Use and Operation
Thermocouples rely upon the difference in temperature between the measuring junction and a reference junction. Traditionally the reference junction is another thermocouple placed in an ice bath, however, the 80TK uses an electronic reference junction. The converter (80TK) must be operated in a thermal environment consistent with its specifications.
Measuring Technique
Making accurate temperature readings using a thermocouple is a matter of identifying and minimizing the causes of error. The largest contributor to errors is the thermal interface between the measurement surface and the thermocouple. The next largest contributor is the temperature difference between the thermocouple probe and its environment.
Here are some suggestions for improving the accuracy of your temperature measurements. Ensure that there is a good connection between the probe and the surface you are measuring. You can do this in many ways:
1.Increase the mounting pressure.
2.Use an interface agent (such as silicone grease) between the thermocouple probe and the surface you are measuring.
3.Use a thermal epoxy to attach the thermocouple.
When measuring temperatures higher than ambient, adjust the connection of the probe to the surface until you get the highest temperature reading. Use any of the suggestions given above to do so.
When measuring temperatures lower than ambient, adjust the connection of the probe to the surface until you get the lowest temperature reading. Use any of the suggestions given above to do so.
When measuring temperatures near ambient, make the reading when the multimeter display is most stable.
Warning
To avoid electrical shock, do not use this instrument when voltages exceeding 24V ac or 60V dc are present. The probe tip is electrically connected to the output terminals.
Temperature Measurement
Follow this procedure to correctly use the 80TK.
1.Plug the 80TK into the multimeter. Ensure that the banana plug with the red dot above it plugs into the voltage input and the other plug is in the COM input.
2.Set the multimeter to the 200, 300, or 400 millivolt range. This setting will read temperatures equal to the number of millivolts the range has (i.e., 320°C or F if the millivolt range reads 320 mV.
3.Use the dc volt setting and ignore the decimal for higher temperatures than can be accomodated by the millivolt range. Less resolution is available when using the volt range.
4.Plug the thermocouple into the 80TK thermocouple input connector. If the thermocouple does not have a plug attached, connect the thermocouple wires to the thermocouple input screws inside the 80TK. The yellow coded wire (chromel) connects to the screw marked ”+”.
5.Turn on the 80TK and the multimeter.
6.Adjust the thermal connection between the measurement surface and the thermocouple as described previously.
7.Read the temperature on the multimeter.
Open Thermocouple Reading
If the thermocouple probe has open circuited (i.e. is broken), the mulimeter will read a steady, constant voltage. The voltage readings are:
Range | Reading |
C | ³ 1.0V |
F | ³ 2.2V |
Battery Condition Test
1.Set the power switch to the OFF position.
2.Connect the 80TK to the multimeter.
3.Set the multimeter to the 200, 300, or 400 mV dc range.
4.Read the battery test voltage on the multimeter. A minimum reading of 75 mV is acceptable and indicates that approximately 100 hours of battery life remain.
Battery Replacement
Warning
To avoid electrical shock, remove the thermocouple from the measurement surface, or disconnect the thermocouple from the instrument before opening the case. Totally reassemble the instrument before attempting to use it.
1.Set the power switch to the OFF position.
2.Disconnect the 80TK from the multimeter.
3.Unplug or disconnect the thermocouple.
4.Turn the 80TK so the power switch is facing down. Remove the single screw located between the banana plugs.
5.Grasp one case half in each hand. Pull the two halves apart, beginning at the end with the banana plugs.
6.Remove and replace the battery.
7.Reassemble the 80TK.
8.To reassemble, mate the two case halves at the end with the thermocouple connector, then "hinge" the two halves together.
80TK Self Test
The following test is an easy way to verify proper operation of the 80TK:
1.Follow the Battery Replacement Procedure to open the case.
2.Using a short piece of bare wire, short the input thermocouple terminals together.
3.Plug the 80TK into the multimeter.
4.Turn the multimeter and the 80TK on. Set the multimeter to 200, 300, or 400 mV range.
5.The multimeter should read the ambient room temperature.
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