Hi.

We have numerous Siemens FX300 Vortex flow meters on site. Every few months these seem to loose power (Loop powered). After looking into this it seems to be due to the voltage been pulled down in the panel. As soon as I open the blades and put my meter to test the voltage it rectifies the problem, I push the blades back in and they power up.
Has anyone ever had this issue before in IO panels and if so what did they do to rectify the problem.

Thanks in advance for you help.

 

Do you have barriers in the middle?
Maybe a earth leakage (if there are barriers)...

 

> Do you have barriers in the middle?
> Maybe a earth leakage (if there are barriers)...

There no barriers or leakage units. When the field cabling is removed, I get 24 vdc out of the card (between +24 and 0v). When the field cabling is reintroduced, I get I get 19v between 24 and 0. The is 3vdc on the 0v wire with reference to earth.

Any help would be appreciated. One solution I guess would be to install an isolator but id rather find out the reason.

 

I guess somehow your current return path resistance is too high and that's why this 3V is generating in the return line.

Also a high current in the line may cause same type of problem.

1. check the port impedance (connecting a variable resistor alone (0-100ohm) apply 24Vdc in the port, and slowly decrease the variable resistance so that current increase in the port. In this situation measure the return line voltage wrt to earth. Increase the current up to rated capacity of the port and check the current value and return line voltage wrt earth.) this will clear where the problem lies, in cable or port. Please post the results.

2. if your meter draws exceptionally high current then similar condition also may arise however chance of this phenomenon is less.

 

> We have numerous Siemens FX300 Vortex flow meters on site.
> Every few months these seem to loose power (Loop powered).
> After looking into this it seems to be due to the voltage
> been pulled down in the panel. As soon as I open the blades
> and put my meter to test the voltage it rectifies the
> problem, I push the blades back in and they power up.
> Has anyone ever had this issue before in IO panels and if so

Have you measured the power supply output current? Perhaps it is cutting back on current limit and you need additional current capability.

A common way to add power supplies is to use one of the potted bridge rectifiers and run one PS to each ~ terminal then draw from the positive. Negative terminals are direct from the PS

If you have a bunch of fuses or breakers distributing the 24 Volts you can put your ammeter across then pull each fuse to measure the current draw in each circuit.