Mitsubishi Q series: Q68AD-G module - does it supply voltage to the connected device?

mylespetro said:

In my experience, analog input cards often do not provide the loop power required to power two-wire devices (analog output cards often do source power to the output devices). You would typically wire from a terminal block with 24VDC to the positive(+) terminal of the transmitter, wire the negative(-) terminal of the transmitter to the positive(+) of your PLC analog input, and connect the negative(-) of your analog input back to the DC power supply common.

I couldn't find anywhere to download a manual or datasheet for that specific module, so I could be wrong, that's just typically how two-wire transmitters are wired to analog inputs.

EDIT: I added a little screenshot of a typical wiring diagram that shows the connection between the card, transmitter, and power supply using terminal blocks. The blue coloured wire is the +24VDC, which is supplied to the + of the transmitter, the green is the signal from the transmitter coming out of the - terminal and going to the + terminal of the analog input, and the red wire is the DC common coming out of the - terminal of the analog input and going back to the - terminal of the 24VDC supply.

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Mas01 said:

Link to specification
https://www.manualslib.com/manual/1298499/Mitsubishi-Electric-Q68ad-G.html

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(3) Power supply to 2-wire transmitter (Q66AD-DG only)
Supplying power to the 2-wire transmitter, the Q66AD-DG does not require the power
supply for the 2-wire transmitter.
Supply power can be switched ON/OFF channel-by-channel by the A/D conversion
enable/disable setting.

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mylespetro said:

In my experience, analog input cards often do not provide the loop power required to power two-wire devices (analog output cards often do source power to the output devices). You would typically wire from a terminal block with 24VDC to the positive(+) terminal of the transmitter, wire the negative(-) terminal of the transmitter to the positive(+) of your PLC analog input, and connect the negative(-) of your analog input back to the DC power supply common.

I couldn't find anywhere to download a manual or datasheet for that specific module, so I could be wrong, that's just typically how two-wire transmitters are wired to analog inputs.

EDIT: I added a little screenshot of a typical wiring diagram that shows the connection between the card, transmitter, and power supply using terminal blocks. The blue coloured wire is the +24VDC, which is supplied to the + of the transmitter, the green is the signal from the transmitter coming out of the - terminal and going to the + terminal of the analog input, and the red wire is the DC common coming out of the - terminal of the analog input and going back to the - terminal of the 24VDC supply.

Click to expand...

Mas01 said:

@mylespetro Thanks for the help - I got the water level sensor connected up to the PLC with your helpful explanation. All working now. Cheers

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mylespetro said:

Glad to help! Understanding different kinds of analog transmitters and how they're wired is pretty important, but fairly simple. Here's a pretty good diagram from an Allen-Bradley analog input card manual that I came across yesterday that shows the different types pretty well:

This is a little simplified, but illustrates the differences pretty well in my opinion.

Click to expand...

mylespetro said:

Glad to help! Understanding different kinds of analog transmitters and how they're wired is pretty important, but fairly simple. Here's a pretty good diagram from an Allen-Bradley analog input card manual that I came across yesterday that shows the different types pretty well:

This is a little simplified, but illustrates the differences pretty well in my opinion.

Click to expand...

Engineerj22 said:

Surprising that's an AB diagram!

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Engineerj22 said:

AB isn't really known for being particularly helpful. And usually a nice diagram eludes them.

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