small volume flow monitoring
small volume flow monitoring
(OP)
I need to find a flow meter that will allow me to program a low and high setpoint window, and turn on an output if the flow is not within the setpoint window.
The flow is quite small. Maybe about 3 CFM
The cycle time is about 15 seconds.
And did I mention that the flow to monitor is vacuum?
Any Ideas?
The flow is quite small. Maybe about 3 CFM
The cycle time is about 15 seconds.
And did I mention that the flow to monitor is vacuum?
Any Ideas?





RE: small volume flow monitoring
Search on the net for "mass flow sensors", you will find interesting stuff. These are the type of sensors like those used in cars for the correct air-gas mixture.
RE: small volume flow monitoring
You talk about a vacuum. How much of a vacuum? What are the residual gases? What is the allowable composition of residual gases? You are likely to be looking at an ionisation flow meter. What ions are allowable in your residual gas composition? Don't look at this problem as a simple component selection process. Look at it as an applied physicist. Every measurement effects everything else. What can you live with?
RE: small volume flow monitoring
What you need to do is serach for a flow transducer that will work in your environment and give you a 4-20ma or 0-10VDC output in the range you need to measure. The fact that is is in a vacuum is important only as an environmental consideration. It will still be the movement of air (or some other gas?) through the transducer that you want to measure right?
"Venditori de oleum-vipera non vigere excordis populi"
RE: small volume flow monitoring
The vacuum source is a vacuum pump with a storage tank. Before the vacuum flows it would be at a level of about 20"Hg. the "gas" is just plain air (and what ever is floating in it) The vacuum is drawn through some channels, but is basicly drawing from open atmosphere.
All I'm really concerned about is tracking wether or not the flow falls between the Hi and Low setpoint values by having an NO or NC contact actuate if flow is outside of the setpoint window.
RE: small volume flow monitoring
"Venditori de oleum-vipera non vigere excordis populi"
RE: small volume flow monitoring
We use vacuum to help reduce the gas burns within the mould while plasticizing. I'm mainly interested in making sure that if there is no flow, or very little flow that there there would be some kind of warning or alarm to indicate that the vacuum isn't working properly.
RE: small volume flow monitoring
h
"Venditori de oleum-vipera non vigere excordis populi"
RE: small volume flow monitoring
to a 1/4 watt resistor. The reistor would be placed outside the air flow path but close enough to the thermistor to
increase its sensitivity. As air flowed past the thermistor,
its resistance would change. The output from a bridge could
be fed to a window comparator.
Some thermistors are so sensitive they can detect very
small amounts of current flowing thru a resistor.
RE: small volume flow monitoring
RE: small volume flow monitoring
use self-heating termistor
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