Host Engineering Forum
General Category => Do-more CPUs and Do-more Designer Software => Topic started by: Watermark_JS on October 17, 2020, 01:09:17 PM
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I could really use some help with this. I am on-site, 1,000 miles from home, and my customer is waiting for me to resolve this issue. I was on the phone with A/D tech support multiple times yesterday and got nowhere.
I have a BX-DM1E-10ED23-D that is sending 19.2mA from WY0 when there is a value of 6553 in the output register. It should measure 4.0mA. A value of 32767 yields 31.7mA. :o
This has been verified with multiple meters and I have connected several different devices to be sure the field device isn't causing this. I have attached a table that shows measured mA at various output values.
To eliminate wiring or interference issues, I removed the PLC from the enclosure and have it sitting on a desk, powered from a different 24VDC supply. The analog output is the only I/O wired at this time. I also cleared all of the PLC memory and re-flashed the firmware. This had no impact on the results. Normally, I would just RMA the unit, thinking there is something wrong with the analog output...
HOWEVER, I when I attach a BX-4AD4DA-3 analog combo card, all of its outputs exhibit the exact same behavior! Could the problem just be the CPU? Is it capable of causing the add-on module to do this? ???
Best case, I get A/D to overnight a CPU for arrival Tuesday. I need to be confident that it will solve the problem, as the customer is waiting. :'(
Any ideas would be appreciated.
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Can you post a picture of your setup including PLC, meter and wiring? Also a picture of the configuration settings in the Analog I/O section of the controller.
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No, the CPU can't cause the module to misbehave in the same way. Leads me to believe something is wired wrong, or the measurements are being done wrong.
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Sorry it took a bit to get this reply out. Had to clean up wiring to get everything in one photo.
WX0 is scaled 0 - 100 at RX0 and is functioning as a stand-in for my field device and also as a secondary meter.
WY0 is scaled 0 - 100 at RY0 and is my sourcing analog out, wired to WX0. My mA meter is on this wire.
The value in RX0 is pretty close to the % my meter is reading. I couldn't get the high-res photo to upload, so there's a closeup of the data view and meter values in the next reply.
Thoughts?
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Here's a closeup of the values.
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I'm not sure about your wiring, but it looks like it is wired to the power supply. Pretty sure that's wrong.
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1C on the CPU is connected to DC- on the power supply to make input WX0 sinking.
1C on the combo module output section is connected to DC+ on the power supply to make those outputs sourcing.
Is that incorrect...? I'm digging into the online manual now...
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1C on the CPU is connected to DC- on the power supply to make input WX0 sinking.
1C on the combo module output section is connected to DC+ on the power supply to make those outputs sourcing.
Is that incorrect...? I'm digging into the online manual now...
That is not correct.
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Thanks BobO! I tied the two commons together and it works. That seemed very wrong.
So, does the combo card auto-detect whether it's sinking or sourcing somehow? I'm not sure I get it.
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It shouldn't be tied to the P/S at all. Commons are tied, input tied to output. There is no sinking or sourcing.
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:o Mind blown.
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:o Mind blown.
BRX internal and -3 analog are fully internally powered. It's a feature. ;)