cn-0209

Hi,

      I need to design a universal analog input module .I have referred to CN-0209.But I could not understand the purpose of ADG442 used in the circuit.Can I get help?

Regards,

Divya

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  • 0
    •  Analog Employees 
    on Mar 4, 2014 10:20 PM

    Hi Divya,

    In response:

    1. I should have mentioned, that AD7193 includes a precision PGA (gain of 1 to 128). This PGA provides a high impedance input for the thermocouple, as well as gaining up the thermocouple signals to utilise more of the ADC range.
    2. The ±10V signals are passed through the ADG1414 switch and are deferentially buffered by the AD8676 to provide a high input impedance. The ADG1414 and AD8676 have ±15V supplies to allow for the ±10V at their inputs. The output of the AD8676 is fed into the AD8275, which performs the level shifting and attenuation (Gain = 0.2) to the range of the ADC.
    3. No, the RTD input would also be connected directly to the AD7193 via the ADG442. The AD8617 provides the excitation current.
    4. This really Depedns on your requirements:
      • You can purchase the CN0209 hardware and an SDP board. The SDP board is a controller board with interface to the PC, it contains a DSP on board. www.analog.com/sdpb
      • Another option is to use the ADuCM361, this is a cortex M3 core with precision 24-bit sigma delta, Mux and PGA. So this would replace the AD7193, and includes the microcontroller. Note that this is a 3.3V devices so the circuit would need to be altered accordingly.
      • Alternately any other micro-controller of your choice. The AD7193 has an SPI compatible interface.

    Regards,

    Derrick

Reply
  • 0
    •  Analog Employees 
    on Mar 4, 2014 10:20 PM

    Hi Divya,

    In response:

    1. I should have mentioned, that AD7193 includes a precision PGA (gain of 1 to 128). This PGA provides a high impedance input for the thermocouple, as well as gaining up the thermocouple signals to utilise more of the ADC range.
    2. The ±10V signals are passed through the ADG1414 switch and are deferentially buffered by the AD8676 to provide a high input impedance. The ADG1414 and AD8676 have ±15V supplies to allow for the ±10V at their inputs. The output of the AD8676 is fed into the AD8275, which performs the level shifting and attenuation (Gain = 0.2) to the range of the ADC.
    3. No, the RTD input would also be connected directly to the AD7193 via the ADG442. The AD8617 provides the excitation current.
    4. This really Depedns on your requirements:
      • You can purchase the CN0209 hardware and an SDP board. The SDP board is a controller board with interface to the PC, it contains a DSP on board. www.analog.com/sdpb
      • Another option is to use the ADuCM361, this is a cortex M3 core with precision 24-bit sigma delta, Mux and PGA. So this would replace the AD7193, and includes the microcontroller. Note that this is a 3.3V devices so the circuit would need to be altered accordingly.
      • Alternately any other micro-controller of your choice. The AD7193 has an SPI compatible interface.

    Regards,

    Derrick

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