PRINCIPLE OF OPERATION Thr THERMODYIllE is a gonoral p"`pOCe Iak,.% rotary temperature controller, designed to oper- ate 0s on "on-off" or proportional controller. The THERMODYNE is used with a resistance thermometer that is the variable arm in on AC Wheatstone bridqe circuit. The bridge is opet- ated at balance by means of an adjustable ratio arm that selects the temperature setting. A change in thermometer resistance produces an AC voltage which is amplified by a resist- ance coupled amplifier. This amplified AC volt- age is The" oppl,ed as 0 bius vvl,vyr I" 0 thy- raton tube energizing cln enclosed mercury plunger relay which turns c1 heater on and off. The controller dead zone, when used as an "on- off" controller is .OOl"C. using tl standard n;cL.vl rarictnnro hulh nf n,,r monufnrture. Model 1315 During proportional operation, a negative feedback signal is applied to produce on "on" period which is directly proportional to the bridge unbolonce voltage. The proportional bond (goin) is odustoble from 0.023OC. to 59°C. (based on the nickel resistance bulb) by means of a ten position gain switch. Proportional control i:. by means of time cycle modulation. A load of up to 25 amps (1 15 VAC non-inductive) may be connected directly to the terminal board mounted on the back of the instrument chassis. When operating as a proportional controller, only one heater is required, elimina- ting the multiple heaters usually employed with "on-off" controllers. SET POINT CONTROLS Setting of the control oolnt temperalure on the standard THERMODYNE IS accomplished through the use of two ten-turn potentiometers. One is for coarse and the other for fine setting. RANGE The range of the standard THERMODYNE is that of the resistance thermometer used OS the primary element. The standard THERMODYNE does not have a calibrated range and is not a direct set instrument. DECADE MODEL A special decade model is available that incorporates two ten-position switches in place of one of the ten-turn potentiometers (coarse). Fixed precision resistors cure selected to cover a specified range and through the use of these decade switches, permits the reselting of the ln:;trumen+ to an approxiL ` , 4 ,~`_.! 1 I?., .: mate control point or previous temperature setting. The standard _: (1'. decade THERMODYNE ranges are 50" IO 500°F. with CI nickel resistance thermometer; 400" to 1OOOOF with CI platinum resist- ance thermometer, and 1000" to 1500°F. with a platinum resist- ance thermomerer. ufher Klnges can be svppl,ed 01 exllu C">I. SPECIFICATIONS Case-The case is constructed of 18 gauge steel, with blue erlorrlalled "lli,ll, `rhc I,"lU pmcI i, %" Ju,ul",,,inu,~n with etched markings. Over-all dimensions are IO" wide, 7'1," high and 8" deep. A pilot light on the panel indicates the action of the control relay. Powcr~x wafts at 115 volt, 60 cycle, nc Contact rating-25 amps, 115 volts, AC non-inducrlve 20 amps. 220 volts, AC non-inductive Connections to case-Terminal board on back of chassis with removable cover on back of case. W&&--l 5 pounds _I ".-. r *

Decade THERMODYNE I'/ `,L e~,a