Your saying about Barometers has dredged up some long forgotten memories. I was posted to 390 Maintenance Unit at RAF Seletar in 1969. The beauty of working at the MU was that I saw all the different types of jobs done at all the bases on the Island. As a singly LAC I think I was the original ‘Spare’ that could be sent off at a moments notice to temporarily fill manning shortages.
One time I was detached across to Tengah and worked in the Instrument Bay on Pitot-Static Instruments. The facility allowed deep stripping and calibration of the Instruments. I still remember using a Cassella Barometer and having to correct for London Laboratory conditions - If it’s hot (above London Lab), drop it (subtract the correction)! 74 Squadron Lightnings doing vertical climbs nearby were a bit of a distraction though. Happy days.