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网上找到一个用arduino测量电容的程序，可是看不懂，求解是什么原理！！！
const int OUT_PIN =A2;
const int IN_PIN = A0;
const float IN_STRAY_CAP_TO_GND = 24.48;//？
const float IN_CAP_TO_GND = IN_STRAY_CAP_TO_GND; //？
const float R_PULLUP =34.8; //？
const int MAX_ADC_VALUE = 1023;
void setup()
{
pinMode(OUT_PIN, OUTPUT);
pinMode(IN_PIN, OUTPUT);
Serial.begin(9600);
}
void loop()
{
pinMode(IN_PIN, INPUT);
digitalWrite(OUT_PIN, HIGH);
int val = analogRead(IN_PIN);
digitalWrite(OUT_PIN, LOW);
if (val < 1000)//？
{
pinMode(IN_PIN, OUTPUT);
float capacitance = (float)val *IN_CAP_TO_GND / (float)(MAX_ADC_VALUE - val);
Serial.print(F("Capacitance Value ="));
Serial.print(capacitance, 3);
Serial.print(F(" pF ("));
Serial.print(val);
Serial.println(F(") "));
}
else
{
pinMode(IN_PIN, OUTPUT);
delay(1);
pinMode(OUT_PIN, INPUT_PULLUP);
unsigned long u1 = micros();
unsigned long t;
int digVal;
do
{
digVal = digitalRead(OUT_PIN);
unsigned long u2 = micros();
t = u2 > u1 ? u2 - u1 : u1 - u2;
} while ((digVal < 1) && (t< 400000L));
pinMode(OUT_PIN, INPUT);
val = analogRead(OUT_PIN);
digitalWrite(IN_PIN, HIGH);
int dischargeTime = (int)(t / 1000L) * 5;
delay(dischargeTime);
pinMode(OUT_PIN, OUTPUT);
digitalWrite(OUT_PIN, LOW);
digitalWrite(IN_PIN, LOW);
float capacitance = -(float)t / R_PULLUP
/ log(1.0 -(float)val / (float)MAX_ADC_VALUE);
Serial.print(F("Capacitance Value ="));
if (capacitance > 1000.0)
{
Serial.print(capacitance / 1000.0, 2);
Serial.print(F(" uF"));
}
else
{
Serial.print(capacitance, 2);
Serial.print(F(" nF"));
}
Serial.print(F(" ("));
Serial.print(digVal == 1 ?F("Normal") : F("HighVal"));
Serial.print(F(", t= "));
Serial.print(t);
Serial.print(F(" us, ADC= "));
Serial.print(val);
Serial.println(F(")"));
}
while (millis() % 1000 != 0);
}
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发表于 2022-4-7 17:22
楼主
