Meter Accessory Heads AAT3 - Hot-wire Anemometer & Psychrometer Accessory Head AAV3 - Air Velocity and Temperature Accessory Head ACH4 - 400A Amp Clamp Accessory Head ACM4 - Carbon Monoxide Detector Accessory ADMN2 - Dual Port Manometer Accessory Head AMN2 - Manometer Accessory Head AOX2 - Oxygen and Carbon Dioxide Accessory Head Retired ARH4 - Digital Psychrometer Accessory Head ARH5 - Psychrometer Accessory Head ASX14 - Superheat & Subcooling Accessory Head ATH4 - Dual Temperature Accessory Head Retired ATIR3 - Infrared Temperature Accessory Head Retired AUA2 - Milliamps & Microamps Accessory Head AVG2 - Digital Vacuum Micron Gauge Accessory Head AVH1 - Volts Accessory Head