Campbell AM416, Instruction Manual

Page 1: ...INSTRUCTION MANUAL AM416 Relay Multiplexer Revision 2 96 C o p y r i g h t c 1 9 8 7 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: ...ther 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 directl...

Page 3: ...surement without Sensor Excitation 10 6 2 Differential Analog Measurement without Sensor Excitation 11 6 3 Half Bridge Measurements 11 6 4 Full Bridge Measurements 13 6 5 Full Bridges with Excitation Compensation 13 6 6 Thermocouple Measurement 14 6 7 Mixed Sensor Types 16 7 GENERAL MEASUREMENT CONSIDERATIONS 18 8 INSTALLATION 8 1 Environmental Constraints 18 APPENDIX A AM416 STUFFING CHART AND SC...

Page 4: ...t 12 11 Potentiometer Hook up and Measurement 12 12 Four Wire Half Bridge Hook up and Measurement 13 13 Differential Measurement with Sensor Excitation 13 14 Full Bridge Measurement with Excitation Compensation 14 15 Differential Thermocouple Measurement with Reference Junction at the Datalogger 15 16 Differential Thermocouple Measurement with Reference Junction at the AM416 15 17 Thermocouple and...

Page 5: ...for future low level analog measurements Customers who need to switch power are directed to CSI s A6REL 12 or A21REL 12 relays Adjacent AM416 channels may be shorted together for up to 5 ms during the clocking procedure Users should consider this when assigning AM416 input channels Sensors that are capable of sourcing current should not be assigned input terminals adjacent to sensors that can sink...

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Page 7: ...ling It is also possible to multiplex sensors of different but compatible types e g thermocouples and soil moisture blocks see Section 6 6 NOTE For a discussion of single ended versus differential analog measurements please consult the Measurement Section of your datalogger manual As purchased the AM416 is intended for use in indoor non condensing environments An enclosure is required for field us...

Page 8: ...ipped and tinned lead wires up to 1 5 mm in diameter The datalogger is connected to the AM416 through a minimum of seven but generally nine individually insulated lead wires AM416 RELAY MULTIPLEXER SHIELD L2 H2 L1 H1 12 11 L2 H2 L1 H1 L2 H2 L1 H1 SHIELD L2 H2 10 COM L2 H2 L1 H1 9 SHIELD SHIELD L2 H2 L1 H1 16 15 L2 H2 L1 H1 L2 H2 L1 H1 14 L2 H2 L1 H1 13 SHIELD SHIELD L2 H2 L1 H1 8 7 L2 H2 L1 H1 L2 ...

Page 9: ...ultiplexing capability please consult CSI for application assistance Switching currents greater than 30 mA occasional 50 mA is acceptable will degrade the contact surfaces of the mechanical relays i e increase their resistance This process will adversely affect 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 vol...

Page 10: ...eactivate is generally used With a 21X or CR7 with older PROMS Instruction 20 is commonly used to activate and deactivate the multiplexer set port high to activate the multiplexer or low to enter quiescent mode 4 1 2 CLOCK The multiplexer clock line CLK controls the switching between sequential sets of relays When reset is set high and the multiplexer is activated the multiplexer s common lines CO...

Page 11: ...heir ability to be recharged lead acid supplies are recommended where solar or AC charging sources are available The datalogger alkaline supply 7 5 AmpHr can be used to power the AM416 in applications where the system current drain is low or where frequently replacing the batteries is not a problem It is advisable to calculate the total power requirements of the system and the expected longevity o...

Page 12: ...ivided into 16 labeled groups Each group consists of four Simultaneously Enabled Terminals SET Within each SET the four terminals are labeled H1 L1 H2 L2 As the AM416 receives clock pulses from the datalogger each SET is switched sequentially into contact with the COM terminals For example when the first clock pulse is received from the datalogger SET 1 bracket annotated with a number 1 is connect...

Page 13: ...cations The 1st 3rd 5th and 6th measurement values will reside in the first 4 input locations The Step Loop Instruction 90 is available in CR10 X s CR7s and 21Xs with a third PROM For 21X dataloggers without a third prom i e without Instruction 90 a separate measurement instruction with one rep is required for each sensor measured within the loop The input location parameter within both measuremen...

Page 14: ...1 Port No BEGINS MEASUREMENT LOOP 02 P87 Beginning of Loop 01 0 Delay 02 16 Loop Count CLOCK PULSE AND DELAY 03 P22 Excitation with Delay 01 1 EX Card 02 2 EX Chan 03 1 Delay w EX units 01 sec 04 1 Delay after EX units 01 sec 05 5000 mV Excitation 04 USER SPECIFIED MEASUREMENT INSTRUCTION ENDS MEASUREMENT LOOP 05 P95 End DEACTIVATES MULTIPLEXER 06 P20 Set Port 01 0 Set low 02 1 EX Card 03 1 Port N...

Page 15: ...ggers To measure sensors of different types different measurement instructions may be used within successive program loops In the following example each loop is terminated with Instruction 95 and the multiplexer is not reset between loops The following example demonstrates measurement of two dissimilar sensor types i e strain gages and potentiometers The program and accompanying wiring diagram are...

Page 16: ...long lead lengths Consult your datalogger manual for additional information on these topics 6 SENSOR HOOK UP AND MEASUREMENT EXAMPLES This section covers sensor AM416 connections as well as AM416 datalogger measurement connections The following are examples only and should not be construed as the only way to make a particular measurement See the Measurement Section of your datalogger manual for mo...

Page 17: ...alled at the datalogger panel e g a CSI 107 probe modified for multiplexer use then three probes per SET may be excited and measured Figure 10 However if the circuit is completed within the sensor e g potentiometers then excitation wiper signal and ground must be multiplexed Because excitation and ground may be multiplexed in common up to two sensors per SET may be measured Figure 11 If measured e...

Page 18: ...d to a datalogger switched excitation channel and the remaining COM line connects to datalogger ground Up to 32 potentiometers may be measured by two single ended datalogger channels 6 3 3 FOUR WIRE HALF BRIDGE WITH MEASURED EXCITATION Sensor to Multiplexer Wiring one sensor per input SET Multiplexer to Datalogger Wiring One COM line is tied to a datalogger excitation channel and two COM lines to ...

Page 19: ... must bypass the AM416 One solution is to multiplex the four signal wires through the AM416 but bypass the AM416 with excitation and ground This means that the sensors will be excited in common which causes a higher current drain possibly exceeding the current available from the datalogger s excitation channels Alternatively the excitation and ground leads may be multiplexed through either an AM32...

Page 20: ...e maintained on either side of the multiplexer e g if constantan wire is input to a L1 terminal then a constantan wire should run between the multiplexer s COM L1 terminal and the datalogger measurement terminal Figures 15 16 depict type T thermocouple applications but other thermocouple types e g E J and K may also be measured and linearized by the dataloggers If thermocouples are measured with r...

Page 21: ...n SETs that are in close proximity to the COM terminals in order to minimize thermal gradients Thermal Gradients Thermal gradients between the AM416 s sensor input terminals and COM terminals can cause errors in thermocouple readings For example with type T thermocouples a one degree gradient between input terminals and the COM terminals will result in a one degree measurement error approximately ...

Page 22: ...thermocouples If the reference junction is at the AM416 CSI 107 thermistor RTD etc then copper wire is used to connect all COM terminals to the datalogger 6 6 3 DIFFERENTIAL THERMOCOUPLE MEASUREMENT Sensor to Multiplexer wiring up to two thermocouples per input SET Multiplexer to Datalogger wiring The wires here can be handled in one of two ways If a reference junction 107 thermistor RTD etc is at...

Page 23: ...nge 03 1 IN Chan 04 1 Type T Copper Constantan 05 1 Ref Temp Loc REFTEMP 06 2 Loc TC 1 07 1 Mult 08 0 Offset MEASURES 1 SOIL MOISTURE BLOCK PER LOOP 07 P5 AC Half Bridge 01 1 Rep 02 14 250 mV fast Range 03 3 IN Chan 04 2 Excite all reps w EXchan 2 05 250 mV Excitation 06 18 Loc SOIL M 1 07 1 Mult 08 0 Offset ENDS MEASUREMENT LOOP 08 P95 End DISABLES MULTIPLEXER 09 P86 Do 01 51 Set low Port 1 CALCU...

Page 24: ... indoor non condensing environment If condensing humidity is a problem or if the multiplexer might be exposed to liquids a water resistant enclosure is required Several enclosures may be purchased through CSI which offer a degree of protection against dust spraying water oil falling dirt or dripping noncorrosive liquids Models AM ENC AM ENCT ENC 24 ENC 30 All the enclosures contain mounting plates...

Page 25: ...A 1 APPENDIX A AM416 STUFFING CHART AND SCHEMATICS ...

Page 26: ...APPENDIX A AM416 STUFFING CHART AND SCHEMATICS A 2 ...

Page 27: ...APPENDIX A AM416 STUFFING CHART AND SCHEMATICS A 3 ...

Page 28: ...APPENDIX A AM416 STUFFING CHART AND SCHEMATICS A 4 This is a blank page ...

Page 29: ...ckaged in an aluminum case that should decrease temperature gradients across the multiplexer terminal strips 3 The AM416 is smaller 4 The AM416 contains terminals and circuitry for sensor shield wires This circuitry allows sensor shield wires to be routed through the multiplexer and grounded at the datalogger 5 The packaging of the AM416 allows for strain relief of lead wires on the multiplexer s ...

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