Brother Joseph M. Walsh
College of Santa Fe Sonto Fe, New Mexico
Construction of an Inexpensive Constant Temperature Device
A simple constant temperature device that finds many uses in the undergraduate science program can be easily constructed for less than five dollars. The wooden framework of the device with the dimensions indicated in the illustration is made of plywood and is securely fastened by screws to a standard ring support. The basic components' are the immersion heater, "Valiant" make, 110 VAC, 250 W; the Fenwal thermoregulator, cartridge type with contacts normally closed, 10 amp capacity, 115 VAC, with a rated temperature range of -100° to +40O0F; the 0.059 W glow lamp (General Electric, type AIA or NE2); and the resistor (150 to 800 Kohm). To raise the cut-off temperature the center screw on the thermoregulator is turned counterclockwise. When the preset temperature is reached, the glow lamp, which is in parallel with the heating element, goes out as the circuit opens. As the temperature drops, the circuit is closed and the glowing neon lamp signals the resumption of heating. Adequate stirring conditions are necessary to obtain the rated * l ° F sensitivity. This constant temperature device ha3 been effective for volumes ranging from 1.6 to 14 l and has been used
in bath control for vacuum distillation and for refluxing organic compounds at other than steam bath temperatures. It has been employed as a standby bath control in physical chemistry experiments allowing the more accurate and expensive temperature regulators to be used more efficiently. It can also be used in biochemical and biological experiments where temperature control is not,demanding.
fl
' The heater is readily available at hardware stores; the glow lamp and resistor, s t electrical srlpply houses; and the therrnoregdator can be purchased from Herbach and Rrtdeman, h e . , 1204 Arch Street, Philadelphia, 7, Pa., for 83.
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a Immersion heater bThermregulotor c.Resistor dGlow lamp
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e. Ring Support
Dimgrom of the simple ternparoture regulofor.
Volume 44, Number
I , Jonuary 1967
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29
