Very small gap and pressure affect

[smiles]

Don't sure this is the right forum for my thread because I am referring about a medical device that is blood analyser.

The problem of this device is it can't suck the blood sample in the pre-dilute mode. The blood will be attracted into a so-called White blood cell basin.

At that time, a plastic pot is at "negative pressure" and it connects to White blood cell basin via a valve. In the others way, the tube that sample will be attracted into also connect to that basin.

So when I test "ON" that valve while no using sample (means the tube is connected to air pressure. The basin get two pressure, "-" from the pot and "+" from air. And so in that test mode, another motor that control the flow of air then control the pressure of that pot will operate, its operation is something like "stop" then "run" then "stop" ... I was said that the reason is there are two kind of pressure in the basin.

Now if I stop the tube 's head then from theory, there is only "-" pressure, then anything in that tube will be sucked in the basin and the motor will operate at one state only but it still the same like before. I check and see no errors on the tube (also the tube connect the pot to the basin is still good) .

Now I discover that one screw make the basin crack like the crack on your glass for drinking, but I think that is very very small gap, so does it affect the pressure inside the basin ?

Thanks.

One more question, when you blow from A to B, then the pressure of A is greater than B caused of your action ?

[GDG]

First, a caveat: I have not used one of these devices before, nor examined their workings. Here is what I think you're talking about.

 

It sounds like you have a sealed chamber (the white blood cell chamber) with two ports: a vacuum/suction port, and an air port. It sounds like the device is designed to move your sample pneumatically, using air flow. If you only apply vacuum, all you are doing is reducing the pressure in the chamber. If you apply vacuum to one side and release air into the chamber, you get a flow of air that should move your sample.

 

As to whether the crack makes a difference, this probably depends on whether or not air can enter through the crack. I assume that you are not drawing a hard vacuum, so it is possible that this is not critical. But possibly it would be a good idea to have it fixed.

 

If this doesn't help, you may want to repost your question on the Medical part of the forums: possibly someone there will have experience with this type of device.