It was designed specifically for the military. The meter itself does have true RMS, unlike it's civilian counterpart. But it also included an HV probe (6kV?), and a custom case to fit it all IIRC (DMM, HV probe, standard probes, spare battery).
That refers to the 27 model, not the 27/FM then, so does that also extend to the 25? The one I have does indeed have the custom case but not the HV probe, the back of the meter also carries a MSHA label (Mine Safety and Health Administration and also states United States Department of Labor but does not mention military apart from an embossing in the moulding at the top.
This embossing states "Meets MIL-STD-810C, method 511.1 procedure 1 explosive atmosphere test"
If I understand you correctly, the answer is No in regard to the 27 v. 27/FM. The 27/FM was the military variant (it's NSN or NATO Stock Number is on a silver sticker on the back of the enclosure). So it wasn't just for the US DoD, but available to all NATO member nations (if you're not aware of these). Since some 27's use the same grey enclosure as the 27/FM, the easiest way to sort this out is by the printing on the LCD cover. So if it's missing 27
/FM, then it's a civilian model. Regardless if it's in a grey or yellow enclosure.
Internally, U2 is a DIP package marked with
Fluke RMS on the main board, while the civilian models don't have it. If repair is necessary, it's all PTH construction save U1.
Of the 8025A, 8025B, 25, 27, 27/FM (military variant), the 27/FM is the only version that has the Fluke RMS chip in it (it's the only SMD part in it BTW). As per the HV probe, it is 6kV peak model (P/N =
80K-6 High Voltage Probe).
The 25 series are all MSHA rated as they were purpose built for that environment. More recent versions used EX after the general P/N, such as the
87V-EX. They also used red for the boot color in order to easily differentiate it was designed for explosive environments. The current intrinsically safe model is the
28 II Ex.
Colors can vary depending on when it was produced (i.e. green, grey, yellow and when they were implemented).
Couple of sources that provide more information:
Hope this helps.
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