Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question dated 2020-09-02
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Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question No. 2020-09-02: Discussion question: 223. What is the difference between grounded and ungrounded thermocouples?
When the hot end of the thermocouple is in contact with the wall of the protective sleeve (which is equivalent to grounding), it is in less contact with the protective tube; as a result, the measurement lag is much smaller, and interference can also be reduced, thereby improving the reliability and accuracy of the measurements. However, whether the hot end of the thermocouple can be grounded depends on the structure of the input circuit of the secondary meter. For the hot end of the thermocouple to be grounded, the input circuit of the secondary meter must not share a common grounding point with the hot end of the thermocouple.
When the hot end of the thermocouple is in contact with the wall of the protective sleeve (which is equivalent to grounding), it is in less contact with the protective tube; as a result, the measurement lag is much smaller, and interference can also be reduced, thereby improving the reliability and accuracy of the measurements. However, whether the hot end of the thermocouple can be grounded depends on the structure of the input circuit of the secondary meter. For the hot end of the thermocouple to be grounded, the input circuit of the secondary meter must not share a common grounding point with the hot end of the thermocouple.
The main difference lies in the internal structure: the thermocouple-grounded protective sleeve is in electrical contact with the thermocouple, which is connected to the front end of the protective tube at the temperature measurement point； Fast response, but prone to interference ； High output, low cost: The ungrounded protective sleeve of the thermocouple isolates it from the thermocouple itself, with the temperature sensing junction and the protective tube being completely insulated as well ； The response is worse than that of the grounded type, but it is less susceptible to interference ； This type is usually used.
The main difference lies in the internal structure: the thermocouple-grounded protective sleeve is in electrical contact with the thermocouple, which is connected to the front end of the protective tube at the temperature measurement point； Fast response, but prone to interference ； High output, low cost: The ungrounded protective sleeve of the thermocouple isolates it from the thermocouple itself, with the temperature sensing junction and the protective tube being completely insulated as well ； The response is worse than that of the grounded type, but it is less susceptible to interference ； This type is usually used.
Published 10 hours ago | Follow only this author. When the hot end of the thermocouple is in contact with the wall of the protective sleeve (which is equivalent to grounding), it has less contact with the protective tube, resulting in much smaller measurement lag. This also helps to reduce interference and improve the reliability and accuracy of measurements. However, whether the hot end of the thermocouple can be grounded depends on the structure of the input circuit of the secondary meter. For the hot end of the thermocouple to be grounded, the input circuit of the secondary meter must not share a common grounding point with the hot end of the thermocouple
When the hot end of the thermocouple is in contact with the wall of the protective sleeve (which is equivalent to grounding), it is in less contact with the protective tube; as a result, the measurement lag is much smaller, and interference can also be reduced, thereby improving the reliability and accuracy of the measurements. However, whether the hot end of the thermocouple can be grounded depends on the structure of the input circuit of the secondary meter. For the hot end of the thermocouple to be grounded, the input circuit of the secondary meter must not share a common grounding point with the hot end of the thermocouple.
When the hot end of the thermocouple is in contact with the wall of the protective sleeve (which is equivalent to grounding), it is in less contact with the protective tube; as a result, the measurement lag is much smaller, and interference can also be reduced, thereby improving the reliability and accuracy of the measurements. However, whether the hot end of the thermocouple can be grounded depends on the structure of the input circuit of the secondary meter. For the hot end of the thermocouple to be grounded, the input circuit of the secondary meter must not share a common grounding point with the hot end of the thermocouple.
When the hot end of the thermocouple is in contact with the wall of the protective sleeve (which is equivalent to grounding), it is in less contact with the protective tube; as a result, the measurement lag is much smaller, and interference can also be reduced, thereby improving the reliability and accuracy of the measurements. However, whether the hot end of the thermocouple can be grounded depends on the structure of the input circuit of the secondary meter. For the hot end of the thermocouple to be grounded, the input circuit of the secondary meter must not share a common grounding point with the hot end of the thermocouple.