Kanalog analog input - Sensor output, VFD output

[greg9504]

Hi,
I have a few 0-10v signals I would like to connect to Kanalog analog input so I can monitor the values in KmotionCnC. I'm confused with how to handle the ground/common.

Example 1:
- VFD has a 0-10V analog out. There are two terminals on the VFD, one for the 0-10v output signal and another labeled analog out common. Do I connect the VFD analog out common to the Kanalog ground? Then the VFD analog out signal to a Kanalog analog input?

Example 2:
- I have a sensor that outputs 0-10v. It has terminals +V, -V, and Output. It needs 24vdc across the +V -V terminals to power it. I have a 24vdc power supply, currently not hooked up to anything else, to power this sensor. Would I need to connect the -V terminal to Kanalog ground? Then the sensor output to a Kanalog analog input?

Or should I be running each of these signals through a 'signal conditioner/isolation' so that there is only one DC common used on kanalog? Something like https://www.automationdirect.com/adc/Sh ... nput/FC-33?

Thanks!
Greg.

[TomKerekes]

Hi Greg,

I think that is all basically correct. The Kanalog analog inputs and outputs are all referenced to KFLOP/Kanalog DC GND. If you require isolation between your device and KFLOP/Kanalog DC GND then you would need to add isolation with such a device as you link to.

HTH

[greg9504]

Hi Tom,

I think things are working OK, I do however have to apply a 'zero offset' correction factor. For the VFD analog out I'm seeing around 7 ADC counts at zero output, which Kmotion reports as 0.034 volts. If I measure this with a DMM I get 0.012 volts, same reading whether Kflop/Kanalog are powered or not (measured at the Kanalog terminals). So what I''m doing to correct for this offset is run a 'find offsets' routine once, that stores the offsets in persist vars, then when I read in the values in the forever loop I subtract the zero offset counts stored in the persist vars.

Does this seem like a logical approach or is this a 'fix' for a possible hardware problem? Other than that the updating of the DROLabels is working great. I have 3 inputs, the VFD analog out configured to output the vfd output amps, a pressure sensor, and a Magnetic proximity sensor connected to an opto in that I'm using as a tach counter (low rpm). I used the Debounce routine found in the C programs dir, although I did have to turn down the #define DBTIME 300 to 30 (higher may have worked, that was my first try) to catch the changes. What unit is the DBTIME in?

Thanks.

[TomKerekes]

Hi Greg,

A few counts of offset would be normal. Kanalog is designed to be precise but not necessarily accurate as 1% resistors are used. Once calibrated to correct for resistance values I wouldn't expect much change.

The DBTIME is in units of "forever loops". With one User Thread running, and one WaitNextTimeSlice() in the loop, the loop will execute every 180us. So 300 would be = 54ms. See how Multitasking works here.