Mains voltage data logger

[treez]

Hi,
Can you see any gremlins in our mains voltage data logger circuit?
Its just to take the maximum peak mains voltage occurring every second.

The data logger gets connected to a USB cable then into a PC...(but the PC doesnt have to be connected for the logging to occur..the PC just collects the logs after the analysis period)...and even though this is not "officially" isolated from the mains, i believe that the PC will not be damaged, due to the 1MEG resistor.
this product is not for sale...its just to monitor the mains voltage in our factory.


[my apologies because this post grew out of this thread which re-directed our attentions because of great advice received from FvM...

https://www.edaboard.com/showthread...ce-of-mains-transformer&p=1642916#post1642916

 

[carpenter]

why do not you measure on the secondary side of the transformer when you already have it?

 

[treez]

thanks, its because it is a cheap transformer and we think it will not react in the expected fashion to VAC input changes.
I mean in the first place, we did like you said (as attached), but then we changed our mind, partly because of advice from FvM in the above thread shown in the top post, regarding the lack of prowess of these cheap transformers as measurement devices.