AM16/32A Relay Multiplexer Revision: 11/07 C o p y r i g h t © 1 9 8 7 - 2 0 0 7 C a m p b e l l S c i e n t i f i c , I n c .
Warranty and Assistance The AM16/32A RELAY MULTIPLEXER is warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and workmanship under normal use and service for twelve (12) months from date of shipment unless specified otherwise. Batteries have no warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is limited to repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products.
AM16/32A Relay Multiplexer Table of Contents PDF viewers note: These page numbers refer to the printed version of this document. Use the Adobe Acrobat® bookmarks tab for links to specific sections. 1. Function........................................................................1 1.1 Typical Applications.................................................................................1 1.2 Compatibility ............................................................................................2 2.
AM16/32A Relay Multiplexer Table of Contents 6.6 Thermocouple Measurement.................................................................. 28 6.6.1 Measurement Considerations ....................................................... 28 6.6.2 Single-ended Thermocouple Measurement .................................. 30 6.6.3 Differential Thermocouple Measurement .................................... 31 6.7 Mixed Sensor Types............................................................................... 31 6.7.
Cautionary Notes The AM16/32A is not designed to multiplex power. Its intended function is to switch low level analog signals. Switched currents in excess of 30 mA will degrade the relay contacts involved, rendering that channel unsuitable for further low level analog measurement. Customers who need to switch power are directed to Campbell Scientific’s SDM-CD16AC, A6REL-12, or A21REL-12 relays.
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AM16/32A Relay Analog Multiplexer 1. Function The primary function of the AM16/32A Multiplexer is to increase the number of sensors that can be measured by a CR1000, CR3000, CR800, CR850, CR23X, CR10(X), 21X, or CR7 datalogger. The AM16/32A is positioned between the sensors and the datalogger. The AM16/32A is a replacement for CSI’s AM16/32 model. Mechanical relays in the AM16/32A connect each of the sensor channels in turn to a common output destined for the datalogger.
AM16/32A Relay Analog Multiplexer NOTE For a discussion of single-ended versus differential analog measurements, please consult the Measurement section of your datalogger manual. As purchased, the AM16/32A is intended for use in indoor, non-condensing environments. An enclosure is required for field or high humidity use. In applications where one or two multiplexers are deployed, the ENC 10/12 (10” x 12”) enclosure is recommended. 1.
AM16/32A Relay Analog Multiplexer FIGURE 1. AM16/32A Relay Multiplexer 3. AM16/32A Specifications Power*: Unregulated 12 VDC Minimum Operating Voltage: from –55C to +40C = 11.3 VDC; from +40C to +85C = 11.8 VDC (See Figure 2 for relay actuation times vs. temperature and supply voltage.) Current Drain: Quiescent: < 210 uA Active: 6 mA typical in “2 x 32” mode 11 mA typical in “4 x 16” mode Reset*: A continuous signal between 3.
AM16/32A Relay Analog Multiplexer Dimensions: Length – 23.9 cm (9.4") Width - 10.2 cm (4.0") Depth - 4.6 cm (1.8") Weight: 1.5 lbs. (approx.), 693 g. Mounting Tab Hole Spacing: Expandability** (nominal): 1 inch x 3 inches x 9 inches. Up to 1/8 inch or 3 mm diameter screws (see Figure 21). Maximum Cable Length: Depends on sensor and scan rate. In general, longer lead lengths necessitate longer measurement delays. Refer to datalogger manual for details.
AM16/32A Relay Analog Multiplexer RELAY ACTUATION TIME (ms) 12.0 10.0 8.0 6.0 4.0 2.0 16 15.6 15.2 14.8 14 14.4 13.6 13.2 12.8 12 12.4 11.6 11.2 10.8 10 10.4 9.6 0.0 POWER SUPPLY VOLTAGE 65C 50C 25C -25C FIGURE 2. AM16/32A Relay Actuation Time vs. Temperature and Battery Voltage. 4. Operation Subsection 4.1 discusses the terminals that control operation of the multiplexer. These terminals are located at the left-hand side of the multiplexer as shown in Figure 1. Subsection 4.
AM16/32A Relay Analog Multiplexer 12V GND CLK RES MUXPOWER SHIELD N O CR800, CR850 CR10X, CR3000, CR1000 G G 12 V CR23X, CR5000 21X CR7 12 V 12 V +12 V 12 V G G G C1-C4 C1-C8 C1-C8 EXCIT 1-4 EXCITATION C1-C4 C1-C8 C1-C8 C1-C8 725 Card Control FIGURE 3. AM16/32A to Datalogger Power/Control Hookup With the 21X or CR7 the AM16/32A connects to the 12 VDC and “ ” terminals for power.
AM16/32A Relay Analog Multiplexer With the 21X and CR7 dataloggers, switched excitation is generally used to clock the multiplexer (Instruction 22 configured for 5000 mV excitation). If no switched excitation channel is available, it is possible to clock using control ports. See Section 5.1 for details. In the case of the CR5000, CR3000, CR800, CR850, CR1000, CR23X, and CR10(X), a control port is generally used to clock the multiplexer.
AM16/32A Relay Analog Multiplexer The average power required to operate an AM16/32A depends on the percentage of time it is active per time period. For example, if a CR10X makes differential measurements on 32 thermocouples every minute, the average current drain due to the AM16/32A would be about ((.030 Sec/chan x 32 chan)/60 Sec) x 6 mA = 0.1 mA. Under the same conditions, a 2 second execution interval rate increases the average system current drain to about ((.030 Sec/chan x 32 chan)/2 Sec) x 6 mA = 2.
AM16/32A Relay Analog Multiplexer 4.2.1 COM Terminals The four terminals dedicated to multiplexer-datalogger connection are located under the blue “COM” next to the mode switch. The terminals are labeled: ODD H, ODD L, EVEN H, and EVEN L. In “4x16” mode the AM16/32A maintains the four “COM” terminals electrically isolated from one another. In “2x32” mode the AM16/32A maintains an internal connection between ODD H and EVEN H and between ODD L and EVEN L.
AM16/32A Relay Analog Multiplexer With panel switch set to “2x32” mode the white channel numbers apply. The SETs are labeled beginning with 1H, 1L and ending with 32H, 32L. In “2x32” mode when the AM16/32A selects a given channel the “H” sensor terminal is relay connected to both COM “H” terminals and the “L” sensor terminal is connected to both COM “L” terminals (COM ODD H connects to COM EVEN H and COM ODD L connects to COM EVEN L when panel switch is in “2x32” mode). 5.
AM16/32A Relay Analog Multiplexer 5.1 Single Loop Instruction Sequence When a number of similar sensors are multiplexed and measured, the Instructions to clock the AM16/32A and to measure the sensors are placed within a program loop. For the CR23X, CR10(X), 21X, and CR7, the generalized structure of a program loop is as follows: TABLE 2.
AM16/32A Relay Analog Multiplexer Example: 2 sensors per SET, 6 sensors total; two reps specified in measurement instruction; two measurement values assigned to indexed input locations (--); P90 step of 2. Loop count of three.
AM16/32A Relay Analog Multiplexer NOTE If more than the datalogger’s default number of input locations are required, then additional input locations must be assigned using the datalogger *A mode. Consult your datalogger manual for details. #6 Optional Processing - Additional processing is sometimes required to convert the reading to the desired units. It may be more efficient if this processing is done outside the measurement loop. A second loop can be used for processing, if necessary.
AM16/32A Relay Analog Multiplexer GENERALIZED “4x16” MODE PROGRAM LOOPS FOR THE CR23X, CR10(X), 21X, and CR7 21X SAMPLE PROGRAM CR7 SAMPLE PROGRAM CR10X, CR23X SAMPLE PGM * * * 1 01: 60 Table 1 Programs Sec. Execution Interval 1 01: 60 Table 1 Programs Sec. Execution Interval :ACTIVATE MULTIPLEXER 1: Set Port (P20) 1: 1 Set high 2: 1 Port Number ;ACTIVATE MULTIPLEXER 1: Set Port (P20) 1: 1 Set high 2: 1 EX Card 3: 1 Port No. 2: Excitation with Delay (P22) 1: 1 Ex Channel 2: 0 Delay w/Ex (0.
AM16/32A Relay Analog Multiplexer EXAMPLE “2x32” MODE PROGRAMS - GENERALIZED PROGRAM LOOPS FOR THE CR23X, 21X, CR10(X), AND CR7. 21X SAMPLE PROGRAM * 1 Table 1 Programs 01: 60 Sec. Execution Interval CR7 SAMPLE PROGRAM * 1 Table 1 Programs 01: 60 Sec. Execution Interval ;ACTIVATE MULTIPLEXER 1: Set Port (P20) 1: 1 Set high 2: 1 Port Number ;ACTIVATE MULTIPLEXER 1: Set Port (P20) 1: 1 Set high 2: 1 EX Card 3: 1 Port No. 2: Excitation with Delay (P22) 1: 1 Ex Channel 2: 0 Delay w/Ex (0.
AM16/32A Relay Analog Multiplexer CR23X AM16/32 IN "4X16" MODE MUX POWER SHIELD GND SETS 1-10 12V H1 G GND L1 C1 RES H2 C2 CLK L2 12V SETS 11-16 EX 1 COM H1 H1 SE 1 COM L1 L1 SE 2 COM H2 H2 COM L2 L2 MUXSIGNAL SHIELD COM FIGURE 9. Wiring Diagram for Strain Gages and Potentiometers #8 Additional Loops - Additional loops may be used if sensors that require different measurement instructions are connected to the same multiplexer.
AM16/32A Relay Analog Multiplexer *1 Table 1 Programs 1: 60 Sec. Execution Interval ;ACTIVATES MULTIPLEXER 1: Do (P86) 1: 41 Set high Port 1 2: Excitation with Delay (P22) 1: 1 Ex Channel 2: 0 Delay w/Ex (0.01 sec units) 3: 15 Delay after Ex (0.01 sec units) 4: 0 mV Excitation ;BEGINS STRAIN GAGE MEASUREMENT LOOP 3: Beginning of Loop (P87) 1: 0 Delay 2: 10 Loop Count ;CLOCK PULSE 4: Do (P86) 1: 72 Pulse Port 2 ;DELAY 5: Excitation with Delay (P22) 1: 1 EX Chan 2: 0 Delay w/EX (units=.
AM16/32A Relay Analog Multiplexer ;DELAY 11: Excitation with Delay (P22) 1: 1 EX Chan 2: 0 Delay w/EX (units=.01sec) 3: 1 Delay after EX (units=.01sec) 4: 0 mV Excitation ;POT. MEASUREMENT INSTRUCTION 12: Excite,Delay,Volt(SE) (P4) 1: 2 Reps 2: 5 5000 mV slow Range 3: 1 IN Chan 4: 2 Excite all reps w/EXchan 2 5: 1 Delay (units .01sec) 6: 5000 mV Excitation 7: 11-Loc [:POT #1 ] 8: 1 Mult 9: 0 Offset ;END POT.
AM16/32A Relay Analog Multiplexer GENERALIZED CRBASIC PROGRAMMING SEQUENCE: ACTIVATE MULTIPLEXER/RESET INDEX Portset (1 ,1) 'Set C1 high to Enable Multiplexer I=0 BEGIN MEASUREMENT LOOP SubScan(0,sec,16) CLOCK PULSE AND DELAY Portset (2,1 ) ‘Set port 2 high Delay (0,20,mSec) Portset (2,0) ‘Set port 2 low INCREMENT INDEX AND MEASURE I=I+1 'User specified measurement instruction ‘Storing results in Variable(I) END MEASUREMENT LOOP NextSubScan DEACTIVATE MULTIPLEXER Portset (1 ,0) 'Set C1 Low to disable Multi
AM16/32A Relay Analog Multiplexer 'CR5000 Example Program to measure 16 100 ohm Platinum Resistance Thermometers ‘connected to an AM16/32A multiplexer used in the 4x16 configuration. The program also ‘measures 6 copper constantan 'thermocouples. 'The Thermocouples are connected to differential channels 1-6.
AM16/32A Relay Analog Multiplexer Wiring for CR1000 Program Example AM16/32A (4x16) CS616* Control/Common Sensor Terminals C4 RES Odd H CS616#1_Green C5 CLK Odd L CS616#2_Green 12 V 12 V Gnd #1,2,3_Blk & Clear Gnd Gnd Even H CS616#3_Green 1H COM Odd H Even L #1,2,3_Orange 1L COM Odd L Gnd Gnd 2H COM Even H C6 COM Even L *Three sensors to each set of AM16/32A terminals.
AM16/32A Relay Analog Multiplexer I=1 ‘set sub scan loop counter SubScan (0,mSec,16) PulsePort (5,10000) ‘Clock Mux CS616 (Period(I),3,1,6,3,1.0,0)‘measure 3ea CS616 probes I=I+3 NextSubScan ‘ For I=1 to 48 ‘convert CS616 period to Volumetric Water Content VWC(I)=a0 + a1*Period(I) + a2*Period(I)^2 Next ‘ PortSet (4,0) ‘Set Mux Reset line Low flag(1)= low EndIf ‘+++++++++++++++++++++++++++ ‘ CallTable Dat30min ‘Call Output Tables NextScan EndProg 5.
AM16/32A Relay Analog Multiplexer NOTE Low level single-ended measurements are not recommended in 21X applications where the 21X's internal 12VDC supply is used to power the multiplexer or other peripherals (see Section 4.1.4). 21X/ CR7 CR10(X) CR23X/CR3000/ CR800/CR850/ 5000 CR1000/CR5000 H H H AG G MUXSIGNAL SHIELD "2 X 32" Mode COM ODD H ODD H (+) SENSOR COM ODD L ODD L (-) SENSOR SHIELD COM AM16/32 FIGURE 10.
AM16/32A Relay Analog Multiplexer 6.3 Half Bridge Measurements Measurements of this type may be subdivided into three categories based on completion resistance and the presence or absence of measured excitation. If the sensor's completion resistor(s) are installed at the datalogger panel (example: a CSI 107 probe modified for multiplexer use), then three probes per SET may be excited and measured in “4x16” mode (Figure 12). However, if the circuit is completed within the sensor (e.g.
AM16/32A Relay Analog Multiplexer CR23X/ CR800/ CR850/ CR1000 21X/ CR7 CR10(X) CR3000/ / CR5000 EX E E VX H H H L L L "4 X 16" Mode 0 COM H (ODD) ODD H H COM L ODD L L COM H (EVEN) EVEN H COM L EVEN L AG G MUXSIGNAL SHIELD COM SHIELD SENSOR SHIELDS FIGURE 13. Potentiometer Hook-up and Measurement 6.3.2 Potentiometer Measurement Sensor to Multiplexer wiring – if panel switch is set to “4x16” mode, up to two potentiometers may be connected to one input SET.
AM16/32A Relay Analog Multiplexer CR23X/ CR800/ CR850/ CR1000 21X/ CR7 CR10(X) CR3000/ CR500/ 0 EX E E VX H H H L L L "4 X 16" Mode 0 COM H (ODD) ODD H H COM L ODD L L COM H (EVEN) EVEN H COM L EVEN L AG H H H H L L L L G COM SHIELD SENSOR SHIELDS FIGURE 14. Four Wire Half Bridge Hook-up and Measurement The CR5000 and CR3000 also have current excitation channels which allow a resistance measurement.
AM16/32A Relay Analog Multiplexer A problem with making full bridge measurements with this configuration is that the resistance of the lead wire and multiplexer relays can cause a voltage drop, reducing the excitation at the bridge. The following section describes a configuration that compensates for this by measuring the excitation at the bridge. 6.
AM16/32A Relay Analog Multiplexer 6.6 Thermocouple Measurement The datalogger manuals contain thorough discussions of thermocouple measurement and error analysis. These topics will not be covered here. 6.6.1 Measurement Considerations Reference Junction - As shown in Figure 17 and 18, two reference junction configurations are possible: 1) reference located at the datalogger or 2) reference at the AM16/32A.
AM16/32A Relay Analog Multiplexer 21X/ CR7 CR10(X) CR3000/ CR800/CR850/ / CR23X/CR10 00/ 0 CR5000 H H H CU L L L CO H H H CU L L L CO G "4 X 16" Mode COM ODD H ODD H COM ODD L ODD L COM EVEN H EVEN H COM EVEN L EVEN L CU CO CU CO SENSOR SHIELDS COM FIGURE 17. Differential Thermocouple Measurement with Reference Junction at the Datalogger.
AM16/32A Relay Analog Multiplexer Thermal Gradients - Thermal gradients between the AM16/32A's sensor input terminals and COM terminals can cause errors in thermocouple readings. For example, with type T thermocouples, a one degree gradient between the input terminals and the COM terminals will result in an approximate one degree measurement error. Installing the aluminum cover plate (included with AM16/32A) helps to minimize gradients.
AM16/32A Relay Analog Multiplexer Multiplexer to Datalogger wiring - If the reference junction is at the datalogger, then the wire that connects the COM ODD H, COM ODD L, and COM EVEN H terminals to the datalogger should be of the same composition as the high side of the thermocouples. Also, the wire that connects COM EVEN L to datalogger ground should be of the same composition as the low side of the thermocouples. If the reference junction is at the AM16/32A (CSI 107 thermistor, RTD, etc.
AM16/32A Relay Analog Multiplexer CR10X Example Program – Thermocouple and Soil Block Measurement AM16/32A AM16/32 CR10(X) G MUXPOWER SHIELD GND 12V 12V G GND C1 RES C2 CLK 1H COM COM 1L SETS 1-16 ODD H ODD L ODD H ODD L EX 1 107 2L SETS 1-16 AG 1K 0.1% EX 2 COM EVEN H EVEN H COM EVEN L EVEN L 2H AG G MUXSIGNAL SHIELD COM FIGURE 20. Thermocouple and Soil Block Measurement for CR10X Example 33 LOCATIONS ALLOCATED TO INPUT STORAGE) *1 1: 60 Table 1 Programs Sec.
AM16/32A Relay Analog Multiplexer CLOCK PULSE 4: Do (P86) 1: 72 Pulse Port 2 5: Excitation with Delay (P22) 1: 1 EX Chan 2: 2 Delay w/EX (units=.01 sec) 3: 0 Delay after EX (units=.01 sec) 4: 1 mV Excitation 5: 0 MEASURES 1 THERMOCOUPLE PER LOOP 6: Thermocouple Temp (DIFF) (P14) 1: 1 Rep 2: 1 2.
AM16/32A Relay Analog Multiplexer 6:TC #5 24:SOIL M #7 7:TC #6 25:SOIL M #8 8:TC #7 26:SOIL M #9 9:TC #8 27:SOIL M#10 10:TC #9 28:SOIL M#11 11:TC #10 29:SOIL M#12 12:TC #11 30:SOIL M#13 13:TC #12 31:SOIL M#14 14:TC #13 32:SOIL M#15 15:TC #14 33:SOIL M#16 16:TC #15 34:_________ 17:TC #16 35:_________ 18:SOIL M #1 36:_________ CR1000 Example Program – Thermocouple and Soil Block Measurement 'CR1000 Series Datalogger 'Declare Public Variables Public PTemp, batt_volt, TCTemp(16), Soil(16) Dim I 'Counter for
AM16/32A Relay Analog Multiplexer 'Deactivate Multiplexer PortSet (1 ,0) 'Call Data Table CallTable Avg15Min Next Scan EndProg 7. General Measurement Considerations Long lead lengths – Longer sensor-to-AM16/32A leads result in greater induced and capacitively coupled voltages (cross-talk) between cable wires. To minimize capacitive effects CSI recommends the use of cabling having Teflon, polyethylene, or polypropylene insulation around individual conductors.
AM16/32A Relay Analog Multiplexer plate with 1-inch hole grid suitable for mounting the AM16/32A. The enclosures have a cable bushing to accommodate the sensor lines. These standard enclosures are rain-tight, but not water-proof. The enclosure lids are gasketed. The screws on the outside of the enclosure should be tightened to form a restrictive seal. In high humidity environments, user supplied foam, putty, or similar material helps to reduce the passage of moisture into the enclosure via cable conduits.
Appendix A. AM16/32A Improvements The AM16/32A replaced the AM16/32 in October 2006. The AM16/32A’s improvements over the AM16/32 are better ESD and surge protection, a main ground lug, and a newer processor. The AM16/32A is wired and programmed the same as its predecessor, the AM16/32.
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