diff --git a/examples/UnitTesting/UnitTesting.ino b/examples/UnitTesting/UnitTesting.ino
index 94ab895..24cf712 100644
--- a/examples/UnitTesting/UnitTesting.ino
+++ b/examples/UnitTesting/UnitTesting.ino
@@ -237,15 +237,24 @@ test(MQ303A_Ethanol)
 {
   MQ303A.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ303A.setA(3.4916); MQ303A.setB(-2.432); // Configure the equation to to calculate Ethanol concentration
-  MQ303A.init(); 
+  MQ303A.init();
   MQ303A.setR0(10);
-  
+
   int ppmExp=944;
   int PPM = MQ303A.setRsR0RatioGetPPM(0.1); // Send and Rs/R0 and return PPM (Using datasheet)
-  
+
   assertEqual(PPM,ppmExp);
 }
 
+test(MQ303A_VoltResolution)
+{
+  float vRes = 4.7;
+  MQ303A.setVoltResolution(vRes);
+  MQ303A.setADC(100);            // provide dummy ADC value
+  MQ303A.readSensor(true);       // dummy read for MQ303A
+  assertEqualFloat(MQ303A.getVoltResolution(), vRes);
+}
+
 test(MQ309A_CO)
 {
   MQ309A.setRegressionMethod(1); //_PPM =  a*ratio^b
diff --git a/src/MQUnifiedsensor.cpp b/src/MQUnifiedsensor.cpp
index 3588f31..49bed51 100644
--- a/src/MQUnifiedsensor.cpp
+++ b/src/MQUnifiedsensor.cpp
@@ -152,8 +152,10 @@ float MQUnifiedsensor::validateEcuation(float ratioInput)
 float MQUnifiedsensor::readSensor(bool isMQ303A, float correctionFactor, bool injected)
 {
   //More explained in: https://jayconsystems.com/blog/understanding-a-gas-sensor
+
+  float voltRes = _VOLT_RESOLUTION; // preserve global resolution
   if(isMQ303A) {
-    _VOLT_RESOLUTION = _VOLT_RESOLUTION - 0.45; //Calculations for RS using mq303a sensor look wrong #42
+    voltRes = voltRes - 0.45; //Calculations for RS using mq303a sensor look wrong #42
   }
   _RS_Calc = ((_VCC*_RL)/_sensor_volt)-_RL; //Get value of RS in a gas
   if(_RS_Calc < 0)  _RS_Calc = 0; //No negative values accepted.