problems with resistor messuaring

[Vanessa (varu)]

I built the tester and it has no problems messuring diods, capazitators 
or transitors. It does measure resistors under 1kΩ or over 150kΩ without 
issue, but every value in between is way of (for example 15kΩ is 
measured as 5,6kΩ).
Id appreate it if someone with more experience on the topic could help 
me.
I attached the circuit im talking about.

[Christoph M. (maije)]

Do you also have a circuit diagram? With the information you provided i 
would say the resistor R42 has a wrong value, and the cable need to be 
black not blue...

[Andreas S. (Firma: Schweigstill IT) (schweigstill)]

Nobody except from you knows what "the tester" you are talking about.

[Georg M. (g_m)]

Andreas S. schrieb:
> Nobody except from you knows what "the tester" you are talking about.

https://www.mikrocontroller.net/articles/AVR_Transistortester

[Ob S. (Firma: 1984now) (observer)]

Vanessa schrieb:

> I built the tester and it has no problems messuring diods, capazitators
> or transitors. It does measure resistors under 1kΩ or over 150kΩ without
> issue, but every value in between is way of (for example 15kΩ is
> measured as 5,6kΩ).

When you encounter the issue, is the ISP adapter plugged or unplugged? 
Or does this happen independently of the connection state of the ISP 
adapter?

[Rüdiger B. (rbruns)]

Christoph M. schrieb:
> and the cable need to be
> black not blue...

NEVER cut the Black one First!