Making a thermo-filter

I’ve been making a thermo-filter, like a SCACE device, to make sure that my machine works as well as I think it does. Up till now, I’ve just been pushing a thermocouple up into the group-head outlet pipe, but this does nothing to control the flow rate or mimic the conditions inside the filter basket.


I’ve made the plastic puc from acetal, turned down on the lathe, then drilled and tapped a hole in the centre. The acetal turns really nicely, and the thread feels very strong.



I made the bottomless porta-filter earlier on my milling machine. The valve is a needle valve from eBay, which will enable me to control the flow rate and mimic different extraction times.

I have a bare-wire thermocouple to take the temperature measurement. They respond much faster than enclosed-type thermocouples, as the heat does not need to be conducted through the probe shell. Considering the extraction is over in about 25 seconds, if it takes the thermocouple 5 seconds to respond it won’t be a particularly revealing test.

I’ll fit the probe later. I’m away at work now, so it will be a couple of weeks before I can make sure it fits my machine and glue the probe in position.

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