Walchem WebMaster ONE Instruction Manual page 82

Level should be selected if a continuous level transmitter is attached to that output. For point level
devices, which do not use a 4-20 mA signal, wire into and program with the Digital Inputs section.
Flow Meter should be selected if an analog flow transmitter is connected to that input.
Generic should be selected if the 4-20 mA transmitter connected to that input is anything other
than the previously mentioned ones. Later when you re-submit the 4-20 mA Input Page, you will
be able to name the input (for example, Phosphate or System Pressure) and also define the Units of
Measure (like mg/l or psi).
4-20 mA Input Calibration Menu
Set 4 mA
Following the instructions for your 4-20 mA transmitter, supply the WebMasterONE with a 4 mA
signal from each transmitter. You should verify that the transmitter is accurate by measuring the
output with an ammeter. You can read the present value of the mA signal as measured by the
WebMasterONE in the second column of the table. If the present value is not exactly 4 mA, click
on the "Set 4 mA" button. You will be asked to verify that you want to change the calibration.
Once this is done, the controller will read the transmitter signal as exactly 4 mA.
Set 20 mA
Repeat this process, supplying the WebMasterONE with a 20 mA signal from each transmitter,
and click on the "Set 20 mA" button in order to calibrate the controller.
1 Pt Cal (if not in Fluorometer Mode)
The 1-Point Calibration allows you to adjust the current reading of the process value to match
what the actual value is as measured by some independent method (such as a laboratory
measurement or handheld instrument). The software will maintain the "4 mA =" setting used to
scale the input, and adjust the "20 mA =" setting to make the reading accurate at the value entered
in the 1-Point Calibration. A new window will open when you click the 1 Pt Cal button.
Current mA
Displays a live reading of the mA output of the transmitter.
Current Value
Displays the live calculated process value, using the existing 4 mA = , 20 mA = and Units
settings.
New Value
Enter the desired new reading for the process value, and then click Continue.
At the end of the calibration, the display will tell you if the calibration was successful or if
the calibration failed. If successful, click Close to resume control. If failed, refer to Section
8 for troubleshooting help.
1 Pt Cal (Fluorometer Mode)
The 1-Point Calibration allows you to adjust the current reading of the process value to match
what the actual value is as measured by some independent method (such as a laboratory
measurement or handheld instrument). The software will maintain the "4 mA =" setting used to
scale the input, and adjust the "20 mA =" setting to make the reading accurate at the value entered
in the 1-Point Calibration. A new window will open when you click the 1 Pt Cal button.
Current mA
Displays a live reading of the mA output of the transmitter.
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