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Team:Valencia/TMS
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| - | == | + | == Temperature measurement system == |
| + | Several of our testing | ||
| + | |||
| + | == Ice bath thermocouple compensation == | ||
| + | Our temperature measurement system is based on the Seebeck effect. The Seebeck effect happens when a junction | ||
| + | of two different metals is exposed to a certain temperature. In the loose ends of the wires appears a | ||
| + | difference of voltage ''proportional'' to the that temperature. | ||
| + | Measuring the generated voltage is possible to determine the temperature which generated de effect. This is | ||
| + | done by means of polynomial interpolation (compatible with the ITS-90 standard). | ||
| + | |||
| + | [[Image:Valencia_thermo_circuit.jpg|thumb|400px|Figure 1. Example of type J thermocouple (Fe and Constantan)]] | ||
| + | |||
| + | |||
| + | In order to use this system is necessary to connect it to a electronic acquisition system. In the new | ||
| + | connection places appear new thermocouple junctions (J1 and J2 in Figure XXX) which modify the original | ||
| + | voltage difference. The are several strategies to deal with this problem. | ||
| + | |||
| + | The electronic acquisition system that we use is the Datalogger | ||
| + | 34970A (Agilent). This device has the possibility to deal the | ||
| + | already mentioned problem with two different strategies. | ||
| + | *Automatic compensation | ||
| + | *Fixed compensation | ||
| + | |||
| + | ===Automatic Compensation === | ||
| + | The automatic compensation is made internally by the device, | ||
| + | measuring the surrounding temperature of the copper junctions, | ||
| + | with solid state sensors. This is a very simple option, but its | ||
| + | precision is very low, and inadequate for our purpose. | ||
| + | |||
| + | [[Image:Valencia_comp_auto.jpgthumb|400px|Figure 2. Automatic | ||
| + | compensation]] | ||
| + | |||
| + | ===Fixed Compensation === | ||
</div> | </div> | ||
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Contents |
Temperature measurement system
Several of our testing
Ice bath thermocouple compensation
Our temperature measurement system is based on the Seebeck effect. The Seebeck effect happens when a junction of two different metals is exposed to a certain temperature. In the loose ends of the wires appears a difference of voltage proportional to the that temperature. Measuring the generated voltage is possible to determine the temperature which generated de effect. This is done by means of polynomial interpolation (compatible with the ITS-90 standard).
In order to use this system is necessary to connect it to a electronic acquisition system. In the new
connection places appear new thermocouple junctions (J1 and J2 in Figure XXX) which modify the original
voltage difference. The are several strategies to deal with this problem.
The electronic acquisition system that we use is the Datalogger 34970A (Agilent). This device has the possibility to deal the already mentioned problem with two different strategies.
- Automatic compensation
- Fixed compensation
Automatic Compensation
The automatic compensation is made internally by the device, measuring the surrounding temperature of the copper junctions, with solid state sensors. This is a very simple option, but its precision is very low, and inadequate for our purpose.
Figure 2. Automatic compensation
