From: "Gust, Jeff"
To: [email protected]
Subject: traceability of barometer
Date: Mon, 2 Aug 1999 12:49:00 -0500

Any barometer has the ability of becoming a traceable barometer, provided that you can develop an appropriate method of calibrating the device to the manufacturers (or other acceptable metrological) specifications.

Some barometers are very difficult to calibrate because they do not have a pressure port that is easily interfaceable to a pressure calibration system. If you beat the interface problem, the rest of the calibration process is relatively easy.

As an example, many barometers are built into a "clock" configuration. They are sealed, and there is no access to the pressure port. Our laboratory uses a bell Jar to calibrate these barometers. We place the whole barometer in the bell jar, and vary the pressure within the bell jar, which is monitored by our pressure calibration system (capacitance manometers or deadweight piston gage). We use this method also to check the barometer above atmospheric pressure, but we have to strap the bell jar down to its base because the increased pressure will lift the bell jar up until it leaks the excess pressure.

Please do not send your barometer out to get a one point calibration, which is simply a single measurement at the ambient pressure of the calibration lab.

Several manufacturers produce great barometers that can easily calibrated. The Davis Instruments Catalog lists several. I personally use the Druck DPI 740 in our electrical standards lab to monitor the barometric pressure as it applies to my standard resistance measurement process. It is easy to calibrate, and is very accurate.