PwmLimits: Use uom quantities for fields not f64s

The Beta Parameter is not dimensionless, and has unit kelvin.
Incorporate that into the type system.

README.md

@@ -95,13 +95,13 @@ formatted as line-delimited JSON.
 | Syntax                                    | Function                                                                      |
 |-------------------------------------------|-------------------------------------------------------------------------------|
 | `report`                                  | Show latest report of channel parameters (see *Reports* section)              |
-| `pwm`                                      | Show current PWM settings                                                     |
+| `output`                                  | Show current output settings                                                  |
-| `pwm <0/1> max_i_pos <amp>`                | Set maximum positive output current, clamped to [0, 2]                        |
+| `output <0/1> max_i_pos <amp>`            | Set maximum positive output current, clamped to [0, 2]                        |
-| `pwm <0/1> max_i_neg <amp>`                | Set maximum negative output current, clamped to [0, 2]                        |
+| `output <0/1> max_i_neg <amp>`            | Set maximum negative output current, clamped to [0, 2]                        |
-| `pwm <0/1> max_v <volt>`                   | Set maximum output voltage, clamped to [0, 4]                                 |
+| `output <0/1> max_v <volt>`               | Set maximum output voltage, clamped to [0, 4]                                 |
-| `pwm <0/1> i_set <amp>`                    | Disengage PID, set fixed output current, clamped to [-2, 2]                   |
+| `output <0/1> i_set <amp>`                | Disengage PID, set fixed output current, clamped to [-2, 2]                   |
-| `pwm <0/1> polarity <normal/reversed>`     | Set output current polarity, with 'normal' being the front panel polarity     |
+| `output <0/1> polarity <normal/reversed>` | Set output current polarity, with 'normal' being the front panel polarity     |
-| `pwm <0/1> pid`                            | Let output current to be controlled by the PID                                |
+| `output <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                           |
 | `pid`                                     | Show PID configuration                                                        |
@@ -183,7 +183,7 @@ postfilter rate can be tuned with the `postfilter` command.
 
 When using a TEC module with the Thermostat, the Thermostat expects the thermal load (where the thermistor is located) to cool down with a positive software current set point, and heat up with a negative current set point.
 
-If the Thermostat is used for temperature control with the Sinara 5432 DAC "Zotino", and is connected via an IDC cable, the TEC polarity may need to be reversed with the `pwm <ch> polarity reversed` TCP command.
+If the Thermostat is used for temperature control with the Sinara 5432 DAC "Zotino", and is connected via an IDC cable, the TEC polarity may need to be reversed with the `output <ch> polarity reversed` TCP command.
 
 Testing heat flow direction with a low set current is recommended before installation of the TEC module.
 
@@ -192,7 +192,7 @@ Testing heat flow direction with a low set current is recommended before install
 Each MAX1968 TEC driver has analog/PWM inputs for setting
 output limits.
 
-Use the `pwm` command to see current settings and maximum values.
+Use the `output` command to see current settings and maximum values.
 
 | Limit       | Unit    | Description                   |
 | ---         | :---:   | ---                           |
@@ -203,28 +203,28 @@ Use the `pwm` command to see current settings and maximum values.
 
 Example: set the maximum voltage of channel 0 to 1.5 V.
 ```
-pwm 0 max_v 1.5
+output 0 max_v 1.5
 ```
 
 Example: set the maximum negative current of channel 0 to -3 A.
 ```
-pwm 0 max_i_neg 3
+output 0 max_i_neg 3
 ```
 
 Example: set the maximum positive current of channel 1 to 3 A.
 ```
-pwm 0 max_i_pos 3
+output 0 max_i_pos 3
 ```
 
 ### Open-loop mode
 
 To manually control TEC output current, set a fixed output current with
-the `pwm` command. Doing so will disengage the PID control for that
+the `output` command. Doing so will disengage the PID control for that
 channel.
 
 Example: set output current of channel 0 to 0 A.
 ```
-pwm 0 i_set 0
+output 0 i_set 0
 ```
 
 ## PID-stabilized temperature control
@@ -237,7 +237,7 @@ pid 0 target 20
 Enter closed-loop mode by switching control of the TEC output current
 of channel 0 to the PID algorithm:
 ```
-pwm 0 pid
+output 0 pid
 ```
 
 ## LED indicators

pytec/autotune.py

@@ -253,9 +253,9 @@ def main():
 
         tuner_out = tuner.output()
 
-        tec.set_param("pwm", channel, "i_set", tuner_out)
+        tec.set_param("output", channel, "i_set", tuner_out)
 
-    tec.set_param("pwm", channel, "i_set", 0)
+    tec.set_param("output", channel, "i_set", 0)
 
 
 if __name__ == "__main__":

pytec/example.py

@@ -2,9 +2,9 @@ from pytec.client import Client
 
 tec = Client() #(host="localhost", port=6667)
 tec.set_param("s-h", 1, "t0", 20)
-print(tec.get_pwm())
+print(tec.get_output())
 print(tec.get_pid())
-print(tec.get_pwm())
+print(tec.get_output())
 print(tec.get_postfilter())
 print(tec.get_steinhart_hart())
 for data in tec.report_mode():

pytec/pytec/client.py

@@ -13,11 +13,11 @@ class Client:
         self._check_zero_limits()
 
     def _check_zero_limits(self):
-        pwm_report = self.get_pwm()
+        output_report = self.get_output()
-        for pwm_channel in pwm_report:
+        for output_channel in output_report:
             for limit in ["max_i_neg", "max_i_pos", "max_v"]:
-                if pwm_channel[limit] == 0.0:
+                if output_channel[limit] == 0.0:
-                    logging.warning("`{}` limit is set to zero on channel {}".format(limit, pwm_channel["channel"]))
+                    logging.warning("`{}` limit is set to zero on channel {}".format(limit, output_channel["channel"]))
 
     def _read_line(self):
         # read more lines
@@ -47,8 +47,8 @@ class Client:
             result[int(item["channel"])] = item
         return result
 
-    def get_pwm(self):
+    def get_output(self):
-        """Retrieve PWM limits for the TEC
+        """Retrieve output limits for the TEC
 
         Example::
             [{'channel': 0,
@@ -67,7 +67,7 @@ class Client:
               'polarity': 'normal',
             ]
         """
-        return self._get_conf("pwm")
+        return self._get_conf("output")
 
     def get_pid(self):
         """Retrieve PID control state
@@ -144,7 +144,7 @@ class Client:
         """Set configuration parameters
 
         Examples::
-            tec.set_param("pwm", 0, "max_v", 2.0)
+            tec.set_param("output", 0, "max_v", 2.0)
             tec.set_param("pid", 1, "output_max", 2.5)
             tec.set_param("s-h", 0, "t0", 20.0)
             tec.set_param("center", 0, "vref")
@@ -161,7 +161,7 @@ class Client:
     def power_up(self, channel, target):
         """Start closed-loop mode"""
         self.set_param("pid", channel, "target", value=target)
-        self.set_param("pwm", channel, "pid")
+        self.set_param("output", channel, "pid")
 
     def save_config(self):
         """Save current configuration to EEPROM"""

src/channel_state.rs

@@ -4,6 +4,7 @@ use crate::{
     config::PwmLimits,
     pid, steinhart_hart as sh,
 };
+use num_traits::Zero;
 use smoltcp::time::{Duration, Instant};
 use uom::si::{
     electric_current::ampere,
@@ -47,9 +48,9 @@ impl ChannelState {
             dac_value: ElectricPotential::new::<volt>(0.0),
             i_set: ElectricCurrent::new::<ampere>(0.0),
             pwm_limits: PwmLimits {
-                max_v: 0.0,
+                max_v: ElectricPotential::zero(),
-                max_i_pos: 0.0,
+                max_i_pos: ElectricCurrent::zero(),
-                max_i_neg: 0.0,
+                max_i_neg: ElectricCurrent::zero(),
             },
             pid_engaged: false,
             pid: pid::Controller::new(pid::Parameters::default()),

src/channels.rs

@@ -144,7 +144,7 @@ impl Channels {
         voltage
     }
 
-    pub fn get_i(&mut self, channel: usize) -> ElectricCurrent {
+    pub fn get_i_set(&mut self, channel: usize) -> ElectricCurrent {
         let i_set = self.channel_state(channel).i_set;
         i_set
     }
@@ -364,15 +364,15 @@ impl Channels {
     }
 
     pub fn get_max_v(&mut self, channel: usize) -> ElectricPotential {
-        ElectricPotential::new::<volt>(self.channel_state(channel).pwm_limits.max_v)
+        self.channel_state(channel).pwm_limits.max_v
     }
 
     pub fn get_max_i_pos(&mut self, channel: usize) -> ElectricCurrent {
-        ElectricCurrent::new::<ampere>(self.channel_state(channel).pwm_limits.max_i_pos)
+        self.channel_state(channel).pwm_limits.max_i_pos
     }
 
     pub fn get_max_i_neg(&mut self, channel: usize) -> ElectricCurrent {
-        ElectricCurrent::new::<ampere>(self.channel_state(channel).pwm_limits.max_i_neg)
+        self.channel_state(channel).pwm_limits.max_i_neg
     }
 
     // Get current passing through TEC
@@ -420,7 +420,7 @@ impl Channels {
         let max_v = max_v.min(MAX_TEC_V).max(ElectricPotential::zero());
         let duty = (max_v / max).get::<ratio>();
         let duty = self.set_pwm(channel, PwmPin::MaxV, duty);
-        self.channel_state(channel).pwm_limits.max_v = max_v.get::<volt>();
+        self.channel_state(channel).pwm_limits.max_v = max_v;
         (duty * max, max)
     }
 
@@ -436,7 +436,7 @@ impl Channels {
             Polarity::Normal => self.set_pwm(channel, PwmPin::MaxIPos, duty),
             Polarity::Reversed => self.set_pwm(channel, PwmPin::MaxINeg, duty),
         };
-        self.channel_state(channel).pwm_limits.max_i_pos = max_i_pos.get::<ampere>();
+        self.channel_state(channel).pwm_limits.max_i_pos = max_i_pos;
         (duty * MAX_TEC_I_DUTY_TO_CURRENT_RATE, max)
     }
 
@@ -452,7 +452,7 @@ impl Channels {
             Polarity::Normal => self.set_pwm(channel, PwmPin::MaxINeg, duty),
             Polarity::Reversed => self.set_pwm(channel, PwmPin::MaxIPos, duty),
         };
-        self.channel_state(channel).pwm_limits.max_i_neg = max_i_neg.get::<ampere>();
+        self.channel_state(channel).pwm_limits.max_i_neg = max_i_neg;
         (duty * MAX_TEC_I_DUTY_TO_CURRENT_RATE, max)
     }
 
@@ -470,7 +470,7 @@ impl Channels {
     }
 
     fn report(&mut self, channel: usize) -> Report {
-        let i_set = self.get_i(channel);
+        let i_set = self.get_i_set(channel);
         let i_tec = self.adc_read(channel, PinsAdcReadTarget::ITec, 16);
         let tec_i = self.get_tec_i(channel);
         let dac_value = self.get_dac(channel);
@@ -521,11 +521,11 @@ impl Channels {
         false
     }
 
-    fn pwm_summary(&mut self, channel: usize) -> PwmSummary {
+    fn output_summary(&mut self, channel: usize) -> OutputSummary {
-        PwmSummary {
+        OutputSummary {
             channel,
             center: CenterPointJson(self.channel_state(channel).center.clone()),
-            i_set: self.get_i(channel),
+            i_set: self.get_i_set(channel),
             max_v: self.get_max_v(channel),
             max_i_pos: self.get_max_i_pos(channel),
             max_i_neg: self.get_max_i_neg(channel),
@@ -533,10 +533,10 @@ impl Channels {
         }
     }
 
-    pub fn pwm_summaries_json(&mut self) -> Result<JsonBuffer, serde_json_core::ser::Error> {
+    pub fn output_summaries_json(&mut self) -> Result<JsonBuffer, serde_json_core::ser::Error> {
         let mut summaries = Vec::<_, U2>::new();
         for channel in 0..CHANNELS {
-            let _ = summaries.push(self.pwm_summary(channel));
+            let _ = summaries.push(self.output_summary(channel));
         }
         serde_json_core::to_vec(&summaries)
     }
@@ -630,7 +630,7 @@ impl Serialize for PolarityJson {
 }
 
 #[derive(Serialize)]
-pub struct PwmSummary {
+pub struct OutputSummary {
     channel: usize,
     center: CenterPointJson,
     i_set: ElectricCurrent,

src/command_handler.rs

@@ -19,7 +19,11 @@ use uom::si::{
     electric_current::ampere,
     electric_potential::volt,
     electrical_resistance::ohm,
-    f64::{ElectricCurrent, ElectricPotential, ElectricalResistance, ThermodynamicTemperature},
+    f64::{
+        ElectricCurrent, ElectricPotential, ElectricalResistance, TemperatureInterval,
+        ThermodynamicTemperature,
+    },
+    temperature_interval::kelvin,
     thermodynamic_temperature::degree_celsius,
 };
 
@@ -96,7 +100,7 @@ impl Handler {
     }
 
     fn show_pwm(socket: &mut TcpSocket, channels: &mut Channels) -> Result<Handler, Error> {
-        match channels.pwm_summaries_json() {
+        match channels.output_summaries_json() {
             Ok(buf) => {
                 send_line(socket, &buf);
             }
@@ -206,7 +210,7 @@ impl Handler {
         channel: usize,
         center: CenterPoint,
     ) -> Result<Handler, Error> {
-        let i_set = channels.get_i(channel);
+        let i_set = channels.get_i_set(channel);
         let state = channels.channel_state(channel);
         state.center = center;
         if !state.pid_engaged {
@@ -248,7 +252,7 @@ impl Handler {
         use super::command_parser::ShParameter::*;
         match parameter {
             T0 => sh.t0 = ThermodynamicTemperature::new::<degree_celsius>(value),
-            B => sh.b = value,
+            B => sh.b = TemperatureInterval::new::<kelvin>(value),
             R0 => sh.r0 = ElectricalResistance::new::<ohm>(value),
         }
         send_line(socket, b"{}");
@@ -475,17 +479,17 @@ impl Handler {
             Command::Quit => Ok(Handler::CloseSocket),
             Command::Show(ShowCommand::Input) => Handler::show_report(socket, channels),
             Command::Show(ShowCommand::Pid) => Handler::show_pid(socket, channels),
-            Command::Show(ShowCommand::Pwm) => Handler::show_pwm(socket, channels),
+            Command::Show(ShowCommand::Output) => Handler::show_pwm(socket, channels),
             Command::Show(ShowCommand::SteinhartHart) => {
                 Handler::show_steinhart_hart(socket, channels)
             }
             Command::Show(ShowCommand::PostFilter) => Handler::show_post_filter(socket, channels),
             Command::Show(ShowCommand::Ipv4) => Handler::show_ipv4(socket, ipv4_config),
-            Command::PwmPid { channel } => Handler::engage_pid(socket, channels, channel),
+            Command::OutputPid { channel } => Handler::engage_pid(socket, channels, channel),
-            Command::PwmPolarity { channel, polarity } => {
+            Command::OutputPolarity { channel, polarity } => {
                 Handler::set_polarity(socket, channels, channel, polarity)
             }
-            Command::Pwm {
+            Command::Output {
                 channel,
                 pin,
                 value,

src/command_parser.rs

@@ -91,7 +91,7 @@ pub struct Ipv4Config {
 #[derive(Debug, Clone, PartialEq)]
 pub enum ShowCommand {
     Input,
-    Pwm,
+    Output,
     Pid,
     SteinhartHart,
     PostFilter,
@@ -149,16 +149,16 @@ pub enum Command {
     Ipv4(Ipv4Config),
     Show(ShowCommand),
     /// PWM parameter setting
-    Pwm {
+    Output {
         channel: usize,
         pin: PwmPin,
         value: f64,
     },
     /// Enable PID control for `i_set`
-    PwmPid {
+    OutputPid {
         channel: usize,
     },
-    PwmPolarity {
+    OutputPolarity {
         channel: usize,
         polarity: Polarity,
     },
@@ -260,12 +260,12 @@ fn pwm_setup(input: &[u8]) -> IResult<&[u8], Result<(PwmPin, f64), Error>> {
     ))(input)
 }
 
-/// `pwm <0-1> pid` - Set PWM to be controlled by PID
+/// `output <0-1> pid` - Set output to be controlled by PID
-fn pwm_pid(input: &[u8]) -> IResult<&[u8], ()> {
+fn output_pid(input: &[u8]) -> IResult<&[u8], ()> {
     value((), tag("pid"))(input)
 }
 
-fn pwm_polarity(input: &[u8]) -> IResult<&[u8], Polarity> {
+fn output_polarity(input: &[u8]) -> IResult<&[u8], Polarity> {
     preceded(
         tag("polarity"),
         preceded(
@@ -278,8 +278,8 @@ fn pwm_polarity(input: &[u8]) -> IResult<&[u8], Polarity> {
     )(input)
 }
 
-fn pwm(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
+fn output(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
-    let (input, _) = tag("pwm")(input)?;
+    let (input, _) = tag("output")(input)?;
     alt((
         |input| {
             let (input, _) = whitespace(input)?;
@@ -287,19 +287,19 @@ fn pwm(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
             let (input, _) = whitespace(input)?;
             let (input, result) = alt((
                 |input| {
-                    let (input, ()) = pwm_pid(input)?;
+                    let (input, ()) = output_pid(input)?;
-                    Ok((input, Ok(Command::PwmPid { channel })))
+                    Ok((input, Ok(Command::OutputPid { channel })))
                 },
                 |input| {
-                    let (input, polarity) = pwm_polarity(input)?;
+                    let (input, polarity) = output_polarity(input)?;
-                    Ok((input, Ok(Command::PwmPolarity { channel, polarity })))
+                    Ok((input, Ok(Command::OutputPolarity { channel, polarity })))
                 },
                 |input| {
                     let (input, config) = pwm_setup(input)?;
                     match config {
                         Ok((pin, value)) => Ok((
                             input,
-                            Ok(Command::Pwm {
+                            Ok(Command::Output {
                                 channel,
                                 pin,
                                 value,
@@ -312,7 +312,7 @@ fn pwm(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
             end(input)?;
             Ok((input, result))
         },
-        value(Ok(Command::Show(ShowCommand::Pwm)), end),
+        value(Ok(Command::Show(ShowCommand::Output)), end),
     ))(input)
 }
 
@@ -569,7 +569,7 @@ fn command(input: &[u8]) -> IResult<&[u8], Result<Command, Error>> {
         value(Ok(Command::Reset), tag("reset")),
         ipv4,
         map(report, Ok),
-        pwm,
+        output,
         center_point,
         pid,
         steinhart_hart,
@@ -664,11 +664,11 @@ mod test {
     }
 
     #[test]
-    fn parse_pwm_i_set() {
+    fn parse_output_i_set() {
-        let command = Command::parse(b"pwm 1 i_set 16383");
+        let command = Command::parse(b"output 1 i_set 16383");
         assert_eq!(
             command,
-            Ok(Command::Pwm {
+            Ok(Command::Output {
                 channel: 1,
                 pin: PwmPin::ISet,
                 value: 16383.0,
@@ -677,11 +677,11 @@ mod test {
     }
 
     #[test]
-    fn parse_pwm_polarity() {
+    fn parse_output_polarity() {
         let command = Command::parse(b"pwm 0 polarity reversed");
         assert_eq!(
             command,
-            Ok(Command::PwmPolarity {
+            Ok(Command::OutputPolarity {
                 channel: 0,
                 polarity: Polarity::Reversed,
             })
@@ -689,17 +689,17 @@ mod test {
     }
 
     #[test]
-    fn parse_pwm_pid() {
+    fn parse_output_pid() {
-        let command = Command::parse(b"pwm 0 pid");
+        let command = Command::parse(b"output 0 pid");
-        assert_eq!(command, Ok(Command::PwmPid { channel: 0 }));
+        assert_eq!(command, Ok(Command::OutputPid { channel: 0 }));
     }
 
     #[test]
-    fn parse_pwm_max_i_pos() {
+    fn parse_output_max_i_pos() {
-        let command = Command::parse(b"pwm 0 max_i_pos 7");
+        let command = Command::parse(b"output 0 max_i_pos 7");
         assert_eq!(
             command,
-            Ok(Command::Pwm {
+            Ok(Command::Output {
                 channel: 0,
                 pin: PwmPin::MaxIPos,
                 value: 7.0,
@@ -708,11 +708,11 @@ mod test {
     }
 
     #[test]
-    fn parse_pwm_max_i_neg() {
+    fn parse_output_max_i_neg() {
-        let command = Command::parse(b"pwm 0 max_i_neg 128");
+        let command = Command::parse(b"output 0 max_i_neg 128");
         assert_eq!(
             command,
-            Ok(Command::Pwm {
+            Ok(Command::Output {
                 channel: 0,
                 pin: PwmPin::MaxINeg,
                 value: 128.0,
@@ -721,11 +721,11 @@ mod test {
     }
 
     #[test]
-    fn parse_pwm_max_v() {
+    fn parse_output_max_v() {
-        let command = Command::parse(b"pwm 0 max_v 32768");
+        let command = Command::parse(b"output 0 max_v 32768");
         assert_eq!(
             command,
-            Ok(Command::Pwm {
+            Ok(Command::Output {
                 channel: 0,
                 pin: PwmPin::MaxV,
                 value: 32768.0,

src/config.rs

@@ -6,11 +6,7 @@ use crate::{
 };
 use num_traits::Zero;
 use serde::{Deserialize, Serialize};
-use uom::si::{
+use uom::si::f64::{ElectricCurrent, ElectricPotential};
-    electric_current::ampere,
-    electric_potential::volt,
-    f64::{ElectricCurrent, ElectricPotential},
-};
 
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
 pub struct ChannelConfig {
@@ -77,9 +73,9 @@ impl ChannelConfig {
 
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
 pub struct PwmLimits {
-    pub max_v: f64,
+    pub max_v: ElectricPotential,
-    pub max_i_pos: f64,
+    pub max_i_pos: ElectricCurrent,
-    pub max_i_neg: f64,
+    pub max_i_neg: ElectricCurrent,
 }
 
 impl PwmLimits {
@@ -88,15 +84,15 @@ impl PwmLimits {
         let max_i_pos = channels.get_max_i_pos(channel);
         let max_i_neg = channels.get_max_i_neg(channel);
         PwmLimits {
-            max_v: max_v.get::<volt>(),
+            max_v,
-            max_i_pos: max_i_pos.get::<ampere>(),
+            max_i_pos,
-            max_i_neg: max_i_neg.get::<ampere>(),
+            max_i_neg,
         }
     }
 
     pub fn apply(&self, channels: &mut Channels, channel: usize) {
-        channels.set_max_v(channel, ElectricPotential::new::<volt>(self.max_v));
+        channels.set_max_v(channel, self.max_v);
-        channels.set_max_i_pos(channel, ElectricCurrent::new::<ampere>(self.max_i_pos));
+        channels.set_max_i_pos(channel, self.max_i_pos);
-        channels.set_max_i_neg(channel, ElectricCurrent::new::<ampere>(self.max_i_neg));
+        channels.set_max_i_neg(channel, self.max_i_neg);
     }
 }

src/steinhart_hart.rs

@@ -2,8 +2,9 @@ use num_traits::float::Float;
 use serde::{Deserialize, Serialize};
 use uom::si::{
     electrical_resistance::ohm,
-    f64::{ElectricalResistance, ThermodynamicTemperature},
+    f64::{ElectricalResistance, TemperatureInterval, ThermodynamicTemperature},
     ratio::ratio,
+    temperature_interval::kelvin as kelvin_interval,
     thermodynamic_temperature::{degree_celsius, kelvin},
 };
 
@@ -12,17 +13,17 @@ use uom::si::{
 pub struct Parameters {
     /// Base temperature
     pub t0: ThermodynamicTemperature,
-    /// Base resistance
+    /// Resistance at base temperature
     pub r0: ElectricalResistance,
     /// Beta
-    pub b: f64,
+    pub b: TemperatureInterval,
 }
 
 impl Parameters {
-    /// Perform the voltage to temperature conversion.
+    /// Perform the resistance to temperature conversion.
     pub fn get_temperature(&self, r: ElectricalResistance) -> ThermodynamicTemperature {
-        let inv_temp = 1.0 / self.t0.get::<kelvin>() + (r / self.r0).get::<ratio>().ln() / self.b;
+        let temp = (self.t0.recip() + (r / self.r0).get::<ratio>().ln() / self.b).recip();
-        ThermodynamicTemperature::new::<kelvin>(1.0 / inv_temp)
+        ThermodynamicTemperature::new::<kelvin>(temp.get::<kelvin_interval>())
     }
 }
 
@@ -31,7 +32,7 @@ impl Default for Parameters {
         Parameters {
             t0: ThermodynamicTemperature::new::<degree_celsius>(25.0),
             r0: ElectricalResistance::new::<ohm>(10_000.0),
-            b: 3800.0,
+            b: TemperatureInterval::new::<kelvin_interval>(3800.0),
         }
     }
 }