Chapter 9
Pressure Compensation
9.1Overview
This chapter defines pressure compensation and describes how to configure it.
Note: All procedures provided in this chapter assume that your computer is already connected to the transmitter and you have established communication. All procedures also assume that you are complying with all applicable safety requirements. See Chapter 2 for more information.
9.2Pressure compensation
The Model 1500 transmitter can compensate for the effect of pressure on the sensor flow tubes. Pressure effect is defined as the change in sensor flow and density sensitivity due to process pressure change away from calibration pressure.
Note: Pressure compensation is optional. Configure pressure compensation only if required by your application.
9.2.1Options
There are two ways to configure pressure compensation:
•If the operating pressure is a known static value, you can enter the external pressure in the software.
•If the operating pressure varies significantly, you can use the transmitter’s Modbus interface to write the current pressure value to the transmitter at appropriate intervals.
Note: If you configure a static pressure value, ensure that it is accurate. If you update the pressure via Modbus, ensure that the external pressure measurement device is accurate and reliable.
9.2.2Pressure correction factors
When configuring pressure compensation, you must provide the flow calibration pressure – the pressure at which the flowmeter was calibrated (which therefore defines the pressure at which there will be no effect on the calibration factor). Refer to the calibration document shipped with your sensor. If the data is unavailable, use 20 psi.
Two additional pressure correction factors may be configured: one for flow and one for density. These are defined as follows:
•Flow factor – the percent change in the flow rate per psi
•Density factor – the change in fluid density, in g/cm3/psi
Compensation
Measurement Performance
Troubleshooting
Defaults
Configuration and Use Manual | 77 |
