User manual

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Section 4 MC-III™ EXP Flow Analyzer
4-20 mA Output
Caution: Before performing any 4-20 mA calibration, ensure that all peripheral equipment con-
nected to the 4-20 mA current loop is either disconnected or disabled. Calibrating and
testing the 4-20 mA output feature on the MC-III EXP with the peripheral equipment in
operation may cause false alarms or erroneous operation of the peripheral device or as-
sociated equipment.
The 4-20 mA Output screen (Figure 4.28) allows users to congure the MC-III EXP to provide a 4-20 mA
output representing ow rate. Zero and full-scale values can be congured to represent any ow rate range
within the range of the owmeter. A test mode function is also included, allowing a user to calibrate and/or
verify the output received by an end device.
Figure 4.28—4-20 mA Output screen
The low (or zero) setting is the ow rate value that will produce a 4-mA output. The high (or full-scale)
setting is the ow rate value that will produce a 20-mA output. Typically, the high value is greater than the
low value.
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:
[ ]
[ ]
MAX MIN
OUT CURR MIN
I I
I RATE Low I
High Low
−
= × − +
−
Where:
I
OUT
= output current
I
MAX
= maximum current output (20 mA)