1640-IN-031-C-08
Page 102 of 104
Eurotherm/Barber-Colman
MACO Series Controller Installation
17. Application Guide for Sensors and Analog Signals
17.1 General
Machine mounted measuring sensors are required to interface with process
variables such as hydraulic pressure, plastic pressure, machine positions and
speeds. The output of these sensors is applied to inputs on the Analog I/O board
and used for display or control purposes. The following information is a general
guide to the type of transducers required by the MACO Series controllers. For the
best noise immunity, use sensors with large voltage swings and low resistance
potentiometers.
17.2 Hydraulic Pressure Transducers
The Analog I/O board has two pressure input channels (other channels may be
used for pressure input, but only two provide for calibration resistors). Typical uses
are ram hydraulic pressure and clamp hydraulic pressure (or melt pressure and die
pressure). The analog inputs on the MACO are specified at 0 to +10 Vdc, which
means that a high level output transducer is required (mV output types cannot be
used directly). An external power supply capable of providing ±14 to ±16 Vdc or
+24 to +32 Vdc at 45 mA will also be required.
17.3 Position Transducers
Position detection for the Ram, Clamp, Accumulators and Ejectors can be linear
potentiometers, magnetostrictive devices, or LVDTs. The analog inputs for these
inputs are also specified as 0 to +10 Vdc. Excitation voltage (+10 Vdc) for
potentiometers (2k to 10k Ohms) is supplied by the analog I/O board.
Operating voltage for these sensors must be provided externally. LVDTs are
generally used for short movements (up to 3 inches) and they are available from
a number of sources.
17.4 Tachometer
The tachometer input will accept up to +15 Vdc at 1kHz. Excitation voltage of +12
Vdc at 10 mA is supplied by the Analog I/O board. The measuring device will
typically put out a series of pulses proportional to the shaft RPM to which it is
mounted. Logic levels for the input are 3.1V ≤V High ≤ 15V; -0.6V ≤ Low ≤0.4V.
Pulses must not exceed +15Vdc and must not go lower than -0.6 Vdc.
17.5 Analog Outputs
The outputs from the Analog I/O board are specified as 0 to +10 Vdc or 0 to -10
Vdc. There are control relays which allow the output to be switched between the
two polarities as required. This allows the outputs to be used with a number of
different drives and devices. There are also Minimum and Maximum Output
setpoints which can be used to set the output signals to match specific drives. For
example: the maximum output can be set to 50% (5 Vdc) and the output applied
to a drive which has a full range of speed from 0 to 5 Vdc.
17.6 Extrusion/Parison Pressure Transducers
When the Analog I/O board is used in extrusion/parison applications, the same
requirements apply as for hydraulic pressure applications. The transducer must
provide a 0 to +10 Vdc output and an external regulated power supply must be used.
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