×
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

Ice Cube Relay and Precision Current Transmission

Ice Cube Relay and Precision Current Transmission

Ice Cube Relay and Precision Current Transmission

(OP)
Not sure if this is the best place for this, but I have an electromagnetic application where we are driving 2 coils with 0.2-2.0 amps with TDK Lambda power supplies. The application requires reversing polarity of the current and this is where we are using the ice cube relay. It is critical that the current is controlled down to single-digit milliamp accuracy which is why we are using the Lambdas. We have another test station setup that isn't automated and are finding that we have a significant amount of discrepancy between the automated/ice cube relays and the manual toggle switches with the manual toggle switches being much more consistent/accurate/repeatable. Are there relays out there that are really good for this kind of application, are there others that aren't? I would really appreciate any advise, council on the subject.

"To be or not to be, that is the question" - William Shakespeare via Hamlet

RE: Ice Cube Relay and Precision Current Transmission

Relays always have varying contact resistance - "it'll never work"

You should be using H-Bridge controllers for accurate reversals like you're looking for.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Ice Cube Relay and Precision Current Transmission

So, there's probably two things going for the manual switches, bigger contact areas and higher contact force through the springs built into the manual switches.

What is your allowable contact resistance? Have you considered using wetted relays, which might be more consistent for low current applications?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Ice Cube Relay and Precision Current Transmission

Switches often have wiping contacts that scrape any oxidation from the surface; I don't recall seeing any relays that have wiping contacts (there might be some), but there should be some instrumentation relays that are designed for consistent resistance. For certain relays are used in precision test equipment to avoid the voltage drops associated with solid state switching.

RE: Ice Cube Relay and Precision Current Transmission

Dave; Most ice-cube relays scrub because they have those long bars for the moving contact and the bar flexes requiring the contact to move back and forth to provide the flexing length. Still they're not going to give repeatable results.

Actually they'll give the worst kind of repeatably - six identical with one far different value, followed by three different ones, and then a bunch at the same value. This will drive the tester, human or otherwise, insane.

Wetted relays work but are becoming an anachronism because the best were mercury.

H-bridges are a dime a dozen, get the right one and be done with it. No more relay variability and wear-out.
Very first one I came up with on an H-Bridge search
Probably cheaper than a relay.

Keith Cress
kcress - http://www.flaminsystems.com

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! Already a Member? Login


Resources

White Paper - PLM and ERP: Their Respective Roles in Modern Manufacturing
Leading manufacturers are aligning their people, processes, and tools from initial product ideation through to field service. They do so by providing access to product and enterprise data in the context of each person’s domain expertise. However, it can be complicated and costly to unite engineering with the factory and supply chain. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close