diff --git a/README.md b/README.md
index 88ed2ec..c3c8cd8 100644
--- a/README.md
+++ b/README.md
@@ -106,7 +106,7 @@ formatted as line-delimited JSON.
 | `pwm <0/1> i_set <amp>`          | Disengage PID, set fixed output current                                       |
 | `pwm <0/1> pid`                  | Let output current to be controlled by the PID                                |
 | `center <0/1> <volt>`            | Set the MAX1968 0A-centerpoint to the specified fixed voltage                 |
-| `center <0/1> vref`              | Set the MAX1968 0A-centerpoint to measure from VREF                           |
+| `center <0/1> vref`              | Set the MAX1968 0A-centerpoint to a stable calibrated VREF                    |
 | `pid`                            | Show PID configuration                                                        |
 | `pid <0/1> target <deg_celsius>` | Set the PID controller target temperature                                     |
 | `pid <0/1> kp <value>`           | Set proportional gain                                                         |
diff --git a/src/channels.rs b/src/channels.rs
index 3b70a6f..66ee00d 100644
--- a/src/channels.rs
+++ b/src/channels.rs
@@ -95,13 +95,15 @@ impl Channels {
         })
     }
 
-    /// calculate the TEC i_set centerpoint
+    /// get the TEC i_set centerpoint
     pub fn get_center(&mut self, channel: usize) -> ElectricPotential {
         match self.channel_state(channel).center {
             CenterPoint::Vref => {
-                let vref = self.read_vref(channel);
-                self.channel_state(channel).vref = vref;
-                vref
+                match channel {
+                    0 => self.channel0.vref_meas,
+                    1 => self.channel1.vref_meas,
+                    _ => unreachable!(),
+                }
             },
             CenterPoint::Override(center_point) =>
                 ElectricPotential::new::<volt>(center_point.into()),
@@ -268,7 +270,7 @@ impl Channels {
         let samples = 50;
         let mut target_voltage = ElectricPotential::new::<volt>(0.0);
         for _ in 0..samples {
-            target_voltage = target_voltage + self.get_center(channel);
+            target_voltage = target_voltage + self.read_vref(channel);
         }
         target_voltage = target_voltage / samples as f64;
         let mut start_value = 1;