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| Method | How it works | Electrical requirements | DAQ requirements | Temp range | Accuracy |
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As temp increases, voltage across diode's base and emitter (V_be) decreases at a known rate. This voltage is amplified, and voila.
To convert the voltage to temperature, simply use the basic formula: Temp in °C = [(Vout in mV) - 500] / 10 |
1- 2.7 - 5.5 VCC (0.05 mA current draw) 2 - analog V_out 3- GND
(1-2-3 left to right, part number facing you) |
Analog voltage input up to 2 V |
-40 - 150 °C
(-40 - 302 °F) |
+/- 0.2°C;
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| Thermocouple | Two different metals form a junction (where we sense temperature), and when a change in temperature occurs, a voltage is generated via the Seebeck effect. This voltage is measured by the DAQ and interpreted to give a temperature. | Self powered | Analog voltage input |
(typical, depends on type [K, J, T etc]); 200 - 1750°C |
(typical) 0.5 - 5 °C;
0.10 - 10 sec |
| Thermistor | Semiconductor typically combined with binders and stabilizers with a negative or positive temperature coefficient. Basically, temperature increases, and resistance of sensing element increases (PTC) or decreases (NTC) | Requires a current | Analog voltage input |
(typical) -100 - 325°C |
as low as +/- 0.05 °C;
0.12 - 10 seconds |
| RTD (resistance temperature detector) | Resistance of a sensing element (usually a pure metal like platinum protected in a sheath/embedded in ceramic) increases as temperature increases | Requires a current | Analog voltage input |
(typical) -200 - 650 °C |
+/- 0.1 to 1 °C;
1 - 50 sec |
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TMP36GZ (image from Adafruit)
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RTD vs thermistor (nice guide from Omega)
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RTD vs Thermocouple (nice guide from McMaster)
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RTD vs thermistor
