We have 8 AD7147 on operating on a single 2-layer PCB which. Devices operate
properly as long as only one AD7147 is exciting the electrodes. From the posts
available at the ENGINEER zone I suspect the problem lies in the interference
caused by the unsynchronized excitation signals. As our board space is quite
limited, we can only have about 4 mm wide GND stripes between the AC shields.
Would a 4-layer PCB with a bottom ground covering all the shields (moving the
2 layers currently used for routing and shielding the electrode signals to the
two topmost PCB layers) sufficiently isolate the AD7147s. Alternatively, is
there perhaps a way to synchronize the excitation signals?
I suspect that the excitation signals from each AD7147 are interfering with
each other. Because they are not synchronized, if the sensors are close to each
other, then the excitations will interfere, and cause noise in the sensor
There are two options - if this is possible, you can modify your sensor design
to keep the sensors controlled by each AD7147 apart, to reduce the
interference. However, I guess this will not be possible if you are tight for