Request arecommended ADC PN for both porpose Thermocouple and Analog signal

Hello,

My customer are trying to select a appropriate ADC for both porpose Thermocouple and Analog signal.

The concept of their product is one main board and eight daughter board.

And there are two kins of dahghter boards.

One has Thermocouple sensor and the other has a analog circuit with analog signal output.

So ADC in main board can receive both Thermocouple sensor output and analog circuit output.

Below are their requirements about ADC that they want to use.

1.For Thermocouple sensor

1) Use Kor T type Thermocouple sensors.

2) +/- 3 degree error range (Need a precise measurement.)

3) Don't need high speed sampling rate

2. For Analog Signal

1) General analog signal with 0~5V or 0~ 10V

2. Need high speed sampling rate (over 10KHz )

3. ADC requirement in main board

1) 24bit resolution

2) Differential 8ch (or 4 ch)

3) Over 10KHz sampling rate per channel

4) If possible, with OP AMp and internal reference voltage.

4. Concept of their product

1) Signal   --> peripheral circuit (OP Amp. or ADP1613 and etc) --> ADC --> CPU

2) Need simplest configuration

Would you recommend ADI ADC product for adapting above conditions?

Please advise me.

If you have any questions, please let me know.

Regards,

Se-woong

Parents
  • Hello,

    I receiver your answers about this request through CIA.ASIA.

    Thank you for your help.

    Regards,

    Se-woong

    PS. For you reference, I attach your answers in below.

    --------------------------------------------------------------------------------------------------------------------------------------

    The main board will have ADC which can accept both thermocouple input and the analog input (daughter cards)?

    Therewould be multiple way to implement this solution.

    For thermocouple measurement, are they planning to do Cold Junction Compensation externally (using RTD)? We have several circuit notes and reference design for this application.

    Please have a look on this circuit note CN0271 - www.analog.com/en/circuits-from-the-lab/cn0271/vc.html , here AD8495 is used for K type thermocouple signal conditioning (which internally does the CJC) and uses AD7790 as the ADC (In fact they  an use any ADC, since they wanted to use single ADC which can accept both slow signals and 10kHz signals, I would recommend ADC on next paragraph).

    If T-type temperature is within this range of any AD849x, they can use this for signal conditioning. They also might have to do linearization of the temperature. Or have to do CJC externally, as per our reference note CN0300

    1. Thermocouple.

     

    Sharing few more circuit notes for thermocouple/RTD measurement application

    CN0172 : Channel Thermocouple Temperature Measurement System with 0.25 ° C Accuracy

    CN0287 : Isolated 4-Channel,Thermocouple/RTD Temperature Measurement System with 0.5°C Accuracy

    CN0206 : Thermocouple Temperature Measurement System with Less Than 500 μA Current Drain

    CN0214 : USB - Based Thermocouple Temperature Measurement System Using ARM7

    CN0221 : USB - Based, Thermocouple Temperature Measurement System Using ARM Cortex - M3

    CN0354 : Low Power Multichannel Thermocouple Measurement System with Cold Junction Compensation

     

    One of the fastest 24 bit ADC which I can recommend is AD7175-2 (But it has only 2 fully differential channel, which can be used as 4 single ended with  one channel as reference (50ksps/channel). If they want to use the same ADC for thermocouple also, they might have to use any 2:1 switch so they can read thermocouple input as well.

    We have new released part AD7768, which has 8 channel simultaneous sampling (~256sps/channel).

    We also have AD7173-8, but each channel has 161uS settling time, so effectively you won’t get 10ksps per channel.

     

    If any of this ADC’s can’t accept 10V input, you can scale down the signal using a resistor divider and buffer using an amplifier or a different  amplifier which has gain less than to scale down the input to the ADC, like AD8279 (G=1/2).

    Let me know which architecture they wanted to follow, so we can give further recommendation.

Reply
  • Hello,

    I receiver your answers about this request through CIA.ASIA.

    Thank you for your help.

    Regards,

    Se-woong

    PS. For you reference, I attach your answers in below.

    --------------------------------------------------------------------------------------------------------------------------------------

    The main board will have ADC which can accept both thermocouple input and the analog input (daughter cards)?

    Therewould be multiple way to implement this solution.

    For thermocouple measurement, are they planning to do Cold Junction Compensation externally (using RTD)? We have several circuit notes and reference design for this application.

    Please have a look on this circuit note CN0271 - www.analog.com/en/circuits-from-the-lab/cn0271/vc.html , here AD8495 is used for K type thermocouple signal conditioning (which internally does the CJC) and uses AD7790 as the ADC (In fact they  an use any ADC, since they wanted to use single ADC which can accept both slow signals and 10kHz signals, I would recommend ADC on next paragraph).

    If T-type temperature is within this range of any AD849x, they can use this for signal conditioning. They also might have to do linearization of the temperature. Or have to do CJC externally, as per our reference note CN0300

    1. Thermocouple.

     

    Sharing few more circuit notes for thermocouple/RTD measurement application

    CN0172 : Channel Thermocouple Temperature Measurement System with 0.25 ° C Accuracy

    CN0287 : Isolated 4-Channel,Thermocouple/RTD Temperature Measurement System with 0.5°C Accuracy

    CN0206 : Thermocouple Temperature Measurement System with Less Than 500 μA Current Drain

    CN0214 : USB - Based Thermocouple Temperature Measurement System Using ARM7

    CN0221 : USB - Based, Thermocouple Temperature Measurement System Using ARM Cortex - M3

    CN0354 : Low Power Multichannel Thermocouple Measurement System with Cold Junction Compensation

     

    One of the fastest 24 bit ADC which I can recommend is AD7175-2 (But it has only 2 fully differential channel, which can be used as 4 single ended with  one channel as reference (50ksps/channel). If they want to use the same ADC for thermocouple also, they might have to use any 2:1 switch so they can read thermocouple input as well.

    We have new released part AD7768, which has 8 channel simultaneous sampling (~256sps/channel).

    We also have AD7173-8, but each channel has 161uS settling time, so effectively you won’t get 10ksps per channel.

     

    If any of this ADC’s can’t accept 10V input, you can scale down the signal using a resistor divider and buffer using an amplifier or a different  amplifier which has gain less than to scale down the input to the ADC, like AD8279 (G=1/2).

    Let me know which architecture they wanted to follow, so we can give further recommendation.

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