Switching Between two 0-5V Signals

[fifty60]

I have an application where I need to switch between two separate 0-5V signals, 1 local and 1 remote. I have recently switched between 2 separate RTD probes using a gold plated bifurcated relay.

Would this same type of relay work on a 0-5V signal? My concern is the 0V part of the 0-5V signal.

 

[Besoeker]

I have an application where I need to switch between two separate 0-5V signals, 1 local and 1 remote. I have recently switched between 2 separate RTD probes using a gold plated bifurcated relay.

Would this same type of relay work on a 0-5V signal? My concern is the 0V part of the 0-5V signal.

Is the zero volt side of the signals common on both local and remote and, if not, can it be made common?
i.e. can they be connected together?

 

[fifty60]

Yes, the zero volt side is common. So is the 0-5V signal not truly 0-5V but only referenced to a non zero voltage and the 0-5V signal is a relative reading? The common for both signals is the common from a 24V power supply.

The power converts 120V into 24VDC. Is the 24VDC only a relative between the + and - terminals of the power supply, and not referenced to a 0V ground...

Yes they are both referenced from the same common, so I am only be switching between 1 wire from each signal. The common remains the same and never switched.

 

[petersonra]

it will probably work ok. take a look at the minimum wetting current the relay contacts require.

 

[fifty60]

The data sheet says 100uA, reference value.

 

[fifty60]

The gold plated bifurcated relays are the lowest I know of for wetting current. I am not sure there would be a better option...

 

[Smart $]

Yes, the zero volt side is common. So is the 0-5V signal not truly 0-5V but only referenced to a non zero voltage and the 0-5V signal is a relative reading? The common for both signals is the common from a 24V power supply.

The power converts 120V into 24VDC. Is the 24VDC only a relative between the + and - terminals of the power supply, and not referenced to a 0V ground...

Yes they are both referenced from the same common, so I am only be switching between 1 wire from each signal. The common remains the same and never switched.

24VDC power supplies can be configured as floating or grounded, but typically the latter. When grounded, the negative is typically referenced (electrically connected) to the supply system ground.

 

[Besoeker]

Yes, the zero volt side is common. So is the 0-5V signal not truly 0-5V but only referenced to a non zero voltage and the 0-5V signal is a relative reading? The common for both signals is the common from a 24V power supply.

The power converts 120V into 24VDC. Is the 24VDC only a relative between the + and - terminals of the power supply, and not referenced to a 0V ground...

Yes they are both referenced from the same common, so I am only be switching between 1 wire from each signal. The common remains the same and never switched.

So why are you concerned about the zero volt common?

 

[GoldDigger]

So why are you concerned about the zero volt common?

He is afraid that when the signal voltage is near zero there will not be enough current flowing to get a reliable connection through the relay contacts.

My take is that, for almost any sort of signalling any contact resistance or voltage offset, etc. will be negligible when gold plated contacts are used. But I do not have direct experience to back that up.

 

[Smart $]

He is afraid that when the signal voltage is near zero there will not be enough current flowing to get a reliable connection through the relay contacts.

My take is that, for almost any sort of signalling any contact resistance or voltage offset, etc. will be negligible when gold plated contacts are used. But I do not have direct experience to back that up.

I have to wonder whether the signals are truly 0-5VDC or 1-5VDC...???