MOUNTING DIMENSIONS
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 main- tained. 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
Front View
(121 mm) 
(140 mm)
Side View
(108 mm) |
4 in. 
(102 mm)
Back View |
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Screw for | Remove Jumper(s) |
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Equipment Ground | to Install |
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| (121 mm) | ||||
| Thermocouple |
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TC1 |
| 120 |
| 120 | |
TC2 |
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| 1/4 in. |
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| (6 mm) |
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| typical |
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| (66 mm) |
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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.
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 thermocou- ple 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 out- put, 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.)
Table 1. Thermocouple Extension Wire Color Code
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Thermocouple | Thermocouple | Color Code/Material | |
Type | Extension Wire | Positive Lead | Negative Lead |
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J | Jx | White/Iron | Red/Constantan |
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K | Kx | Yellow/Chromel | Red/Alumel |
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Table 2. Thermocouple Extension Wire Loop Resistance in Ohms per Foot at 68°F
Size |
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Type “J” |
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| Type “K” |
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AWG No. |
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14 |
| .07 |
| .146 |
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16 |
| .137 |
| .230 |
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18 |
| .222 |
| .374 |
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20 |
| .357 |
| .586 |
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24 |
| .878 |
| 1.490 |
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Thermocouple lead length: 150 ohm lead resis- tance affects monitor accuracy less than 1°.