Are there any precautions that should be taken when measuring Open Circuit Voltage (OCV)?

Any fixture that includes a ballast with an Ignitor will have high voltage pulses at the lamp socket, when power is applied to the ballast and the lamp is not operating, that can damage a voltmeter used to measure OCV. The Ignitor should be disabled or the meter protected by a high voltage capacitor (approximately .0027 uF, 2,000 V) across the input. Metering could also be connected after the lamps starts (at which time the ignitor shuts off).