1. Manuals
  2. Brands
  3. Campbell Manuals
  4. Multiplexer
  5. AM25T
  6. Instruction manual

Campbell AM25T Instruction Manual

Solid state multiplexer
Hide thumbs Also See for AM25T:
Table of Contents

Advertisement

Quick Links

Download this manual
AM25T Solid State Multiplexer
Revision: 1/10
C o p y r i g h t
©
1 9 9 5 - 2 0 1 0
C a m p b e l l
S c i e n t i f i c ,
I n c .

Advertisement

Table of Contents
loading

Related Manuals for Campbell AM25T

Summary of Contents for Campbell AM25T

  • Page 1 AM25T Solid State Multiplexer Revision: 1/10 C o p y r i g h t © 1 9 9 5 - 2 0 1 0 C a m p b e l l S c i e n t i f i c , I n c .
  • Page 2 If the form is not received within three days of product receipt or is incomplete, the product will be returned to the customer at the customer’s expense. Campbell Scientific reserves the right to refuse service on products that were exposed to contaminants that may cause health or safety...

  • Page 3: Table Of Contents

    AM25T Solid State 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. General .................1 1.1 AM25T Specifications................1 1.2 Physical Description .................2 1.3 Operation ....................3 2.
  • Page 4 AM25T Solid State Multiplexer Table of Contents Figures 1. AM25T Thermocouple Multiplexer............3 2. External Battery Connections ..............6 3. Differential Measurement of Type T Thermocouple ......... 7 4. Differential Voltage Measurement............. 7 A-1. Single-Ended Measurement of a Type T Thermocouple ....A-2 A-2.

  • Page 5: General

    1. General The AM25T Multiplexer increases the number of channels for measuring thermocouples or voltage sensors with Campbell Scientific dataloggers. The AM25T is positioned between the sensors and the datalogger. The datalogger controls the AM25T's solid state relays, sequentially connecting each sensor to the datalogger.

  • Page 6: Physical Description

    AM25T Solid State Multiplexer OPERATING TEMPERATURE Standard: -40°C to +85°C RTD accuracy ±0.4°C OPERATING HUMIDITY Noncondensing: 0 to 95% DIMENSIONS Length: 23.6 cm (9.3”) Width: 5.10 cm (2.0") Depth: 13.2 cm (5.2”) WEIGHT 0.91 kg (2.0 lbs) 3.6 kg (8.0 lbs); Shipping EXPANDABILITY (nominal)** 2 AM25Ts per CR800 or CR850...

  • Page 7: Operation

    In low current drain applications, it is convenient to power the AM25T from the datalogger's battery. For power intensive operations, use a high Amp hour 12 VDC battery. See Campbell Scientific’s application note on power supplies for information on calculating the power requirements of your system.

  • Page 8: Installation

    The standard AM25T may be operated in a non-condensing environment. An enclosure is required for field use. Campbell Scientific’s ENC12/14 and ENC16/18 enclosures offer a degree of protection against dust, spraying water, oil, falling dirt, or dripping non-corrosive liquids. The enclosures contain plates for multiplexer mounting and conduit bushings for cable entry.

  • Page 9: Datalogger To Am25T Wiring

    AM25T Solid State Multiplexer U-bolts are used to attach the enclosures to a 1.25" NPT pipe. The enclosure may also be lag-bolted to a wall or similar flat surface. Fasten the AM25T to the enclosure backplate. Securely fasten the leads to the strain relief flange running between the AM25T terminal strips and install the cover to reduce temperature gradients during thermocouple measurements.

  • Page 10: Sensor To Am25T Wiring

    AM25T Solid State Multiplexer AM25T FIGURE 2. External Battery Connections 4. Sensor to AM25T Wiring This section and the examples describe differential voltage measurements of thermocouples. It is possible to make single-ended measurements with the AM25T, however they are more likely to have problems (Appendix A). Shield wires are connected to the ground terminal next to the measurement channel and left unattached at the sensor.

  • Page 11: Differential Analog Measurements

    AM25T Solid State Multiplexer FIGURE 3. Differential Measurement of Type T Thermocouple 4.2 Differential Analog Measurements Connect one differential sensor to a differential AM25T input channel. Connect the sensor shields to the ground terminals next to the input channel. Up to 25 differential sensors may be measured by one differential channel on the datalogger (Figure 4).

  • Page 12: General Measurement Considerations

    5. General Measurement Considerations Cables have additional capacitance that increases the time required for a signal to settle its true value. To reduce settling time, Campbell Scientific recommends use of Teflon, polyethylene, or polypropylene insulation around individual conductors. Do not use PVC as conductor insulation. PVC may be used as a cable jacket.
  • Page 13 AM25T Solid State Multiplexer is greater than 1, the Dest parameter must be a variable array. If 0 is entered, the only measurement that is made is the reference temperature measurement. Range: The Range parameter is the expected voltage range of the input from the sensor.
  • Page 14 AM25T Solid State Multiplexer ClkPort: The ClkPort argument is the control port that will be used to clock the AM25T. One clock port may be used with several AM25Ts. A numeric code is entered for this argument: Code Description Control Port 1 Control Port 2 Control Port 3 Control Port 4...

  • Page 15: Example Crbasic Programs

    AM25T Solid State Multiplexer Mult, Offset: The Mult and Offset parameters are each a constant, variable, array, or expression by which to scale the results of the measurement. With a multiplier (mult) of 1 and an offset of 0, the output is in degrees Celsius. NOTE The AM25T instruction must NOT be placed in a conditional statement when running in pipeline mode.

  • Page 16: Cr1000 Example Program 2

    AM25T Solid State Multiplexer ‘Main Program BeginProg Scan (1,Sec,0,0) AM25T (TC(),25,mV2_5C,1,1,TypeT,Tref,5,4,Vx1,True,0,250,1.0,0) CallTable Dat15sec CallTable Dat5min NextScan EndProg 6.1.1.2 CR1000 Example Program 2 In this example, one AM25T instruction is used to measure the on-board PRT, and another AM25T instruction is used to measure ten type T thermocouples. Table 6-2 provides the wiring for the example.

  • Page 17: Edlog Programming

    AM25T Solid State Multiplexer 'Only the Reference Temperature is measured and stored in RTemp_C. 'To do this, enter 0 for the REP value AM25T(RTemp_C,0,mV2_5C,1,1,TypeT,RTemp_C,2,1,1,True,0,250,1,0) 'Ten Type T (copper-constantan) are measured on the AM25T. 'Thermocouple measurements are stored in the Temp_C() variable AM25T(Temp_C(1),10,mV2_5C,1,1,TypeT,RTemp_C,2,1,0,True,0,_60Hz,1,0) 'Call Data Tables and Store Data CallTable(Table1)

  • Page 18: Example Cr10(X) Programs

    AM25T Solid State Multiplexer TABLE 6-3. RTD Excitation Voltage and Measurement Range for AM25T Multiplexers Prior to Serial Number 1839 Datalogger Temperature Range Excitation voltage Vs Range Vx Range ± 5 mV ± 500 mV -40 to 85°C 250 mV -24 to 65°C 350 mV ±...
  • Page 19 AM25T Solid State Multiplexer 03: Full Bridge (P6) ;Measure the output of the reference temp. full bridge 1: 1 Reps 2: 23 25 mV 60 Hz Rejection Range ;See Table 6-1 for older AM25T multiplexers 3: 1 DIFF Channel 4: 1 Excite all reps w/Exchan 1 5: 1200 mV Excitation...

  • Page 20: The Differential Thermocouple Instruction And Long Lead Length Compensation On The Rtd Measurement

    AM25T Solid State Multiplexer Example 4. CR10(X) Program for Measuring 25 Type T Thermocouples with the Differential Thermocouple Instruction and Long Lead Length Compensation on the RTD Measurement *Table 1 Program 01: 10 Execution Interval (seconds) 01: Set Port(s) (P20) ;Configure Control Ports for 1 millisecond pulse 1: 9999 C8..C5 = nc/nc/nc/nc...
  • Page 21 AM25T Solid State Multiplexer 09: BR Transform Rf[X/(1-X)] (P59) ;Calculate RTD resistance R/R0 1: 1 Reps 2: 1 Loc [ RefTemp_C ] 3: 10.025 Multiplier (Rf) 10: Temperature RTD (P16) ;Calculate reference temperature 1: 1 Reps 2: 1 R/R0 Loc [ RefTemp_C ] 3: 1 Loc [ RefTemp_C ] 4: 1.0...

  • Page 22: Example Cr23X Program

    AM25T Solid State Multiplexer 6.2.2 Example CR23X Program The CR23X uses Instruction 134 for measuring thermocouples or voltages with the AM25T. Example 5 is a portion of a datalogger program that uses the instruction to measure 25 type T thermocouples. Instruction 134 automatically compensates for long lead lengths.

  • Page 23: Single-Ended Measurements

    Appendix A. Single-Ended Measurements Single-ended measurements with the AM25T are not recommended. This is not due to any problem with the AM25T. Single-ended measurements have some problems that differential measurements avoid. The problems with single-ended measurements are: • Reduced noise rejection. •...

  • Page 24: A-1. Single-Ended Measurement Of A Type T Thermocouple

    Appendix A. Single-Ended Measurements A.1.1 Thermocouple Measurements Wire the high side of each thermocouple into an input terminal. The low side of each thermocouple is wired into the adjacent ground terminal (Figure A-1). FIGURE A-1. Single-ended Measurement of a Type T Thermocouple Example A-1.
  • Page 25 Appendix A. Single-Ended Measurements 05: Temperature RTD (P16) ;Calculate reference temperature 1: 1 Reps 2: 1 R/R0 Loc [ RefTemp_C ] 3: 1 Loc [ RefTemp_C ] 4: 1.0 Mult 5: 0.0 Offset 06: Beginning of Loop (P87) ;Loop through thermocouple channels 1: 0 Delay 2: 25...
  • Page 26 Appendix A. Single-Ended Measurements 03: BR Transform Rf[X/(1-X)] (P59) ;Calculate RTD resistance R/R0 1: 1 Reps 2: 1 Loc [ RefTemp_C ] 3: 10.025 Multiplier (Rf) 04: Temperature RTD (P16) ;Calculate reference temperature 1: 1 Reps 2: 1 R/R0 Loc [ RefTemp_C ] 3: 1 Loc [ RefTemp_C ] 4: 1.0...

  • Page 27: Indexing With Loops

    Appendix A. Single-Ended Measurements FIGURE A-2. Single-Ended Measurement A.2 Indexing with Loops When a multiplexer is measured with a measurement instruction within a loop, the input locations in which to store measurements must be indexed to the loop counter so the measurement is stored in the next input location each pass through the loop.

  • Page 28: A-2. Values In Input Storage; With Input Location Index And Without Step Loop Index Instruction

    Appendix A. Single-Ended Measurements instruction has one repetition. If the instruction has two repetitions, then every other Input Location will be over written. This effect is illustrated in Table A- 2. The program fragment in Example A-4 generated this effect. The multiplexer control instructions are not included in the NOTE example program fragment.
  • Page 29 Appendix A. Single-Ended Measurements Example A-4. Measuring Single Ended Thermocouples with the Input Location Indexed and no Step Loop Index 01: Beginning of Loop (P87) 1: 0 Delay 2: 6Loop Count 02: Thermocouple Temp (SE) (P13) 1: 2 Reps 2: 21 2.5 mV 60 Hz Rejection Range 3: 1 SE Channel...
  • Page 30 Appendix A. Single-Ended Measurements...

  • Page 31: Differences Between The Am25T, Am416, And The Am32

    Appendix B. Differences Between the AM25T, AM416, and the AM32 The AM25T differs from Campbell Scientific's AM416 and AM32 multiplexers in the following ways: 1. The AM25T cannot be used to multiplex power and is not suitable for bridge measurements because of the high impedance of the solid state relays.
  • Page 32 Appendix B. Differences Between the AM25T, AM416, and the AM32...
  • Page 34 Campbell Scientific Companies Campbell Scientific, Inc. (CSI) 815 West 1800 North Logan, Utah 84321 UNITED STATES www.campbellsci.com • info@campbellsci.com Campbell Scientific Africa Pty. Ltd. (CSAf) PO Box 2450 Somerset West 7129 SOUTH AFRICA www.csafrica.co.za • cleroux@csafrica.co.za Campbell Scientific Australia Pty. Ltd. (CSA)

Table of Contents