diff --git a/src/channel_state.rs b/src/channel_state.rs
index 586aae0..7cc5def 100644
--- a/src/channel_state.rs
+++ b/src/channel_state.rs
@@ -16,11 +16,13 @@ use crate::{
 };
 
 const R_INNER: f64 = 2.0 * 5100.0;
+const VREF_SENS: f64 = 3.3 / 2.0;
 
 pub struct ChannelState {
     pub adc_data: Option<u32>,
     pub adc_calibration: ad7172::ChannelCalibration,
     pub adc_time: Instant,
+    /// VREF for the TEC (1.5V)
     pub vref: ElectricPotential,
     pub dac_value: ElectricPotential,
     pub pid_engaged: bool,
@@ -62,8 +64,9 @@ impl ChannelState {
     /// Get `SENS[01]` input resistance
     pub fn get_sens(&self) -> Option<ElectricalResistance> {
         let r_inner = ElectricalResistance::new::<ohm>(R_INNER);
+        let vref = ElectricPotential::new::<volt>(VREF_SENS);
         let adc_input = self.get_adc()?;
-        let r = r_inner * adc_input / (self.vref - adc_input);
+        let r = r_inner * adc_input / (vref - adc_input);
         Some(r)
     }
 
diff --git a/src/channels.rs b/src/channels.rs
index c6ee771..02a6772 100644
--- a/src/channels.rs
+++ b/src/channels.rs
@@ -51,8 +51,7 @@ impl Channels {
         let pwm = pins.pwm;
         let mut channels = Channels { channel0, channel1, adc, pins_adc, pwm };
         for channel in 0..CHANNELS {
-            // FIXME: this reads 1.5 V instead of the expected 1.65 V.
-            // channels.channel_state(channel).vref = channels.read_vref(channel);
+            channels.channel_state(channel).vref = channels.read_vref(channel);
             channels.calibrate_dac_value(channel);
         }
         channels
diff --git a/src/main.rs b/src/main.rs
index 0999bbd..d14fa84 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -170,11 +170,11 @@ fn main() -> ! {
                                 Command::Show(ShowCommand::Input) => {
                                     for channel in 0..CHANNELS {
                                         if let Some(adc_input) = channels.channel_state(channel).get_adc() {
-                                            let vref = channels.read_vref(channel);
+                                            let vref = channels.channel_state(channel).vref;
                                             let dac_feedback = channels.read_dac_feedback(channel);
 
                                             let itec = channels.read_itec(channel);
-                                            let tec_i = -(itec - ElectricPotential::new::<volt>(1.5)) / ElectricalResistance::new::<ohm>(0.4);
+                                            let tec_i = (itec - vref) / ElectricalResistance::new::<ohm>(0.4);
 
                                             let tec_u_meas = channels.read_tec_u_meas(channel);