Monarch Instrument DC1250 - Manual (Page 14)

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signal marked IN+, and a low or common signal marked IN-. The terminal marked Vo
is the Auxiliary voltage output used to drive external sensors at +5Vdc and a maximum
of 50mA. The terminal marked I+ is the 1mA current required for RTDs or resistors.
Any screen or shield (often the braided wire) should connect directly to the system
ground and is used to shield the low level input signals from induced noise pick up.
Connect the signal wires to the terminal block in the manner described above. Use wire
of adequate gauge to carry the signal. The mA input requires the use of an external 250
ohm shunt (Check with supplier). Thermocouples should be connected with
thermocouple wire of the same type as the input; the terminal block is the reference
junction. Connect any sheath or braid to the GROUND connection. RTDs have an
additional wire, the current source, which is connected to the terminal marked I+. See
Figure 2.4 .
WARNING: Unused inputs must have IN+ and IN- commoned together.
CAUTION: Never run signal and power or control wiring together in the same
conduit. This practice will prevent possible recording error due to induced signals
between lines. Route signal wires away from power wires at the rear panel.
NOTE: Ground cable shields at one end only to eliminate the possibility of
interference due to ground loop currents. When grounded transducers are used, the
shield should be grounded at the sensor end only.
2.3.3 Relay Output Connections
To prevent the possibility of electrical shock, use extreme
caution when wiring contact output connections. Hazardous
potentials may exist on contact output terminals that are
floating with respect to instrument ground.
WIRES FROM
REMOTE SOURCES MAY CONTAIN DANGEROUS
POTENTIALS. ENSURE ALL POWER SOURCES ARE
DISCONNECTED BEFORE WIRING RELAY CONTACTS.
The relay contacts are rated for AC or DC operation (Maximum recommended
voltage - 30 Volts.) Each relay has a set of potential free contacts. There is no polarity
to the terminals; it is a normally open contact that closes in alarm condition. These
contacts are internally suppressed for EMI/RFI and High Voltage transients resulting
from inductive loads. The relays may be programmed as fail safe, which means they
are energized in the “off” condition. This way if the power should fail the relays will open
into the alarm condition. See note below.
2.3.4 Digital Input
The digital input is optically isolated and is activated by an external dc supply of 5 to
12Vdc at 20mA. The input is via the DIGITAL INPUT + and
– terminals. The -
connection is the COMMON for the external input, while the + is the input for the
positive voltage.
The digital input may be used as an External Trigger to stop or start recording, or may
be used to change the sampling speed. Thus the unit can be set to record only when a
conveyor is running for example. The External Trigger may also be linked internally to
the optional Relay Output. This could be used as a remote "record active" indicator.
Refer to Sections on
Relay setup and External Input setup.
Note:
In order to fully comply with the CE EMC Directive 2004/108/EC cables to the
relay output and digital input should be looped through a ferrite (Type Steward
28R2025-0R0 or similar) close to the terminals.
WARNING
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