k-firmware: If a voltage around 2.5V is detected at the pin for the external reference, it's used. You can disable the external reference by removing it or modifying the source.
m-firmware: If HW_REF25 is defined and a voltage around 2.5V is detected at the pin for the external reference, it's used. You can disable the external reference by removing it or undefining HW_REF25.
I don't believe or it doesn't make any sense that 2.5v reference really have to be an order of magnitude more accurate than the Vcc regulator to get more accurate measurements? Most of the Chinese clones use a standard TL431 which has 2% accuracy and a Vcc regulator 7550 which has 3% accuracy. So if the 2.5v reference have to be an order of magnitude more accurate to get better performance then it doesn't make sense why they would have the TL431.
The external 2.5V voltage reference should be only enabled if it's at least 10 times more precise than the voltage regulator. Otherwise it would make the results worse.
Thanks for the info, so let say I have the 5v Vcc regulator and 2.5v reference both are 1% accurate. Which way would I get more accurate measurement, removing the 2.5v reference so the tester will be using the Vcc as reference or leaving the 2.5v reference so the tester will be using the 2.5v as reference?
I don't believe or it doesn't make any sense that 2.5v reference really have to be an order of magnitude more accurate than the Vcc regulator to get more accurate measurements? Most of the Chinese clones use a standard TL431 which has 2% accuracy and a Vcc regulator 7550 which has 3% accuracy. So if the 2.5v reference have to be an order of magnitude more accurate to get better performance then it doesn't make sense why they would have the TL431.
Do you believe that all the Chinese "manufacturers" read or understand every detail in the manual? They just look at the schematic.
That topic is called error calculation Based on the current hardware and software design the maximum total error is larger when the 5V regulator and the 2.5V reference got about the same accuracy. If the 2.5V reference is around 5 times more accurate the total error is the same as having just the 5V regulator. And at about 8 times the external reference starts to provide a real benefit.
If there was a particular post or series of posts over there that make my words not true, please post a link to it.
If that is the case, then to obtain a more accurate performance of these testers every Chinese tester owner should remove the 2.5v reference as I am not aware of any of them using a more accurate 2.5v reference than an LM341 which has only a 3% accuracy. If your Vcc regulator is 7550 which has a 3% accuracy then you would need a 2.5v reference better than 0.5% which would be an LM4040 type or better.
After address set to read (CGRAM,DDRAM,IRAM.....)a DUMMY READ is required.
avrdude -c USBasp -P usb -p m328p -U flash:w:TransistorTester.hex \-U eeprom:w:TransistorTester.eep \-U lfuse:w:0xf7:m \-U hfuse:w:0xd9:m \-U efuse:w:0xfc:m