Figure 7.

Schematic block diagram of the furnace control system.

TC: Chromel-P/Alumel thermocouple

DC AMP: Chopper type d-c amplifier.

REC-TRANS: Strip chart recorder plus transmitting variable resistor.

CONT: Three-mode controller.

POWER REG: Solid-solid gate drive, full-wave silicon-controlled rectifier, plus transformer package.

R₁(S): Standard resistor (10 Ω) for bias voltage source.

R₂(S): Standard resistor (10 Ω) for monitoring bias voltage source.

R(V): Variable resistor for adjusting bias voltage.

BA(Hg): Mercury cells.