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Synchronizing Measurements

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Section 8. Operation 8.1.10.3 RS-232 Sensors RS-232 sensor cable lengths should be limited to 50 feet. 8.1.10.4 SDI-12 Sensors The SDI-12 standard allows cable lengths of up to 200 feet. Campbell Scientific does not recommend SDI-12 sensor lead lengths greater than 200 feet; however, longer lead lengths can sometimes be accommodated by increasing the wire gage or powering the sensor with a second 12-Vdc power supply placed near the sensor. 8.1.11 Synchronizing Measurements Timing of a measurement is usually controlled relative to the CR800 clock. When sensors in a sensor network are measured by a single CR800, measurement times are synchronized, often within a few milliseconds, depending on sensor number and measurement type. Large numbers of sensors, cable length restrictions, or long distances between measurement sites may require use of multiple CR800s. Techniques outlined below enable network administrators to synchronize CR800 clocks and measurements in a CR800 network. Care should be taken when a clock-change operation is planned. Any time the CR800 clock is changed, the deviation of the new time from the old time may be sufficient to cause a skipped record in data tables. Any command used to synchronize clocks should be executed after any CallTable() instructions and timed so as to execute well clear of data output intervals. Techniques to synchronize measurements across a network include: 1. LoggerNet (p. 76) - when reliable telecommunications are common to all CR800s in a network, the LoggerNet automated clock check provides a simple time synchronization function. Accuracy is limited by the system clock on the PC running the LoggerNet server. Precision is limited by network transmission latencies. LoggerNet compensates for latencies in many telecommunications systems and can achieve synchronies of

Section	Page
Revision and Copyright Information	1
Warranty	3
Assistance	5
Table of Contents	7
Section 1. Introduction	27
1.1 HELLO	27
1.2 Typography	27
Section 2. Cautionary Statements	29
Section 3. Initial Inspection	31
Section 4. Quickstart Tutorial	33
4.1 Primer – CR800 Data-Acquisition	33
4.1.1 Components of a Data-Acquisition System	33
4.1.1.1 Sensors	33
4.1.1.2 Datalogger	33
4.1.1.3 Data Retrieval	33
4.1.2 CR800 Module and Power Supply	34
4.1.2.1 Wiring Panel	34
4.1.2.2 Power Supply	36
4.1.2.3 Backup Battery	36
4.1.3 Sensors	36
4.1.3.1 Analog Sensors	36
4.1.3.2 Bridge Sensors	37
4.1.3.2.1 Voltage Excitation	37
4.1.3.3 Pulse Sensors	38
4.1.3.3.1 Pulses Measured	39
4.1.3.3.2 Pulse-Input Channels	39
4.1.3.3.3 Pulse Sensor Wiring	40
4.1.3.4 RS-232 Sensors	40
4.1.4 Digital I/O Ports	42
4.1.5 SDM Channels	42
4.1.6 Input Expansion Modules	42
4.2 Hands-On: Measuring a Thermocouple	43
4.2.1 What You Will Need	43
4.2.2 Hardware Setup	43
4.2.2.1 External Power Supply	43
4.2.3 PC200W Software Setup	44
4.2.4 Write Program with Short Cut	46
4.2.4.1 Procedure: (Short Cut Steps 1 to 6)	46
4.2.4.2 Procedure: (Short Cut Steps 7 to 9)	47
4.2.4.3 Procedure: (Short Cut Steps 10 to 11)	48
4.2.4.4 Procedure: (Short Cut Steps 12 to 16)	49
4.2.4.5 Procedure: (Short Cut Step 17 to 18)	50
4.2.5 Send Program and Collect Data	51
4.2.5.1 Procedure: (PC200W Step 1)	51
4.2.5.2 Procedure: (PC200W Steps 2 to 4)	51
4.2.5.3 Procedure: (PC200W Step 5)	53
4.2.5.4 Procedure: (PC200W Step 6)	54
4.2.5.5 Procedure: (PC200W Steps 7 to 9)	54
4.2.5.6 Procedure: (PC200W Steps 10 to 11)	56
4.2.5.7 Procedure: (PC200W Steps 12 to 13)	56
Section 5. System Overview	57
5.1 CR800 Datalogger	58
5.1.1 Clock	59
5.1.2 Sensor Support	59
5.1.3 CR800 Wiring Panel	60
5.1.3.1 Measurement Inputs	60
5.1.3.2 Voltage Outputs	61
5.1.3.3 Grounding Terminals	62
5.1.3.4 Power Terminals	62
5.1.3.4.1 Power In	62
5.1.3.4.2 Power Out	62
5.1.3.5 Communications Ports	63
5.1.3.6 Integrated Keyboard Display	63
5.1.4 CR1000KD Keyboard Display	64
5.1.5 Power Requirements	64
5.1.6 Programming	65
5.1.6.1 Operating System and Settings	65
5.1.6.2 User Programming	65
5.1.7 Memory and Final Data Storage	66
5.1.8 Data Retrieval	67
5.1.8.1 Via Telecommunications	67
5.1.8.2 Via Mass-Storage Device	67
5.1.8.3 Data File-Formats in CR800 Memory	67
5.1.8.4 Data Format on Computer	68
5.1.9 Communications	68
5.1.9.1 PakBus	68
5.1.9.2 Modbus	69
5.1.9.3 DNP3 Communication	69
5.1.9.4 Keyboard Display	69
5.1.9.4.1 Custom Menus	69
5.1.10 Security	70
5.1.10.1 Vulnerabilities	71
5.1.10.2 Pass-code Lockout	72
5.1.10.2.1 Security By-Pass	73
5.1.10.3 Passwords	73
5.1.10.3.1 .csipasswd	73
5.1.10.3.2 PakBus Instructions	74
5.1.10.3.3 IS Instructions	74
5.1.10.3.4 Settings	74
5.1.10.4 File Encryption	74
5.1.10.5 Communications Encryption	75
5.1.10.6 Hiding Files	75
5.1.10.7 Signatures	75
5.1.11 Maintenance	75
5.1.11.1 Protection from Water	75
5.1.11.2 Protection from Voltage Transients	75
5.1.11.3 Calibration	76
5.1.11.4 Internal Battery	76
5.2 Datalogger Support Software	76
Section 6. CR800 Specifications	79
Section 7. Installation	81
7.1 Moisture Protection	81
7.2 Temperature Range	81
7.3 Enclosures	81
7.4 Power Sources	82
7.4.1 CR800 Power Requirement	83
7.4.2 Calculating Power Consumption	83
7.4.3 Power Supplies	83
7.4.3.1 External Batteries	83
7.4.4 Vehicle Power Connections	83
7.4.5 Powering Sensors and Devices	84
7.4.5.1 Switched Voltage Excitation	85
7.4.5.2 Continuous Regulated (5 Volt)	85
7.4.5.3 Continuous Unregulated (Nominal 12 Volt)	86
7.4.5.4 Switched Unregulated (Nominal 12 Volt)	86
7.5 Grounding	86
7.5.1 ESD Protection	86
7.5.1.1 Lightning Protection	88
7.5.2 Single-Ended Measurement Reference	90
7.5.3 Ground Potential Differences	90
7.5.3.1 Soil Temperature Thermocouple	90
7.5.3.2 External Signal Conditioner	90
7.5.4 Ground Looping in Ionic Measurements	91
7.6 CR800 Configuration	92
7.6.1 Device Configuration Utility	92
7.6.2 Sending the Operating System	94
7.6.2.1 Sending OS with DevConfig	94
7.6.2.2 Sending OS with Program Send	96
7.6.2.3 Sending OS with External Memory	96
7.6.3 Settings	96
7.6.3.1 Settings via DevConfig	96
7.6.3.1.1 Deployment Tab	98
7.6.3.2 Settings via CRBasic	102
7.6.3.3 Durable Settings	103
7.6.3.3.1 \	103
7.6.3.3.2 Default.cr8 File	105
7.6.3.4 Program Run Priorities	106
7.6.3.5 Network Planner	107
7.6.3.5.1 Overview	107
7.6.3.5.2 Basics	108
7.7 Programming	108
7.7.1 Writing and Editing Programs	108
7.7.1.1 Short Cut Editor and Program Generator	108
7.7.1.2 CRBasic Editor	109
7.7.1.2.1 Inserting Comments into Program	109
7.7.2 Sending Programs	110
7.7.2.1 Preserving Data at Program Send	110
7.7.3 Syntax	112
7.7.3.1 Numerical Formats	112
7.7.3.2 Structure	113
7.7.3.3 Command Line	115
7.7.3.3.1 Multiple Statements on One Line	115
7.7.3.3.2 One Statement on Multiple Lines	115
7.7.3.4 Single-Line Declarations	116
7.7.3.4.1 Variables	116
7.7.3.4.2 Constants	122
7.7.3.4.3 Alias and Unit Declarations	124
7.7.3.5 Declared Sequences	125
7.7.3.5.1 Data Tables	125
7.7.3.5.2 Subroutines	131
7.7.3.5.3 Incidental Sequences	132
7.7.3.6 Execution and Task Priority	132
7.7.3.6.1 Pipeline Mode	133
7.7.3.6.2 Sequential Mode	134
7.7.3.7 Execution Timing	135
7.7.3.7.1 Scan() / NextScan	135
7.7.3.7.2 SlowSequence / EndSequence	136
7.7.3.7.3 SubScan() / NextSubScan	137
7.7.3.7.4 Scan Priorities in Sequential Mode	137
7.7.3.8 Instructions	139
7.7.3.8.1 Measurement and Data-Storage Processing	139
7.7.3.8.2 Argument Types	140
7.7.3.8.3 Names in Arguments	140
7.7.3.8.4 Expressions in Arguments	141
7.7.3.8.5 Arrays of Multipliers and Offsets	141
7.7.3.9 Expressions	142
7.7.3.9.1 Floating-Point Arithmetic	143
7.7.3.9.2 Mathematical Operations	143
7.7.3.9.3 Expressions with Numeric Data Types	143
7.7.3.9.4 Logical Expressions	145
7.7.3.9.5 String Expressions	147
7.7.3.10 Program Access to Data Tables	148
7.7.3.11 System Signatures	150
7.7.4 Tips	150
7.7.4.1 Use of Variable Arrays to Conserve Code Space	150
7.7.4.2 Use of Move() to Conserve Code Space	151
7.8 Programming Resource Library	151
7.8.1 Calibration Using FieldCal() and FieldCalStrain()	151
7.8.1.1 CAL Files	151
7.8.1.2 CRBasic Programming	152
7.8.1.3 Calibration Wizard Overview	152
7.8.1.4 Manual Calibration Overview	152
7.8.1.4.1 Single-Point Calibrations (zero, offset, or zero basis)	153
7.8.1.4.2 Two-point Calibrations (multiplier / gain)	153
7.8.1.5 FieldCal() Demonstration Programs	154
7.8.1.5.1 Zero or Tare (Option 0)	154
7.8.1.5.2 Offset (Option 1)	156
7.8.1.5.3 Zero Basis (Option 4)	157
7.8.1.5.4 Two-Point Slope and Offset (Option 2)	159
7.8.1.5.5 Two-Point Slope Only (Option 3)	161
7.8.1.6 FieldCalStrain() Demonstration Program	162
7.8.1.6.1 Quarter-Bridge Shunt (Option 13)	165
7.8.1.6.2 Quarter-Bridge Zero (Option 10)	166
7.8.2 Information Services	167
7.8.2.1 PakBus Over TCP/IP and Callback	168
7.8.2.2 Default HTTP Web Server	168
7.8.2.3 Custom HTTP Web Server	169
7.8.2.4 FTP Server	172
7.8.2.5 FTP Client	172
7.8.2.6 Telnet	172
7.8.2.7 SNMP	172
7.8.2.8 Ping	172
7.8.2.9 Micro-Serial Server	173
7.8.2.10 Modbus TCP/IP	173
7.8.2.11 DHCP	173
7.8.2.12 DNS	173
7.8.2.13 SMTP	173
7.8.3 SDI-12 Sensor Support	173
7.8.3.1 SDI-12 Transparent Mode	174
7.8.3.1.1 SDI-12 Transparent Mode Commands	175
7.8.3.2 SDI-12 Programmed Modes	178
7.8.3.2.1 SDI-12 Recorder Mode	178
7.8.3.2.2 SDI-12 Sensor Mode	185
7.8.3.3 SDI-12 Power Considerations	186
7.8.4 Subroutines	188
7.8.5 Wind Vector	189
7.8.5.1 OutputOpt Parameters	190
7.8.5.2 Wind Vector Processing	190
7.8.5.2.1 Measured Raw Data	191
7.8.5.2.2 Calculations	191
7.8.6 Custom Menus	194
7.8.7 Conditional Compilation	199
7.8.8 Serial I/O	201
7.8.8.1 Introduction	202
7.8.8.2 I/O Ports	203
7.8.8.3 Protocols	203
7.8.8.4 Glossary of Terms	204
7.8.8.5 CRBasic Programming	205
7.8.8.5.1 Input Instruction Set Basics	206
7.8.8.5.2 Input Programming Basics	207
7.8.8.5.3 Output Programming Basics	208
7.8.8.5.4 Translating Bytes	209
7.8.8.5.5 Memory Considerations	210
7.8.8.5.6 Demonstration Program	211
7.8.8.6 Testing Applications	212
7.8.8.6.1 Configure HyperTerminal	212
7.8.8.6.2 Create Send Text File	215
7.8.8.6.3 Create Text-Capture File	215
7.8.8.6.4 Serial Input Test Program	215
7.8.8.7 Q & A	221
7.8.9 TrigVar and DisableVar — Controlling Data Output and Processing	223
7.8.10 NSEC Data Type	224
7.8.10.1 NSEC Options	225
7.8.11 Bool8 Data Type	228
7.8.12 Faster Measurement Rates	232
7.8.12.1 Measurements from 1 Hz to 100 Hz	233
7.8.12.2 Measurement Rate: 101 to 600 Hz	234
7.8.12.2.1 SubScan() / NextSubScan Details	235
7.8.12.3 Measurement Rate: 601 to 2000 Hz	236
7.8.13 String Operations	237
7.8.13.1 String Operators	238
7.8.13.2 String Concatenation	239
7.8.13.3 String NULL Character	239
7.8.13.4 Inserting String Characters	240
7.8.13.5 Extracting String Characters	240
7.8.13.6 String Use of ASCII / ANSII Codes	240
7.8.13.7 Formatting Strings	241
7.8.13.8 Formatting String Hexadecimal Variables	241
7.8.14 Data Tables	241
7.8.15 PulseCountReset Instruction	242
7.8.16 Program Signatures	243
7.8.16.1 Text Signature	243
7.8.16.2 Binary Runtime Signature	243
7.8.16.3 Executable Code Signatures	243
7.8.17 Advanced Programming Examples	244
7.8.17.1 Miscellaneous Features	244
7.8.17.2 Running Average and Total of Rain	247
7.8.17.3 Use of Multiple Scans	247
7.8.17.4 Groundwater Pump Test	248
7.8.17.5 Scaling Array	251
7.8.17.6 Conditional Output	252
7.8.17.7 Capturing Events	253
7.8.18 PRT Measurement	254
7.8.18.1 PRT Calculation Standards	254
7.8.18.2 Measuring PT100s (100-Ohm PRTs)	258
7.8.18.2.1 Self-Heating and Resolution	258
7.8.18.2.2 PT100 in Four-Wire Half-Bridge	258
7.8.18.2.3 PT100 in Three-Wire Half-Bridge	260
7.8.18.2.4 PT100 in Four-Wire Full-Bridge	262
7.8.19 Running Average	264
Section 8. Operation	269
8.1 Measurements	269
8.1.1 Time	269
8.1.1.1 Time Stamps	269
8.1.2 Voltage	270
8.1.2.1 Input Limits	271
8.1.2.2 Reducing Error	272
8.1.2.3 Measurement Sequence	273
8.1.2.4 Measurement Accuracy	274
8.1.2.5 Voltage Range	276
8.1.2.5.1 AutoRange	276
8.1.2.5.2 Fixed Voltage Ranges	277
8.1.2.5.3 Common Mode Null / Open Input Detect	277
8.1.2.6 Offset Voltage Compensation	278
8.1.2.6.1 Input and Excitation Reversal	278
8.1.2.6.2 Ground Reference Offset Voltage	279
8.1.2.6.3 Background Calibration	279
8.1.2.7 Integration	279
8.1.2.7.1 ac Power Line Noise Rejection	280
8.1.2.8 Signal Settling Time	282
8.1.2.8.1 Minimizing Settling Errors	283
8.1.2.8.2 Measuring the Necessary Settling Time	283
8.1.2.9 Self-Calibration	285
8.1.2.10 Time Skew Between Measurements	290
8.1.3 Resistance Measurements	291
8.1.3.1 ac Excitation	293
8.1.3.2 Accuracy of Ratiometric-Resistance Measurements	294
8.1.3.3 Strain Calculations	296
8.1.4 Thermocouple	297
8.1.5 Pulse	297
8.1.5.1 Pulse-Input Channels (P1 - P2)	299
8.1.5.1.1 High-frequency Pulse (P1 - P2)	300
8.1.5.1.2 Low-Level ac (P1 - P2)	300
8.1.5.1.3 Switch Closure (P1 - P2)	300
8.1.5.2 Pulse Input on Digital I/O Channels C1 - C4	301
8.1.5.2.1 High Frequency Mode	301
8.1.5.2.2 Low-Frequency Mode	302
8.1.5.3 Pulse Measurement Tips	302
8.1.5.3.1 Frequency Resolution	303
8.1.5.4 Pulse Measurement Problems	305
8.1.5.4.1 Pay Attention to Specifications	305
8.1.5.4.2 Input Filters and Signal Attenuation	305
8.1.5.4.3 Switch Bounce and NAN	307
8.1.6 Period Averaging	307
8.1.7 SDI-12 Recording	308
8.1.8 RS-232 and TTL	308
8.1.9 Field Calibration	309
8.1.10 Cabling Effects	309
8.1.10.1 Analog Sensor Cables	309
8.1.10.2 Pulse Sensors	309
8.1.10.3 RS-232 Sensors	310
8.1.10.4 SDI-12 Sensors	310
8.1.11 Synchronizing Measurements	310
8.2 Measurement and Control Peripherals	311
8.2.1 Analog-Input Expansion Modules	312
8.2.2 Pulse-Input Expansion Modules	312
8.2.3 Serial-Input Expansion Modules	312
8.2.4 Control Outputs	312
8.2.4.1 Digital I/O Ports	312
8.2.4.2 Relays and Relay Drivers	313
8.2.4.3 Component-Built Relays	313
8.2.5 Analog Control / Output Devices	314
8.2.6 TIMs	315
8.2.7 Vibrating Wire	315
8.2.8 Low-level ac	315
8.3 Memory and Final Data Storage	315
8.3.1 Storage Media	315
8.3.1.1 Data Storage	318
8.3.1.1.1 Data Table SRAM	318
8.3.1.1.2 CPU: Drive	318
8.3.1.1.3 USR: Drive	318
8.3.1.1.4 USB: Drive	319
8.3.1.1.5 Data File Formats	319
8.3.2 Memory Conservation	323
8.3.3 Memory Reset	323
8.3.3.1 Full Memory Reset	323
8.3.3.2 Program Send Reset	324
8.3.3.3 Manual Data-Table Reset	324
8.3.3.4 Formatting Drives	324
8.3.4 File Management	324
8.3.4.1 File Attributes	326
8.3.4.2 Data Preservation	326
8.3.4.3 External Memory Power-up	327
8.3.4.3.1 Creating and Editing Powerup.ini	328
8.3.4.4 File Management Q & A	330
8.3.5 File Names	331
8.3.6 File System Errors	331
8.4 Telecommunications and Data Retrieval	332
8.4.1 Hardware and Carrier Signal	333
8.4.2 Protocols	333
8.4.3 Initiating Telecommunications (Callback)	333
8.5 PakBus Overview	334
8.5.1 PakBus Addresses	335
8.5.2 Nodes: Leaf Nodes and Routers	335
8.5.2.1 Router and Leaf-Node Configuration	335
8.5.3 Linking PakBus Nodes: Neighbor Discovery	337
8.5.3.1 Hello-message (two-way exchange)	337
8.5.3.2 Beacon (one-way broadcast)	337
8.5.3.3 Hello-request (one-way broadcast)	338
8.5.3.4 Neighbor Lists	338
8.5.3.5 Adjusting Links	338
8.5.3.6 Maintaining Links	338
8.5.4 PakBus Troubleshooting	339
8.5.4.1 Link Integrity	339
8.5.4.1.1 Automatic Packet-Size Adjustment	339
8.5.4.2 Ping	339
8.5.4.3 Traffic Flow	340
8.5.5 LoggerNet Network-Map Configuration	340
8.5.6 PakBus LAN Example	341
8.5.6.1 LAN Wiring	341
8.5.6.2 LAN Setup	342
8.5.6.3 LoggerNet Setup	344
8.5.7 PakBus Encryption	346
8.6 Alternate Telecommunications	347
8.6.1 DNP3	347
8.6.1.1 Overview	347
8.6.1.2 Programming for DNP3	347
8.6.1.2.1 Declarations	347
8.6.1.2.2 CRBasic Instructions	348
8.6.1.2.3 Programming for Data-Acquisition	349
8.6.2 Modbus	350
8.6.2.1 Overview	350
8.6.2.2 Terminology	351
8.6.2.2.1 Glossary of Terms	351
8.6.2.3 Programming for Modbus	352
8.6.2.3.1 Declarations	352
8.6.2.3.2 CRBasic Instructions - Modbus	352
8.6.2.3.3 Addressing (ModbusAddr)	353
8.6.2.3.4 Supported Function Codes (Function)	353
8.6.2.3.5 Reading Inverse-Format Registers	353
8.6.2.4 Troubleshooting	353
8.6.2.5 Modbus over IP	354
8.6.2.6 Modbus tidBytes	354
8.6.2.7 Converting 16-bit to 32-bit Longs	354
8.6.3 Web Service API	355
8.6.3.1 Authentication	355
8.6.3.2 Command Syntax	356
8.6.3.3 Time Syntax	358
8.6.3.4 Data Management	358
8.6.3.4.1 BrowseSymbols Command	358
8.6.3.4.2 DataQuery Command	362
8.6.3.5 Control	368
8.6.3.5.1 SetValueEx Command	368
8.6.3.6 Clock Functions	370
8.6.3.6.1 ClockSet Command	370
8.6.3.6.2 ClockCheck Command	372
8.6.3.7 Files Management	374
8.6.3.7.1 Sending a File to a Datalogger	374
8.6.3.7.2 FileControl Command	375
8.6.3.7.3 ListFiles Command	377
8.6.3.7.4 NewestFile Command	381
8.7 Support Software	382
8.8 Using the Keyboard Display	382
8.8.1 Data Display	385
8.8.1.1 Real-Time Tables and Graphs	386
8.8.1.2 Real-Time Custom	386
8.8.1.3 Final-Storage Tables	388
8.8.2 Run/Stop Program	389
8.8.3 File Display	390
8.8.3.1 File: Edit	391
8.8.4 Ports and Status	392
8.8.5 Settings	392
8.8.5.1 Set Time / Date	393
8.8.5.2 PakBus Settings	393
8.8.6 Configure Display	393
8.9 Program and OS File Compression	393
Section 9. Maintenance	397
9.1 Moisture Protection	397
9.2 Replacing the Internal Battery	397
9.3 Repair	400
Section 10. Troubleshooting	403
10.1 Status Table	403
10.2 Operating Systems	403
10.3 Programming	403
10.3.1 Status Table as Debug Resource	403
10.3.1.1 CompileResults	404
10.3.1.2 SkippedScan	405
10.3.1.3 SkippedSlowScan	405
10.3.1.4 SkippedRecord	405
10.3.1.5 ProgErrors	406
10.3.1.6 MemoryFree	406
10.3.1.7 VarOutOfBounds	406
10.3.1.8 WatchdogErrors	406
10.3.1.8.1 Status Table WatchdogErrors	406
10.3.1.8.2 Watchdoginfo.txt File	407
10.3.2 Program Does Not Compile	407
10.3.3 Program Compiles / Does Not Run Correctly	407
10.3.4 NAN and ±INF	408
10.3.4.1 Measurements and NAN	408
10.3.4.1.1 Voltage Measurements	408
10.3.4.1.2 SDI-12 Measurements	408
10.3.4.2 Floating-Point Math, NAN, and ±INF	408
10.3.4.3 Data Types, NAN, and ±INF	409
10.3.4.4 Output Processing and NAN	410
10.4 Communications	411
10.4.1 RS-232	411
10.4.2 Communicating with Multiple PCs	411
10.4.3 Comms Memory Errors	411
10.4.3.1 CommsMemFree(1)	411
10.4.3.2 CommsMemFree(2)	413
10.4.3.3 CommsMemFree(3)	413
10.5 Power Supplies	414
10.5.1 Overview	414
10.5.2 Troubleshooting Power at a Glance	415
10.5.3 Diagnosis and Fix Procedures	415
10.5.3.1 Battery Test	415
10.5.3.2 Charging Regulator with Solar-Panel Test	416
10.5.3.3 Charging Regulator with Transformer Test	418
10.5.3.4 Adjusting Charging Voltage	419
10.6 Terminal Emulator	421

Match case Limit results 1 per page

Section 8.

Operation

310

8.1.10.3 RS-232 Sensors

RS-232 sensor cable lengths should be limited to 50 feet.

8.1.10.4 SDI-12 Sensors

The SDI-12 standard allows cable lengths of up to 200 feet. Campbell Scientific

does not recommend SDI-12 sensor lead lengths greater than 200 feet; however,

longer lead lengths can sometimes be accommodated by increasing the wire gage

or powering the sensor with a second 12-Vdc power supply placed near the

sensor.

8.1.11 Synchronizing Measurements

Timing of a measurement is usually controlled relative to the CR800 clock.

When sensors in a sensor network are measured by a single CR800, measurement

times are synchronized, often within a few milliseconds, depending on sensor

number and measurement type.

Large numbers of sensors, cable length

restrictions, or long distances between measurement sites may require use of

multiple CR800s.

Techniques outlined below enable network administrators to

synchronize CR800 clocks and measurements in a CR800 network.

Care should be taken when a clock-change operation is planned.

Any time the

CR800 clock is changed, the deviation of the new time from the old time may be

sufficient to cause a skipped record in data tables.

Any command used to

synchronize clocks should be executed after any

CallTable()

instructions and

timed so as to execute well clear of data output intervals.

Techniques to synchronize measurements across a network include:

LoggerNet

(p. 76)

– when reliable telecommunications are common to all

CR800s in a network, the

LoggerNet

automated clock check provides a simple

time synchronization function.

Accuracy is limited by the system clock on the

PC running the

LoggerNet

server.

Precision is limited by network

transmission latencies.

LoggerNet

compensates for latencies in many

telecommunications systems and can achieve synchronies of <100 ms

deviation.

Errors of 2 to 3 second may be seen on very busy RF connections

or long distance internet connections.

Note

Common PC clocks are notoriously inaccurate.

An easy way to keep a PC

clock accurate is to utilize public domain software available at

http://www.nist.gov/pml/div688/grp40/its.cfm

Digital trigger – a digital trigger, rather than a clock, can provide the

synchronization signal.

When cabling can be run from CR800 to CR800, each

CR800 can catch the rising edge of a digital pulse from the Master CR800 and

synchronize measurements or other functions, using the

WaitDigTrig()

instructions, independent of CR800 clocks or data time stamps.

When

programs are running in pipeline mode, measurements can be synchronized to

within a few microseconds (see

WaitDigTrig Scans

PakBus commands – the CR800 is a PakBus device, so it is capable of being a

node in a PakBus network.

Node clocks in a PakBus network are

synchronized using the

SendGetVariable()

ClockReport()

, or

PakBusClock()

commands.

The CR800 clock has a resolution of 10 ms,