Sharing a shunt with other devices

[DevoDave]

Hi,

Are there any inaccuracies introduced when more than one device is connected to the same shunt?

Up until recently I had a Xantrex battery monitor only, however I have now added a WBJr as well as a BEP marine DC systems monitor.

Up until I actually read the WBjr installation instructions where it offers the option of connecting more than one sensor to the shunt, I thought it was necessary to have a shunt for each device.

If you have two devices (or three in my case) hanging off the same shunt, wouldn't the increased draw-down of the other devices make the readings inaccurate?
 

[Vic]

Hi Dave,

Generally,  the circuit that monitors this Shunt voltage are high-ish impedance,  and should exhibit very little loading on the shunt voltage.  You could test this by trying to individually applying each set of leads for each device,  and look for a  change in the reading of the other/s.

However,  it is probably a good thing if each cable set to each device connected to the shunt is shielded,  or at least twisted,  and not too long.   This is because inverters and CCs and many other electronic devices are switchers,   or use power switching when they operate.  Generally,  shorter leads allow less noise pick-up.  Noise can disturb accurate readings.

If you decide to use shielded cables,  ground only one end of each cable,  and ground each to the same point,  with as short a lead as reasonably possible.

Oh,  and YOU are Devo!

YMMV,  Vic