/ tuesdaytooling

Tooling Tuesday - Component Tester

So the source of this blog post was a Twitter conversation where CleoQC posted about a resistor's unclear colour coding.

So how can you check a resistor?

Well first there are a series of 4/5 coloured bands that can be decoded.


For this I use a handy website where I can enter the colour code and it will provide the value. Link to website

But sometimes the colours are badly printed, printed on a blue resistor or just not there. So how can we check their value? Well using a multimeter is the next step.

Here we see the ANENG AN8008 Multimeter, my trusty meter checking a 330Ω resistor. The reading of 354Ω is due to the leads having ~26Ω resistance.

I have used this method many times in the workshop and in the field and typically it works really well for me.

So what about this component tester?

Ok yes back to the point. A component tester is much more than a resistor checker! With it we can test...

  • Resistors
  • Diodes
  • Capacitors
  • Random 3 pin chips (transistors, MOSFET etc)


All we need to do is insert the component into the slots, for example this 2n2222 NPN transistor has been inserted into slots 1,2,3 and then the lever closed to lightly lock the component in place. Then we press the button and the device works its magic.

I placed the same 330Ω resistor into the tester and it returned that it was 327.5Ω which was close enough.

Why not 330Ω exactly?
Well the last band on the resistor colour code is the tolerance, i.e the precision of the resistor. For my 330Ω resistor it had the colour code Orange - Orange - Brown - Gold. And Gold refers to a 5% tolerance. 5% of 330 is 16.5Ω so for it to be within tolerance of a 330Ω resistor, the value can be +/- 16.5Ω

With the component tester we can also check an 1N4001 diode, we don't even have to worry about polarity as the tester will determine that.

So where can you buy this from?

I purchased mine from eBay for ~ £8 quite some time ago, but they can be found in plentiful supply all over eBay and Aliexpress, just search for component tester and if you can get one in a case, then do so as the screen is a little fragile.

Extra information

Recently a few of my friends have purchased these testers.

During another Twitter conversation I was reminded that the component tester is really just an Arduino compatible device and that there is an active hacking / modding community around the board. So head over to [EEVblog and dig into the huge forum thread!]https://www.eevblog.com/2017/09/11/eevblog-1020-is-a-7-lcr-component-tester-any-good/

Happy Hacking