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Precise measurement using AD8228

Question asked by xcuresme on May 22, 2013
Latest reply on Jun 14, 2013 by xcuresme

I am developing a precise current sensor based on shunt and instrumentation amplifier AD8228 sensing the load current of H-bridge.

Figure 1 is the H-bridge. The switches are IGBT switching at 30k~40k on fixed duty cycle. Vsense is the voltage of shunt ranging from -10mV to 75mV.

f1.jpg

Figure 1

Because the IA cannot handle the common-mode voltage of 160V, I use an isolated voltage to supply AD8228 as shown in Figure 2. It should also be noted that the ground of the AD8228 is different from that of the H-bridge. So the common-mode voltage referred to AD8228 is 0 in this case!

f2.jpg

Figure 2

But I’m not very sure whether AD8228 can work precisely and safety in such arrangement. Could anyone give me some advice?

 

PS: I know there are some types of instrumentation amplifiers, current sense amplifiers and isolation amplifiers can handle the common-mode voltage higher than 160V. But they all seem not to meet my requirement of precision.

 

       Thanks in advance!

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