Questions about the compensation principle of the Rosemount temperature variable ambient temperature bridge?
Thread Content
RT, please explain the principle of the temperature transmitter’s built-in cold-end compensation bridge circuit.
Don't think about the complexity. Who still uses the bridge compensation circuit found only in textbooks for current temperature transmitters? It basically uses PN junction compensation. First, the circuit is simple, low cost, and the effect is good. I guess the built-in one on the second floor is also a PN junction.
After replying to the post, I saw that the poster posted two posts about this matter and has been asking questions about the bridge compensation circuit. In view of the poster's implementation, I will provide another piece of information for the poster to learn from.* .
Thermocouple bridge compensation uses the unbalanced potential generated by the temperature change of the bridge as the compensation potential for compensation. In the bridge in the figure below, there is a resistor Rt in the bridge arm whose resistance changes with temperature. When the ambient temperature is equal to the compensation temperature (for example: 25℃), the bridge is balanced. The potential at the +- terminal of the bridge is zero ； When the ambient temperature deviates from the compensation temperature, Rt changes and the bridge becomes unbalanced. At this time, a potential will be generated at the +- end of the bridge ； Select the resistance value of each bridge arm resistor so that the potential generated by the bridge circuit with temperature changes is equal to the required compensation potential, which can play a compensation role. Thermocouple bridge compensation is rarely used now due to the large errors caused by the discreteness caused by the manufacturing process.