API

This part covers the complete api documentation of the heatcapacity library.

heatcapacity Package

from slave.transport import LinuxGpib
import heatcapacity as hc

# We use a Keithley model 6221 as current source,
source = hc.K6221CurrentSource(LinuxGpib(8))

# a Keithley model 2182A Nanovoltmeter to measure the voltage drop at the
# heater,
powermeter = hc.K2182Powermeter(LinuxGpib(9))

#and a lakeshore model 370 to determine the platform temperature.
thermometer = hc.LS370Thermometer(LinuxGpib(10))

# We sample at a rate of 0.1 s and use a step pulse with 1 uA to excite the
# system.
sampling_time = 0.1
pulse_sequence = [0.] * 60 * sampling_time + [1.] * 60 * sampling_time

# The PulseMeasurement object is used to acquire the data.
measurement = hc.PulseMeasurement(currentsource, powermeter, thermometer,
                                  pulse, sampling_time)
timestamp, power, temperature = measurement.start()

# We fit a first order model to get the heat capacity.
model = hc.FirstOrderModel.fit(timestamp, temperature, power)

print('C {}; K {}'.format(model.heat_capacity, model.thermal_conductivity))

fit module

class heatcapacity.fit.FirstOrder(b, a)

Bases: scipy.signal.ltisys.lti

First order heat capacity differential equation model.

The first oder heat capacity differential equation is

C * dy/dt + K * y = u

with C the heat capacity, K the thermal conductivity, y the temperature and u the heater power. This is a special case of a linear time invariant first order system

a0 * dy/dt + a1 * y = b0 * du(t)/dt + b1 * u(t)

The corresponding transferfunction is

b0 * s^1 + b1 * s^0

G(s) = ——————-

a0 * s^1 + a1 * s^0

Note

We normalize the transfer function to a0 = 1. on instatiation.

Parameters:

• b – Numerator polynom.
• a – Denominator polynom.

classmethod fit(t, y, u)

Fits a first order heat capacity model.

Parameters:

• t – A sequence of timestamps.
• y – A sequence of temperatures.
• u – A sequence of heater power values.

classmethod from_ck(heat_capacity, thermal_conductivity)

heat_capacity

thermal_conductivity

measure module

class heatcapacity.measure.CurrentSource

Bases: future.types.newobject.newobject

Abstract base class defining the current source interface.

current

class heatcapacity.measure.Measurement(currentsource, powermeter, thermometer)

Bases: future.types.newobject.newobject

Abstract base class defining the heat capacity measurement interface.

Parameters:

• currentsource – An object implementing the CurrentSource interface.
• powermeter – An object implementing the Powermeter interface.
• thermometer – An object implementing the Thermometer interface.

measure()

Measures the time, heater power and platform temperature.

start()

Starts the heat capacity measurement.

class heatcapacity.measure.Powermeter

Bases: future.types.newobject.newobject

Abstract base class defining the powermeter interface.

voltage

class heatcapacity.measure.PulseMeasurement(currentsource, powermeter, thermometer, pulse, sampling_time)

Bases: heatcapacity.measure.Measurement

A heat capacity measurement using a predefined pulse sequence.

Parameters:

• currentsource – An object implementing the CurrentSource interface.
• powermeter – An object implementing the Powermeter interface.
• thermometer – An object implementing the Thermometer interface.
• pulse – A sequence of current values.
• sampling_time – The sampling time.

start()

Starts the heat capacity measurement.

class heatcapacity.measure.Thermometer

Bases: future.types.newobject.newobject

Abstract base class defining the thermometer interface.

temperature

simulation module

class heatcapacity.simulation.Simulation(model, heater_resistance, noise_level)

Bases: object

The Simulation object can be used if a real experiment is not available.

Parameters:

• model – An lti model used to simulate the temperature output.
• heater_resistance – A resistance in ohm used to calculate the voltage drop.
• noise_level – A sample taken from the standard normal distribution scaled by the noise_level is added to the simulated temperature output.

E.g.:

import heatcapacity as hc

sim = hc.Simulation(
    hc.FirstOrder.from_ck(0.005, 0.002),
    heater_resistance=1e3,
    temperature_noise=0.1
)
sampling_time = 0.1
pulse_sequence = [0.] * 60 * sampling_time + [1.] * 60 * sampling_time

measurement = hc.PulsMeasurement(
    currentsource=sim, powermeter=sim, thermometer=sim,
    pulse=pulse_sequence, sampling_time=sampling_time)

measurement.start()

temperature

Simulates the temperature response to the current change.

voltage