Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs

Dashboard
Notifications
Mark all as read
Q&A

Resistance of digital ampmeter

+1
−0

Can we find the internal resistance of a multimeter ,when we use the multimeter like a ampmeter, from its datasheet?

I am trying to find the internal resistance of IDM 505 and I went to the datasheet to the current section and the most relevant thing I could find was the accuracy but as far as I know we cannot translate the accuracy to the internal resistance when used as a ampmeter.Any help?

I am asking because I didn't go to university today and we had lab hours. In the laboratory we use a Protek IDM 505 and I didn't measure some circuits which are for homework so I am searching it online to see if I can find anything.

Why does this post require moderator attention?
You might want to add some details to your flag.
Why should this post be closed?

1 comment thread

What actual problem are you trying to solve? (4 comments)

2 answers

+1
−0

What you linked to is more of a user's manual than a datasheet. Particularly for more consumer-oriented meters, this spec may not be explicitly available.

However, you can easily measure it. Use an ohmmeter to measure the resistance of the ammeter. You should see the ammeter report a small current. You should also see that the resistance goes down as you switch to less sensitive scales on the ammeter.

A good guess is that the voltage developed across the current-sense resistor at full scale is the same as the full scale voltage of the most sensitive voltage scale. That's usually what the native meter does internally. Different current scales then basically switch different resistors across this internal voltmeter.

For example, let's assume the most sensitive voltage setting goes to 200 mV full scale. If the lowest current scale goes to 2 mA, then the resistance of that current scale is probably (200 mV)/(2 mA) = 100 Ω. For the 20 mA scale, it would be 10 Ω, for 200 mA 1 Ω, etc.

Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+1
−0

Image alt text

You might get lucky and be able to measure the input resistance using this method. It should work because the black socket (common) is shared by all measurements.

Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

Sign up to answer this question »

This community is part of the Codidact network. We have other communities too — take a look!

You can also join us in chat!

Want to advertise this community? Use our templates!

Like what we're doing? Support us! Donate