To measure volume/injection in a CRI engine injector tester, various methods can be employed. One suggestion is to catch the spent fuel during a set number of injections to measure the total volume accurately. Another approach involves using a flow meter installed in the high-pressure supply line to obtain direct readings. Options for flow meters include thermal mass flow meters, ultrasonic Doppler flowmetry, and laser Doppler velocity measurement. Accurate measurement of injector performance can also be inferred from consistent exhaust temperatures.