Nordson 303 779B, Руководство пользователя по изделию

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Profile Verification with Thermocouples
C 5-3
E
1998 Nordson Corporation
All rights reserved
303 779B
Issued 11/98
Manual 12-44
If you must calibrate the thermocouple, place it into the known, elevated
temperature source, and adjust the calibration recorder output matches
the known temperature. Zero the thermocouples again after calibration
to check for any changes. Repeat the process of zeroing and calibrating
until no more adjustments are needed. A calibration adjustment separate
from the zeroing adjustment should be located on the recording
instrument.
Make a number of checks to be sure the data collected during the testing
is valid. Frequently, the data required deals with the temperature
repeatability or uniformity across the board. In this situation, it is most
important to have consistent readings. Achieve this by taking as many
readings as possible with the same thermocouple, without physically
removing it from the board or altering it in any way. Since the test is
performed using only one thermocouple, errors resulting from using more
than one thermocouple are eliminated.
For instance, when temperature readings on the operator side and the
hinge side of the process cavity are desired, a thermocouple mounted on
one side of a board can be used. This thermocouple should be equal
distance from the leading edge and the trailing edge of the board.
Once a stabilized temperature profile on one edge of the board is
established, the board can be turned around and the profile for the other
side of the process cavity can be observed. Use this same procedure to
get temperature profiles for the leading edge and trailing edge of the
board. A valid temperature profile should be repeatable, within the
margin of error, at least three times. The standard margin of error for a
J-type thermocouple is
±
2.2
°
C (36
_
F) between 0
°
and 277
°
C
(32–530.6
_
F).
In other situations, accurate data concerning the actual temperature at a
point may be required. In this case it is better to measure the
temperature in one spot with more than one thermocouple to provide a
check of the absolute accuracy of the measurements. Run several tests
to get an average over time. Complete enough testing with each
thermocouple to get a stabilized profile. Data which is not within a
reasonable range of the average could be an indication of a
thermocouple problem and should be examined more closely.
A typical test board has six thermocouples attached to it, and by passing
the board through the oven in the four different orientations shown, a
complete profile of the oven can be evaluated. The temperature in each
position is measured by two different thermocouples. For example, the
temperature at the leading hinge side corner is measured by
thermocouple 1 in orientation A and by thermocouple number 6 in
orientation C.
5. Testing