A Suggested Improvement for the Fabrication of Low-Cost Manometers D. Dewayne Garrett and M. C. Banta Sam Houston State University, Huntsville. TX 77341 The low-cost plastic manometers discussed in this Journal' are safe and practical for the general lahoratory. A simple modification can significantly improve the readability and mechanical stability. This alteration is done by cutting out the edges of a meter stick to create grooved edges such that the meniscus lies close to the millimeter markings. The procedure first requires making a simple jig so that a straight, reproducible groove can he cut in the meter stick. This jig can be made from a scrap piece of hoard approximatelv 1.4 m lone: (a 2 X 4 works well.) Affix to the board an -16-&I length o;broken meterstick on eachend, flush with the edae of the hoard, as illustrated in Fieure 1: leave iust enough space for a full meter stick to set in-between them. Second, the meter stick, to be grooved, is attached to the jig with three #6, brass, flat-head wood screws as shown in Figure 1. The screws should be counter sunk so that the router guide can freely slide. The jig should be clamped in a vise for ease and safety. Third. dace a %-in. V-moove router bit into a hand router. ~laceiheguide"ontheioutersothat it is adjusted tocut a V moove in the center of the meter stick's edee. With care it can be adjusted so that the inner wall of the Tygon tubing
will he located partially behind the ends of the graduation markings on the meter stick. This will allow ease of reading because the meniscus is close to the graduations and increase both the rigidity of the apparatus as well as the precision. Router the other edge in a similar manner. Fourth, affix approximately 2.4 m of 'la-in.-o.d., 3/s-in.-i.d. Tygon tubing. We used small plastic self-loclting ties about every 20 cm, which work satisfactorily and provide a more "student-proof' connection than clear plastic tape. Teflon, %-in. Swagelok unions were affixed on one end. Fifth, mount the manometer on a 1 X 4 that has heen cut -1.05 m in length and painted black. This assembly can be now attached to a ring stand or other rigid support, as shown in Figure 2.
I
Pollnow, G. F. J. Chem. Educ. 1989,66333.
Side View 100 cm
Meter S k k goes here
U
Figure 1. Side view and end view.
Flgure 2. The manometer.
Volume 67 Number 6 June 1990
523
