How to calculate and configure the Zero and Full scale value for a PM8000 Analog Input
Issue
Configuring the analog input on a PM8000.
Product Line
PM8000 series
Environment
Meter Configuration
Cause
Unlike other ION devices, the PM8000 analog input is only rated for 4-20mA rather than 0-20mA.
Resolution
Per the ION Reference, the Zero Scale can be calculated as follow:
Zero Scale = FullScale - (FullScale - X)(Af - Ax)/(Af - Aa)
where
The previous equation can be simplified to:
Zero Scale = FullScale - (FullScale - X)*(Af - Ax)/(Af - Aa)
Zero Scale = FullScale - (FullScale - X)*(20 mA - 4mA)/(20 mA - 4mA)
Zero Scale = FullScale - (FullScale - X)
Zero Scale = X
Therefore, the Zero Scale should correspond with the 4mA value.
For example, if a PM8000 meter is monitoring a 0 to 120 kW system and receiving the power information via a 4 - 20 mA analog signal, the PM8000 would need to be configured to have a Zero Scale of 0 and a Full Scale value of 120.
For instructions on programming the Zero Scale and Full Scale values, see attachment below.
Note: From firmware v3.0.0 the PM8000 has an optional Analog I/O (METSEPM890024) version 001.002.000 for 4-20 mA and 0-20 mA.
Configuring the analog input on a PM8000.
Product Line
PM8000 series
Environment
Meter Configuration
Cause
Unlike other ION devices, the PM8000 analog input is only rated for 4-20mA rather than 0-20mA.
Resolution
Per the ION Reference, the Zero Scale can be calculated as follow:
Zero Scale = FullScale - (FullScale - X)(Af - Ax)/(Af - Aa)
where
| Aa | is the analog hardware output minimum range value. | (For the PM8000, Aa is equal to 4 mA.) |
| Af | is the analog hardware output maximum range value. | (For the PM8000, Af is equal to 20 mA.) |
| Ax | is the analog hardware output minimum value. | (For the PM8000, Ax is equal to 4 mA.) |
| X | is the scaled equivalent of Aa. | (This is determined by the device sending the Analog signal.) |
The previous equation can be simplified to:
Zero Scale = FullScale - (FullScale - X)*(Af - Ax)/(Af - Aa)
Zero Scale = FullScale - (FullScale - X)*(20 mA - 4mA)/(20 mA - 4mA)
Zero Scale = FullScale - (FullScale - X)
Zero Scale = X
Therefore, the Zero Scale should correspond with the 4mA value.
For example, if a PM8000 meter is monitoring a 0 to 120 kW system and receiving the power information via a 4 - 20 mA analog signal, the PM8000 would need to be configured to have a Zero Scale of 0 and a Full Scale value of 120.
For instructions on programming the Zero Scale and Full Scale values, see attachment below.
Note: From firmware v3.0.0 the PM8000 has an optional Analog I/O (METSEPM890024) version 001.002.000 for 4-20 mA and 0-20 mA.