Murphy MDTM89 User Manual
MDTM-8907N page 1 of 4
MDTM-8907N
Revised 10-07
Section 10
(00-02-0165)
Description
Murphy's model MDTM89 is an electronic, dual-temperature monitor. It monitors two thermocouples, displays the temperature of the
thermocouple selected, and has adjustable trip points for each input.
A toggle switch provides for selection of the thermocouple to be displayed and/or the temperature trip point to be checked/adjusted. If
either trip point is reached, the associated output “turns on” and can
be used as a control signal, or to initiate alarms and/or shutdown.
Specifications
Power Requirements (Operating Voltages):
MDTM89-A: 100 to 350
††
VDC, CD ignition, negative
ground (FET outputs).
MDTM89-B: 100 to 350
††
VDC, CD ignition, negative or
positive ground (SCR outputs).
MDTM89-C: 12 to 24
†
VDC, negative ground, 15 milliwatts
(FET outputs).
MDTM89-D: 120 VAC (MDTM89-C with 120 V isolation module #IT-1)
(FET outputs.) Model NOT approved by CSA or Factory Mutual.
Power Consumption: CD ignition: 350 µa @ 100V;
120 VAC: 0.6 watts; 24 VDC: 0.5 watts.
Outputs: Model B: output turns on above trip point; output turns off
when power is switched off; two (2) isolated SCR outputs, 0.5 amp
@ 250 VDC.
Models A, C and D: output turns on above trip point; output turns off
below trip point; two (2) isolated FET outputs, 0.5 amp @ 250 VDC.
Ambient Cold Junction Compensation Range:
32 to 122°F (1°C from 0 to 50°C).
Operating Temperature: -4 to 158°F (-20 to 70°C).
Storage Temperature: -40 to 300°F (-40 to 150°C).
Case: Die cast aluminum.
Reset Differential: FET models: Decreases 3 Degrees (°F or °C).
SCR model: turn input power off to reset.
Measurement Range: Monitor Range 0-1999°F or °C (specify “F” or
“C” in part number).
Accuracy: With J-type thermocouple: from 150-1200°F (66°-649°C)
±1.5% of reading. With K-type thermocouple: from 400-2000°F
(204-1076°C) ±1.5% of reading. At calibration temperature.
Laboratory Approvals: CSA
†
and Factory Mutual††approved for
Class I, Division 2, Group D, hazardous locations).
Thermocouple Lead Length: 150 ohm lead resistance affects moni-
tor accuracy less than 1°.
Trip Point Accuracy: ±3°F (±2°C) of reading.
Trip Point Adjustment Range: 0-1999 Degrees.
MDTM89 Interface Capabilities
Model Power Source Rating
LCDT CD Ign., 120 VAC, 12/24 VDC Cl.I, Div.1, Gr.D, Haz. areas
*
S1400 120 VAC or 12/24 VDC Cl.I, Div.1, Gr.D, Haz. areas
*
MARK II and IV CD Ignition, pos. or neg. grnd Cl.I, Div.2, Gr.D, Haz. areas
**
TATTLETALE
®
CD Ign., 120 VAC, 12/24 VDC Non-Hazardous areas
*
An isolation barrier is needed between the MDTM89 and an Annunciator rated for
Class I, Division 1, Group D, Hazardous Areas.
**
When used with approved ignition. Contact Murphy for details.
†
When used with approved ignitions or 12-24 VDC. Contact Murphy for details.
††
Approved for CD ignition, 80–250 VDC.
Instructions for Installation and Operation
Model Series MDTM89,
Dual Temperature SWICHGAGE
®
Please read the following information before installing. A visual inspection before mounting for any damage during shipping is
recommended. General information and installation instructions are intended for all MDTM89 Series models.
GENERAL INFORMATION
BEFORE BEGINNING INSTALLATION OF THIS MURPHY PRODUCT
✔✔
Disconnect all electrical power to the machine.
✔✔
Make sure the machine cannot operate during installation.
✔✔
Follow all safety warnings of the machine manufacturer.
✔✔
Read and follow all installation instructions.
†
††
WARNING
MDTM-8907N page 2 of 4
One Thermocouple Only
Even though the MDTM89 is a dual temperature monitor, it will monitor
and display one temperature with equal results.
When monitoring one temperature, always jumper the unused thermocouple terminals on the back of the MDTM89 with a short length of wire.
The unused channel will display approximate ambient temperature.
Open Thermocouple Input
An open thermocouple input forces the monitor into upscale overrange.
The monitor indicates an overrange by displaying the numeral “1” in the
left most digit of the display. An overrange will turn on the trip point output, for the respective thermocouple.
MDTM89 Wiring and Adjustment
Instructions
A. Using Thermocouple Extension Wire
1. After thermocouple installation, connect the thermocouple leads to
the MDTM89 according to the instructions.
IMPORTANT: Use correct wire for the thermocouple selected.
USE ONLY THERMOCOUPLE EXTENSION WIRE.
2. If the thermocouple leads are not long enough you will need to use
shielded thermocouple extension wire. The thermocouple extension
wires, from your thermocouple lead wires to the terminals of the
MDTM89, must be of the same material as the thermocouple lead
wires. (See Table 1.)
Mount the MDTM89 temperature SWICHGAGE
®
in a place where it
will be protected from rain and splashing water. A minimum distance of
12 in. (305 mm) from any ignition coils or coil leads should be maintained. The MDTM89 flush mount case is intended for mounting in a flat
panel .032 in. (1 mm) to .125 in. (3 mm) thick.
First, cut a 4-
3
/4 in. (121 mm) diameter hole and three
1
/4 in. (6 mm)
diameter fastening holes as shown below. Insert the SWICHGAGE
®
from the back side of the panel. Using the three 10-24 screws, included
with the SWICHGAGE
®
, secure to the panel.
Mounting Hole Pattern
JJxWhite/Iron Red/Constantan
KKxYellow/Chromel Red/Alumel
Table 1. Thermocouple Extension Wire Color Code
Thermocouple
Type
Thermocouple
Extension Wire
Color Code/Material
Positive Lead Negative Lead
14 .07 .146
16 .137 .230
18 .222 .374
20 .357 .586
24 .878 1.490
Table 2. Thermocouple Extension Wire Loop
Resistance in Ohms per Foot at 68°F
Size
AWG No.
Type “J” Type “K”
Thermocouple lead length: 150 ohm lead resistance affects monitor accuracy less than 1°.
Back View
Side View
Front View
MOUNTING DIMENSIONS
WIRING AND ADJUSTMENT INFORMATION
CAUTION:
Perform the wiring operation with the power source “OFF”. Make sure the voltage and current requirements are
within the SWICHGAGE®ratings. Keep all high voltage wiring, such as spark plug wires away from THERMOCOUPLES
AND EXTENSION WIRING. Before wiring determine the voltage and polarity for the application.
4-3/4 in.
(121 mm)
5-1/2 in.
(140 mm)
4-1/4 in.
(108 mm)
4 in.
(102 mm)
Screw for
Equipment Ground
Remove Jumper(s)
to Install
Thermocouple
TC1
TC2
4-3/4 in.
(121 mm)
120
120
2-39/64 in. radius
(66 mm)
1/4 in.
(6 mm)
typical
diameter
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