P R O G R A M M E D T E M P E R A T U R E R E G U L A T I O N BY M E A N S

OF AN A U T O M A T I C R E C O R D I N G P O T E N T I O M E T E R

(UDC 62-533.6)

N. P. B i r o n t

Translated from I zmer i t e l ' n aya Tekhnika, No. 7, pp. 62-63, July, 1965

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Fig. 1. 1) Moving bushing; 2) spring; 3) pres- sure roller lever; 4) brush KI; 5) pressure roller; 6) current collectors; 7) brush Kl; 8) stationary contact of brush Kl; 9) stat ionary contact of

brush KI; 10) stationary bushing; 11) l ead-ou t

wire from the stationary contact.

~-~ 22J V ~ ~,s ~f~ t-~ I "~ ~2~ v

eo "~ 22ov Fig, 2,

In the hea t t reatment of cer ta in mater ia l s and finished ar-

ticles, it is necessary to measure the temperature of an oven at a given rate. Thus, in drying thermal cements , the rise of t e m -

perature in the oven should not exceed 5 ~ per minute with ex- posures at 50 ,100 , 150, and 200~ In order to fuse glazing, i t is necessary to raise the temperature by 5-6 ~ per minute up to 850~ with an exposure at that temperature for 2 h. Existing

regulators, types TYP-720, PRS, PR provide programmed t e m - perature control up to 200~ These regulators are rather c o m - plex and are expensive to manufacture.

In this a r t ic le a s imple method of programmed t empera - ture regulat ion by means of a PSR-1 automat ic recording poten- t iometer with a joint ly ca l ibra ted KhA thermocouple is described.

The control program is set on the tape chart by punching holes with different in teraxia l distances. S i lver -p la ted strips with leadout wires are inserted into two grooves 15 m m long and 2.5 m m wide which are cut in the stat ionary bushing of the tape-

propell ing mechanism. The pressure roller of the mechanism is provided with two sliding brushes (Fig. 1).

The chart is propel led between the stat ionary bushing and the roller with its contact brushes, The speed of tape propulsion is chosen by the operator from a table. The most convenient

speed for a programmed temperature control amounts to 6.7 �9 10 -s m / s e e . The regulator 's operation amounts to the fol low- ing. A roll of chart tape with a given tempera ture- regula t ion program is inserted into the tape-prope l l ing mechanism, and a

synchronous motor is switched on for propel l ing the paper by means of the driving bushings�9

When contact K 1 (Fig. 2) drops into a hole punched in the chart tape, re lay P operates and disconnects with its contacts KP the winding supply circui t of magne t ic starter MS, thus discon-

necting the mains from the e l ec t r i ca l oven. However, the t em- perature in the oven will st i l l rise owing to its thermal inertia�9 The chart wil l continue to be displaced. When contact K 1 is broken, re lay P becomes de-energ ized and connects with its con-

tacts KP magnet ic starter MS, which in turn switches on the supply to e tec t r ic oven R 0. Thus, i t is possible to set the

required oven-heat ing program on the chart tape.

In order to mainta in the art icles for a certain t ime at a given temperature and then raise the temperature st i l l

further, the posit ional regulat ing device of instrument PSR-1 is used.

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Contact KP z of the posit ional regulator remains closed until the required temperature is reached. For instance, if it is necessary to expose the ma te r i a l at a temperature of 900~ for 2 h, the posit ional regulator disc for contacts KP~ is set to break them at 890~ After the breaking of contact KP z, the temperature is controlled by the posit ional regulator contact KP r

The posit ional regulator disc is provided with a temperature setting at 900~ In order to ensure the changing over from posit ional temperature regulat ion to a further rise of temperature, a second sliding contact K 2 is used for

shunting KP I and thus switching in the oven supply.

The posit ional regulator discs continue rotating and after a certain lapse of t ime close their contacts KP t and KP 2. Contact K s is then disconnected. A further rise in temperature is provided by the program set on the chart tape and positional discs.

The error of the programmed temperature regulation does not exceed ~ 1.0% of the fu l l - sca le deflection.

The operat ion of the above programmed regulator has proved to be successful.

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