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512 HANDBOOK OF PROJECTION FOR
The right way to measure the temperature of a part is to bed the thermometer bulb in a ball of rather stiff putty, and then place the putty against the suspected part, leaving it a sufficient time for the putty to get as hot as the part is. This will cause the thermometer to accurately register the temperature of the part.
Roughly, as applies to projection rooms, we may say that any part that is not more than 50 degrees C (90 degrees Fahr.) higher than the actual temperature of the room, is not exceeding the above named limit, and unless this limit be exceeded, the equipment will not be damaged.
NOTE. — To reduce Centigrade to Fahrenheit (C. to Fahr.) multiply the degrees Centigrade by 1.8 and then add 32. For instance, assuming a temperature of 40 degrees C, how much is it Fahr.? 40x1.8=72 and 72+32=104 degrees.
THE HERTNER TRANSVERTER.— The Transverter needs no introduction. It is giving service in projection rooms all over this and other lands. The earlier machines were all of the "upright" type in that the armature stood vertical with the D. C. element at the upper end. With the addition of the later units of larger capacity these were made horizontal and at the present time all machines of 100 ampere capacity and higher are made horizontal while the smaller ones can be specified either way.
The trade name "Transverter" was originally limited to the series machines built by this Company for the reason that they were all of the series type from 1915 when the first was put in service until 1919, when the multiple machine was also produced. It was the intention then to limit the use of the word Transverter to the series type, but it was afterwards found that its use was so firmly tied in with both types of the Company's product that it is today applied to both.
In the series type the generator is shunt wound, the double arc machine being designed to maintain practically constant amperage under a variation of from 50 to 130 in voltage. In practice this means that the generator voltage rises from its normal of between 50 and 60 volts when one arc is operating, to from 100 to 130 volts when two arcs are burning, without causing any change in amperage. This is accomplished without the use of any resistance in series with the arc, the maintenance of constant amperage under variation in voltage being entirely automatic.
The motor is mounted in the same frame with and immediately beneath the generator. In all but the 20 and 30 ampere