Justin Fisher wrote:
>
> On a similar subject: which do people prefer - needle meters or LCD
> displays?

Analog. I always go for the needle.

Nine times out of ten, all I want is a voltage or resistance or current
number, so digital might be a little more useful. However, the tenth
time is when I want to see the needle move. For that, I'll always go
analog.

As a little aside, I sometimes like to see what is going on "inside" an
Nv or Nu neuron. The problem: how do I make a voltage measurement
without having the meter affect the circuit?

A few months back, I discovered the voltage follower circuit. It's just
an op-amp (I use the LM324), with the probe connected to the (+) input
and the output feeding back to the (-) input. Whatever voltage is
applied to the probe will show up on the output. The effect on the
circuit is minimal. The only trick is that the op-amp will have a
maximum output that's a couple of volts below it's supply voltage, so I
use a separate 9v battery to power the LM324.

With this arrangement, I can stick a probe into the heart of a neuron
and watch the needle swing as the voltage rises and falls. This has
helped me a couple to times to troubleshoot mysterious bugs in my
circuits.

Bruce