Hello,

I have some problems with the registers during the calibration.

In the AN-1771, page 11, is described how to calculate the xVGAIN register, but I didn't understand the formulas.

If I solve the equation (1) to (3) and put it in (2) I get (4), which means my value is 1.

Where is my failure ?

For example (1) I have an VoltageInput= 0,0076V, the ADE convert it to VRMS = 83200 -> Vconstant = 0,0911µV

Calculation of xVGAIN

(2) I take the values from (1) and my result is 2^23

Can you give me a definition or an example of the different values in the formula ?

Kind regards

Hi Bastler,

(1) Voltage Input [V] - is the actual input voltage from an accurate source, therfore the line voltage that the part is monitoring.

(2) xVRMS [LSBs] - This is the actual LSB's that the part measures, in other words, the actual measured xVRMS register value.

(3) Vconstant [Volts/LSB] - This is a calculated value, this is a value that is meant to be able to directly convert the value in the xVRMS register to a real world voltage value. This needs to be calculated once to get an idea of what the value is and then it can be adjusted using the xVGAIN register using the equations from AN-1171.

That 76mV RMS is directly at the input of the ADE, usually this Vconstant is calculated with the actual voltage input before the attenuation network giving a practical real world value, for example the 220V line being measured. Then this real world voltage and the xVRMS register reading is used to calculate Vconstant. Then this preliminary Vconstant value can be adjusted with xVGAIN as seen fit. For calibration, the actual inputs that you expect the part to be measuring should be used.

How did you calculate this expected value? The actual register value would be different based on slight part to part variation.

Best Regards,

Dlath