3-wire Flowmeter with 2 or 4 wire sensor

adilehanceanu

Hi!

As title says, I have to check/rewire 4 gass detectors that use a 3-wire connection, as you can see in attached picture(*). They were wired by someone else as some kind of 2 wire sensor (AI module inputs configured "2-DMU") and connected 1(+)<->2(M0+), 2(S)<->3(M0-) and 3(-)<->20(M). According to connection diagram of the sensor, I might say that is more likely a 4-wire sensor (but with sensor's L- supply conected to S- signal). I've searched in documentation but I couldn'd find any information of how 7KF02 is internally wired if "4-DMU" is selected because if I supply the detector from L+ and M and connect a 250 ohm resitor in series with a digital multimeter, I have correct readings between 2(S) and M, as it should be; the question is: it will work if I switch the module channels to "4-DMU" and connect the sensor as following: 1(+)<->1(L+), 2(S)<->2(M0+) and 3(-)<->3(M0-)<->20(M) ?

And how Mana should be connected?

Thanks you very much

Attachment:senseplus.jpg (44 Downloads)

Thank you very much, [b]H-H[/b] and [b]Pioneer[/b] (in my original post).

For those 4 sensors I had to use galvanic isolators because the signal was used also to drive another device, but now they want two more sensors, so I'll use your conection diagram.

Regards,

Adi Lehănceanu