The MM1005 DC input alarm monitors
a 4/20mA DC input signal and trips a
dpdt relay when the input exceeds the
setpoint. Specifically designed for use
with two-wire and other 24 VDC
powered transmitters, the MM1005
contains an integral 24 VDC transmitter
power supply.
The MM1005 can be supplied as a HI
or LO alarm. The output relay is normally
energized, and de-energizes for an
alarm condition. This provides alarm
indication upon loss of power to the
alarm. A set of red/green LEDs
indicates alarm status.
A 25 turn deadband adjustment, allows
deadband settings between 0.5% and
100% of span. The deadband is
symmetrical about the setpoint.
OPTIONS
The following options are available on the
MM1005. Options installed are listed on
the label attached to the side of the module.
H/L
H = High alarm.
Alarm occurs on an increasing
signal.
L = Low alarm.
Alarm occurs on a decreasing
signal.
R
The Normal condition for the
relay is energized. It de-
energizes for an alarm condition
(Failsafe). Option R (Reverse
Sense) reverses this logic.
U
All circuit boards conformal
coated for protection against
moisture.
MM1005
4-20mA SINGLE ALARM
WITH 24VDC POWER
SUPPLY FOR TWO-WIRE
TRANSMITTER
SPECIFICATIONS
INPUT RANGE
4/20 mA
INPUT RESISTANCE
61.9 ohms
TRANSMITTER POWER SUPPLY
24 VDC regulated, 30 mA max
DEADBAND
0.5% to 100% of span
SETPOINT
0 to 100% of span
RESPONSE TIME
20 ms typical
OPERATING TEMPERATURE
14°F to 140°F/-10°C to 60°C
RELAY CONTACTS
(dpdt)
Resistive Load:
5 A max, 150 W max,
220 VAC max, 30 VDC max
Inductive Load
(Power Factor
³
0.4):
2.5 A max, 75 W max,
220 VAC max, 30 VDC max
POWER OPTIONS
115 VAC ±10%, 50/60 Hz
230 VAC ±10%, 50/60 Hz
(2.5 W max)
CONTROLS
The MM1005 alarm module contains two
adjustments: setpoint and deadband. No
other calibrations are needed.
CALIBRATION
Connect a 4/20 mA calibration signal to
the module input and set it for the
desired trip point. Turn the DEADBAND
control fully ccw. Adjust the SETPOINT
until the alarm trips (LED turns from green
to red).
Adjust the DEADBAND control for the
desired amount of deadband. Vary the
input signal up and down to check the
levels at which the relay trips and rests.
The setpoint will remain centered in the
middle of the deadband.
RELAY CONTACT PROTECTION
When inductive loads such as motors,
relays or transformers are switched,
voltage transients may be generated
which exceed the ratings of the relay
contacts. The resulting arcing can
quickly destroy the contacts. (Refer to
the SPECIFICATIONS below for the relay
contact ratings.)
Surge suppression is required across
inductive loads to guard against
premature relay failure. Figure 1
illustrates diode surge suppression for
a DC load. The diode's operating (peak
inverse) voltage should exceed the
load's supply voltage by at least 50%
and should have a current fating of at
least one ampere.
Figure 2 shows surge suppression for
an AC load, using an MOV (Metal Oxide
Varistor) and a capacitor. The
breakdown voltage ratings of both the
MOV and the capacitor must exceed the
peak AC voltage.
With normal sine-wave power, PEAK =
1.414 x RMS voltage. For 115 VAC
power a 200 volt peak rating is
recommended.
1
2
