A2N3819 FETprovides a solid-state VOM. The 2N3819 acts as a cathode follower in a VOM. The bias offset (meter null) is obtained with R14 and R12 sets full-scale calibration. R2 through R9 should total about 10 MO.
RlO is a protective resistor, and C2 provides ac bypassing to limit rf and noise pickup.