1khz ac bandwidth seriously ?? Any serious company should have a 100khz on any modern meter
well, it can calculate TRMS on anything between 20Hz and 1kHz, but it can measure frequencies up to
60MHz according to the above datasheet. bear in mind that TRMS, if done digitally, requires a fair bit of oversampling to work.
also of note, temperature can be measured with either k-type thermocouple or a resistive PT100 sensor.
from the inside views, it looks like there is a 5-wire connector off the multimeter PCB running to the AC PSU and serial PCBs. an educated guess is that this carries a single-ended supply (2-wires) and opto-isolated serial (3-wires). if this is the case, modification for battery powered may well be on the cards
cheers,
rob :-)