Cameron NUFLO 1141C, User Manual

Page: 49 / 120

Chapter 3: Main Circuit Board Wiring
49
Magnetic Pickup Coil
(Non-incendive)
In this mode, the pulse input is directly
connected to a standard variable-reluctance
pickup coil. It is used on NuFlo gas and
liquid turbine meters and other meters of
similar design. The input uses a difference
amplifier that provides common mode
rejection, allowing the Scanner to operate
with accuracy in noisy environments.
Shielded cable such as Belden 9322 is
required.
Figure 3.19—DIP switch settings and wiring diagram
for a magnetic pickup coil output
Status Inputs and Outputs
Status input resources A03, A04, A05 and A06 are used to read the state of an external device, which can
be either passive (e.g. contact closures) or active where excitation is provided by an external source.
•
When a passive input is selected, an internal power source attempts to drive a 50-mA current through
the circuit. The voltage through this circuit is limited to 3.2 VDC.
•
When an active input is selected, the user can select a voltage threshold of 2, 7 or 10 volts. Below the
threshold, the input will be false (off); above the threshold, the input will be true (on).
Outputs are used for status (e.g. alarms) or pulse train (e.g. accumulated volume) and are selected via
ScanWin software. The circuits are suitable for a variety of end devices including small inductive loads
such as electromechanical counters. The output circuits have limited protection against inductive
“kickback” from such devices, but additional safety can be achieved by strapping a diode across the load.
Current requirements in excess of 100 mA require the use of interposing relays. Excitation should be
drawn from an external source.
Resources A03 through A06 are capable of both status inputs and outputs (Figure 3.20).