Placing Of Pyrometers

: The Working Of Steel

When installing a pyrometer, care should be

taken that it reaches directly to the point desired to be measured,

that the cold junction is kept cold, and that the wires leading to

the recording instrument are kept in good shape. The length of

these lead wires have an effect; the longer they are, the lower

the apparent temperature.

When pyrometers placed in a number of furnaces are connected up

in series, and a multiple switch is used for control, it becomes

apparent that pyrometers could not be interchanged between furnaces

near and far from the instrument without affecting the uniformity

of product from each furnace.

Calibration can best be done without disturbing the working pyrometer,

by inserting the master instrument into each furnace separately, place

it alongside the hot junction of the working pyrometer, and compare

the reading given on the indicator connected with the multiple


Protection tubes should be replaced when cracked, as it is important

that no foreign substance is allowed to freeze in the tube, so

that the enclosed junction becomes a part of a solid mass joined

in electrical contact with the outside protecting tube. Wires over

the furnaces must be carefully inspected from time to time, as no

true reading can be had on an instrument, if insulation is burned

off and short circuits result.

If the standard calibrating instrument used contains a dry battery,

it should be examined from time to time to be sure it is in good