Edit per May, 2013: Do not get the Polder thermometer illustrated here. Three out of four I've tried to disassemble wouldn't come apart. GS
Inspired by AndyPanda's use of thermometry on a Gaggia
and a Cremina, I've attached the same thermometer to my pre-Millennium La Pavoni Europiccola. I'm employing the same Polder thermometer he uses that sells for about $10 at Bed, Bath and Beyond and probably other places. This is a food thermometer with the temperature sensor inside a steel sheath. Adapting this to my Europiccola involved removing the sheath, finding a place to mount it, and shielding the thermometer from the heat of the machine. With my first test this evening it works. We used this type of thermometry to carefully monitor the temperature of the group on this machine and compare it to an Olympia Cremina '67 with a similar thermometer attached. Doing this we were able to use identical dose and grind in an Elektra double basket to reliably duplicate shots across machines.
Added: For anyone seeking to add a group thermometer to a machine built between 1961 and 1974, where the group is threaded directly into the boiler, here's the thread
on how to do that.
Here are photos of the procedure. First, the thermometer and the rotary tool with a cutting wheel used to cut the plastic around the steel sheath for removal. Be sure to use protective eyewear when using a cutting wheel as these can fragment and fly off. At the top are two high temperature silicone rubber pads I cut to shield the thermometer from the heat of the machine.
The pads were cut using a leather punch on the gasket material:
The leather punch was an inexpensive eBay set that came in metric sizes:
I used Blue Tack to stick the thermometer and the tip of the probe wires to the machine.
First I rolled and applied a bead of tack to the sightglass bracket:
Then I applied a silicone pad as a heat insulator:
Next I applied tack on top. To securely hold the thermometer I added a second set of these:
I used some more tack to make sure the wire leads are not touching the Pavoni boiler. Here tack is attaching the end of the probe wires to the back of the group:
Here's how the machine looks with the thermometer installed:
I will dial in shots using taste as a guide and correlate that with the group temperature readings. These will not be the actual temperature inside the group but should correlate very closely. AndyPanda used partial pumps to heat the group, and I'll follow that procedure. Without thermometry one otherwise monitors temperature with the manometer I installed on top of the sightglass. This is a machine that is manually operated with Low and High switches to get to temperature. It pulls great shots and is a powerful steamer once you learn how to "drive" it.