here is the post I mentioned above.
Not sure how accurate this user is though or if Langmuir can comment about the validity of this, but knowledge is power.
" Hmm,
Further testing has revealed that the Everlast manual is correct about the division ratios. They are indead 16:1 and 50:1
BUT:
Many THC’s must have some sort of scaling resistance internally to scale the input voltage to suit their internal ADC. They may see the Everlast division resistors as an extension of their divider network and display erroneous results.
So shorting out a resistor as shown may work on one THC but be incorrect on another.
In my case, my THC hasa 0-10 volt sensing range internally and can be configured using an external resistor to whatever you like;
So with the divided voltage disconnected from my voltage sensing hardware, a multimeter shows the dividers are indeed 16:1 and 50:1 but as soon as plug the wires into my sensing hardware, the voltage division at the same point becomes:
CODE: SELECT ALL
Native 0-10V range Dividers of 32:1 and 100:1
Extended 0-20V range Dividers of 24:1 and 75:1
So it seems you need to test against a known voltage to confirm the final dividers on your hardware. Just also be aware that an unloaded DC switch mode power supply may still have a significant AC ripple in it."