Rtd Current Calibration; Calibrating The Rtd Current; Connecting Resistance; Calibration Recall - Omega RD8800 User Manual

Chapter 6 Calibration

6.4 RTD Current Calibration

The ADC current source is used for RTD measurements and needs calibration for the RTD's.

6.4.1 Calibrating the RTD Current

The following procedure contains step-by-step instructions on Calibrating the Current source. A 250Ω ±0.05%
resistor must be connected across the + and - terminals of a free input and the current source return path C
must be connected to the - input terminal. The Recorder then applies 1mA of Current through the resistance to
Calibrate Current. These programming steps are discussed in menu order.
NOTE: Before Calibrating Currents, ensure that the Zero Calibration and 1.25 Volt Scale range has been
calibrated per the previous sections as this will affect the accuracy of Current Calibration.

6.4.1.1 Connecting Resistance

Select a free set of input terminals on the rear of the unit, or remove any connections
from the set of terminals to be used. Connect the 250Ω ±0.05% resistor across the +
and - terminals of this input and connect the Current source return path C to the - input
terminal (see Figure 6-1).
6.4.1.2 Calibrating the RTD Current
To Calibrate the RTD Current:
From the Hidden Menu use the UP (↑ ↑ ↑ ↑ ↑ ) or DOWN (↓ ↓ ↓ ↓ ↓ ) button to select ADC control and
then press the ENTER button. The only available option is Cal Adc so just press the
ENTER button. Use the UP (↑ ↑ ↑ ↑ ↑ ) or DOWN (↓ ↓ ↓ ↓ ↓ ) button to highlight Cal currents and
press the ENTER button. You will be prompted with "cal input? X". Use the UP (↑ ↑ ↑ ↑ ↑ ) or
DOWN (↓ ↓ ↓ ↓ ↓ ) button to select the channel input number (1, 2, 3, 4, 5 or 6) to which the
resistor is connected and press the ENTER button. You will be prompted with "APPLY
[resistor value]". To allow the Recorder to detect the actual value of the Current, press
the OK? button. A window will appear showing the reading of the Current connected.
Press the CAL. button. You will then be prompted with "Are You Sure?". Press the
CAL. button to continue the calibration or the NO button to abort. If the CAL. button is
pressed, the Recorder program will store the adjusted value from a nominal 1mA of
Current. Calibration of Currents is complete.

6.5 Calibration Recall

If the calibration equipment listed above is not available, the factory Calibration for the Zero Calibration and Scales
(sections 6.2 and 6.3) can be recalled. All channels will be recalled.
To Recall the factory Calibration:
From the Hidden Menu use the UP (↑ ↑ ↑ ↑ ↑ ) or DOWN (↓ ↓ ↓ ↓ ↓ ) button to select ADC control and then press the ENTER
button. The only available option is Cal Adc so just press the ENTER button. Use the UP (↑ ↑ ↑ ↑ ↑ ) or DOWN (↓ ↓ ↓ ↓ ↓ ) button
to highlight Cal recall and press the ENTER button. You will be prompted with "Are You Sure?". Press the YES
button to retrieve the factory Calibration settings or the NO button to abort.

6.6 Factory Set

This option is for factory use only and overwrites the default factory Calibration constants with the current ones in
the analog board. This makes the Current Calibration constants the default, and it is these values that will be
recalled when attempting to restore factory Calibration.
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Page 6-3
Figure 6-1
Calibration
Resistor
Connection