How to set Analog Output in I/O expansion board to use 4-20 mA instead of 0-20mA?
Title
Analog Output Scaling Formula and Calculation Method for Zero Scale and Full Scale
Language
English
Issue
Users need to calculate Zero Scale and Full Scale values when configuring analog outputs whose hardware output ranges differ from the receiving device’s expected input range.
Product Line
ION Meters
PM8000 Series
ION9000 Series
ION Setup
I/O expansion board
Environment
Meter configuration using ION Setup
Analog Output scaling
Cause
Analog output scaling settings must be calculated when the meter’s analog hardware output range does not match the receiving device’s signal range.
Resolution
The analog output module uses a linear relationship between the Source input and the hardware output. Scaling requires defining the minimum and maximum hardware output values and computing the corresponding Zero Scale and Full Scale values.
Definitions:
Aa = analog hardware output minimum range value
Af = analog hardware output maximum range value
Ax = analog hardware output minimum value
X = scaled equivalent of Aa
The mathematical relationship between the values is shown by the following equation:
(FullScale – X) / (FullScale – ZeroScale) = (Af – Aa) / (Af – Ax)
Example
A meter monitors a 0–120 kW system.
The receiving device requires 4–20 mA.
The meter’s analog output hardware range is 0–20 mA.
Variables:
FullScale = 120
X = 0
Af = 20
Ax = 0
Aa = 4
From the scaling equation, Zero Scale = −30
Full Scale = 120
These values produce a 0–120 kW output represented as a 4–20 mA analog signal.
After connecting to your meter in ION Setup, open setup assistant and navigate to Analog Out and choose which output you want to configure.
You can configure the Source, Zero Scale, Full Scale, and port to use for that Analog Output as below: