Max error without reference junction

In summary, the conversation discusses using a thermocouple as a temperature sensor inside a soldering handle and amplifying the voltage using AD623. The speaker mentions not being able to use an ice bath to set the reference junction at 0 degrees Celsius and instead using a table and formula to calculate temperature. They ask about the maximum error without using any compensation and mention the desired temperature range for regulation.
  • #1
Hammer
2
0
Hi I'm using thermocuple as a temp. sensor, it is inside soldering handle output is 0 mV (tested with digital voltmeter at range 200 mV) at room temperature.
I'll amplify that voltage using AD623

I cannot use Ice bath to set ref. junction at 0 deg C. I thought using table (ref junction at 0 deg C) and formula to calculate temperature.

My question is what max error without using any compensation will I have.

Will it be actual temp of soldering hand + room temp or will it be low error like +-1 deg C which will suit me (I don't need it to be so precise)?

I will regulate temp automaticly from 160 deg C to 460 deg C
 
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  • #2
Your thermocouples output is proportional to temperature change. So put you TC in a know temperatrue source (say boiling water) and note the mV reading. Then put it in another know temperature source (say ice water) and note this mV reading. Now you have your scale.
 
  • #3
Without a reference junction, the maximum error you can expect will depend on the type of thermocouple you are using and the accuracy of the amplifier. However, without any compensation, the error will likely be significant and could potentially be as high as several degrees Celsius. This is because without a reference junction, the temperature difference between the two junctions of the thermocouple will not be accurately measured, leading to a larger error in the temperature reading.

Using a table and formula to calculate the temperature can help reduce the error, but it will not completely eliminate it. The error will still depend on the accuracy of the table and formula, as well as any external factors that could affect the temperature reading, such as ambient temperature fluctuations.

To achieve a more accurate temperature reading, it is recommended to use a reference junction or a cold junction compensation circuit. This will help to accurately measure the temperature difference between the junctions of the thermocouple and reduce the error significantly.

In your case, where you do not need a very precise temperature reading, a maximum error of +-1 degree Celsius may be acceptable. However, it is important to keep in mind that the error could still be larger than this, especially at higher temperatures. It is always recommended to use a reference junction or compensation circuit for more accurate temperature measurements.
 

1. What is "Max error without reference junction"?

"Max error without reference junction" refers to the maximum potential error that can occur in a temperature measurement when a thermocouple is used without a reference junction. A reference junction is a point where the temperature is known and used as a reference to measure the temperature of the thermocouple. Without a reference junction, the measurement can be affected by ambient temperature changes, leading to potential errors.

2. How does the absence of a reference junction affect temperature measurements?

The absence of a reference junction can cause errors in temperature measurements because the thermocouple is not being compared to a known temperature. As a result, any changes in ambient temperature can affect the reading and lead to inaccurate measurements.

3. Is it necessary to use a reference junction for temperature measurements with a thermocouple?

Yes, using a reference junction is necessary for accurate temperature measurements with a thermocouple. Without a reference junction, the measurement can be affected by external factors and lead to erroneous readings. It is important to have a known reference point to compare the thermocouple temperature to.

4. Can the "Max error without reference junction" be reduced or eliminated?

The "Max error without reference junction" can be minimized by using techniques such as cold junction compensation, which involves measuring the temperature at the reference junction and using that as a correction factor for the thermocouple reading. However, complete elimination of the error is not possible without a reference junction.

5. Are there any other factors besides ambient temperature that can affect "Max error without reference junction"?

Yes, there are other factors that can affect "Max error without reference junction", such as the type of thermocouple used, the material of the thermocouple wires, and the accuracy of the temperature measuring device. It is important to consider all these factors when trying to minimize the error without a reference junction.

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