= Luis Chioye
{c}
\b[Luis Chioye] writes about precision <analog-to-digital converters> and their measurement circuits. The author biography in a 2013 Texas Instruments reference design identifies him as an applications engineer in its Precision Analog group, with degrees in <electrical engineering> from the University of Arizona and Walden University/NTU School of Engineering and Applied Science.<Precision Thermocouple Measurement with the ADS1118 by Mike Beckman and Luis Chioye>[§9, p. 23, author biography at the time of publication]{ref}
His work includes <ratiometric measurement> with <resistance thermometers>: sharing an excitation <electric current> can cancel its variation, but the input and reference filters must preserve that shared variation consistently.<RTD Ratiometric Measurements and Filtering Using the ADS1148 and ADS1248 Family of Devices by Luis Chioye>[Abstract and filter-design discussion, matched signal and reference paths]{ref} This is the engineering distinction captured by <ratiometric cancellation with matched signal and reference filters>.
With <Mike Beckman>, Chioye also published a <thermocouple> reference design. Its <reference-junction temperature sweep in thermocouple testing> keeps the measurement junction in a stable bath while changing the temperature of the connector and converter board; the acquisition computer stays outside the temperature-controlled chamber. This isolates reference-side effects from changing the temperature being measured.<Precision Thermocouple Measurement with the ADS1118 by Mike Beckman and Luis Chioye>[§7, p. 20, Figure 17]{ref}
\Image[/thermocouple-reference-junction-test.png]
{title=Reference-junction temperature sweep: keep the measurement bath fixed while varying the connector and converter temperature. Original schematic of the test principle.}
An original ideal calculation explains the test. Let $E(T)$ be the <thermocouple> <electromotive force> response from the <Seebeck effect> relative to $0\,{}^\circ\mathrm C$. With isothermal connector junctions at $T_c$, the measured <electric potential difference> is $V=E(T_h)-E(T_c)$. <Cold-junction compensation> reconstructs $E(T_h)=V+E(T_c)$ before applying the <inverse function> of the response. In the stipulated linear model $E(T)=ST$ with $S=40\,\mathrm{\mu V/K}$, a fixed $T_h=100\,{}^\circ\mathrm C$ gives $V=3.2\,\mathrm{mV}$ at $T_c=20\,{}^\circ\mathrm C$ and $2.8\,\mathrm{mV}$ at $30\,{}^\circ\mathrm C$. Correct compensation gives \b[the same $100\,{}^\circ\mathrm C$] in both cases. These are constructed values, not measured performance or a calibration table for a particular <thermocouple>.
<Cold-junction thermal coupling> matters because the <temperature sensor> must represent the connector temperature. A precise converter reading cannot by itself remove an unmeasured temperature difference between those locations.<Precision Thermocouple Measurement with the ADS1118 by Mike Beckman and Luis Chioye>[§2, p. 5, isothermal connector junctions and their temperature measurement]{ref}
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