Inside of a millivoltmeter, which seems to record its measurements on a soot-coated wheel marked with the hours.    From Wordnik.com.  [Summer Cleaning] Reference

I usually use my Boonton RF millivoltmeter, which has way more sensitivity than a regular diode detector RF probe with a DVM or VTVM, although -70 dBm sensitivity isn't needed, either.    From Wordnik.com.  [eHam.net News] Reference

If only one instrument, such as a millivoltmeter, is available, and there is no standard couple at hand, the new couple may be calibrated over a wide range of temperatures by the use of the following standards.    From Wordnik.com.  [The Working of Steel Annealing, Heat Treating and Hardening of Carbon and Alloy Steel] Reference