4.0 Current Loop I/O
The Emech current loop hardware is capable of operating across the standard 4-20mA range. By default the linear
control range, for both input and output, has been limited to the range of 5-19mA.
Values outside this range on the loop input represent non-linear behaviors such as closed, cold only or hot only.
Values outside the 5-19mA range on the loop output are used to signal error conditions. Contact Armstrong for
customized configuration settings
4.1 Standard Configuration of Current Loop Input for emperature Controller Mode
The unit will respond to the current loop input when in REMOTE mode only (Refer to section 6.4). The full control
range in Temperature Controller mode is 0-100°C or 32-212°F. This corresponds to a Loop Input range of 5 to 19mA.
Calibrate the current loop transmitter (usually an external PLC or Controller) according to the following equations.
Temperature Linear Range Calculation ° Celsius
Temperature Linear Range Calculation ° Fahrenheit
If given a signal outside the 5 - 19 mA range, the Actuator will not control temperature, but will move to a fixed angle
depending on the Actuator configuration. Refer to Figure 4.1 for a graphical description of Loop Input behavior in
Temperature Controller mode for several standard configuration types
4.0 Current Loop I/O
Current input (mA) = (0.14 x Temperature required (°C)) + 5
Current input (mA) = (0.0778 x Temperature required (°F)) + 2.511
WARNING !!
The voltage range required for the latest version actuators current loop input will vary from 3.5Vdc
for 4mA of current to 5.6Vdc for 20mA of current at the terminals. Therefore, the PLC controller
will need to be setup to provide at the actuator 3.5Vdc at 4mA to a maximum of 5.6Vdc at
20mA.
If the voltage at the actuator current loop input terminals exceed about 9Vdc or about 50mA
threshold, the input circuit protection will be activated and the current loop signal will be clamped
to ground. This has the effect of ‘locking out the PLC signal and closing the actuator on “loss of
signal”. This situation remains until the PLC signal is reduced below this threshold, whereby control
is restored. Therefore, the PLC controller must be setup to avoid sending a current loop
signal to the actuator of 50mA or higher.
Armstrong
International
221
Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Phone (269) 279-3602 Toll Free (888) HOT-HOSE (468-4673)
Designs, materials, weights and performance ratings are
approximate and subject to change without notice. Visit
armstrong
international.com/emech for up-to-date information.
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