Question
I got a request from one of my customers to provide him a highlyintegrated AFE for 3 wire sensors, this could be RTDs, pressure sensors, etc.
He would like to connect up to 3 sensors to one AFE. I found the AD7124-8.
Since he want to work with pt100 and measure the temperature in a range between-40°C and +125°C with 0,1°C steps or less 11bit would be enough.
1.Do you have any 16bit with integrated reference, IDAC, pga ?
2.how is the schematic, if connects tree sensors at one time to the AFE?
3.Is AD7124-8 the right choise for this demand? Seems to be a little bitoversized.
Answer
1. We have the AD7794/5 but they are only 6-channel.
2. Here is a 2-RTD 3-wire example with the AD7793 (a 3 channel device):
The AD7794 has 6 differential inputs. However, one of these inputs is also theexc current. So, one AD7794 can support up to 5 4-wire RTDs. An external mux isrequired to direct the exc current to each of the RTDs. The lowside of all theRTDs can be connected to the REFIN+ pin. An external precision resistor isneeded to generate the reference voltage. So, the exc current will flow throughthe RTD and through the precision resistor i.e. a ratiometric configuration isneeded.
3. AD717x series for example has excellent performance in terms of speed andnoise. They can be used to different types of applications such as temperatureand pressure measurements. However, it does not have an internal PGA that isvery useful for RTDs and TCs measurements. Because the output from thesesensors are small, an external circuitry might be necessary to amplify thesignal from TCs or RTDs. The AD7124-8 includes most of the required systembuilding blocks for TCs and RTDs measurements that will make your design simpleand which eliminates the needs for external circuitry. We also have anavailable reference circuits on the AD7124 product page that can help youregarding this matter. Please see link below and look for the reference designssection.http://www.analog.com/en/products/analog-to-digital-converters/precision-adc-10msps/ad7124-8.html#product-designs
Best regards,
Christopher MurphyApplications EngineerEuropean Centralized Application Center (CAC)Analog DevicesCIC@analog.com
Analog Devices (ADI) makes no warranties and assumes no liability forapplications assistance or customerproduct design. Please be aware you are fully responsible for all designdecisions and engineering with regard toyour products, including decisions relating to application of ADI products. Byproviding technical information, ADIdoes not intend to offer or provide engineering services or advice concerningyour designs.
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HI Analog, I got a request from one of my customers to provide him a highlyintegrated AFE for 3 wire sensors, this could be RTDs, pressure sensors, etc.
He would like to connect up to 3 sensors to one AFE. I found the AD7124-8.
Since he want to work with pt100 and measure the temperature in a range between-40°C and +125°C with 0,1°C steps or less 11bit would be enough.
1.Do you have any 16bit with integrated reference, IDAC, pga ?
2.how is the schematic, if connects tree sensors at one time to the AFE?
3.Is AD7124-8 the right choise for this demand? Seems to be a little bitoversized.
Regards
Thank You
Waldemar