# Meaning of Scaled and Inverted in context of picoammeter analog voltage output

1. Jul 30, 2012

### ThereIam

Meaning of "Scaled" and "Inverted" in context of picoammeter analog voltage output

I'm trying connect a picoammeter to an oscilloscope, and I noticed that its analog voltage output was described as "scaled" and "inverted". I'm just curious as to what that means about the oscilloscope is going to "see".

Very new to electronics, and cursory google searched yielded many pages using the adjectives "scaled" and "inverted" but all with the assumption that I knew what they meant.

What do they mean? What is the signal scaled to, and what does the fact that it's inverted imply about how its processing the current measurements...?

If that question even makes sense.

Thanks much.

2. Jul 30, 2012

### ThereIam

Re: Meaning of "Scaled" and "Inverted" in context of picoammeter analog voltage outpu

Well, I think I figured out the "scaled" part. The ammeter scales the current measured in the range of 2mA to -2mA to the voltage output range of 2V to -2V.

I think.

It's not particularly helpful for me because I'm measuring a current of about 3 pA and looking for fluctuations on that scale, so the output would vary by a part in a billion... Guess I'll have to use an amplifier.

3. Jul 30, 2012

### jim hardy

Re: Meaning of "Scaled" and "Inverted" in context of picoammeter analog voltage outpu

i thinnk it's scaled to represent whatever scale is selected.

I hail from the days of analog
where the instrument had a nice big analog meter driven by an amplifier
and a rotary switch to select the scale.
In those days the analog output represented the ends of the meter
for whichever scale you had selected.

so on a 2 pa scale , 2v would be 2 picoamps
and on a 2 amp scale 2v would be 2 amps

I'd be astonished if the digital meter were different
that's the whole reason for the analog output so you can record an expanded scale
and surely the range information is on one of the ports, rs232 or ieee488