Reference_4_SBE_38_Digital_Oceanographic_Thermometer_With_RS-232_or_Optional_RS-485_Manual_No._14_4-25-13.pdf

SBE 38 Digital Oceanographic Thermometer

With RS-232 or optional RS-485 Interface

User’s Manual Sea-Bird Electronics, Inc.

13431 NE 20th Street Bellevue, Washington 98005 USA Telephone: +1 425-643-9866 Fax: +1 425-643-9954 E-mail: seabird@seabird.com Manual Version #014, 04/25/13 Website: www.seabird.com Firmware Version 1.4 and later

Limited Liability Statement

Extreme care should be exercised when using or servicing this equipment. It should be used or serviced only by personnel with knowledge of and training in the use and maintenance of oceanographic electronic equipment.

SEA-BIRD ELECTRONICS, INC. disclaims all product liability risks arising from the use or servicing of this system. SEA-BIRD ELECTRONICS, INC. has no way of controlling the use of this equipment or of choosing the personnel to operate it, and therefore cannot take steps to comply with laws pertaining to product liability, including laws which impose a duty to warn the user of any dangers involved in operating this equipment. Therefore, acceptance of this system by the customer shall be conclusively deemed to include a covenant by the customer to defend, indemnify, and hold SEA-BIRD ELECTRONICS, INC. harmless from all product liability claims arising from the use or servicing of this system.

Manual revision 014 Table of Contents SBE 38

Declaration of Conformity

Manual revision 014 Table of Contents SBE 38

Table of Contents Limited Liability Statement

Declaration of Conformity

Table of Contents

Section 1: Introduction About this Manual Quick Start Unpacking SBE 38

Section 2: Description of SBE 38 System Description Specifications Dimensions and End Cap Connector Cables and Wiring

Section 3: Preparing SBE 38 for Deployment Installing Software Power and Communications Test

Test Setup Test

Section 4: Deploying and Operating RS-232 SBE 38 Sampling Modes

Polled Sampling Continuous Sampling

Baud Rate, Cable Length, and Power Command Descriptions Data Formats Deployment Recovery

Section 5: Routine Maintenance and Calibration Corrosion Precautions Connector Mating and Maintenance Sensor Calibration

Glossary

Appendix I: Functional Description Sensor Interface Settings

Appendix II: Electronics Disassembly/Reassembly

Appendix III: RS-485 Interface Operation Description Command Descriptions Data Formats Wiring Conversion of RS-232 to RS-485 or RS-485 to RS-232

Appendix IV: RS-232 Command Summary

Appendix V: Replacement Parts

Appendix VI: Manual Revision History

Index

Manual revision 014 Section 1: Introduction SBE 38

Section 1: Introduction

This section includes a Quick Start procedure, and photos of a standard SBE 38 shipment.

About this Manual

This manual is to be used with the SBE 38 Digital Oceanographic Thermometer. It is organized to guide the user from installation through operation and data collection. We’ve included detailed specifications, command descriptions, maintenance and calibration information, and helpful notes throughout the manual.

Sea-Bird welcomes suggestions for new features and enhancements of our products and/or documentation. Please contact us with any comments or suggestions (seabird@seabird.com or 425-643-9866). Our business hours are Monday through Friday, 0800 to 1700 Pacific Standard Time (1600 to 0100 Universal Time) in winter and 0800 to 1700 Pacific Daylight Time (1500 to 0000 Universal Time) the rest of the year.

Quick Start

Follow these steps to get a Quick Start using the SBE 38 with a standard RS-232 interface. The manual provides step-by-step details for performing each task:

1. Test Power and Communications (see Section 3: Preparing SBE 38 for Deployment).

2. Deploy the SBE 38 (see Section 4: Deploying and Operating RS-232 SBE 38 for a complete description of setup, or see Appendix IV: RS-232 Command Summary):

A. Establish setup parameters.

B. Check status (DS) and calibration coefficients (DC) to verify setup.

C. Use one of the following sequences to start sampling:

• If AutoRun=N: Send Go to start sampling continuously now, or TS or TH to take a single sample.

• If AutoRun=Y: Apply power to start sampling continuously now.

D. Deploy SBE 38.

For an SBE 38 with optional RS-485 interface, see Appendix III: RS-485 Interface for details.

Manual revision 014 Section 1: Introduction SBE 38

Unpacking SBE 38

Shown below is a typical SBE 38 shipment.

Software, and Electronic Copies of Software Manuals and User Manual

SBE 38

I/O Cable with 9V battery snap connector and 9V battery

Manual revision 014 Section 2: Description of SBE 38 SBE 38

Section 2: Description of SBE 38

This section describes the functions and features of the SBE 38, including specifications and dimensions.

System Description

Sophisticated A/D acquisition electronics, ultra-stable thermistor, and state-of-the-art calibration provide the standards-level performance of an expensive AC bridge and platinum thermometer at a small fraction of the cost. The SBE 38 is unaffected by shock and vibration, has high accuracy and stability, and is easy to use. It has a rugged, corrosion-proof, 10,500 meter (34,400 foot) titanium pressure housing. Real-time temperature data is transmitted in ASCII characters (in °C or raw counts) via an RS-232 or optional RS-485 serial interface for display or logging by PC or data logger.

The SBE 38’s measurement range is -5 to +35 °C. Absolute accuracy is better than 0.001 °C (1 mK) and resolution is approximately 0.00025 °C (0.25 mK).

Each sensor includes certification that demonstrates drift of less than 0.001 °C (1 mK) during a six-month period.

Applications include calibration baths, oceanographic/aquatic research, and environmental monitoring.

The SBE 38 operates in one of three ways:

• RS-232 (full duplex) with one SBE 38 connected to the interface

• RS-485 (half duplex) with one SBE 38 connected to the interface

• RS-485 (half duplex) with several RS-485 sensors sharing one pair of wires

On power-up, the SBE 38 reads its EEPROM, which includes calibration coefficients and other setup information. As programmed, the SBE 38 samples and transmits temperature continuously, or waits for a command to begin sampling. Note that for RS-485 applications with several sensors sharing one pair of wires, the SBE 38 cannot sample continuously.

The SBE 38 is frequently integrated as a remote temperature sensor with one of our thermosalinographs (SBE 21 Thermosalinograph or SBE 45 MicroTSG), to provide accurate sea surface temperature. See the manuals for those instruments for integration information.

The SBE 38 is supplied with a powerful Windows software package, Seasoft V2, which includes:

• Seaterm terminal program for easy communication.

• Seasave V7 real-time data acquisition and SBE Data Processing post-processing programs –Seasave V7 and SBE Data Processing can be used to view and process the entire data stream, including data from the SBE 38, when the SBE 38 is integrated with one of the following -

- SBE 21 or 45 thermosalinograph;

- SBE 16plus, 16plus V2, or 16plus-IM V2 SeaCAT C-T Recorder; or SBE 19plus V2 SeaCAT CTD Profiler.

- SBE 25plus Sealogger CTD (SBE 38 data cannot be viewed in real-time with this CTD)

Notes:

• Help files provide detailed information on the software.

• Separate software manuals on

CD-ROM contain detailed information on Seasave V7 and SBE Data Processing.

• Sea-Bird supplies the current version of our software when you purchase an instrument. As software revisions occur, we post the revised software on our FTP site. See our website (www.seabird.com) for the latest software version number, a description of the software changes, and instructions for downloading the software from the FTP site.

Specifications

Measurement Range -5 to +35 °C

Initial Accuracy 1 ± 0.001 °C (1 mK)

Typical Stability 0.001 °C (1 mK) in 6 months, certified

Resolution 0.00025 °C (0.25 mK)

Calibration -1 to +32 °C

Response Time 2 500 milliseconds

Self-Heating Error less than 200 µK

RMS Noise (at temperature equivalent of 8.5 °C)

NAvg Noise (°C) 1 0.000673 2 0.000408 4 0.000191 8 0.000133 16 0.000081 32 0.000052

Note:

NAvg = number of A/D cycles per sample.

Interval between samples (seconds) = (0.133 * NAvg) + 0.339

External Power

RS-232 (standard):

8 – 15 VDC at 15 milliamps average

RS-485 half-duplex (optional):

8 – 15 VDC at 10 milliamps average

Materials Titanium pressure case rated at 10,500 meters (34,400 feet)

Weight In water: 0.5 kg (1.2 lbs) In air: 0.9 kg (2.0 lbs)

Notes:

1 NIST-traceable calibration applying over the entire range.

2 Time to reach 63% of final value following a step change in temperature.

Note:

If the SBE 38 is sampling data and the voltage is less than

6.5 volts for 10 consecutive scans, the SBE 38 halts sampling and displays a low battery indication in the data.

Dimensions and End Cap Connector

The SBE 38 is available with a 4-pin XSG-4-BCL-HP-SS or optional MCBH-4MP (WB), TI (3/8” length base, ½-20 thread) (wet-pluggable) external connector.

Cables and Wiring

Pin Signal 1 Common 2 RS-232 Receive or RS-485 A 3 RS-232 Transmit or RS-485 B 4 Power

4-pin to DB9 - SBE 38 to computer (Note: also available with battery snap; see

DN 32604 [RMG

connector] and

32490 [MCIL

connector])

Manual revision 014 Section 3: Preparing SBE 38 for Deployment SBE 38

Section 3:

Preparing SBE 38 for Deployment

This section describes the software installation and the pre-check procedure for preparing the SBE 38 for deployment.

Installing Software

Seasoft V2 was designed to work with a PC running Windows XP service pack 2 or later, Windows Vista, or Windows 7.

If not already installed, install Sea-Bird software programs on your computer using the supplied software CD:

1. Insert the CD in your CD drive.

2. Install software: Double click on SeasoftV2.exe. Follow the dialog box directions to install the software. The installation program allows you to install the desired components. Install all the components, or just install Seaterm, Seasave V7, and SBE Data Processing

The default location for the software is c:\Program Files\Sea-Bird. Within that folder is a sub-directory for each program.

Power and Communications Test

Test Setup

1. If applicable, remove locking sleeve and dummy plug from bulkhead connector:

A. By hand, unscrew the locking sleeve from the SBE 38’s bulkhead connector. If you must use a wrench or pliers, be careful not to loosen the bulkhead connector instead of the locking sleeve.

B. Remove the dummy plug from the SBE 38’s bulkhead connector by pulling the plug firmly away from the connector.

2. Install the Sea-Bird I/O cable on the SBE 38:

• XSG Connector (shown in photos) - Align the raised bump on the side of the connector with the large pin (pin 1 - ground) on the

SBE 38.

• MCBH Connector (optional) – Align the pins.

3. Connect the I/O cable connector to your computer’s serial port.

4. Connect the I/O cable battery terminal clip to a 9-volt battery. Note that the 9-volt battery supplied with the SBE 38 will provide approximately 50 hours of operation.

Cable

Locking sleeve

Dummy plug

Notes:

• Help files provide detailed information on the software.

Separate software manuals on the CD-ROM contain detailed information on Seasave V7 and SBE Data Processing.

• It is possible to use the SBE 38 without the Seaterm terminal program by sending direct commands from a dumb terminal or terminal emulator, such as Windows HyperTerminal.

• Sea-Bird supplies the current version of our software when you purchase an instrument. As software revisions occur, we post the revised software on our FTP site. See our website (www.seabird.com) for the latest software version number, a description of the software changes, and instructions for downloading the software from the FTP site.

Test

1. Double click on Seaterm.exe. If this is the first time the program is used, the setup dialog box may appear:

Select the instrument type (SBE 38) and the computer COM port for communication with the SBE 38. Click OK.

2. The main screen looks like this:

• Menus – Contains tasks and frequently executed instrument commands.

• Toolbar – Contains buttons for frequently executed tasks and instrument commands. All tasks and commands accessed through the Toolbar are also available in the Menus. To display or hide the Toolbar, select View Toolbar in the View menu. Grayed out Toolbar buttons are not applicable.

• Command/Data Echo Area – Echoes a command executed using a Menu or Toolbar button, as well as the instrument’s response.

Additionally, a command can be manually typed in this area, from the available commands for the instrument. Note that the instrument must be awake for it to respond to a command (use Connect on the Toolbar to wake up the instrument).

• Status bar – Provides status information. To display or hide the Status bar, select View Status bar in the View menu.

Note:

See SEeaterm’s help files.

Note:

There is at least one way, and as many as three ways, to enter a command:

• Manually type a command in

Command/Data Echo Area

• Use a menu to automatically generate a command

• Use a Toolbar button to automatically generate a command

Note:

Once the system is configured and connected (Steps 3 through 5 below), to update the Status bar:

• on the Toolbar, click Status; or

• from the Utilities menu, select

Instrument Status.

Seaterm sends the status command, which displays in the Command/Data Echo Area, and updates the Status bar.

Status bar

Menus

Command/Data Echo Area Toolbar

Instrument Computer COM port

Instrument EPROM version

Baud rate, data bits, stop bits, and parity

Capture to file status – grayed out if not capturing

SBE 38

Following are the Toolbar buttons applicable to the SBE 38:

Toolbar Button Description Equivalent

Command*

Connect Re-establish communications with SBE 38.

Computer responds with S> prompt.

(press Enter key)

Status Display instrument setup and status (number of A/D cycles per sample, sampling status, etc.). DS

Coefficients Display calibration coefficients. DC

Capture

Capture instrument responses on screen to file.

File has .cap extension. Press Capture again to turn off capture. Capture status displays in Status bar.

Disconnect Free computer COM port used to communicate with SBE 38. COM port can then be used by another program.

*See Command Descriptions in Section 4: Deploying and Operating

RS-232 SBE 38.

3. In the Configure menu, select SBE 38. The dialog box looks like this:

Make the selections in the Configuration Options dialog box:

• COMM Port: COM 1 through COM 10, as applicable

• Baud Rate: 9600 (documented on Configuration Sheet)

• Data Bits: 8

• Parity: None

• Mode: RS-232 (Full Duplex) or RS-485 (Half Duplex) Click OK to save the settings.

Computer COM port, baud rate, data bits, and parity for communication between computer and SBE 38

Interface for communication between computer and

SBE 38

Notes:

• Seaterm’s baud rate must be the same as the SBE 38 baud rate (set with Baud=). Baud= is factory-set to 9600, but can be changed by the user (see Command Descriptions in Section 4: Deploying and Operating

RS-232 SBE 38).

• When you click OK, Seaterm saves the Configuration Options settings to the SeaTerm.ini file in your Windows directory. SeaTerm.ini contains the last saved settings for each instrument.

When you open Seaterm and select the desired instrument (SBE 38, 39, etc.) in the Configure menu, the Configuration Options dialog box shows the last saved settings for that instrument.

4. In the Communications menu, select Options / Cycle baud when connecting.

5. Click Connect on the Toolbar. Seaterm tries to connect to the SBE 38 at the baud set in Step 3. If it cannot, it cycles through all other possible baud rates to try to connect. When it connects, the display looks like this:

SBE 38 V 1.4 S/N 0090 (this line may not appear) S>

This shows that correct communications between the computer and the SBE 38 has been established.

If the system does not provide the S> prompt:

• Click Connect again.

• Verify the correct instrument was selected in the Configure menu and the settings were entered correctly in the Configuration Options dialog box. Note that the baud rate’s factory setting is documented on the Configuration Sheet in this manual.

• Check cabling between the computer and the SBE 38.

6. Display SBE 38 status information by clicking Status on the Toolbar. The display looks like this:

SBE 38 V 1.4 S/N = 0090

NAVG=1

Not sampling data Automatically start sampling on power up Default interface is RS-232

7. Command the SBE 38 to take a sample by typing TS and pressing the Enter key. The display looks like this if the output format was set to converted data (Format=C) with 4 digits to the right of the decimal place (Digits=4):

23.7658 where 23.7658 = temperature in degrees Celsius This number should be reasonable; i.e., room temperature.

The SBE 38 is ready for programming and deployment.

See Appendix III: RS-485 Interface for details on sending commands to an SBE 38 with optional RS-485 interface.

Manual revision 014 Section 4: Deploying and Operating RS-232 SBE 38 SBE 38

Section 4:

Deploying and Operating RS-232 SBE 38

This section includes:

• system operation description, including example sets of operation commands

• baud rate, cable length, and power limitations

• detailed command descriptions

• data formats

• instructions for deploying and recovering the SBE 38

Sampling Modes

The SBE 38 has two sampling modes:

• Polled Sampling – take a single sample on command

• Continuous Sampling – sample continuously; start when power is applied or on command, depending on the setup

Descriptions and examples follow for an SBE 38 with RS-232 Interface. Note that the SBE 38’s response to each command is not shown in the examples.

Review the sampling modes and the commands described in Command Descriptions before setting up your system.

Polled Sampling

The SBE 38 takes one sample of data on command. Transmission of data to the computer is dependent on the particular command used.

Example: (user input in bold) Apply power and establish communications. Set up to average 4 measurements per sample and output converted data with 3 digits after decimal place. Command SBE 38 to take a sample and send data to computer.

(Apply power and then click Connect on Toolbar.)

S>NAVG=4

S>FORMAT=C

S>DIGITS=3

S>DS (to verify setup)

S>TS

Note:

See Appendix III: RS-485 Interface for details on deploying and operating an SBE 38 with optional RS-485 interface.

Continuous Sampling

The SBE 38 continuously samples and transmits real-time data.

Sampling is started by:

• Sending Go, or

• Setting AutoRun=Y. If AutoRun=Y, sampling automatically starts when power is applied.

Sampling is stopped by:

• Sending Stop, or

• Removing power.

Example: Continuous Sampling (user input in bold) Example 1 AutoRun=N: Apply power and establish communications. Set up to average 4 measurements per sample and output converted data with 3 digits after decimal place. Set up to wait for a command when power is applied. Remove power.

(Apply power and then click Connect on Toolbar.)

S>NAVG=4

S>FORMAT=C

S>DIGITS=3

S>AUTORUN=N

S>DS (to verify setup) (Remove power.)

When ready to start sampling, apply power and establish communications. Send command to start sampling continuously, outputting real-time data. When desired, send command to stop sampling.

(Apply power and then click Connect on Toolbar.)

S>GO

S>STOP (You may need to send Stop several times to interrupt sampling.)

Example 2 AutoRun=Y: Apply power and establish communication. Set up to average 4 measurements per sample and output converted data with 3 digits after decimal place. Set up to automatically begin sampling when power is applied. Remove power.

(Apply power and then click Connect on Toolbar.)

S>NAVG=4

S>FORMAT=C

S>DIGITS=3

S>AUTORUN=Y

S>DS (to verify setup) (Remove power.)

To start sampling, apply power. SBE 38 begins sampling continuously, outputting real-time data.

To stop sampling, remove power.

To change setup: apply power, and then stop sampling by command.

(Apply power) (Press Enter key to get S> prompt) S>STOP (You may need to send Stop several times to interrupt sampling.)

(Enter commands as desired to change setup.)

Baud Rate, Cable Length, and Power

On the ship, cables longer than 3 meters should be installed inside an earthed metal conduit by a qualified electrician. This minimizes the potential for external signals to disrupt communication and ensures that high voltage lines (such as the sea cable) are sufficiently protected. Cables shorter than 3 meters can be used without shielding when installing or bench testing the instrument.

Baud Rate and Cable Length

For RS-232, the length of cable that the SBE 38 can drive to transmit real-time data is dependent on the baud rate. The allowable combinations are:

Maximum Cable Length (meters) Maximum Baud Rate 800 1200 400 2400 200 4800 100 9600

Power and Cable Length

There are two issues to consider:

• Limiting the communication IR loss to 1 volt if transmitting real-time data via RS-232; higher IR loss will cause the instrument to transmit data that does not meet the RS-232 communication standard.

• Supplying enough power at the power source so that sufficient power is available at the instrument after considering IR loss.

Looking at each issue separately:

Limiting IR Loss to 1 Volt

The limit to cable length is typically reached when the maximum communication current times the power common wire resistance is more than 1 volt.

V limit = 1 volt = IR limit Where I = current required by SBE 38 (15 mA for RS-232; 10 mA for RS-485).

Maximum cable length = R limit / wire resistance per foot

• Baud rate is set with Baud=

(see Command Descriptions in this section).

• For RS-485, see Appendix III:

RS-485 Interface for baud rate limitations.

Example 1 – For 18 gauge wire, what is maximum distance to transmit power to RS-232 SBE 38?

Is this controlling factor for maximum cable length if wanting to transmit at 1200 baud?

R limit = V limit / I = 1 volt / 0.015 Amps = 67 ohms For 18 gauge wire, resistance is 0.0064 ohms/foot.

Therefore, maximum cable length is 67 ohms / 0.0064 ohms/foot = 10417 feet = 3176 meters.

Note that 3176 meters > 800 meters (maximum distance SBE 38 can transmit data at 1200 baud), so IR loss is not controlling factor for this example.

Example 2 – Same as above, but there are 4 SBE 38s powered from the same power supply.

R limit = V limit / I = 1 volt / (0.015 Amps * 4 SBE 38s) = 17 ohms For 18 gauge wire, resistance is 0.0064 ohms/foot.

Therefore, maximum cable length is 17 ohms / 0.0064 ohms/foot = 2604 feet = 794 meters (cable length to SBE 38 furthest from power source).

Note:

Common wire resistances:

Gauge Resistance (ohms/foot)

12 0.0016 14 0.0025 16 0.0040 18 0.0064 19 0.0081 20 0.0107 22 0.0162 24 0.0257 26 0.0410 28 0.0653

Supplying Enough Power to SBE 38

Another consideration in determining maximum cable length is supplying enough power at the power source so that sufficient voltage is available, after the IR loss in the cable, to power the SBE 38.

Example 1 – For 18 gauge wire, what is maximum distance to transmit power to RS-232 SBE 38 if using 8.5 volt power source to supply power? Is this controlling factor for maximum cable length if wanting to transmit at 1200 baud?

SBE 38’s input power specification is 8 – 15 volts. Therefore, a 0.5 volt IR drop (8.5 volts – 8 volts) would still provide enough power to SBE 38.

V = IR 0.5 volts = (0.015 Amps) * (0.0064 ohms/foot * cable length) Cable length = 5208 ft = 1588 meters Note that 1588 meters > 800 meters (maximum distance SBE 38 can transmit data at 1200 baud), so IR drop in power is not controlling factor for this example.

Example 2 – Same as above, but there are 4 SBE 38s powered from the same power supply.

V = IR 0.5 volts = (0.015 Amps * 4 SBE 38s) * (0.0064 ohms/foot * cable length) Cable length = 1302 ft = 397 meters (cable length to SBE 38 furthest from power source).

Note that 397 meters < 800 meters (maximum distance SBE 38 can transmit data at 1200 baud), so IR drop in power is controlling factor for this example. Using a higher voltage power supply or a different wire gauge (12 or 14 gauge) would provide sufficient power at SBE 38 to allow 800 meter cable length.

Command Descriptions

This section describes commands and provides sample outputs. See Appendix IV: RS-232 Command Summary for a summarized command list.

When entering commands:

• Input commands to the SBE 38 in upper or lower case letters and register commands by pressing the Enter key.

• The SBE 38 sends ? CMD if an invalid command is entered.

• If the system does not return an S> prompt after executing a command, press the Enter key to get the S> prompt.

Status Command

DS Display status and setup parameters.

Equivalent to Status on Toolbar.

Description in example includes, where applicable, command used to modify parameter.

Setup Commands

Interface=x x=232: Set interface to RS-232.

x=485: Set interface to RS-485. See Appendix III:

RS-485 Interface for all details.

Baud=x x= baud rate (1200, 2400, 4800, 9600).

Default 9600.

Format=x x=C: Output converted data (°C).

x=R: Output raw data (counts).

Digits=x x= number of digits (0 – 6) to right of decimal point for converted temperature (°C). Applicable only if Format=C.

NAvg=x x= number of A/D cycles to average per sample

(1 – 127).

Time between samples (seconds) = (0.133 * NAvg) + 0.339 (Time between samples for continuous sampling;

minimum time required for each polled sample.)

AutoRun=x x=N: Wait for a command when power is applied.

x=Y: Start continuous sampling automatically when power is applied.

Example: (user input in bold).

S>DS

SBE 38 V 1.4 S/N = 0090 (firmware version, serial number) NAVG=1 (number of A/D cycles to average for each sample [NAvg=]) Not sampling data (sampling status) Automatically start sampling on power up (sampling start-up mode [AutoRun=]) Default interface is RS-232 (RS-232 or RS-485 interface [Interface=])

Note:

If the voltage is below 6.5 volts, the following displays in response to DS:

WARNING: LOW BATTERY VOLTAGE!!

Note:

The SBE 38’s baud (set with Baud=) must be the same as Seaterm’s baud rate (set in Configure menu).

Note:

After you send AutoRun=Y, to start sampling immediately:

• Turn power off and then on again, or

• Send Go.

Notes:

• The SBE 38 transmits data after it has completed the previous sample and before it starts the next sample.

• For continuous sampling with an RS-485 interface, set NAvg > 30.

See Appendix III: RS-485 Interface.

Sampling Commands

These commands are used to request data from the SBE 38.

For all sampling commands:

• Output format is determined by Format= and Digits=.

• Number of A/D cycles per sample is defined by NAvg.

Go Start sampling data continuously, and transmit data real-time.

Time between samples (seconds) = (0.133 * NAvg) + 0.339

Stop Stop continuous sampling. Press Enter key to get

S> prompt before entering Stop.

TS Take 1 sample and transmit data.

TH Take 1 sample and hold data in SBE 38 buffer.

SH Transmit data that was held in SBE 38 buffer.

SL Transmit data from last sample from

SBE 38 buffer.

SLT Transmit data from last sample from SBE 38 buffer, and then take 1 new sample and hold data in buffer.

Calibration Coefficients Commands

DC Display calibration coefficients.

Equivalent to Coefficients on Toolbar.

The individual Coefficient Commands listed below modify a particular coefficient or date:

TCalDate=S S=Temperature calibration date A0=F F=Temperature A0 A1=F F=Temperature A1 A2=F F=Temperature A2 A3=F F=Temperature A3 Slope=F F=Temperature slope (default 1.0) Offset=F F=Temperature offset (°C) (default 0.0)

Example: Display coefficients for SBE 38 (user input in bold).

S>DC

SBE 38 V 1.4 S/N = 0090

Cal Date: 08-apr-96 A0 =-9.420702e-05 A1 = 2.937924e-04 A2 =-3.739471e-06 A3 = 1.909551e-07 Slope = 1.000000 Offset = 0.0000

Notes:

• Date shown is when calibration was performed. Calibration coefficients are initially factory-set and should agree with Calibration Certificate shipped with SBE 38.

• See individual Coefficient Commands below for definitions of the data in the example.

Note:

F = floating point number S = string with no spaces

Note:

You may need to send Stop several times to get the SBE 38 to respond.

Notes:

• To capture real-time data to a file, do this before starting sampling:

1. Click Toolbar’s Capture button.

2. Enter desired file name in dialog box. Capture status displays in status bar at bottom of screen.

• If the SBE 38 is sampling data and the voltage is less than 6.5 volts for ten consecutive scans, the SBE 38 halts sampling and sets the status to low battery.

Data Formats

Converted Data (Format=C) ttt.ttt where:

t = temperature (degrees Celsius, ITS-90) Number of digits to right of decimal point is defined by Digits=.

Raw Data (Format=R) nnnnnn.n where:

n= counts

Deployment

1. Install the I/O cable:

A. Lightly lubricate the inside of the cable connector with silicone grease (DC-4 or equivalent).

B. XSG Connector (shown in photo) - Install the cable connector, aligning the raised bump on the side of the connector with the large pin (pin 1 - ground) on the SBE 38. Remove any trapped air by burping or gently squeezing the connector near the top and moving your fingers toward the end cap. OR MCBH Connector (optional) – Install the cable connector, aligning the pins.

C. Place the locking sleeve over the connector. Tighten the locking sleeve finger tight only. Do not overtighten the locking sleeve and do not use a wrench or pliers.

2. Mount the SBE 38.

3. Verify that the hardware and external fittings are secure.

4. Use one of the following sequences to start sampling:

• If AutoRun=N: Send Go to start sampling continuously now, or TS or TH to take a single sample.

• If AutoRun=Y: Apply power to start sampling continuously now.

5. Deploy the SBE 38.

• Each line of output is followed by a carriage return and line feed.

• For converted data, leading zeros for temperature output are suppressed, except for one zero to the left of the decimal point (for example, 0.1034).

• See Appendix III: RS-485 Interface for data output format for an SBE 38 with optional RS-485 interface.

CAUTION:

Do not use WD-40 or other petroleum-based lubricants, as they will damage the connector.

Locking sleeve

I/O cable

Recovery

1. Use one of the following sequences to stop sampling:

• Press Enter key to get S> prompt, and then send Stop to stop sampling continuously. OR

• Remove power.

2. Rinse the SBE 38 with fresh water, and dry thoroughly.

WARNING!

If the SBE 38 stops working while underwater, is unresponsive to commands, or shows other signs of flooding or damage, carefully secure it away from people until you have determined that abnormal internal pressure does not exist or has been relieved. Pressure housings may flood under pressure due to dirty or damaged o-rings, or other failed seals. When a sealed pressure housing floods at great depths and is subsequently raised to the surface, water may be trapped at the pressure at which it entered the housing, presenting a danger if the housing is opened before relieving the internal pressure. Instances of such flooding are rare. However, a housing that floods at 5000 meters depth holds an internal pressure of more than 7000 psia, and has the potential to eject the end cap with lethal force.

A housing that floods at 50 meters holds an internal pressure of more then 85 psia; this force could still cause injury.

If you suspect the SBE 38 is flooded, point it in a safe direction away from people, and loosen the bulkhead connector very slowly, at least 1 turn.

This opens an o-ring seal under the connector. Look for signs of internal pressure (hissing or water leak). If internal pressure is detected, let it bleed off slowly past the connector o-ring. Then, you can safely remove the end cap.

Manual revision 014 Section 5: Routine Maintenance and Calibration SBE 38

Section 5: Routine Maintenance and Calibration

This section reviews corrosion precautions, connector mating and maintenance, and sensor calibration. The SBE 38’s accuracy is sustained by the care and calibration of the sensor and by establishing proper handling practices.

Corrosion Precautions

All exposed materials are titanium or plastic. No corrosion precautions are required, but direct electrical connection of the SBE 38 housing to mooring or other dissimilar metal hardware should be avoided. Rinse the SBE 38 with fresh water after use and prior to storage.

Connector Mating and Maintenance

Clean and inspect the connectors, cable, and dummy plug before every deployment and as part of your yearly equipment maintenance. Inspect connectors that are unmated for signs of corrosion product around the pins, and for cuts, nicks or other flaws that may compromise the seal.

When remating:

1. Lightly lubricate the inside of the cable connector with silicone grease

(DC-4 or equivalent).

2. XSG Connector - Install the cable connector, aligning the raised bump on the side of the plug/cable connector with the large pin (pin 1 - ground) on the SBE 38. Remove any trapped air by burping or gently squeezing the connector near the top and moving your fingers toward the end cap. OR

MCBH Connector (optional) - Install the cable connector, aligning the pins.

3. Place the locking sleeve over the cable connector. Tighten the locking sleeve finger tight only. Do not overtighten the locking sleeve and do not use a wrench or pliers.

Verify that a cable is installed on the SBE 38 before deployment.

CAUTION:

Do not use WD-40 or other petroleum-based lubricants, as they will damage the connector.

Note:

See Application Note 57: Connector Care and Cable Installation.

Manual revision 014 Section 5: Routine Maintenance and Calibration SBE 38

Sensor Calibration

Sea-Bird sensors are calibrated by subjecting them to known physical conditions and measuring the sensor responses. Coefficients are then computed, which may be used with appropriate algorithms to obtain engineering units. The temperature sensor on the SBE 38 is supplied fully calibrated, with coefficients printed on the Calibration Certificate (see back of manual). These coefficients have been stored in the SBE 38’s EEPROM.

We recommend that the SBE 38 be returned to Sea-Bird for calibration.

The primary source of temperature sensor calibration drift is the aging of the thermistor element. Sensor drift is not substantially dependent upon the environmental conditions of use, and — unlike platinum or copper elements

— the thermistor is insensitive to shock.

Sea-Bird’s Calibration Methodology

The SBE 38 is calibrated in Sea-Bird’s state-of-the-art calibration laboratory, which maintains primary temperature standards (water triple point [TPW] and gallium melting point [GaMP] cells), ITS-90 certified and standards-grade platinum resistance thermometers, and a low-gradient temperature bath.

Temperature is computed using the Steinhart-Hart polynomial for thermistors (Steinhart and Hart, 1968; Bennett, 1972), which is based on thermistor physics. The equation characterizes the non-linear temperature versus resistance response of the sensor. Note that thermistors require individualized coefficients to the Steinhart-Hart equation, because the thermistor material is an individualized mix of dopants:

t90 = 1.0 - 273.15 * Slope + Offset [°C] a0 + a1 * [ln(n)] + a2 * [ln 2 (n)] + a3 * [ln 3 (n)] where n = SBE 38 raw output (counts).

Manual revision 014 Glossary SBE 38

Glossary

PCB – Printed Circuit Board.

SBE 38 – High-accuracy digital oceanographic thermometer.

SBE Data Processing – Sea-Bird’s Windows data processing software, which calculates and plots measured and derived variables.

SBE Data Processing can be used to view and process the entire data stream, including data from the SBE 38, when the SBE 38 is integrated with one of the following:

• SBE 21 or 45 thermosalinograph,

• SBE 16plus, 16plus V2, or 16plus -IM V2 SeaCAT C-T Recorder

• SBE 19plus V2 SeaCAT CTD Profiler

• SBE 25plus Sealogger CTD

Scan – One data sample.

Seasave V7 – Sea-Bird’s Windows software used to acquire, convert, and display real-time or archived raw data. Seasave V7 can be used to view and process the entire data stream, including data from the SBE 38, when the SBE 38 is integrated with one of the following:

• SBE 21 or 45 thermosalinograph,

• SBE 16plus, 16plus V2, or 16plus -IM V2 C-T Recorder

• SBE 19plus V2 CTD Profiler

• SBE 25plus Sealogger CTD (Seasave can acquire SBE 38 data with this

CTD, but SBE 38 data cannot be viewed in real-time)

Seasoft V2 – Sea-Bird’s complete Windows software package, which includes software for communication, real-time data acquisition, and data analysis and display. Seasoft V2 includes Seaterm, SeatermAF, SeatermV2, Seasave V7, SBE Data Processing, and Plot39.

Seaterm – Sea-Bird’s Windows terminal program used to communicate with the SBE 38.

All Sea-Bird software listed was designed to work with a computer running Windows XP service pack 2 or later, Windows Vista, or Windows 7.

Manual revision 014 Appendix I: Functional Description SBE 38

Appendix I: Functional Description

Sensor Interface

Temperature is acquired by applying an AC excitation to a hermetically sealed VISHAY reference resistor and an ultra-stable aged thermistor with a drift rate of less than 0.002°C per year. A 24-bit A/D converter digitizes the outputs of the reference resistor and thermistor. AC excitation and ratiometric comparison using a common processing channel avoids errors caused by parasitic thermocouples, offset voltages, leakage currents, and reference errors.

Maximum power dissipated in the thermistor is 0.5 microwatts, and contributes less than 200 µK of overheat error.

A raw count (ratio) is related to resistance measurements:

raw counts = 1048576 * (NT) / (NR) where NR = output from reference resistor NT = thermistor output

The SBE 38’s output is computed from the raw count and the calibration coefficients that are stored in EEPROM.

The number of acquisition cycles (raw counts) averaged per measurement is user-programmable (NAvg=; see Section 4: Deploying and Operating RS-232 SBE 38). Increasing the number of cycles per measurement increases the time to acquire the measurement and the interval between measurements, while reducing the RMS temperature noise from the sensor. The interval between measurements is:

interval [seconds] = (0.133 * NAvg) + 0.339 where NAvg = number of acquisition cycles per measurement

The SBE 38 transmits data after it has completed the previous sample and before it starts the next sample.

Time to transmit data = (number of characters * 10 bits/character) / baud rate where number of characters is dependent on the output format. Include the decimal point when counting characters; add 2 to the number of characters output, to account for the carriage return and line feed at the end of each scan.

Settings

Calibration coefficients and setup parameters (Baud=, NAvg=, Interface=, etc.) are written to EEPROM and are non-volatile. These settings do not change if power is removed.

Manual revision 014 Appendix II: Electronics Disassembly/Reassembly SBE 38

Appendix II: Electronics Disassembly/Reassembly

1. Remove the titanium end cap and electronics from the housing as follows:

A. Wipe the outside of the end cap and housing dry, being careful to remove any water at the seam between them.

B. Unscrew the end cap.

C. Pull the end cap and attached electronics out of the housing. Note that the PCB is electrically connected to the I/O connector.

D. Remove any water from the end cap O-ring and mating surfaces inside the housing with a lint-free cloth or tissue.

E. Be careful to protect the O-ring from damage or contamination.

2. Reinstall the end cap and electronics in the housing as follows:

A. Remove any water from the O-ring and mating surfaces in the housing with a lint-free cloth or tissue. Inspect the O-ring and mating surfaces for dirt, nicks, and cuts. Clean as necessary. Apply a light coat of O-ring lubricant (Parker Super O Lube) to O-ring and mating surfaces.

B. Carefully fit the electronics into the housing.

C. Screw the end cap into the housing.

Before delivery, a desiccant bag is placed in the housing, and the electronics chamber is filled with dry Argon gas. These measures help prevent condensation.

To ensure proper functioning:

1. Install a new desiccant bag each time you open the housing. If a new bag is not available, see Application Note 71: Desiccant Use and Regeneration (drying).

2. If possible, dry gas backfill each time you open the housing. If you cannot, wait at least 24 hours before redeploying, to allow the desiccant to remove any moisture from the chamber.

End cap

O-ring

Manual revision 014 Appendix III: RS-485 Interface SBE 38

Appendix III: RS-485 Interface

Operation Description

Commands can be directed to one SBE 38 or globally to all SBE 38s. If IDReq=Y, a command prefix (#ii) is used to direct commands to an SBE 38 with the same ID (ii = ID). Global commands do not use a prefix, regardless of the setting for IDReq=, and are recognized by all SBE 38s attached to the RS-485 interface.

An example follows for a system with two SBE 38s (IDs 01 and 02) online. Note that the SBE 38’s response to each command is not shown in the example. Review the commands described in Command Descriptions and the example below before setting up your system.

Example: Wake up all SBE 38s. Set up all SBE 38s to average 40 measurements per sample and output converted data with 3 digits to the right of the decimal place. Command all SBE 38s to take a sample and hold data in buffer, and then command each SBE 38 to transmit data from buffer. Repeat sampling sequence a number of times. (user input in bold) (Apply power and click Connect on Toolbar to wake up all SBE 38s.)

S>IDREQ=Y (command to require ID prefix) S>#01NAVG=40 (set number of measurements per sample to 40 for SBE 38 with ID=01) S>#02NAVG=40 (set number of measurements per sample to 40 for SBE 38 with ID=02) S>#01FORMAT=C (set output format to converted data for SBE 38 with ID=01) S>#02FORMAT=C (set output format to converted data for SBE 38 with ID=02) S>#01DIGITS=3 (set number of digits to right of decimal point to 3 for SBE 38 with ID=01) S>#02DIGITS=3 (set number of digits to right of decimal point to 3 for SBE 38 with ID=02) S>#01DS (verify setup with status command for SBE 38 with ID=01) S>#02DS (verify setup with status command for SBE 38 with ID=02) S>GDATA (global command to all SBE 38s to take sample and hold data in buffer) S>DATA01 (get data from buffer of SBE 38 with ID=01) S>DATA02 (get data from buffer of SBE 38 with ID=02) (Repeat GDATA through DATA02 as desired)

Notes:

• IDReq=Y does not require a #ii prefix. IDReq=N does require a #ii prefix (#iiIDReq=N).

• For customers using their own terminal program software:

Terminate all commands with CR only, not CRLF.

• See Application Note 56: Interfacing to RS-485 Sensors for information on RS-485 adapters and converters.

Command Descriptions

RS-485 Commands

Global Commands

Global commands are recognized by all SBE 38s attached to the RS-485 interface.

TxDelay=x x= delay after SBE 38 transmits a reply until

SBE 38 transmitter is disabled (1 – 500 milliseconds). Default 25 milliseconds.

RxDelay=x x= delay after SBE 38 receives a command until SBE 38 transmitter is enabled (1 – 500 milliseconds). Default 25 milliseconds.

GData Command all SBE 38s to take 1 sample and hold data in SBE 38 buffer until receiving:

- DATAii;

- SH, SL, or SLT (if #iiIDReq=N); or

- #iiSH, #iiSL, or #iiSLT (if IDReq=Y).

AData Command all SBE 38s to take 1 sample and hold data in SBE 38 buffer until receiving:

- DATAii;

- SH, SL, or SLT (if #iiIDReq=N); or

- #iiSH, #iiSL, or #iiSLT (if IDReq=Y).

Get Data Command

DATAii Get data obtained with GData or AData from

SBE 38 with ID = ii (ii = 0 -99).

ID Required Command

IDReq=Y Precede commands to individual SBE 38s with #ii, where ii= ID (ii = 0 -99). Use this setting for systems with multiple RS-485 instruments on 1 pair of wires. Note that the use of a prefix does not apply to Global, Get Data, or ID commands.

#iiIDReq=N Do not precede commands to individual SBE 38s with #ii. Use this setting for systems with only

1 SBE 38.

For reliable operation, all commands may need to be preceded with two @ characters to clear the buffers.

Example (status command for SBE 38 with ID=01):

S>@@#01DS

Note:

GData and AData perform the same function in the SBE 38. Both are included here to provide compatibility with RS-485 MicroCATs.

Example 1: Multiple RS-485 instruments on 1 pair of wires (user input in bold) S>IDREQ=Y (command to require ID prefix) S>#01NAVG=40 (set number of A/D cycles to average for SBE 38 with ID=01) S>#02NAVG=40 (set number of A/D cycles to average for SBE 38 with ID=02) S>#01DS (verify setup with status command for SBE 38 with ID=01) S>#02DS (verify setup with status command for SBE 38 with ID=02)

Example 2: Only 1 SBE 38 on 1 pair of wires, with ID=01 (user input in bold) S>#01IDREQ=N (command to not require ID prefix; note that #ii prefix is required) S>NAVG=40 (set number of A/D cycles to average for SBE 38, no ID required as part of command) S>DS (verify setup with status command for SBE 38, no ID required as part of command)

Note:

IDReq=Y does not require a #ii prefix.

IDReq=N does require a #ii prefix (#iiIDReq=N).

ID Commands

Only one SBE 38 can be online when sending these commands.

ID? Display SBE 38 ID (ID = ii, where ii= 0-99) and whether ID is required as a prefix for commands to individual SBE 38s (see IDReq=).

*ID=ii Set SBE 38 ID to ii, where ii= 0-99. *ID= must be sent twice, because the SBE 38 requests verification. If more than one RS-485 instrument is online when sending this command, all instruments online will be set to same ID.

All Other Commands

All other commands (status, setup, sampling, and coefficients) are listed in Section 4: Deploying and Operating RS-232 SBE 38 and in Appendix IV: RS-232 Command Summary.

Notes on use of these commands for an SBE 38 with RS-485 interface:

• Effect of IDReq=:

If IDReq=Y, precede these commands with #ii (ii = 0 – 99) to direct a command to a particular SBE 38.

If #iiIDReq=N, do not precede these commands with #ii. This setting works only for a system with one SBE 38.

• The RS-485 interface cannot accommodate multiple instruments transmitting real-time data at the same time. Therefore, do not set AutoRun=Y (start sampling continuously when power is applied) for a system with more than one RS-485 instrument on a pair of wires.

Similarly, do not attempt to send Go to multiple SBE 38s on a pair of wires, as the system cannot transmit a command to one instrument while another instrument is transmitting real-time data.

• If planning to sample continuously: If AutoRun=Y (sample continuously when power is applied) or using the Go command to start sampling continuously, set NAvg= (A/D cycles to average per sample) to a value greater than or equal to 30.

Data Formats

Converted Data (Format=C) Output from continuous sampling: ttt.ttt Output from DATAii, #iiTS, TS, #iiSH, SH, #iiSL, SL, #iiSLT, or SLT:

ii, sssss, ttt.ttt where:

t = temperature (°C, ITS-90) (number of digits to right of decimal point is defined by Digits=) ii = ID (0 – 99) sssss = SBE 38 serial number

Raw Data (Format=R) nnnnnn.n where:

n = counts

Notes:

• Each line of output is followed by a carriage return and line feed.

• For converted data, leading zeros for temperature output are suppressed, except for one zero to the left of the decimal point (for example, 0.1034).

Note:

IDReq=Y does not require a #ii prefix.

IDReq=N does require a #ii prefix (#iiIDReq=N).

Wiring

When configured with the RS-485 interface, the SBE 38 can transmit data over up to 1200 meters of 26 AWG twisted pair wire cable.

The MAX1483 transceivers used in the SBE 38 are designed for bi-directional data communications on multi-point bus transmission lines. To minimize reflections, terminate the line at both ends in its characteristic impedance.

Also, keep stub lengths off the main line as short as possible (although the slew-rate-limited MAX1483 is more tolerant of imperfect termination than standard RS-485 ICs).

Conversion of RS-232 to RS-485 or RS-485 to RS-232

Sea-Bird supplies the SBE 38 with the correct jumper settings on the Printed Circuit Board (PCB) for your ordered configuration (standard RS-232 or optional RS-485). If desired, you can modify the jumper settings to change the configuration:

Wiring: connect -

• Pin 2 (black) to RS-232 RX / RS-485 ‘A’

• Pin 3 (green) to RS-232 TX / RS-485 ’B’

• See Appendix II: Electronics

Disassembly / Reassembly to access the PCB.

• Send Interface=232 or Interface=485 to program the SBE 38 to match the wired configuration.

Optional

RS-485

terminating resistor solder points

Note:

See Power and Cable Length in Section 4: Deploying and Operating RS-232 SBE 38 for cable limitations related to the supply of power.

Manual revision 014 Appendix IV: RS-232 Command Summary SBE 38

Appendix IV: RS-232 Command Summary

CATEGORY COMMAND DESCRIPTION

Status DS Display status and setup parameters.

Setup

Interface=x x=232: RS-232 interface.

x=485: RS-485 interface.

Baud=x x= baud rate (1200, 2400, 4800, 9600).

Default 9600.

Format=x x=C: Output converted data (°C).

x=R: Output raw data (counts).

Digits=x x= number of digits (0 – 6) to right of decimal point for converted temperature (°C). Applicable only if Format=C

NAvg=x x= A/D cycles to average per sample (1 – 127).

AutoRun=x x=N: Wait for a command when power applied.

x=Y: Start continuous sampling automatically when power applied.

Sampling

Go Start continuous sampling now.

Stop Stop continuous sampling.

Press Enter key to get S> prompt before entering Stop.

TS Take 1 sample and transmit data.

TH Take 1 sample and hold data in buffer.

SH Transmit data that was held in buffer.

SL Transmit data from last sample from buffer.

SLT

Transmit data from last sample from buffer, and then take 1 new sample and hold data in buffer.

Coefficients (F=floating point number; S=string with no spaces) Date shown is when calibration was performed.

Calibration coefficients are initially factory-set and should agree with Calibration

Certificate shipped with SBE 38.

DC

Display calibration coefficients; all coefficients and dates listed below are included. Use individual commands below to modify a particular coefficient or date.

CalDate=S S=Temperature calibration date.

A0=F F=Temperature A0.

A1=F F=Temperature A1.

A2=F F=Temperature A2.

A3=F F=Temperature A3.

Slope=F F=Temperature slope (default 1.0).

Offset=F F=Temperature offset (default 0.0).

• See Command Descriptions in Section 4: Deploying and Operating RS-232 SBE 38 for…