Cameron NUFLO MC-III, Руководство пользователя

Страница: 31 / 120

31
MC-III™ Panel Mount Flow Analyzer Section 3
Configuring the 4-20 mA Rate Output
Caution: Before performing any 4-20 mA configuration, ensure that all peripheral equipment
connected to the 4-20 mA current loop is either disconnected or disabled. Configur-
ing and testing the 4-20 mA output feature on the MC-III Panel Mount with the peripheral
equipment in operation may cause false alarms or erroneous operation of the peripheral
device or associated equipment.
The MC-III Panel Mount has a 4-20 mA output feature that represents flow rate. Zero and full-scale values
can be configured to represent any flow rate range within the range of the flow meter.
The low (or zero) setting is the flow rate value that will produce a 4-mA output. The high (or full-scale)
setting is the flow rate value that will produce a 20-mA output. Typically, the high value is greater than the
low value; this scenario is defined as “direct mode” in Figure 3.1.
Alternatively, users may configure the 4-mA and 20-mA outputs to have an inverse relationship, such that the
high value is less than the low value. This scenario is defined as “indirect mode” in Figure 3.1.
Figure 3.1—Two options for configuring a 4-20 mA output
See Section 2 for instructions on installing and wiring the 4-20 mA rate output.
Flow rates in-between the minimum and maximum rate setpoints will result in an output of current between
4 mA and 20 mA according to the following calculation: