GermanOgre
Chemical
Greetings,
I am finishing the setup of a thermal conductivity measurement device. The device consists of a "comparison" block, the specimen and two heat sources (one at 20°c and one at 40°C). The specimen and the block are sandwiched between the two sources. On both sides of the comparison block (one on the side next to the specimen and one on the side next one of the heat source) are thermocouples. The temperature difference which emerges once equilibrium is reached, is compared to a calibration curve. The calibration curve is based on temperature difference (or delta voltage from the thermacouples) of materials with known thermal conductivity values. Based on this curve we hope to determine the thermal conductivity of the specimen.
Given preliminary tests with the unit I'll need at least a temperature difference reading accuracy of 0.01°C, which translates to 0.4µV for the type K thermocouples we are using. I have found a 16 bit USB thermocouple input DMM that has an input range from 0 to 15mV. This should be resolution equivalent to 0.23µV. The measurement resolution should be high enough. Before I order the unit I read a lot about emf being a problem at these low voltages. Are the voltages too small to accurately measure with this device? What are typical emf values I could encounter? Will I need to amplify the signal and what type of amp would I look for if needed.
The device will be hooked up to a computer in a room with a densometer.
Here is the DMM link:
Thanks a ton in advanced!
Chris
I am finishing the setup of a thermal conductivity measurement device. The device consists of a "comparison" block, the specimen and two heat sources (one at 20°c and one at 40°C). The specimen and the block are sandwiched between the two sources. On both sides of the comparison block (one on the side next to the specimen and one on the side next one of the heat source) are thermocouples. The temperature difference which emerges once equilibrium is reached, is compared to a calibration curve. The calibration curve is based on temperature difference (or delta voltage from the thermacouples) of materials with known thermal conductivity values. Based on this curve we hope to determine the thermal conductivity of the specimen.
Given preliminary tests with the unit I'll need at least a temperature difference reading accuracy of 0.01°C, which translates to 0.4µV for the type K thermocouples we are using. I have found a 16 bit USB thermocouple input DMM that has an input range from 0 to 15mV. This should be resolution equivalent to 0.23µV. The measurement resolution should be high enough. Before I order the unit I read a lot about emf being a problem at these low voltages. Are the voltages too small to accurately measure with this device? What are typical emf values I could encounter? Will I need to amplify the signal and what type of amp would I look for if needed.
The device will be hooked up to a computer in a room with a densometer.
Here is the DMM link:
Thanks a ton in advanced!
Chris