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ADE7880 settling time RMS-Measuremnt

Question asked by Bastler on Apr 17, 2014
Latest reply on May 22, 2014 by Bastler

Hy,

I've got a problem with the results of the rms-register.

I do 2 tests with different currents and get some amazing results.

I use an omikron as current source and in addition a fluke precision multimeter, to measure the real voltage at our shunt (10mOhm); PGA = 8 and don't calibrate the ADE, I just look at the difference of my result    

 

1) I = 0,5A   -> IRMS : 0x71500    after 3 Minutes IRMS : 0x71500

2) I = 5A      -> IRMS : 0x471100  after 3 Minutes IRMS : 0x473A00

 

Now I change the CONFIG register, turn on the integrator CONIG : 0x0003, I do the tests again

 

1) I = 0,5A   -> IRMS : 0x71500    after 3 Minutes IRMS : 0x71500

2) I = 5A      -> IRMS : 0x46C800  after 3 Minutes IRMS : 0x471700

 

My question, what happens inside the ADE or what ist my mistake ? What can I do to get a constant value ?

 

The voltage across the shunt is constant, there is no settling.

 

Kind regards

 

I had an idea and make another measurment, the same assembly but I reduce the PGA = 1 1) I = 0,5A   -> IRMS : 0xE300 2) I = 5A      -> IRMS : 0x92000       after a few minutes IRMS : 0x8DE Now the value decrease, with a high PGA the value increase, crazy ?

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