A comparison test pump is a device by which pressure gauges can be calibrated in comparison with masterpressure gauges. These can also be used for comparison of master gauges with normal use pressure gauges after periodic intervals to detect a drift in calibration. The unit is portable and comes in handy during pressure gauge calibration verification in ISO 9000 companies. Standard process connection provided is 3/8" BSP female. Adaptors to suit individual pressure gauges can be provided as accessories.