The calculation method of temperature compensation error of sapphire pressure sensor is not the same as that of the United States, Europe and other countries or domestic calculation methods. The calculation method of temperature compensation error of sapphire pressure sensor is not the same as that of the United States, Europe and other countries or domestic calculation methods. This is determined by the physical and mechanical properties of sapphire. Since the change in the input signal of the sapphire sensor is non-linear (approximately parabolic), the supplementary error specified in %/10 OC is not meaningful for this type of sensor.
If the temperature error is compensated by the microprocessor method, it must be clear that for the pressure sensor of the titanium-silicon sapphire principle, the temperature characteristics, whether it is the initial zero signal or the sensitivity, are parabolic, ie UT=Uo +AT+BT*T. Temperature characteristics cannot be described by means of linear functions.
Russia uses a method that specifies the range of temperature error ΔT to determine the temperature error.
The horizontal axis represents the temperature of the measured medium; the vertical axis represents the sensor input signal at a certain pressure.
The sapphire pressure sensor is not temperature compensated by point, but is temperature compensated at a certain temperature interval.
T0—This is the customer's measured media operating temperature (eg T0 is +1000C). It is at this temperature that the calibration of the sensor is performed, and at this temperature, its basic error (that is, the deviation between the actual curve and the ideal 4-20 mA) will not exceed that listed in the certificate. Error (0.1%, 0.2%, 0.50%). The temperature compensation is performed in the range of 50 OC ~ +150 OC, that is, within the interval of 100 degrees around the operating temperature. When the difference between the temperature of the measured medium and the operating temperature T0 changes in the low direction (temperature T1) or changes in the high direction (temperature T2), the output signal will change (as shown). At this time, an auxiliary error is generated. Also, the change in signal is non-linear (approximately parabolic). Therefore, it is meaningless to set the auxiliary error according to the %/10 OC method.
Here, a method of determining the auxiliary temperature error region ΔT is employed. When the temperature of the measured medium changes within a range of 100 OC around the operating temperature, the output signal will vary within the limits of ΔT.
Therefore, if the operating temperature of the transmitter is close to the operating temperature T0, the auxiliary temperature error is only (10/50) 2 = 1/25 ΔT.
If based on the temperature profile data (item 3 in the accompanying data sheet), draw a parabola through the three values of the initial signal (only one parabola), then any parabola can be calculated along this parabola Zero signal at temperature. Moreover, the deviation of these zero signals from the actual values is very small. Similarly, if the range of variation of the output signal (Umax-Uo) is calculated at 3 temperatures and a parabola is formed along these values, the value of the range at any temperature can also be calculated. If these two parabolas are stored in the microprocessor, the temperature can be compensated with extremely high precision. Data on temperature can be obtained by measuring the bridge resistance of the sensor.
October 10, 2023
