Hi Andy,
In order to determine if you can make impedance measurements on 6 channels using a single ADuCM350, I need to know a little more about the type of measurement you are trying to make.
Is it a 2-wire measurement or a 4-wire measurement?
Does your load require DC isolation?
Can the return paths of your (6) loads be tied together?
- Assuming a 2-wire measurement where the return paths can indeed be tied together, you can connect the excite paths to 6 different AFE pins and use the switch matrix to connect them one at a time to the excitation amplifier output (D node) of the ADuCM350 AFE. All 6 return paths would connect to a single AFE pin which would internally be connected to the TIA input (T node). As the switch matrix can be configured in software, switching between the different loads is easily done by either the AFE Controller or the Cortex core.
- Different components of the AFE have different settling times, so this depends on the type of measurement you are performing. But if you are referring to simply switching between loads as in the above example, we typically allow 100us settling time when changing the switch matrix state in our example sequences.
- For an impedance measurement, the DFT hardware accelerator is used to return a real and imaginary result. The sample rate of the DFT is 78sps. When switching between different channels, allowing for settling etc., this could be further reduced to ~75sps.
Rgds,
Eoghan.