Journal of Thermal Analysis and Calorimetry

, Volume 111, Issue 1, pp 857–867 | Cite as

Sensor placement in temperature-based control strategies to improve baseline stability in Tian–Calvet microcalorimeters

  • Luis E. Vilchız-Bravo
  • Arturo Pacheco-Vega
  • Brent E. Handy
Article

Abstract

We address the issue of hardware placement in the development of robust temperature control strategies that can be used to maintain a stable baseline during microcalorimetric experiments. The two different control loops, each defined by the location of sensor within the calorimeter that is used to achieve control, were first developed and then tested in a fully instrumented experimental system. Both control strategies were structured on proportional-integral-derivative controllers, after which calorimetric experiments were carried out to test the efficiency and robustness of the corresponding methodology. Results indicate that sensor placement plays a fundamental role in the controlled baseline stability and that is better to place the sensing device closer to the heater than to the central core. As part of this study, comparisons were also done against a previously reported control scheme based on heat-flow measurements. Results indicate that controlling only one variable, either temperature or heat flow is sufficient to compensate for heater-induced noise, but not for external fluctuations for which a combined strategy may be necessary.

Keywords

Tian–Calvet microcalorimeter Temperature control Sensor placement Baseline signal 

List of symbols

e

Error signal

kDkIkP

PID controller gains

\({\mathcal{K}}\)

Calibration constant

L

Characteristic length

P

Electric power (W)

Q

Heat-flow rate (W)

T

Temperature (K)

T1

Temperature at T1 (K)

T2

Temperature at T2 (K)

t

Time

uT

Input voltage signal (V)

Greek symbols

α

Thermal diffusivity (m2/s)

δt

Time interval (s)

τ

Thermal lag

Subscripts and superscripts

p

Prediction

set

Setpoint

SHT

Heat-flow sensor

SP

Sample heat-flow sensing cup

Abbreviations

CDC

Continuously modulated direct-current

CTC

Conventional temperature control

DAQ

Data acquisition

DC

Direct current

HFC

Heat-flow control

PC

Personal computer

PID

Proportional-integral-derivative

PMS

Power modulation system

SHT

Heat-flow sensor

SP

Sample sensing cup

T1

Thermocouple in heat-sink unit

T2

Thermocouple close to SHT

TC

Tian–Calvet

SISO

Single-input single-output

SSR

Solid-state relay

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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2012

Authors and Affiliations

  • Luis E. Vilchız-Bravo
    • 1
  • Arturo Pacheco-Vega
    • 2
  • Brent E. Handy
    • 3
  1. 1.Facultad de Ingeniería QuímicaUniversidad Autónoma de YucatánMéridaMéxico
  2. 2.Department of Mechanical EngineeringCalifornia State University Los AngelesLos AngelesUSA
  3. 3.CIEP-Facultad de Ciencias QuímicasUniversidad Autónoma de San Luis PotosíSan Luis PotosíMéxico

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