Figure 7: Script to get temperature and change units of reported depth.

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After entering in Notepad, save the file with a name such as “test.cmd” and press the “Execute” button. As the script runs, alternating yellow to green should appear. If a red flashes as the messages are displayed, recheck the script and try again. Once the commands above have been executed, the probe will now be set to read temperature in Fahrenheit and retrieve the depth in units of mm (millimeters). The probe has an EEROM (Electrically Erasable Read Only Memory) that can hold its settings even after the power has been disconnected. To test this, edit the script in notepad and put “ ‘ “ in front of the line with the remark “Change temp F”, “Get temp”, the next two lines, and at the beginning of the “Set output to mm to decimal places.” Run the script to see the results. VI. Calibrating the probe to Zero Execute the XS! command to vent the probe to the atmosphere and change the units. After running, the value read should be less than 1 mm. Make sure to remove the black cap at the bottom of the desiccant container so that it is open to the atmosphere. Here is a script: 0I ‘Identify the probe 0XS ‘Vent probe Wait PrvRspSec ‘Wait command to finish 0M ‘Measure depth WaitSR 0XUP+5+2 'Set output mm to decimal places 0M WaitSR 0D0

Figure 8: Script to zero probe. Here is a script to read the depth of water. Put the probe into a measured amount of water and execute a script to measure to see if the value returned is reasonable. 0I ‘Identify the probe 0M ‘Take measurement WaitSR 0D0 ‘Read measurement

Figure 9: Script to retrieve a depth.

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Figure 10: Put the probe in a measured amount of water to determine whether it is

reading. VII. Care of probe.

Figure 11: The desiccant inside the plastic tube must be replaced periodically. Don’t forget

to remove the cap from the bottom before calibrating or using in the field. The desiccant must be replaced periodically depending upon local conditions of humidity. Replace with a Drierite, Indicating (4 Mesh) that can be purchased from VWR or other lab

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products vendor. If installing the probe outdoors, it is a good idea to house the desiccant container inside a PVC pipe with some electrical duct seal on top where the thin tube goes to the probe to keep water and sun off of it. Leave the bottom of the PVC pipe open and mount it in an upright position. Don’t forget to remove the cap when calibrating or actively using the probe. VIII. Using the probe with a Campbell CR205 datalogger. (To be continued).

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REFERENCES

Documents: Series 500 SDI-12 Transducers, User’s Manual, February, 2002, Pressure Systems, Inc., 24 pages, c2002. KPSI Integrated Transducer Software, Configuring and Querying a Site, Chapter 3, Pressure Systems, Inc., 28 pages, c2002. KPSI Integrated Transducer Software, Appendix S, Script File Formats, Pressure Systems, Inc., 19 pages, c2002. SDI-12 A Serial-Digital Interface Standard for Microprocessor-Based Sensors Version 1.3, 45 pages, SDI-12 Support Group, c2002. Websites: SDI-12: http://www.sdi-12.org/ Pressure Systems: http://www.pressuresystems.com/ RadioShack: http://www.radioshack.com/