Step 1: Disconnect the thermocouple from the bottom of the gas control.
Step 2: Set your voltmeter to millivolts (mV) and direct current (DC).
Step 3: Set gas controls for pilot lighting.
Step 4: Attach the positive lead (Red) to the bare copper, and the common lead (Black) to the end of the thermocouple.
Step 5: Light the pilot, and continue to hold the pilot switch down until maximum voltage is reached. Normal operation for most water heaters is 17-32 mV. If it falls below this range a replacement thermocouple may be needed.