Problems with using thermocouples to measure temperature
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Using a multimeter to measure the temperature at the site with a thermocouple, the MV value is merely E(t,t1). What is the unknown value of t? t1 is the ambient temperature at the on-site junction box. Extended to the control room via compensation wires, it also involves the ambient temperature t2 at the cabinet. What is the calculation method when using an electrometer calibration table?
E(t,t1)=E(t,0)-E(t1,0) E(t,0)=E(t,t1)+E(t1,0) E(t,t1) is determined using a multimeter, while E(t1,0) is obtained from a table; once the values are known, the temperature of t can be found by referring to the table. As for t2, it doesn’t really make any sense; if t2 is to be used, then the value of E(t,t2) needs to be measured. The formula remains the same, with only t1 being replaced by t2.
For K-type thermocouples, here’s a formula that allows you to determine the approximate temperature without needing to consult a table: millivolts * 25 + room temperature
Could you explain the basis for this formula?
The temperature measured on-site is t1, but the DCS temperature compensation is based on t2; it’s not right to ignore t2