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Hi. I am using ADE7758 in my energy monitoring system project. I am able to use SPI to communicate with my Arduino and it is able to display the results. However, I am having some problem calibrating VRMS with the steps given in the ADE7758 datasheet in page 55. By following the steps, I have writen the values into LCYCMODE and MASK like below:
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In cpp. file
void ADE7758::setLineCyc(int l)
{ write16 (LINECYC, l); }
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In Arduino Setup
void ADE7758::setMASK(long e)
{ write24 (MASK, e); }
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Then, I followed step 4 by taking N=100,
In cpp file
long ADE7758::Avrms() {
char i=0;
long v=0;
getAVRMS(); //Ignore first reading to avoid garbage
for(i=0;i<100;++i)
{ v+=getAVRMS(); }
return v/100;
}
long ADE7758::getAVRMS(void) {
long lastupdate = 0;
ADE7758::getresetInterruptStatus(); // Clear all interrupts
lastupdate = millis();
while( ! ( ADE7758::getInterruptStatus() & ZXA ) ) // wait Zero-Crossing
{ // wait for the selected interrupt to occur
if ( ( millis() - lastupdate ) > 100)
{ wdt_reset();
Serial.println("\n--> getAVRMS Timeout - no AC input");
break;
}
}
return read24(AVRMS);
}
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With this code, I am able to produce different values for different input voltage. But the changes are very small.
In order to use the AVRMSOS formula, my readings after using a 10:1 step down transformer:
V_min = 2.5, V_nom = 24
and the values obtained are as below:
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(formula can be found in pg 55 of datasheet)
So, substituting the value into the formula:
| V_in= 5.7V | V_in= 24.5V | V_in= 49V |
|---|---|---|
--> before calibration VRMS_100: 16767890.0000 --> after calibration VRMS_100: 1341.5760498046 | --> before calibration VRMS_100: 16705047.0000 --> after calibration VRMS_100: 1336.5480957031 | --> before calibration VRMS_100: 16693657.0000 --> after calibration VRMS_100: 1335.6367187500 |
--> before calibration VRMS_100: 16766609.0000 --> after calibration VRMS_100: 1341.4735107421 | --> before calibration VRMS_100: 16762652.0000 --> after calibration VRMS_100: 1341.1569824218 | --> before calibration VRMS_100: 16506393.0000 --> after calibration VRMS_100: 1320.6540527343 |
--> before calibration VRMS_100: 16771791.0000 --> after calibration VRMS_100: 1341.8881835937 | --> before calibration VRMS_100: 16767304.0000 --> after calibration VRMS_100: 1341.5291748046 | --> before calibration VRMS_100: 16777212.0000 --> after calibration VRMS_100: 1342.3218994140 |
Hence, AVRMSOS = 0x00E (Taking only the last 3 LSB)
The readings obtained are very large. Does this have to do with the VRMSGAIN? I have not written any values into the VRMSGAIN. May I know how can I obtain the correct value of VRMSGAIN?
The connectivity for the circuit is as below:
Much of the codes are refered from this link: https://code.google.com/p/ardugrid7753/source/browse/#svn%2Ftrunk
Thank you.