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The 3095 multi-variable transmitter can simultaneously measure the differential pressure, static pressure, and process temperature variables necessary for calculating flow rate. Changhui Instruments has prepared a tutorial on calibrating the 3095 multi-variable transmitter (http://yunrun.com.cn/tech/2395.html) to help instrument technicians make the most of this transmitter. Calibration of the Rosemount 3095 multivariable transmitter can be performed using the 3095 EA (Engineering Assistant) HART software, or via a HART handheld device. Changhui Instruments recommends using the HART475 handheld communicator for the quick calibration of 3095 multivariable transmitters. Changhui Instruments describes in this article the equipment required for calibrating the 3095 multivariable transmitter, as well as the specific steps for calibrating the temperature, pressure, and differential pressure sections of the 3095 multivariable transmitter. http://yunrun.com.cn/upload/201903/04/201903042034067365.png 1. Standards for calibrating the 3095 multi-variable transmitter: ① Precision resistance box: accuracy of 0.01 level; ② Digital pressure controller: range 0-20 kPa, accuracy of 0.01 level; ③ Digital pressure controller: range 0-3500 kPa, accuracy of 0.01 level; ④ 1 HART475 handheld device; ⑤ 1 24V DC power supply; ⑥ Accessories for connecting the digital pressure controller to the 3095 transmitter. 2. Known parameters of the 3095 multi-variable transmitter: The parameters vary depending on the model of the 3095 multi-variable transmitter. The parameters of the 3095 multi-variable transmitter mentioned in this article are as follows: ◆ Temperature: -40°C to 60°C; ◆ Differential pressure: 0-16 kPa; ◆ Absolute pressure: 101.325-2101.325 kPa. 3. Calibration method for the 3095 multi-variable transmitter: ① Connect the 3095 multi-variable transmitter to the HART475 handheld device as shown in the diagram below, and properly connect the DC24V power supply to the 3095 transmitter. Turn on the power supplies for both the DC24V and HART475 devices. Click the HART function on the HART475 communicator; if the “online” button is displayed, it means that the 3095 is properly connected to the HART475 communicator. ②Using the main menus of the HART475 handheld device: To access the menu of the HART475 handheld device, sensor calibration is primarily carried out in the “Sensor Trim” menu. Follow these steps: Click on the “Online” menu to enter the “Device Setup” menu tree, select “Diag/Service”. Under the “Diag/Service” sub-menu, there is an option called “Calibration”. Enter this “Calibration” menu and select “Sensor Trim”. In this menu, you can find options for “DP Sensor Trim” (differential pressure sensor calibration), “GP Sensor Trim” (gauge pressure sensor calibration), and “Temp Sensor Trim” (temperature sensor calibration). Each of these 3 menus contains 4 sub-menus: “Display X sensor”, “Trim X sensor”, “Factory X sensor”, “Zero X sensor”. These 4 menus allow you to view the ranges of the temperature, differential pressure, and pressure sensors; thereafter, linear calibration can be performed using the two-point method, enabling real-time monitoring of the parameters. ③For the temperature calibration of the 3095 multivariable transmitter, select “Display Temp sensor”; the temperature range of this 3095 multivariable transmitter is -40℃ to 60℃. Connect the 4 thermistor wires of 3095 to the precision resistor box. Enter “Trim Temp sensor”. Select the temperature unit as “℃”, and use the thermistor calibration table for linear calibration; the “offset” setting is used for zero-point calibration. According to the calibration table, the resistance value at -40℃ is 84.27Ω. Adjust the precision resistor box so that its value is 84.27Ω, then click “Enter” on the HART475 handheld device to confirm the zero point. "\"Slope\" is used for full-scale calibration; referring to the scale table, the resistance value corresponding to 60°C is 123.24Ω. Adjust the precision resistor box so that its value is 123.24Ω, then click \"Enter\" on the HART475 handheld device to confirm the full scale – thereby completing the two-point calibration of the temperature sensor. ④Calibration of the differential pressure section of the 3095 multivariable transmitter: Keep the transmitter level, open the balance valve of the 3095, and connect the output terminal of the digital pressure controller to the H terminal of the 3095 multivariable transmitter. Select “Display DP sensor” to see that the differential pressure range of this 3095 multi-variable transmitter is 0-16 kPa. Enter \"Trim DP sensor\", select the differential pressure unit as \"kPa\", and perform linear calibration; \"offset\" is used for zero-point calibration. Under atmospheric conditions, 3095 is set as the default zero point. Click “Enter” on the HART475 handheld to confirm the zero point. "\"Slope\" mode is used for full-scale calibration: a standard pressure of 16 kPa is set on the pressure controller, and once the pressure stabilizes, the \"Enter\" button on the HART475 handheld device is used to confirm the full scale, thereby enabling two-point calibration of the differential pressure sensor. ⑤Calibration of the pressure section of the 3095 multivariable transmitter: Turn off the balance valve of the 3095, and use a tee to connect the output terminal of the digital pressure controller to both the H and L terminals of the 3095 multivariable transmitter. Select “Display GP sensor” to view that the pressure range of this multivariable transmitter is 101.325–2101.325 kPa. Enter \"Trim DP sensor\", select the differential pressure unit as \"kPa\", and perform linear calibration; under atmospheric conditions, 3095 is set to atmospheric pressure by default. “\"Slope\" refers to full-scale calibration: a standard pressure of 2000 kPa is set on the pressure controller, and once the pressure stabilizes, pressing \"Enter\" on the HART475 handheld device confirms the full scale, thereby enabling two-point calibration of the pressure sensor. If it is necessary to calibrate the atmospheric pressure, this is done through “ATM press cnfg”. ⑥For the calibration of instantaneous flow rate calculation in the 3095 multivariable transmitter, go to the first sub-menu under the “Device Setup” menu, namely “Process Variables”, and then select “View FID Dev Values” to view the instantaneous parameters: 1: DP differential pressure, 2: AP absolute pressure, 3: TEMP temperature, 4: GP gauge pressure, 5: Flow instantaneous flow rate, 6: Flow Total cumulative flow rate ； At this point, the SY/T6143 standard is used to verify whether the flow rate calculation is accurate. The formula for the calculation error is as follows: △ = (Qm – Qs) / Qs × 100%. In this formula, △ represents the calculation error of the instantaneous flow rate of the 3095 multi-variable transmitter ； Qm is the theoretical flow rate calculated according to the SY/T6143 standard ； Qs is the actual flow rate displayed by the 3095 multivariable transmitter. If an error occurs, it indicates that there may be vulnerabilities or errors in the calculation program embedded within the 3095 multivariable transmitter. Using the HART475 handheld communicator to connect the 3095 multivariable transmitter is fast and portable, allowing for quick parameter reading, resetting, low-flow cutoff, and configuration on-site. By using a standard orifice plate in combination with a 3095 multivariable transmitter to form a differential pressure flow meter, the drawback of the narrow range ratio (3:1) of standard orifice plate flow meters is overcome, **improving the accuracy of measurement.