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ADS114S08: getting full scale reading on ADS114S08

Part Number: ADS114S08

Hi Bob B,

Thanks for giving time for this running case and give us proper suggestions.

As you suggested after connecting RESET pin to IOVdd we should not issue a RESET command many times so we are using only POR(Power On Reset).
In our earlier response we send you excel sheet regarding power applied on each supply pin of ADS114S08. make sure our power supply is isolated.
So there is no transient voltage present in power supply to ADS114S08.

As you mentioned during RREG command we are sending commands instead of NOPs(0x00). So we made change in our RREG command as you suggested and sending NOP(0x00) for operation. sending you image for verification.
But here also we want to add that when we connect earth to thermal block the conversion result become zero.
if we remove earth from thermal block we are getting response which is varying with between 6.296mV to 6.735mV, But at that time DMM reading is 6.44mV constant.
we can not figure out the cause of this variation in result so help us with that.

Here Voltage measurement of TC+(AINO) to AVSS and TC-(AIN1) to AVSS when we connected earth to thermal block,
TC+(AIN0) to AVSS = -0.51 mV
TC-(AIN1) to AVSS = -6.94 mV
TC+ to TC- = 6.43 mV

Here Voltage measurement of TC+(AINO) to AVSS and TC-(AIN1) to AVSS when we did not connect earth to thermal block,
TC+(AIN0) to AVSS = 0.8204 V
TC-(AIN1) to AVSS =0.8140 V
TC+ to TC- = 6.46 V

As you can see we are getting data for ungrounded thermocouple at any time even if we are sending commands after RDATA command instead of NOP commands.
Can you just give us brief details for your comment to use NOP instead of commmands after RDATA command? Because for ungrounded thermocouples those instructions are working ok and for grounded thermocouple we are getting issue.
We still did not getting proper reason why the ADS114S08 is not giving proper result for all types of thermocouple even if we made all connections as per datasheet suggestions.
If any changes required at hardware side than please inform us for same.

Waiting for your quick reply.

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