How to check a Magflow meter?

[ricbritain]

I have a magflow meter which seem to have stopped working. It is giving spurious reading even when nothing is passing through it. I have removed it and not found any kind of coating or damage to the internal wall. We have ordered a replacement, however I am not sure if there is anything else I can check to be sure it is in some way damaged. It has been installed without issue for more than 10 years as far as I know.

I just wondered if there is anything I can check? I understand that there is an exciter and a measure circuit. Is there anything I can measure in terms of resistance?

I do not know the manufacturer as there is 10 years of pain covering everything.

Thanks.

 

[danw2]

Most magmeter vendors publish service data that includes coil resistance. Checking for coil short to ground is typical. Most also have a troubleshooting chart. But it helps to have the right manual.

Strange, impossible flow readings are actually normal in an empty magmeter. I had a 1" (25mm) tube powered up on the bench today and it showed 13-14 lpm flow rate with no liquid in the tube. It's fully functional. Works normally when the tube is full.

 

[ricbritain]

Thanks for that. It is reading wrong when in service as well as when empty. I am away from work at the minute but will try to find some data for it when I get back.

 

[zdas04]

danw2,
That is an odd reading for an empty tube. I almost always see some number that indicates all registers are full (something around 64k of whatever units it is calibrated to display) when a mag meter is partially full or fully empty. A number in the realm of reality is really quite scary.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[danw2]

David,

I agree. Siemens Mag 5000.

 

[roydm]

You can also measure the electrodes to make sure they are not grounded, should read infinity if the tube is empty. I have seen where just one grounded and the reading dropped to ~ 1/2

 

[jbr549]

Why would I care what a flow meter is reading when it is empty?
Unless the electronics has some version of empty pipe detection that would lock it to 4MA at a preset level, the tube output will jump all over the place when empty. Seems normal to me??