Hi!
A friend of mine bought a thermometer for remote measurings temperature of working valves,
he reads 242degC at EL34 in PP OPS,
someone told him that the temperatures >220degC might be danderous for valve lifetime.
Do you know what should be optimal/max temperatures of the bulbs?
A friend of mine bought a thermometer for remote measurings temperature of working valves,
he reads 242degC at EL34 in PP OPS,
someone told him that the temperatures >220degC might be danderous for valve lifetime.
Do you know what should be optimal/max temperatures of the bulbs?
The maximum EL34 bulb temperature is 250C, see the attached datasheet. It is obviously better to keep the temperature lower.
Svetlana ans Shuguang both claim the highest surface temperature of 250 °C in their EL34 datasheets.
If your friend is using an infrared thermometer, might he be reading an internal temperature, not the glass envelope?
No, the glass used is opaque to IR radiation. It's the glass temperature that is
measured.
There's also the issue of emissivity. Emissivity of rough aluminum is somewhere around 0.1, and emissivity of glass is more like 0.9. Generally an IR thermometer that is not adjustable for emissivity will be setup to measure metal temperatures.
A far, far more reliable approach is to use a small thermocouple and just touch it on the glass until the temperature stabilizes.
A far, far more reliable approach is to use a small thermocouple and just touch it on the glass until the temperature stabilizes.
Due to my work I had to do this kind of measurement many times and I have found that a tiny drop of thermal paste on the tip of the thermocouple really improves this kind of measurement a lot. Keep in mind that your thermocouple can act as a heatsink which drains heat from the sensitive tip. But Audiowize is right, if you want to measure the temperature to within, lets say a degree, your best bet would be a thermocouple. Alternatively you can glue one of these miniature PT100 thingies to the glass and log the temperature with someonething like a benchtop multimeter in a 4 wire measurement
https://lh3.googleusercontent.com/p...W3IDUzEeaWMOpzGCHknPeIp-Bq1DCKi3OABDkMIQTCjOQ
https://lh3.googleusercontent.com/p...W3IDUzEeaWMOpzGCHknPeIp-Bq1DCKi3OABDkMIQTCjOQ
