Since the liquids in nearly every dough need to be tempered, I went looking for some straight forward, repeatable method to get the temperature I wanted. My answer was to use the microwave. The next step was to figure out how to get the right time for any mass of water or milk, and for any temperature change.
We can see that the time required (Sec) is proportional to the mass of the water (M) and to the change in temperature (ΔT), multiplied by some constant (C).
M × ΔT = C × Sec
Rearranging to solve for the time; Sec = M × ΔT / C
With my microwave oven, the constant is 312.5 for weight in grams and temp in Fahrenheit. There's a kink in the formula though. My oven requires about 3 seconds to come up to speed, so I add that to the calculated time. For example, let's say I have 350g of 40F milk from the frig that needs to be 65F for an intensively mixed Vienna style dough. I need to raise the temp by 25F, so 350×25/312.5+3 yields 31sec to raise the temp to 65F.
How do you find your magic number? Measure some water, say in the 300-450g range. Take its temperature, and zap it for some reasonable time, e.g. 30 seconds. Measure the temp. Repeat with the same weight of water, for a different length of time. Plot the two tests on graph paper (or use a spreadsheet or graphing calculator), and extend the line through the points to where it crosses the zero temperature change line. Where it intercepts the zero temp, the time line will have some small value. That's your start-up time. Now multiply the weight of the liquid by the temperature change and divide by the time less the start-up time. For example, 350 × 25 / (31 - 3) = 312.5 Notice that that is from my own earlier example. Do the math on your other test(s). The C values should closely agree.
Once you have your magic number, any weight of water or milk and any (upward) temperature adjustment will provide the zapping time for your microwave.