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Issues with 4-20mA output
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<blockquote data-quote="persjere" data-source="post: 589" data-attributes="member: 199"><p>I have the Industrial Automation Hat. I have successfully tested the mA inputs and discrete outputs but I can't seem to get the 4-20mA outputs to work. I followed the schematic from the manual (+DC to load, negative of load to +mA output on hat, -mA output on hat to -DC) and seem to be writing the values to the appropriate registers. I included the crude test code that I used below.</p><p></p><p>The current loads that I have are passive. One thing that I noticed is that the outputs are providing a voltage value even with the load disconnected. As the diagram in the manual shows an external DC supply in series (page 12 of the User's Guide Version 3.2), I expected the outputs to be passive and not provide a voltage. I tried connecting these to a 250 ohm resistor to see if the outputs are active. The output provided well over the 1 to 5V I would expect for a 250 ohm load and the resistor heated up significantly.</p><p></p><p>Does anyone have any suggestions?</p><p></p><p> print("Output values:")</p><p> i = 1</p><p> while i<=4:</p><p> set4_20Out(2,i,outputVal)</p><p> print(get4_20Out(2,i))</p><p> i+=1</p><p></p><p> if outputVal < 20:</p><p> outputVal += 0.5</p><p> else:</p><p> outputVal = 4</p></blockquote><p></p>
[QUOTE="persjere, post: 589, member: 199"] I have the Industrial Automation Hat. I have successfully tested the mA inputs and discrete outputs but I can't seem to get the 4-20mA outputs to work. I followed the schematic from the manual (+DC to load, negative of load to +mA output on hat, -mA output on hat to -DC) and seem to be writing the values to the appropriate registers. I included the crude test code that I used below. The current loads that I have are passive. One thing that I noticed is that the outputs are providing a voltage value even with the load disconnected. As the diagram in the manual shows an external DC supply in series (page 12 of the User's Guide Version 3.2), I expected the outputs to be passive and not provide a voltage. I tried connecting these to a 250 ohm resistor to see if the outputs are active. The output provided well over the 1 to 5V I would expect for a 250 ohm load and the resistor heated up significantly. Does anyone have any suggestions? print("Output values:") i = 1 while i<=4: set4_20Out(2,i,outputVal) print(get4_20Out(2,i)) i+=1 if outputVal < 20: outputVal += 0.5 else: outputVal = 4 [/QUOTE]
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