Operation And Maintenance Of 1P3060 Pyrometer Group{0776} Caterpillar

Operation And Maintenance Of 1P3060 Pyrometer Group{0776}

Usage:

All Engines

The 1P3060 Pyrometer Group is used to measure temperature on a scale of 0° to 1600° F (-18°C to 870°C). An iron-constantan thermocouple is used to generate a millivolt signal that is proportional to temperature. The pyrometer reads the output of the thermocouple and converts it to temperature. Thermocouples are self powered devices, so there is no need for batteries or other external source of power. Use of the pyrometer at ambient temperatures below 0° F (-18° C) will cause incorrect readings.

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NOTICE

Use care not to damage the thermocouple lead wire. Sharp bends can cause incorrect readings.

NOTE: The use of 8B1931, 3B7721 and 4M5317 Adapters will aid in the installation of thermocouples on Caterpillar engines.

1P3060 Pyrometer Group Specifications

Components Of The 1P3060 Pyrometer Group

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NOTICE

Turn the switch to "0" when the instrument is not in use.

1 The 1P3060 Pyrometer Group consists of box (1), 3H7974 Pyrometer (2), 6H3050 Thermometer (3), two 20639 Adapters (4), and two 8L4439 Thermocouples (5). The storage area of box (1) will hold eight thermocouples. The lead length of thermocouples (5) is 120" (3048); optional 1N7494 Thermocouples with a lead length of 480" (12192) are available from the Parts Department. All of the thermocouples have alloy connecting wires. Pyrometer (2) automatically compensates for the cold end temperature.

Use Of The 1P3060 Pyrometer Group

1 Place pyrometer (1) in a location free from excessive vibration.

NOTE: Turn the selector switch to (0) position when the unit is not in use; this dampens needle movement and the unit is less susceptible to damage from vibration or shock.

2 Install thermocouple (2)^*. One of the following adapter bushings may be required; 4M5317 - 1/8" × 1/4" NPT; 3B7721 - 1/8" × 3/8" NPT; 8B1931 - 1/8" × 1/2" NPT. The tip of each thermocouple should reach the center of the exhaust pipe or chamber; all tips should have the same spacing from exhaust ports. Refer to the chart on page 15 for probe installation location.

^*IMPORTANT: The fitting on thermocouple (2) is only initially adjustable. When sealing nut (3) is tightened, the ferrule is imbedded into the metal and cannot be repositioned.

3 With fitting (3) positioned as shown, thermocouple (2) will adapt to most exhaust systems.

4 When tube length-to-thread distance must be shortened, add a 20639 Adapter (4) as shown, or position fitting (3) to the correct length required.

NOTE: If additional 20639 Adapters (4) are needed, they must be drilled out with a .266" Ø (6.8 Ø) drill so they will slide over the .250" Ø (6.4 Ø) thermocouple tube. In situations where thermocouples are used temporarily in a number of engines where probe depth requirements vary, it may be advisable to have several thermocouples (2), each with a fitting (3) for various short length and long length positions. Additional fittings (3) can be made using a 1P3861 Connector, 3D8093 Nut and a 3D8094 Sleeve.

5 Fasten the thermocouple leads to the pyrometer; fasten white wire (+) to white terminal (+) and red wire (-) to red terminal (-).

NOTE: Approximately every six months or after rough handling of the instrument, check the reference junction temperature. See ADJUSTMENT OF REFERENCE JUNCTION TEMPERATURE.

6 Turn the selector switch to bring into the circuit whichever thermocouple is to be measured and then observe the pointer. Temperatures may be quite variable from engine to engine (same model) and from cylinder to cylinder. Factors that affect engine exhaust temperature are:

1. Air cleaner restriction

2. Exhaust restriction

3. Ambient temperature

4. Internal friction of the engine

5. Fuel rate, fuel system condition or settings

6. Altitude

7. Valve portings

8. Thermocouple condition

9. Thermocouple location

Consequently, exhaust temperature, by itself, is not a reliable method of determining engine condition. Pyrometers can best be used in detecting a temperature change from one inspection to another, or indicating a gradual increase or decrease in temperature over a period of time.

NOTE: If specific information is needed for temperatures expected for a particular engine, make reference to the Technical Information File.

7 When the pyrometer fails to respond to sudden changes in exhaust temperature, remove the accumulated carbon from the stem of thermocouple (2). Thermocouples can be checked by using an accurate ohmmeter across the leads; 120" (3048) lead 8L4439 Thermocouples should read 2.2 ohms and 480" (12192) lead 1N7494 Thermocouples should read 8.7 ohms.

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NOTICE

Never use a battery to test the pyrometer's circuitry. The excessive voltage will damage the unit. Never splice copper wiring to the thermocouple leads to obtain additional length. The copper wiring will alter the reference junction temperature, increase the lead resistance and cause the pyrometer to be inaccurate. Always keep the pyrometer free from excessive vibrations.

Adjustment Of Reference Junction Temperature

With the selector switch at (0) position, place the bulb thermometer (1) near the pyrometer terminals and allow the unit to stabilize for an hour, while the ambient temperature is stable and the instrument is shielded from drafts or direct radiation. If the thermometer reading and pyrometer pointer disagree, turn the cold end adjustment screw so the readings correspond. CAUTION: Never set the pyrometer pointer to zero (0) unless ambient temperature is actually 0° F.

Calibration Of The 1P3060 Pyrometer Group

The pyrometer of the 1P3060 Pyrometer Group is a millivolt meter that is calibrated in degrees Fahrenheit (° F), instead of millivolts (mV). A thermocouple (T/C) with a 3 ohm resistance, that generates a voltage proportional to temperature (not a linear function) is the signal source.

To calibrate the pyrometer, apply a millivolt signal, that corresponds to a temperature on standard iron-constantan thermocouple chart, to the pyrometer. This voltage must be developed across a 3-4 ohm resistance that simulates a thermocouple.

NOTE: Before calibration of the pyrometer group, adjust the reference junction temperature. See ADJUSTMENT OF REFERENCE JUNCTION TEMPERATURE in this instruction.

Make a calibration circuit like the one shown above. Component explanation is as follows:

1 - 12V DC - This can be a 12 volt automotive battery, or a bench power supply.

2 - 750 ohm resistor.

3 - Digital Voltmeter (DVM).

4 - R1 is a carbon potentiometer (volume control).

5 - White binding post.

6 - 1P3060 Pyrometer.

7 - 10 ohm resistors (three).

8 - Red binding post.

The 12V DC (1), is reduced to millivolts across the three parallel resistors (7), to simulate the output of a thermocouple with a resistance of 3.33 ohms. The R1 potentiometer (4) is adjusted until the DVM (3) shows the millivolt values given in the chart, and the pyrometer shows the corresponding temperature. If there is pyrometer error greater than ± 16° F, at any of the calibration points, the pyrometer must be returned to Alnor Instrument Company for repair. For repair service, return the pyrometer to:

Alnor Instrument Company
Repair Department
7300 North Natchez Ave.
Niles, IL. 60648
Telephone: (312) 647-7866

NOTE: For dealers that do not have the equipment to do this calibration procedure, the 1P3060 Pyrometer Group and the calibration information can be taken to most television repair shops to have the calibration work performed.

If a bench with an adjustable power supply is available, R1 can be zero ohms, and the power supply voltage can be adjusted to give the needed calibration voltages.