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1560 Thermometer Readout
User's Guide
13.3.5
13.3.5.1
13.3.5.2
13.3.5.3
13.3.6
13.4
13.4.1
158
Suggestions for Optimum Accuracy
The sensitivity of thermocouple measurements, especially when using internal
CJC, requires that the user take certain precautions to ensure accuracy as ex-
plained in the following sections.
Warm-up Time
Measurements may change slightly as the 2566 module warms up after being
powered on. For best accuracy allow the 2566 to warm up for one hour before
making precision measurements.
Ambient Environment
When using internal cold-junction compensation the connectors and internal
sensors are sensitive to ambient temperature disturbances. The 2566 should be
operated in a stable environment free from large and sudden ambient tempera-
ture variations. The 2566 will also be more accurate if the ambient temperature
in which it is operated is close to the ambient temperature in which it was cali-
brated. Internal CJC is more accurate for the eight inputs near the center of the
module. Use these channels for more precise measurements rather than the four
inputs on the outside.
Thermal Settling
The process of removing and inserting thermocouple plugs into the 2566 pro-
duces temperature transients. This heat can cause a small error in the measure-
ment for up to two to four minutes after the thermocouple is plugged in. For
best results wait at least two minutes before making precision measurements.
Setup Parameters
The SET UP DEVICE function in the MODULE menu (see Section 5.4.2) al-
lows access to two setup parameters. SAMP PER selects the sample period be-
tween 2 (normal) and 10 seconds. POS shows the detected position of the
module in the stack. The purpose of these options is mainly for troubleshooting
and they should not need to be accessed or changed during normal operation.
Calibration
This section explains the calibration procedure for the 2566 Thermocouple
Scanner Module.
Calibration Parameters
Eighteen adjustable parameters are used for calibration. They are listed in Table
29.
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