OCR small image with Tessnet

Question

I am trying to OCR following image using tessnet.

Unfortunately it doesn't work. I've tried to Re-scale image or convert this image to bitonal image, but it didn't help.

I am using english language pack with following whitelist _ocr.SetVariable("tessedit_char_whitelist", "0123456789.,abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");

and OCR code:

 var resultScaled = _ocr.DoOCR(bmpScaled, Rectangle.Empty);

Can you please advise what operations I can perform in order to improve quality of image for tessnet ?