| Products > Test Equipment |
| Measuring the temperature of a soldering iron tip |
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| colorado.rob:
Somewhat off-topic but when my X-tronic died, I opted for a Thermaltronics TMT-9000S-1 after hearing Chris talk about his Thermaltronics soldering iron with Dave on The Amp Hour a couple years back. Never looking back. That thing is freaking awesome. |
| JimKnopf:
There is one thing i dont understand with the K-Type Thermocouple. At room temperature the values of my devices is nearly the same. In the first picture you can't see the K-Sensor from DMM6500 between the FG-100 and the Hygrotemp24 device to have all sensors together as near as possible. I found the K-Type Thermocouple reference table https://reotemp.com/wp-content/uploads/2015/12/type-k-thermocouple-reference-table.pdf. But the values doesn't match. The Keithley DMM6500 measures nearly 0 mV at around 23°C. But the reference table says 0 mV should be around 0°C. I attached some examples i measured with the DMM6500 sensor and the solderiron. Both K-Type sensors, the one from the FG-100 clone and the one from the DMM6500 have 0mV at around 23°C. Maybe someone can explain this offset? There is a temperature setting in the DMM6500 menu for the device temperature. It's set to 23°C. |
| jonpaul:
see cold junction compensation for thermocouples. Most high end meters have a built in TXC ><temp function and CJ comp j |
| wraper:
When there is no temperature gradient over thermocouple it outputs no voltage. Thermocouple does not measure absolute temperature, only temperature difference. |
| IanB:
--- Quote from: JimKnopf on August 21, 2023, 06:05:48 pm ---I found the K-Type Thermocouple reference table https://reotemp.com/wp-content/uploads/2015/12/type-k-thermocouple-reference-table.pdf. But the values doesn't match. The Keithley DMM6500 measures nearly 0 mV at around 23°C. But the reference table says 0 mV should be around 0°C. I attached some examples i measured with the DMM6500 sensor and the solderiron. Both K-Type sensors, the one from the FG-100 clone and the one from the DMM6500 have 0mV at around 23°C. --- End quote --- In the same way that voltage is measured as the difference between two points, thermocouple temperatures are measured as the difference between two junctions. Every "thermocouple" is actually two thermocouples, a reference junction and and a sensor junction. Hence, the reference table says that 0 mV should be measured when the difference between the two junctions is 0 deg. C (not 0°C absolute temperature). Thermocouple instruments have the reference junction inside the case, and this is thermally adjacent to (or bonded to) a reference temperature sensor such as a thermistor or solid state temperature sensor. The instrument uses the independently measured reference temperature along with a compensation table or algorithm to deduce the actual temperature of the probe based on the voltage difference between the two junctions and the actual reference temperature (which is typically room temperature, but room temperature can vary). |
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