I was testing some amps for power output and the displayed value seemed off, so took the voltage displayed off the oscilloscope and calculated the wattage the usual way. For a 150W RMS output into 8 ohms the kit is displaying ~ 206W RMS. I’m measuring a 1 KHz sine wave into a non inductive audio load. All other functions of the kit seem to be normal.
Is there any way to change the calibration of the power display?
Either you scope measurement/calculation or the K8098 is wrong.
K8098 does not require adjustment. An assembly error can lead to inaccurate readouts. Check complete assembly, especially resistor values. If you cannot finf the cause of troubles, youncan return the kit for inpection/ repair.
Resistor and capacitor values and polarity are correct. C8 polarity is reversed per PVPA20’1 errata. No soldering errors that I can detect.
I guess I’ll have to send it in for checkout. What is the procedure for doing so?
Please return it with a detailed fault description to:
Velleman Projects Tech. Dept.
Legen Heirweg 33
9890 Gavere
Belgium
In overviewing the other forums I discovered that you have a USA support location in Texas, since I reside actually only a few miles away from it, I will try contacting them to start.
Thank you.
You can call them for RMA at (817) 284 7785
Took the kit over to your USA location shortly after the timeframe of this discussion, they’ve had it for 5 weeks now and after two phone calls and two visits my impression is that the technician seems to be clueless about what may be wrong with it. He didn’t say that he found any construction errors and wasn’t of the opinion that the PIC or Op amp or any other components were bad. The kit seemed to be fully functional except for having incorrect values on power readings. I don’t believe I damaged it either, I have been working in the electronics field for many years now and know about the precautions one should take with static sensitive components and electronics in general. I am not aware if he tried to substitute a known good PIC. I also don’t know if he has tried to contact anyone from an engineering aspect on your side. The only other conclusion I can reach from the available evidence is that the scaling in the amplifier section or the calculation routines in the PIC are incorrect, but if this were so there would surely be other complaints. I am at a loss. I apologize for the tone of this but after spending over $60 on this device and waiting 5 weeks I would like some resolution of this issue.
Thank you for your attention,
Dave
We apologize for the inconvenience. We will look into the matter and take steps to resolve the issue as quickly as possible.
I just recently received my K8098 kit back from your US service location, the only indication in the enclosed note was that there was no problem found. I’m baffled that the technician reached this conclusion if I assume he tested the unit under actual conditions. I retested the RMS power function and the inaccuracy is still present, it consistently reads greater than the actual value. My test instruments are in calibration. My only conclusion is that I’m now out the 60 plus dollars I spent on this kit as it is useless for any quantitative measurements. The only even apparently useful functions it now has are the spectrum analysis scales and they’re only good for a relative display of overall frequency response with no reference to any absolute values. I welcome any suggestions as to how this issue could be resolved.
To anyone else following this thread and has had experience with this kit I would welcome any comments.
Dave
It would appear now that the response to my problem is to just ignore it, he doesn’t have a clue, etc. If that the way it’s going to go, fine. I got the kit to work after a fashion by changing the gain of the input amplifier , it’s now within about 5% of the actual value, unfortunately the other functions now seem to be off (if they were ever accurate) especially the mean and peak dBu functions since I have no idea what the PIC is doing. It’s not a huge issue since my primary desire in acquiring the kit was to measure amp output quickly and secondarily use the spectrum analyzer scales to monitor program material in my live performance sound systems. However I am still on the whole disappointed in the whole affair. Did your engineering people back check any of this or is it their attitude that they’re never wrong? Either that or we calculate audio wattage and levels differently here in the states.
Dave