Campbell AM32, Instruction Manual

Page 1: ...INSTRUCTION MANUAL AM32 Multiplexer Revision 2 96 C o p y r i g h t c 1 9 8 3 1 9 9 6 C a m p b e l l S c i e n t i f i c I n c ...

Page 2: ... warranties expressed or implied including warranties of merchantability or fitness for a particular purpose CAMPBELL SCIENTIFIC INC is not liable for special indirect incidental or consequential damages Products may not be returned without prior authorization The following contact information is for US and International customers residing in countries served by Campbell Scientific Inc directly Af...

Page 3: ...gle Ended Analog Measurements 7 5 2 Differential Measurements 9 5 3 Half Bridge Measurements 9 5 3 1 Half Bridge Measurement with Completion Resistor at Datalogger9 5 4 Mixed Sensor Types 9 6 Thermocouple Wiring and Measurement Considerations 9 6 1 Reference Junctions 9 6 2 Thermal Gradients 10 7 Programming Examples 11 7 1 CR10 X Programming Example 32 Soil Moisture Blocks Model 223 11 7 2 21X Pr...

Page 4: ...rement with Resistor at the Datalogger 9 6 1 Differential Thermocouple Measurement with Reference Junction at the Datalogger 10 6 2 Differential Thermocouple Measurement with Reference Junction at the AM32 10 7 1 Wiring Diagram for CR10 X AM32 and 223 Soil Moisture Block Example 11 7 2 Wiring Diagram for 21X and Thermocouples with Reference at the Datalogger 14 7 3 Wiring Diagram for Example of CR...

Page 5: ... to a cable connected to the datalogger Two lines are switched simultaneously a maximum of 32 sets of 2 lines 32 channels may be scanned Signals from analog sensors are multiplexed into either a single ended or a differential channel For a discussion of single ended versus differential analog measurements please consult the Measurement Section of your datalogger manual FIGURE 1 1 Plan view of the ...

Page 6: ...cceptable will degrade the contact surfaces of the mechanical relays increasing their resistance This process adversely affects the suitability of these relays to multiplex low voltage signals Although a relay used in this manner will not be of use in future low voltage measurements it may continue to be used for switching current in excess of 30mA CONTACT SPECIFICATIONS Initial contact resistance...

Page 7: ...r s common lines COM HI COM LO are not connected to any of the sensor input terminals When the first clock pulse is received the common lines are connected to multiplexer channel 1 1H 1L When a second clock pulse is received the common lines are connected to multiplexer channel 2 2H 2L and so forth The multiplexer is clocked on the leading edge of the voltage pulse i e voltage level must raise fro...

Page 8: ... where the system current drain is low or where frequently replacing the batteries is not a problem Sealed rechargeable supplies are recommended where solar or AC charging sources are available For power intensive operations a higher capacity external rechargeable 12VDC source should be considered To determine the life of the power supply calculate the system current drain and divide it into the p...

Page 9: ...h of the multiplexer in two parallel groups Each channel has two terminals labeled H and L standing for High and Low As the AM32 receives clock pulses from the datalogger each channel is connected sequentially with COM terminals For example when the first clock pulse is received from the datalogger 1H is connected with COM HI and 1L with COM LO When the second clock pulse is received the first cha...

Page 10: ...ure Enter the instruction needed to measure the sensor s Only one repetition is entered for the measurement instruction The Input Location in which to store the measurement is Indexed so that it is incremented by one with each pass through the loop INDEXING An Input Location entered in an instruction that is in a loop may be Indexed by keying C before keying A to enter the Input location two dashe...

Page 11: ...d should not be construed as the only way to make a particular measurement See the Measurement Section of your datalogger manual for more information on the basic measurements 5 1 SINGLE ENDED ANALOG MEASUREMENTS Sensor to Multiplexer wiring One single ended analog signal can be connected to each AM32 input channel for measurement Multiplexer to Datalogger wiring Signal lines from the COM terminal...

Page 12: ...nt 02 32 Loop Count CLOCK PULSE DELAY CLOCK PULSE DELAY CLOCK PULSE 03 P22 Excitation 03 P22 Excitation 03 P86 Do with delay with delay 72 Pulse Port 2 01 1 EX Chan 01 1 EX Chan 02 1 Delay w EX 02 2 EX Chan units 03 1 Delay w EX 01 sec units 03 1 Delay after 01 sec EX units 04 1 Delay after 01 sec EX units 04 5000 mV 01 sec Excitation 05 5000 mV Excitation 04 USER SPECIFIED 04 USER SPECIFIED 05 US...

Page 13: ...e contact Campbell Scientific for support 6 0 THERMOCOUPLE WIRING AND MEASUREMENT CONSIDERATIONS This section contains considerations for multiplexing thermocouple measurements The Measurement Section of your datalogger manual contains a thorough discussion of thermocouple measurement and error analysis these topics will not be covered here 6 1 REFERENCE JUNCTIONS Thermocouple measurements must al...

Page 14: ...ng resistance to the non thermocouple sensor circuit For example constantan is approximately 26 times more resistive than copper If a mix of TC s and other low level signals are multiplexed through the AM32 it is generally best to locate the reference junction on the AM32 as shown in Figure 6 2 So that copper wire instead of thermocouple wire can be run between the AM32 and datalogger If the other...

Page 15: ...t this wiring convention remains consistent so that current flow is confined to the interior of the block minimizing ground loops A 1k ohm resistor between the input and excitation channel is used to complete the half bridge as shown in Figure 7 1 Instruction 5 AC Half Bridge is used to excite and measure the 223 The output from Instruction 5 is the ratio of signal voltage to excitation voltage Fo...

Page 16: ...unt 04 P86 Do clock the AM32 01 76 Pulse Port 6 05 P22 Excitation with delay 01 1 EX Chan 02 0 Delay w EX units 01 sec 03 1 Delay after EX units 01 sec 04 0 mV Excitation 06 P5 AC Half Bridge measure moisture 01 1 Rep blocks 02 14 250 mV fast Range 03 1 IN Chan 04 2 Excite all reps w EXchan 2 05 250 mV Excitation 06 1 Loc SM Bars 1 07 1 Mult 08 0 Offset 07 P59 BR Transform Rf X 1 X 01 1 Rep conver...

Page 17: ...3 1 Z Loc SM Bars 1 13 P55 Polynomial 2 to 10 Bars 01 1 Rep 02 1 X Loc SM Bars 1 03 1 F X Loc SM Bars 1 04 15836 C0 05 6 1445 C1 06 8 4189 C2 07 9 2493 C3 08 3 1685 C4 09 3392 C5 14 P94 Else 15 P95 End 2 to 10 Bars 16 P95 End 0 1 to 2 Bars 17 P95 End Loop 18 P86 Do deactivate AM32 01 51 Set low Port 1 19 P86 Do 01 10 Set high Flag 0 output 20 P77 Real Time 01 1110 Year Day Hour Minute 21 P70 Sampl...

Page 18: ...17 26 SM Bar 26 35 _________ 9 SM Bars 9 18 SM Bar 18 27 SM Bar 27 36 _________ 7 2 21X PROGRAMMING EXAMPLE THERMOCOUPLES WITH REFERENCE AT THE DATALOGGER The following example explains the wiring and programming necessary to make measurements of 10 copper constantan thermocouples type T using the AM32 multiplexer The AM32 should be enclosed in an AM ENCT enclosure In the example program thermocou...

Page 19: ...w EX units 01sec 03 1 Delay after EX units 01sec 04 5000 mV Excitation 05 P14 Thermocouple Temp DIFF 01 1 Rep measure TC 02 1 5 mV slow Range 03 5 IN Chan 04 1 Type T Copper Constantan 05 11 Ref Temp Loc ref temp 06 1 Loc TC temp 1 07 1 Mult 08 0 Offset 06 P95 End end loop 07 P86 Do disable AM32 01 51 Set low Port 1 08 P End Table 1 A Mode 10 Memory Allocation 01 28 Input Locations 02 64 Intermedi...

Page 20: ...hermocouple reference temperature could also be made at the datalogger Thermocouple wire would have to be run from the AM32 to the datalogger The use of constantan wire as the low common lead has no effect on the moisture block measurement The impedance of the switched excitation port is great enough that when off the thermocouple measurement is not affected by the connection to the excitation por...

Page 21: ... 41 Set high Port 1 04 P87 Beginning of Loop start loop to 01 0 Delay measure and clock 02 16 Loop Count 05 P86 Do clock the AM32 01 76 Pulse Port 6 06 P22 Excitation with delay 01 1 EX Chan 02 0 Delay w EX units 01 sec 03 1 Delay after EX units 01 sec 04 0 mV Excitation 07 P5 AC Half Bridge measure moisture 01 1 Rep blocks 02 14 250 mV fast Range 03 3 IN Chan 04 2 Excite all reps w EXchan 2 05 25...

Page 22: ...ars 1 fit polynomial 02 0 1 F 03 1 Z Loc SM Bars 1 14 P55 Polynomial 2 to 10 Bars 01 1 Rep 02 1 X Loc SM Bars 1 03 1 F X Loc SM Bars 1 04 15836 C0 05 6 1445 C1 06 8 4189 C2 07 9 2493 C3 08 3 1685 C4 09 33392 C5 15 P94 Else 16 P95 End 2 to 10 Bars 17 P95 End 0 1 to 2 Bars 18 P95 End loop 19 P87 Beginning of Loop start loop for TC 01 0 Delay 02 16 Loop Count 20 P86 Do clock AM32 01 76 Pulse Port 6 2...

Page 23: ... hour if then do 29 P End Table 1 A Mode 10 Memory Allocation 01 40 Input Locations 02 64 Intermediate Locations 03 0 0000 Final Storage Area 2 Input Location Labels 1 SM bars 1 10 SM bar 10 19 TCtemp 3 28 TCtemp 12 2 SM bars 2 11 SM bar 11 20 TCtemp 4 29 TCtemp 13 3 SM bars 3 12 SM bar 12 21 TCtemp 5 30 TCtemp 14 4 SM bars 4 13 SM bar 13 22 TCtemp 6 31 TCtemp 15 5 SM bars 5 14 SM bar 14 23 TCtemp...

Page 24: ...om the analog input to ground Sensor shields should be tied together at the multiplexer and brought back to earth ground at the datalogger COM HI is tied to an excitation channel and COM LO to a single ended analog channel Instruction 22 is used to clock the AM32 with an excitation channel FIGURE 7 4 Wiring diagram for example using 21X datalogger to measure 107 temperature probes NOTE Tape the gr...

Page 25: ... power ground establishes a common ground The Installation Maintenance Section of your datalogger manual has more information on grounding procedures 3 Completion resistors In some applications it may be advisable to place completion resistors at the datalogger terminal strips In some cases sensors specific to the use of multiplexers are available from CSI Examples include soil moisture probes and...

Page 26: ...olts are provided to attach the enclosure to a 1 25 diameter pipe The enclosure may also be lag bolted to a wall or similar flat surface 9 1 ENVIRONMENTAL CONSTRAINTS The AM32 operating temperature range is 40 C to 65 C The multiplexer is susceptible to corrosion at high relative humidity Desiccant packs are available and they should be used inside the enclosure to remove water vapor 10 0 DIFFEREN...

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