ADS124S08: Reference design

Hi Kai,

TI does not have a specific reference design that meets all the criteria in a single design. We can help with the design concepts with a little more information.

For example, there are a couple methods of making the bipolar current and voltage measurements. One is using a unipolar analog supply (5V) and another using bipolar analog supplies (+/-2.5V). So what type of analog supply would be used?

Another question is how many thermocouples will be connected? And how will the cold junction temperature be measured? This might be accomplished using the ADS124S08 alone, but would depend on how many of the inputs will be used for thermocouples?

The overvoltage protection would also require a little more specific information. The box circled covers many different scenarios which would require different approaches and components to be used.

You can get a general idea of how various sensors and voltages/currents can be measured by taking a look at the ADS124S08EVM user's guide (SBAU272A).

With a little more information we should be able to show you how this might be accomplished.

Best regards,
Bob B

Kai,


As an additional comment, there is a new application note on the measurement of thermocouples with precision ADCs. The note is titled "A Basic Guide to Thermocouple Measurements" and can be found in the link below:

www.ti.com/.../sbaa274.pdf


Joseph Wu

Kai,


The ADS124S08 has a configurable multiplexer that has 12 analog inputs plus an AINCOM input. Are you asking for a multiplexer to use with the EVM?

If you're looking for a multiplexer to use with the EVM, I don't have a specific recommendation for a device. For different measurements, the multiplexer resistance and leakage may be a concern. In many thermocouple applications, neither are particularly a problem, but in RTD measurements both may be a factor, depending on how the excitation currents are routed.


Joseph Wu