×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

dc voltage readings

dc voltage readings

dc voltage readings

(OP)
Greetings,
I am not an electrician or electronics anything beyond putting the stereo in the car. I have been troubleshooting a machine here a t work with the help of phone support technicians. It appears the problem is power, according to the techs. and thus we have been looking for a power drop in a dc circuit. Today I discovered there is a difference in the voltage reading based on where I ground the VOM. When checking voltage at the power amplifier on the hot wire and the ground pin on the amplifier I read the required 165 VDC. However when I use the chassis ground and the hot wire in I get 82 VDC. Checking the continuity between the chassis ground and the power amplifier I get a closed circuit. Why then is a 50% voltage drop?

Thanks

Fasedie

RE: dc voltage readings

This is most likely because there is a bridge rectifier that feeds the DC Circuit.

As it happens, such a rectifier produces a symmetrical voltage with respect to supply ground (draw the diodes and you will see why). So, if you measure between DC Negative and Positive, you get one voltage and if you measure from Ground to DC Positive you get half that voltage. You may, if you measure carefully, get 82.5 V and 165 V.

Nothing wrong there. If you are satified with the 165 V is OK, that is.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: dc voltage readings

(OP)
Thanks - the actual read voltages were 164.4 and 82.2 so we are good.

Faseddie

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources