Advantage Controls MegaTron Installation, Maintenance And Repair Manual page 19

3.4 4-20mA Input Calibration
4-20mA inputs can be calibrated to insure 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.
>CURRENT LOOP CALIBRATION<
INPUT 1
INPUT 2
>mA INPUT 1 CALIBRATION<
20mA
4mA
MAX
LOW
OFFSET
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 scale 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 3750 and 4mA around 750. If the A/D numbers are
not in this range check input device.
The MAX and LOW calibration inputs are for telling the controller what to display for a 20mA input and a 4mA
input. For example if the input is a drum level sensor monitoring a 55 gallon drum the value for MAX should
be 55 and LOW should be 0. The controller then displays a number automatically ranging between 55 and
0 based on the input value. The units of measure (gallons for example) is set in the Customize menu from
the Home page.
OFFSET - Offsets current displayed value of the 4-20mA input reading to allow for a manual 1pt calibration.
4. Timers
A unit may have up to 5 selectable timers for each system on a controller. All timers are associated with their
system, so for a % of post bleed timer looks at the bleed of that system.
>SYSTEM 1 TIMERS<
TIMER 1
TIMER 2
TIMER 3
TIMER 4
TIMER 5
Select the Input to be calibrated
3750 INPUT 1 CAL HIGH
750 3750 A/D
200 PUT 20mA ON INPUT THEN
0 PRESS ENTER
DISABLED
TIMERS - Select the type (28-day, pulse, limit, percent
or percent of post blowdown) as well as the run times of
each timer available per system.
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>mA INPUT 1 20mA CAL<