Most good panel meters (Triplet, etc) 2" or larger in diameter in thick
Bakelite cases having glass windows are probably insulated well enough to
safely be used in the high voltage side up to at least 1kv (or more). I
wouldn't try it with a cheap imported meter in a thin plastic case and a
plastic window. Back in the days when REAL transmitters were housed in relay
rack cabinets it was the norm to put an ammeter in the HV lead. Note that
trying to switch a single meter between grid, screen, plate, and HV readings
(meter is used as a voltmeter and reads voltage across shunts for current)
gets tricky, a WELL insulated switch is required with good isolation between
selections! Using every other position of a rotary switch and yanking out the
unused contacts might have been common.

My Geloso transmitter just adopts the arrangement you mention. But I would
prefer to avoid it, mainly because of the HV present on the meter switch.

The Hall-effect transducer seems to be perfect for measuring current forgetting
about HV. When I will get it I will report whether it really works fine for our
applications or not.

73

Tony I0JX