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CN0209: Universal AFE questions

1- How would I do the same circuit for 8 channels (CN0209 is for 2 channels), and with minimal components? (RTD 2-3 wires (no 4 wires), TC, 4-20mA)

2- What is the configuration of the ADG1414 for each measurement mode?

3- What is the correct connection for TC (figure 2)? The connection is JX-3, JX-3 ???????

Thanks a lot.

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  • Hi Ching.

    First of all, the initial requeriments of my project:

         - 8 universal analog inputs (RTD, TC, 4-20, Voltage). 3 header pins.

         - Each channel can be configurated independently for RTD, TC ... measurement mode. Another choice if this option complicates the design (cost &      component number (PCB size)), 2 blocks (4+4 inputs) and can configurated each block for each measurement mode.

         - The sample rate is not a critical factor.

         - This is controlled for a 32 bits ARM Cortex kinetis, communications Ethernet, CAN and RS-485. It´ll be a web based application.

         I´ll configure each analog input (with switches and analog multiplexers, jumpers no allowed), with a software through communications, and monitoring         too.

    (1) The inputs must be differential.  I've thought about putting 2 ADCS (1 for each block).
    (2) Sorry, i want give you the phone number, but i don´t speak English.

         I attempt to explain how the circuit works (CN-0209),  and if I'm wrong tell me.
         mA input: single ended, through AIN4, AIN8.
         Voltage input: Single ended, closed the switches of ADG1414, tied to AD8676-AD8275-AIN3
         TC input: Differential, through ADG442-(AIN1-AIN2)&(AIN5-AIN6). AD8617 is used in the path of thermocouple circuit?? is my doubt.
         RTD input: Differential, through ADG442-(AIN1-AIN2)&(AIN5-AIN6). AD8617 is used for current source.
    (3) Solved.
    I don´t have the EVAL-CN0209-SDPZ, i am doing my own prototipe board.
    Regards.
Reply
  • Hi Ching.

    First of all, the initial requeriments of my project:

         - 8 universal analog inputs (RTD, TC, 4-20, Voltage). 3 header pins.

         - Each channel can be configurated independently for RTD, TC ... measurement mode. Another choice if this option complicates the design (cost &      component number (PCB size)), 2 blocks (4+4 inputs) and can configurated each block for each measurement mode.

         - The sample rate is not a critical factor.

         - This is controlled for a 32 bits ARM Cortex kinetis, communications Ethernet, CAN and RS-485. It´ll be a web based application.

         I´ll configure each analog input (with switches and analog multiplexers, jumpers no allowed), with a software through communications, and monitoring         too.

    (1) The inputs must be differential.  I've thought about putting 2 ADCS (1 for each block).
    (2) Sorry, i want give you the phone number, but i don´t speak English.

         I attempt to explain how the circuit works (CN-0209),  and if I'm wrong tell me.
         mA input: single ended, through AIN4, AIN8.
         Voltage input: Single ended, closed the switches of ADG1414, tied to AD8676-AD8275-AIN3
         TC input: Differential, through ADG442-(AIN1-AIN2)&(AIN5-AIN6). AD8617 is used in the path of thermocouple circuit?? is my doubt.
         RTD input: Differential, through ADG442-(AIN1-AIN2)&(AIN5-AIN6). AD8617 is used for current source.
    (3) Solved.
    I don´t have the EVAL-CN0209-SDPZ, i am doing my own prototipe board.
    Regards.
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