ADC Ridge analogue/aneroid altimeter (Szalay 2010).
There are a number of devices on the market that can determine your elevation, or to use a cooler mountaineering term: altitude. While pilots may use any type of altimeter, such as radar altimeters, alpinists only use aneroid altimeters. Aneroid altimeters measure the barometric pressure, or the air’s weight, to correspond to the altitude.
Digital altimeters, like the watches from Suunto or Casio or a GPS device with elevation output, and analogue altimeters, like my ADC Ridge shown in the picture above all have pros and cons. Digital altimeters are also aneroid devices, which use a barometric scale that corresponds to altitude, but the output of data is presented digitally instead of on a pressure gauge. The biggest advantage of a digital device is that it distinguishes barometric pressure changes from weather system from real elevation changes; analogue altimeters require the user to make the adjustments manually. The downside is that digital devices are electronic and dependent on batteries though both are equally susceptible to moisture.
The analogue altimeter requires a bit of work to operate. To properly determine your elevation with an analogue instrument you must adjust the dial to place the known elevation at the appropriate altitude. However, the device requires the user to confirm higher elevations on its gauge at known points, to counter for non-climbing changes to the detected barometric pressure. This requires the user to be using their navigation skills. In this way, the altimeter compliments a hiker’s or climber’s information about his or her location, but it doesn’t replace map and compass skills.
In fact, if used properly, the analogue altimeter can help the hiker or climber be more aware of his or her terrain. The compass determines bearings, the map can identify topography, and an altimeter can help confirm both. By comparison, a digital altimeter provides the same output, but an analogue instrument encourages the user to actively think about the clues of the landscape.
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The Suburban Mountaineer 
Thank you for putting this information out there. For years I have transversed mountain ranges and ice fields and most of the time I have been in ignorance of elevation unless finding out my position on a map. I remember REI used to sell mechanical altimeters and when I could buy one they didn’t sell them anymore. I didn’t trust the electronic ones because of the electrical power issue and I could possibly be 200 miles from the nearest battery outlet. Everything I learned about navigation I did it on my own. Thank you.