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8.2 Calibration Menu Functions
8.2.1 Reference Voltages
The calibration of the analogue inputs is based on the voltage of a temperature compensated voltage
reference integrated circuit. There are 4 voltages generated from the standard reference voltage. They will
vary by about 1% from one transmitter to another but can be trimmed by setting the actual voltages into
Calibration Menu functions #01 to #04.
8.2.2 Output Channel 1 and 2 Calibration
Options: Auto Calibrated / Manually Calibrated
Calibrate 4mA / Calibrate 20mA
Default:
Auto Calibrated
The analog 4-20mA output calibration can be set either Auto or Manual.
If Auto Calibrated is selected the transmitter will go through an output calibration cycle when the power is
turned on or when the A
input and automatically set the 4mA and 20mA calibration.
If Manually Calibrated is selected, then the 4mA and 20mA calibration must be set in the next two functions.
For the full explanation see chapter 10.1.2 Calibration of the Outputs.
8.2.3 Ambient Temperature Calibration
The ambient temperature measurement is used as the cold junction temperature for the thermocouple
measurements. Use an independent temperature sensor to measure the temperature inside the transmitter
case near the screw terminal #1. Enter this temperature into the calibration function 11 by using the O
buttons and then the E
NTER
8.2.4 Low Oxygen Calibration
Options: 80.0% to 120.0% in 0.1% increments
Default:
100.0%
The low oxygen calibration factors can be used to fine tune the oxygen calculation at low oxygen readings. It
will not affect the measurement at 20.9%. They are included to allow oxygen probes made by other
manufacturers to be used on a Novatech transmitter. The default is 100% but can be set to between 80 and
120%.
8.2.5 Reference Air Probe 1 and Probe 2
Options: Ambient Air or 0.1% to 25% in 0.1% increments
Default:
Ambient Air
The oxygen sensor measures oxygen concentration in the process gas relative to the oxygen concentration
in the gas exposed to the reference side of the sensor. In most installations the reference gas used is
atmospheric air, which has a (dry) oxygen concentration of 20.95%. In some specialised cases the
reference gas may be provided by other means such as gas generators or cylinders containing a fixed
oxygen content.
Warning: adjusting this number will affect the calculation of process gas oxygen. It is essential that this
setting be left on ambient air unless a specific certified oxygen gas is being used for reference air.
8.2.6 Transmitter Output Scale
Options: 0-20mA / 4-20mA
0-20mA over-scale limit / 4-20mA over-scale limit
Default:
4-20mA
The transmitter can drive the outputs to ~24mA for loads <700 ohms and by default the transmitter will allow
the transmitter outputs to transmit out of range (below 4mA or above 20mA) if the process variable scaling is
also out of range. To prevent the transmitter outputs from retransmitting out of range set this option to either
'0-20mA over-scale limit' or '4-20mA over-scale limit'
Technical Manual
46
C
button is pressed in the Setup Menu. This will divert the outputs back to the
UTO
AL
button.
PTION
August 2018
1732 Oxygen Transmitter
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