Operating Description

1. The USC701 will produce a 4-20mA output proportional to the Gas Flow Rate.
2. The Gas Flow Rate is calculated from the following equation:
   
   where the units are:
• Kg/sec for the Mass Flow Rate.
• m² for A the cross-sectional area of flow
• m/sec for v the gas velocity
• °K for T the temperature
• for R the Gas Constant
3. The Gas Constant has to be entered for the particular gas. This is done by configuring (con_e) in the Equation using the COA703 or changing "Gas Con" using the AM702 in trim mode. Some examples are:
• 0.287 (air).
• 0.189(CO₂).
• 0.297(CO carbon monoxide).
• 0.518 (CH₄methane).
• 0.276(C₂H₆ ethane).
4. The information for A the cross-sectional area of flow is entered at con_a using the COA703 or changing "Diam mm" using the AM702 in trim mode. For example, if the flow is in a pipe enter the diameter of the pipe (in mm). The USC program calculates the area in m².
5. The gas velocity input is via the Pulse Input P1 channel. The appropriate signal type and calibration is set in the P1 input section. For example, if the volume is 400 m³ /hr then the user must convert this to .
   This would be 22.1 m/sec in this example. This value is entered in the Eng. Units max.
6. The Pressure input is via the CH1 Input channel. The appropriate signal type and calibration is set in the CH1 input section. For example, the input might be 4-20mA representing 0-250hPa. This Eng.unit must be converted to kPa (in this case 0-25kPa).
7. The Temperature input is via the CH2 Input channel. The appropriate signal type and calibration is set in the CH2 input section. For example, the input might be 4-20mA representing 0-100°C. The USC converts this to °K.
8. The user can set the 4-20mA output to represent the required mass flow (eg 0-0.0337kg/sec).

Program Declarations

USC Programs

File	Comment
Help	If unexpected results occur when loading the .usc file press back and click on help for instructions.
UAP00351.usc	First Issue.