Rotary switches for calibration changes, type question
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Re: Rotary switches for calibration changes, type question
There was a good reason that I changed from resistor ladders to diodes.... I'll leave it to the reader to figure out why it was a step in the right direction
Re: Rotary switches for calibration changes, type question
Go on, Pat, put me out of my misery and explain, as the temperature variation argument is quite compelling, and my brain hurts lol.
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Re: Rotary switches for calibration changes, type question
You bought a job lot of diodes?
Re: Rotary switches for calibration changes, type question
"Based on..." 0.1 mA - we can't assume current flowing through circuit to that low - when using diodes.
Hence current flowing through circuit is greater than that, as diode does not limit forward flowing current to that low level. So - forward voltage slope is definitely greater than (60 mA).
Hence current flowing through circuit is greater than that, as diode does not limit forward flowing current to that low level. So - forward voltage slope is definitely greater than (60 mA).
Last edited by Benkku on Thu Dec 01, 2011 2:43 am, edited 1 time in total.
Re: Rotary switches for calibration changes, type question
What that 'good reason' might be?pat wrote:There was a good reason that I changed from resistor ladders to diodes.... I'll leave it to the reader to figure out why it was a step in the right direction
In my opinion - it is more difficult to measure circuit -in fault finding situations, when using diodes without first powering circuit and/or dismantling switch from instrument panel.
Re: Rotary switches for calibration changes, type question
Indeed...but temperature curve is worse at lower currents, hence me using that :s
Re: Rotary switches for calibration changes, type question
and also worse, than when using foil resistors, despite of flowing current. Hence - one reason why all ADC binary and laddering circuits, are made with resistors.
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Re: Rotary switches for calibration changes, type question
I am glad I never went into politics, I'd have started a few wars by now.... I never knew what to me was a simple question would cause so much discourse amongst experts I think I'll get my coat....
Re: Rotary switches for calibration changes, type question
War - nah... It's just opinions with reasoning why.
Think for example that '60 mV' slope. In switch position 7 'worst case' difference is 420 mV at minimum (actually more than that
) when temp change is approximately 20-30 Deg C. ...Then when you have different forward voltage diodes connected in series, bit more temperature change... - you get the point.
Think for example that '60 mV' slope. In switch position 7 'worst case' difference is 420 mV at minimum (actually more than that
) when temp change is approximately 20-30 Deg C. ...Then when you have different forward voltage diodes connected in series, bit more temperature change... - you get the point.
Re: Rotary switches for calibration changes, type question
Topic started...
I also wish to know "good" reason to use diodes?
It is not possible to do 10-position switch with diodes (from 5V supply).Chris Wilson wrote:I want to make some 10 position rotary switches for .....
I also wish to know "good" reason to use diodes?