If one were to adjust the positive temperature in an experiment, they would use a heating plate, or a stovetop.
How would one adjust negative temperatures in an experiment? (Not keeping the temperature constant, but decreasing and increasing the temperature at my will in specific amounts).
What I tried so far: "Spraying" liquid nitrogen at my work surface until it cools to the desired temperature. It is really inaccurate though.
Answer
Peltier element
Here's another idea: it's quite practical to pump heat just by passing electrical current through a device, which is usually just a plate with two wires:
I just love these things.
What's especially cool about them is that by simply reversing the current you reverse the heat flow! This just begs for a trivial control loop via thermocouple feedback.
A quick google query reveals commercial offers of heat baths built on this promising whopping 0.01 °C precision of regulation!
The elements are easily available in electronics shops, so with a good power supply it wouldn't be too hard to build your own low-cost precision heat bath.
Hope that helps!
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