Honeywell ERX, User Manual, Page: 22 / 84

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Two-Point Temperature Calibration
A Two-point Temperature Calibration requires that two different temperatures be applied to the
instrument's temperature probe and be sampled by the data acquisition circuits. A low
temperature source, usually a 32 degrees F ice bath is used to determine the Temperature Zero
Calibration. A higher temperature source is used to determine the Temperature Span Calibration
(gain). The default calibration parameters require the Span Temperature exceed the Zero
Temperature by at least 15% of the instrument temperature range.
The temperature probe provides a nonlinear, but very predictable temperature response for all
rated temperatures. The instrument's firmware chip contains the required information to produce
a linear temperature response for any connected temperature probe. The Two-Point Calibration
process uses the temperature offset and temperature span values to adjust for individual
variations. Once these two points have been calculated and stored in memory, all other applied
temperatures can be determined by a linear interpolation.
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