The system and method for testing thermal insulation uses a cryostatic insulation tester having a vacuum chamber and a cold mass including a test chamber and upper and lower guard chambers adjacent thereto. A technique for acquiring calibration data faster and easily is provided to attain high time precision and respond to multi-channeling of detectors. The pre-decoded row address counter counts and outputs a regular pre-decoded row address in response to the refresh control signal. Preferably, load shed circuit includes an isolation circuit and a bidirectional switch that is coupled in parallel with a return ballasting capacitor within inverter.