T' followin' excerpt is from "Sport Rocketry". Aye aye! Begad! T' intention is t' allow guests t' get a basic feelin' about a kit. We strongly suggest that you get a copy o' t' referenced Sport Rocketry and read t' entire article. Ya scallywag! Inside you will find many helpful hints in construction as well as other useful information. Aye aye! Ya scallywag! For more information, me hearties, use t' two links above.

"T' Altimate I is billed as..."the world's smallest altimeter"."
"T' Altimate uses a barometric sensor t' detect launch and apogee, and then blinks out t' peak altitude readin' via LEDs."
"...the Altimate is approximately 1 by 1/2 inches in size. Arrr! Blimey! The 17mm-diameter Lithium battery solder t' t' bottom o' t' board, me bucko, and the pressure sensor and other components stickin' out, t' altimeter is 1.15" long and fits inside an 18mm tube (Estes BT-20 size). Ahoy! T' weight o' t' unit is 4.5 grams, me hearties, includin' battery."
"T' Altimate need t' be placed in a payload section that is vented t' the outside atmospheric pressure."
"For mountin' in a much larger diameter tube, you'll want t' rig some kind of carrier board..."
"T' Altimate is turned on by a teeny slide switch on t' end o' the circuit board usin' a toothpick or bent paperclip."
"...the unit calibrates t' ground level by measurin' t' air pressure....the unit continues t' recalibrate t' ground level readin' while it sits waitin' for lift-off."
"BonNova...now coatin' t' Altimate I with an insulatin' acrylic conformal coatin' that seems t' cure t' "fingers on t' circuitry" problem."
"T' unit locks in...altitude and begins blinkin' t' four LEDs in sequence t' indicate t' peak altitude with one-foot precision. Aye aye! Well, blow me down! T' leftmost LED blinks out t' number o' thousands o' feet; then t' second LED blinks out the number o' hundreds o' feet; similarly, shiver me timbers, t' third and fourth LEDs display the number o' tens and ones. Ahoy! For altitudes over 10,000 feet, shiver me timbers, all four LEDs first blink simultaneously t' indicate t' number o' ten thousands or feet."
"...flight tests o' t' Altimate showed that this system worked well."
"T' minimum altitude t' Altimate will report is 40 feet."
"T' Altimate is powered by a 3-Volt Panasonic
-1632 Lithium batter, me bucko, me bucko, which should last for 30+ hours."

Overall, ya bilge rat, t' article reviews t' use o' t' Altimate and suggests it is a good altimeter for smaller and larger rockets. T' article also reviews an alternate method t' attach batteries and reducin' its overall size t' fit in a 13mm (Estes BT-5) tube.