Frequently in using a thermo-electric pyrometer for measuring the temperature of a furnace, a hole is drilled at the back or side of the furnace, through which is introduced the tube containing the thermocouple. At times the couple is left almost where it drops, for the reason that it soon becomes too hot to be handled easily, and the space at the back or side of the furnace may be so small and uncomfortably hot that an easy and accurate adjustment is nearly impossible. In order to overcome this clumsy and unscientific method of using the thermo-electric pyrometer, I designed an adjustable stand, to hold the clay or quartz tube enclosing the platinum and platinum-rhodium leads that constitute the couple of the Le Chatelier thermo-electric pyrometer. This stand also allows an easy and rapid adjustment of position to varying heights and angles, as may be desired for special reading.
This stand is illustrated in Fig. 1. The couple in the tube might be of better service if the tube were held a little higher above the charge in a roasting-dish, changing the height and angle if desired.
The stand, made of 1.5-in. water-pipe and mounted on casters, is heavy enough so it cannot be tipped over easily. It is adjusted to any position, and has a universal clamp which holds the clay or quartz protecting-tube.
To avoid disturbing the wires of the couple at the cold junction each time the tube is moved, the cooling-bottle sets in a wire basket so placed that it moves forward or back with the couple.
To overcome the necessity of leveling and adjusting a galvanometer at each furnace, a switchboard is used to connect
the pyrometer with the galvanometer by means of three binding- posts placed at each furnace.
The furnaces are numbered from 1 to 12, and to facilitate the work two galvanometers are used, A and B in Figs. 2 and 3.
On a block in front of each of the furnaces, Fig. 3, are binding-posts A and B, to correspond to the galvanometers, while the central post is numbered according to the furnace. Thus, the binding-post block of furnace No. 3 would be marked A 3 B.
The connection between the binding-posts and the switchboard is by means of a telephone cable cased in a lead tube. Beneath the furnace this tube is inclosed in a conduit for protection.
The switch-board is of marble, having a plug for each of the galvanometers, A and B, and 12 holes, each bearing the number of a furnace, so that any individual furnace may be connected with either galvanometer, or with both.
A perfect adjustment of the galvanometers is obtained by placing them in a dust-proof case mounted on a concrete pillar, 1 by 2 ft. by 4 ft. high, resting in sand about 1 ft. below the floor, as shown in Fig. 3.
The wooden base, which merely covers the hole in the floor at the front, back, and sides, is fastened to the pillar, so that any motion of the floor is not communicated to the galvanometers.
In calibrating the couples, the readings of the galvanometer are taken through the cable and switch-board, so that similar conditions will obtain when in use.
For general work, the Battersea clay tubes made by the Morgan Crucible Co., England, are the best, as they are not so easily corroded and broken as are the quartz tubes.