Tone Generator Usage

[eight_bools]

Anybody have any experience using a tone generator on analog signal wires? Trying to locate two analog level sensors in an old plc5 panel that has been converted to RIO with an L55 control logix.

No schematic is available, and the processor doesn’t store comments. Im thinking of using a Klein tone generator to trace the wires I’m looking for in this panel. Any idea if it could damage the analog inputs or sensors?

 

[Bit_Bucket_07]

I've never even considered connecting a tone generator to a live wire. I do know that shielded cable does a pretty good job of attenuating the tone, which makes it difficult to trace a shielded cable.

 

[I_Automation]

I've never even considered connecting a tone generator to a live wire. I do know that shielded cable does a pretty good job of attenuating the tone, which makes it difficult to trace a shielded cable.

If you disconnect the cable shield from ground and hook the tone generator to the shield then that might be traceable. However if the shield is not connected at the sensor end like it shouldn't be the tone generator might not run through the cable.


To make sure it doesn't effect the PLC analog input I would disconnect it, and hope it doesn't effect the sensor.

 

[eight_bools]

I've never even considered connecting a tone generator to a live wire. I do know that shielded cable does a pretty good job of attenuating the tone, which makes it difficult to trace a shielded cable.

Never considered it because it’s a bad idea or just never thought of it? I’m starting to think it may not be worth the risk. I checked the data sheet for the tone generator and it’s not clear what voltage it outputs to generate the tone. It does say that it can withstand 60v though I think.

 

[chelton]

How many analogue cards in the rack? You could look through the program for MSG instructions. RIO analogue cards require MSG instructions of type BTR/BTW for configuration and reading/writing data which require the rack/group/module.

 

[eight_bools]

How many analogue cards in the rack? You could look through the program for MSG instructions. RIO analogue cards require MSG instructions of type BTR/BTW for configuration and reading/writing data which require the rack/group/module.

Its the rack group module that I don't understand. Any idea how that relates to the actual input on the analog card?

I know its Rack 3, and I identified that IO rack. Its in group 7, which I assume is input card #7 (8th slot?) and then is the module the input?

For some reason the PLC5 I/O cards have always confused me.

 

[chelton]

Its the rack group module that I don't understand. Any idea how that relates to the actual input on the analog card?

I know its Rack 3, and I identified that IO rack. Its in group 7, which I assume is input card #7 (8th slot?) and then is the module the input?

For some reason the PLC5 I/O cards have always confused me.

The R/G/M does not represent the individual analogue channels at all. R/G/M designate the physical position of the card in the rack which is also dependant on how the rack addressing is configured. PLC5 racks can be configured for 1/2 1 or 2 slot addressing.
If your MSG command is reading/writing to 3/7/0 and the analogue module is in slot 7, your adaptor is set for 1 slot addressing.
To find the individual channel data you need to first find out the type of module you have, then look at the manual for the card. This will give you the 16 bit word mappings that is required to configure the module and to read or write to the card for either inputs or outputs.
A 1771-IFE/A set to use all 16 channels for example requires a 37 word configuration to be written at startup using a BTW. A 20 word BTR is then continuously polled to read the analogue input data.
The data in this 20 word array will contain the individual analogue channels, and other diagnostic data.

 

[BryanG]

You don't say if the analogue signal is voltage or 4-20mA. so this may be even less helpful than I think it might be. I have a lot of useless information in my head, one example is that the HART Protocol superimposes a signal on top of a 4-20mA signal. So in theory it would be possible to add something to a 4-20mA signal without harming or changing the original 4-20mA signal.

The first website I found that describes HART:
https://instrumentationtools.com/what-is-hart-protocol/