Hello,
I have a Load Cell (Omega LC202-2K) connected to a Signal Conditioner (Omega DMD4059-DC) which has an Output of 0 mV to 10 VDC Analog Signal (or I can switch to mA output). I am looking for a converter that would take the analog output and convert it to a digital signal, perhaps outputting using an ethernet cable and DIN Rail Mounted. Does DigiKey have something to offer? Or is there a Signal Conditioner that my Load Cell could connect to that would output a digital signal?
Hello Jerry,
Welcome to the DigiKey forum.
The 0 to 10 volt and the 4-20 mA signals are common in industrial controls and automation.
My first recommendation is a small Programmable Logic Controller (PLC). The advantage of using a PLC is that you will be able to add local monitoring, notification, and with the correct PLC, display capabilities.
You could use microcontroller for the process. This may or may not be more involved than you wish.
On the other hand, you may be interested in devices to display the value. One of the fancier examples is this Red Lion Display:
Please tell us more about your application so that we can guide you to the optimal solution.
Best Wishes,
APDahlen
P.S. Know that both devices will require some programming.
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Hi Aaron,
I was not wanting to go through all the explanations but, I am using a Yaskawa Controller that has PLC logic built in and it uses Lader Logic programming to control an actuator that is part of my machine that I am building. I also have an HMI that is logging data as the Load Cell produces it. My main problem here is that the Signal Conditioner, which is what my Load Cell operates through, is picking up some electrical interference from the machine Controller. In my endeavors, I have to move the Load Cell / Signal Conditioner away from the Controller about 3-1/2 feet and install it into its own small cabinet. And provide power to it from a different source other than the power going into the machine cabinet. Now when I connect my Analog Output from the Signal Conditioner to my Machine Controller, I start reading 0**.982 volts** interference/noise) which equates to almost 200 pounds of force on my load cell. It has been suggested by the machine controller manufacturer that I connect my output from the signal conditioner to a “Remote IO” unit. This would turn it into a digital signal and make it so I could use an ethernet cable and plug that into my controller using digital connections. His thought is that by converting the signal to digital and inputting it through different digital inputs, it might clean up the signal and not give me false readings.
I have been trying everything imaginable for almost a year now trying to get the Signal Conditioner not to pick up any electrical signal that comes out of the controller when it energizes the servo motor.
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Seems like a good application for a 4-20mA output rather than 0-10V. The 4-20mA format is far more resistant to noise than voltage signals.
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Not fun!
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Have you tried using a “boxcar” filter on the data? Here the term boxcar implies a running average of perhaps 10 to 100 samples depending on the speed of your system. If the noise is random, you may be very happy with the results. If it has a DC component (offset), it will not help.
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Does the PLC have remote I/O capabilities? It will be much easier to keep all controls in the same family. It’s a question of the protocol as spoken by your primary PLC e.g., MODBUS or Ethernet.
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I assume you have used shielded wire with no results.
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Other?
Please reply with the family / model number of your PLC and I’ll take a look.
Sincerely,
Aaron
P.S. Are the PLC and load cell system independent of each other?
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Aaron,
- using a “boxcar” filter on the data. The data as you call it, cannot be used until I get rid of the electrical noise first. So, no.
- Does the PLC have remote I/O capabilities? Yes, it has ethernet and/or I/O connections with only one analog input. I have connected the controller to a switch box which I am using in the machine and my HMI is connected to it. This is where I would like to try connecting my Signal Conditioner using a digital signal.
- Yes, I am using shielded wire with no results.
- Other. Ground wires out the ass. I have even tried less grounding.
Like I explained, the only thing that has helped is removing the Power 24 V power supply and the Signal Conditioner away from the Controller.
My Controller is MP2600iec - Yaskawa
My part number is, SGD7S-5R5AE0A000300
P.S. Are the PLC and load cell system independent of each other? YES
Cheers,
Jerry
Maybe if I switched to the 4-20mA output, I could put it back in the machine’s control cabinet. 
However, I believe that I would need to go to digital.
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As it sounds like your device has this capability, that’s the first thing I would try. You may well end up having to convert to a digital signal, but it would be worth trying this first.
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Isolators?
Emphasis on:
Also, I wouldn’t give up on the filter.
If the nose is emanation from the drive unit, you may have no choice.
r/
APD
I was looking through our signal conditioners, and it seemed like all of those I checked did have isolation, but if @jerry.bennett’s conditioner did not have isolation, that would definitely be a problem, particularly when using separate power supplies.
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One final thought,
There are a series of edge devices that could be used. Devices such as this are in the middle ground between PLC and computer.
With wireless capabilities, the entire system is isolated.
r/
APD
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David,
My Signal Conditioner was one that Omega recommend for my Load Cell. I am not experienced enough with electronics to know what I could use to replace it. I can take information that you suggest and bounce them off the Yaskawa Rep that has been selling me this equipment and trying to tutor me through this assembly.
Jerry
If you can tell us the model number of the signal conditioner, we could take a look at its specs. If it is not isolated, then we can look at options that are.
Edit: Never mind, I see you have model numbers entered above. I’ll take a look.
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Hi jerry.bennett,
It looks like your signal conditioner is isolated, so that itself isn’t the problem. It could still be a problem depending on how you connected things, though.
Regarding grounding, since your signal conditioner’s output signal is isolated from the rest of the device, you would want to tie your cable shield only to the MP2600iec ground, and not back to the signal conditioner ground. Otherwise, you negate the isolation benefit of the signal conditioner by creating a ground loop.
I still believe that using 4-20mA interface would likely help significantly. However, looking through the documentation for the MP2600iec, the single analog input can only take a +/-10V signal. You would need another signal conditioner to convert 4-20mA back into a 0-10V signal if you went this route.
The filtering that @APDahlen mentioned would also likely help significantly. Basically, you take a number of readings and average them. This averaging effectively reduces the noise impact on your signal significantly, and is common practice for signal sampling in noisy environments, particularly when you don’t need sub-millisecond response times.