diff --git a/drivers/analog/analog.cpp b/drivers/analog/analog.cpp
index f3179a7e..42caf012 100644
--- a/drivers/analog/analog.cpp
+++ b/drivers/analog/analog.cpp
@@ -2,11 +2,14 @@
 
 namespace pimoroni {
     uint16_t Analog::read_raw() {
+      adc_select_input(pin - 26);
       return adc_read();
     }
 
     float Analog::read_voltage() {
-      return ((float)adc_read() * 3.3f) / (1 << 12) / amplifier_gain;
+      adc_select_input(pin - 26);
+      float voltage = ((((float)adc_read() * 3.3f) / (1 << 12)) + offset) / amplifier_gain;
+      return MAX(voltage, 0.0f);
     }
 
     float Analog::read_current() {
diff --git a/drivers/analog/analog.hpp b/drivers/analog/analog.hpp
index cad26e46..7f321b0d 100644
--- a/drivers/analog/analog.hpp
+++ b/drivers/analog/analog.hpp
@@ -9,8 +9,8 @@ namespace pimoroni {
 
   class Analog {
   public:
-    Analog(uint pin, float amplifier_gain = 1.0f, float resistor = 0.0f) :
-    pin(pin), amplifier_gain(amplifier_gain), resistor(resistor) {
+    Analog(uint pin, float amplifier_gain = 1.0f, float resistor = 0.0f, float offset = 0.0f) :
+    pin(pin), amplifier_gain(amplifier_gain), resistor(resistor), offset(offset) {
       adc_init();
 
       //Make sure GPIO is high-impedance, no pullups etc
@@ -26,6 +26,7 @@ namespace pimoroni {
     uint pin;
     float amplifier_gain;
     float resistor;
+    float offset;
   };
 
 }
\ No newline at end of file