This week I ran into a most bizarre situation.
The x-mitters (2 of them) are Celesco PT800 serie LVDT. There range is 0-6" but we use them as 0-20mm (our display is calibrated for 0-20mm=0-20.0)
They where setup individually with there own 24Vdc supplys. They emit 4-20mA and with resistors we interface them with a 0-10V input dispalys.
All is OK on this setup and it's been working with satisfactory precision for a few years.
I connected them in parallel into an Fx2N-4AD extension module with the main 24Vdc power supply.
When one of them is connected its OK. As soon as I connect the second one the signal goes wild. It varies by about 1 Volt up and down when I start the process line .
We have tryed using them with there own isolated supply. Same thing.
We have tryed using them with ungroundes sheilded cables run on the goround floor for testing purposes. Same thing.
We have tryed using them with grounded sheilded cables run on the goround floor for testing purposes. Same thing.
We have tryed using them in a mA loop. Same thing.
We have tryed capacitors. Same thing.
We have tryed using them on 2 different seperated extension module (4AD). Same thing.
We have tryed all those with central and seperated 24 volts supplys.
Lord we have tryed hitting the control panel on the side with a hammer. Well, not really but we liked too
What is most bizarre about this is that no noise is apparent when we run the procces line with any one of them. Or any two of them with the 6 last motors stopped.
The noise is there ONLY WITH 2 x-mitter AND the last 6 motors all running AND when they are connected to the AD modules. Running any of those motors individually does not induce noise.
All those motors have Inverters. (5 AC, 1 DC)
We have connected them with the central PS and not connected to the AD modules and we have no voltage variation.
Any ideas?
The x-mitters (2 of them) are Celesco PT800 serie LVDT. There range is 0-6" but we use them as 0-20mm (our display is calibrated for 0-20mm=0-20.0)
They where setup individually with there own 24Vdc supplys. They emit 4-20mA and with resistors we interface them with a 0-10V input dispalys.
All is OK on this setup and it's been working with satisfactory precision for a few years.
I connected them in parallel into an Fx2N-4AD extension module with the main 24Vdc power supply.
When one of them is connected its OK. As soon as I connect the second one the signal goes wild. It varies by about 1 Volt up and down when I start the process line .
We have tryed using them with there own isolated supply. Same thing.
We have tryed using them with ungroundes sheilded cables run on the goround floor for testing purposes. Same thing.
We have tryed using them with grounded sheilded cables run on the goround floor for testing purposes. Same thing.
We have tryed using them in a mA loop. Same thing.
We have tryed capacitors. Same thing.
We have tryed using them on 2 different seperated extension module (4AD). Same thing.
We have tryed all those with central and seperated 24 volts supplys.
Lord we have tryed hitting the control panel on the side with a hammer. Well, not really but we liked too
What is most bizarre about this is that no noise is apparent when we run the procces line with any one of them. Or any two of them with the 6 last motors stopped.
The noise is there ONLY WITH 2 x-mitter AND the last 6 motors all running AND when they are connected to the AD modules. Running any of those motors individually does not induce noise.
All those motors have Inverters. (5 AC, 1 DC)
We have connected them with the central PS and not connected to the AD modules and we have no voltage variation.
Any ideas?
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