FAQ #8
Q. How do I set the oven flow on a 491 MB base instrument?
A. Place the instrument in the Span position with the Flow toggle button pushed to display the flow amount on the panel meter. Dial the Dilution Flow Adjust knob counterclockwise until finger tight. The remaining flow amount seen on the display will be the oven flow. Turn the Oven Flow Adjust knob clockwise to increase the flow until it reads at least 0.10 slpm. This sets the required 100 cc/min of oven flow. Now turn the Dilution Flow Adjust knob clockwise to increase flow to your calculated level. When you switch to the Zero position you will be able to read the Dilution Flow setting only because the Oven Flow is vented and not metered.
In the Standby position, Oven Flow is also vented and dilution flow is stopped. In Standby there will be no flow displayed and the panel will read “0.00”.