Advantage Controls MegaTronMT Installation Maintenance Repair Manual page 23

3.4 4-20mA Input Calibration
If a mA Input is receiving an A/D value 50% below the stored value for 4mA, the reading is viewed as invalid,
and control logic is suspended. This is represented on the RUN screen with a #.
The MAX and LOW calibration inputs define what to display for a 20mA input and a 4mA input. For a
drum level sensor on a 55-gallon drum, the value for MAX should be 55 and MIN should be 0. A number is
automatically displayed between 55 and 0 based on the input value. The scale and units of measure (gallons
for example) are set in the Customize menu from the Home page. If the decimal position is changed in
Customize, all mA input settings and MIN/MAX will need to be reset.
OFFSET - Changes the current displayed value of the 4-20mA input reading to allow for a manual 1pt
calibration of the displayed value.
FACTORY DEFAULT - If the 20mA or 4mA calibration has been incorrectly set (not at 4 or 20) this will reset
the settings back to a factory value for 4 and 20.
While in the High or Low calibration pop-up screen use
the up and down arrows to change the output value
being read with the voltmeter. Adjust the High value
for the 20-mA reading and the Low value for the 4-mA
value.
4-20mA inputs can be calibrated to ensure that the
input seen by the controller from the external device
match. It also allows for setting the 4-20mA input into
a number range that relates to the value being read.
Select the Input to be calibrated.
Firmware version MT.16.03 and newer have logic that
suspends any control logic if the mA received is 50%
below the stored 4mA value. A # will be placed in the
RUN screen for any mA value in this invalid state.
The 20mA and 4mA values are where the controller's
raw analog to digital value is adjusted to match a 20mA
(full scale) and 4mA (bottom of scale) signal from
the external device inputting the 4-20mA input. The
external device must be connected to the controller and
showing either full or bottom of scale when calibrating
each. The number shown along with either the 20mA or
4mA while calibrating is the raw A/D value, and is only a
reference. A 20mA input should be around 5,500, and
4mA around 1,100. If the A/D numbers are not in this
range, check the input device.
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