Inverted U with bar symbol mean moving frame
Diode symbol mean fitted with rectifier
Alternative symbol mean for AC reading
Star symbol is for dielectric test, here 1.5Kv
And it is specified that to read full scale you need 1.734Vrms across 3k6 resistor (not fitted)
Really look like a standard Vu to me...now as a GRM in a compressor, ballistic may be too slow...or not, depending of taste and what you want to see.