Graph reading

[guzzler]

How on earth do you read graphs like the one I've attached?? I don't know how you read the x-axis (resistance). Any help much appreciated...

g

[10SNE1]

>>I don't know how you read the x-axis (resistance). <<

That is a logarithmic scale of a resistance range.

Not sure where the difficulty lies - it's simply showing how the device's quiescent current is governed by the value of resistor (R) in the circuit.

[guzzler]

its just the way the scale changes between each value of 10. And I know its a graph of quiescent current and resistance. So say for a current of 8mA, what is the corresponding resistance??

thanks, i know this sounds dumb!

g

[Arzela]

The vertical lines increment linearly in
each of the groups 10-100, 100- 1k, and 1k to 10k....

So 8ma is 200k.

14 ma is 20k

6 ma is 400 k

[10SNE1]

>>for a current of 8mA, what is the corresponding resistance??<

Each increment on the Resistance (X) axis between the 100 ohm and 1000 ohm range is x*100 ohms where x is 2 - 9.

So the first 'tick' mark after 100 ohms represents 200 ohms which is where the quiescent current is 8 ma. At 400 ohms, it appears to be around 6 ma.

Log scales are used when the relationships are non-linear.

[guzzler]

ah, got it now! I'm still at high-school and we've only just started doing logarithms in maths and physics, so I'm now ahead!

thanks all

g