What products are involved in this article?
This article is based on the use of RCP (Rheonics Control Panel) connected to the SME (Smart Module Electronics) operating SRD, DVP, and DVM. Hence it can be used for any of these Rheonics sensors.
What is the purpose of this article?
Explain the process to get a temperature compensated density when it has a linear trend. Usual applications are with fluids with a linear dependency on temperature.
1. Temperature-compensated Density
Density, defined as the substance's mass per unit of volume is an important fluid property that has an increasing presence in monitoring processes and control systems.
Density is affected by temperature and pressure. For most liquids, the Density decreases with temperature. As pressure increases, the density of any stable material also increases, markedly in gases, and almost negligibly in liquids and solids.
In most cases, we want to monitor the fluid density at a constant reference temperature. If the process temperature isn’t constant, an additional source of error to the control system is added. To avoid the temperature dependence on the fluid’s density and truly monitor its consistency, the temperature compensated density is introduced.
To compensate for temperature effects, the Rheonics Control Panel offers the following models Linear, Polynomial, or ASTM functions.
2. Math model
The SRD sensor can measure inline and temperature. With the use of mathematical models, temperature compensated measurements can be obtained.
3. Checking the data
The first step to achieving a compensated density requires the user to take samples of density at different temperatures, these temperatures must be higher and lower than the operation temperature range in your process. Once enough data is obtained (to see the linear behavior), the user should define the reference temperature. For this example, the blue point (15°C) is used as the typical set-point temperature of the process line.
The following steps outline the correct procedure for data analysis:
3.1. Select the reference temperature and density from data obtained in tests. Here, reference temperature and density are highlighted in blue in the next Table, we want to create a correlation at 15°C where we expect a density of 1.00 g/cc.
|Temperature [°C]||Density [g/cc]|
Table 1. Data points from inline measurements.
3.2. Plot data points of Density vs Temperature to study the behavior of the data. In this scenario, a straight line can represent the data behavior.
Figure 1: Plot chart Density vs Temperature
4. How to load models into the Sensor electronics?
The calculation tab on RCP allows configuring the Sensor to run mathematical models for viscosity, density, and concentration. Expert mode needs to be enabled for this.
Figure 3. Calculation tab for the linear model of density.
The following steps are needed to load the models into the Sensor electronics:
Figure 6. Modbus TCP/IP register
4.2 Demonstration Video
Video 1. Configuration Density Linear model in RPC Software.