Identify value in ohms relative of coil relay

[Jasonbit]

Hello folks,

I need know how many resistance the coil of 40.31 relay finder has. Because I am calculating the schematic where I will use a simply transistor PNP to control this relay. I am trying identify the value in ohm relative to the coil of the relay. I am search around on the web and I found this article: https://na.industrial.panasonic.com/blog/how-measure-contact-resistance-relays

After I read the article (my level english it is not very good) but I don't understand how this test works. Because when I turn on the coil and the contacts close my power supply 6VDC/1A will short circuit, right?

Anyway, how can I identify the value of this coil (in ohm's)? I use the test diode of multimeter (like this image: https://snag.gy/3lFeEU.jpg). My multimeter shows the value 81 in display. The unit of this value is ohms?

Datasheet: https://docs-emea.rs-online.com/webdocs/138b/0900766b8138ba16.pdf

Thanks

[PTR_1275]

That document you linked to is measuring contact resistance not coil resistance

What relay are you using? Do you have a data sheet?

[Jasonbit]

That document you linked to is measuring contact resistance not coil resistance

What relay are you using? Do you have a data sheet?

But how can I measuring contact resistance? You're going to short-circuit, right?
I intend using this relay: 40.31 https://docs-emea.rs-online.com/webdocs/138b/0900766b8138ba16.pdf

Thanks

[PTR_1275]

One way of measuring low resistances is with a known current (say 1.0000A) and measuring the voltage drop between 2 points. You may think it’s shorted, but if it’s 10mOhm, you will see 10mV across the contacts (at 1.0000A)

The data sheet gives lots of info and variables on the coil.

What voltage are you running the relay from? The data sheet says 0.65 watts for dc operation. That gives a current of ~54mA and should have a resistance of around 200ohms. This would be measurable with the normal ohms range on a multimeter. Keep in mind the tolerances will vary that figure.

[Jasonbit]

One way of measuring low resistances is with a known current (say 1.0000A) and measuring the voltage drop between 2 points. You may think it’s shorted, but if it’s 10mOhm, you will see 10mV across the contacts (at 1.0000A)

The data sheet gives lots of info and variables on the coil.

What voltage are you running the relay from? The data sheet says 0.65 watts for dc operation. That gives a current of ~54mA and should have a resistance of around 200ohms. This would be measurable with the normal ohms range on a multimeter. Keep in mind the tolerances will vary that figure.

Thanks to your reply,
I will study and do again this steps in laboratory. I will share the results in this thread.

Thanks

[PTR_1275]

No problems.

I forgot to mention in my previous post that those figures given were for a 12v coil. If you are running a different voltage, the figures will change

[Jasonbit]

On this link: https://www.finder-relais.net/en/finder-relays-series-40.pdf
I can see the specifications about relay 40.31. On this board, page 1 of 8, https://snag.gy/QxL97M.jpg, I can discovery which the current I will need to energize the coil with 6VDC. Because the power necessary is 0.65W to 6VDC, this means which my current will be: 0.65/6=0.108A, right?

Thanks

[mansaxel]

Hmm.
  (what am I, a newbie, missing?)
On page 7 in the document you linked to, there are all the data you need, in plain text.

Code: [Select]

Nominal     Coil     Operating range    Resistance Rated coil     DC: Release
voltage     code                                   consumption    resistance**
UN                   Umin      Umax     R          I at UN        R DC
V                    V         V        Ω          mA             Ω
6           6.006    4.8       6.6      33         165            62

So, 33Ω, 165mA and 6V. Don't forget the snubber diode! 

[sarahMCML]

Hi Jasonbit,

If you are using the 0.65W relay #9006, 6V, the coil resistance is 55 ohms, giving a current of 109 mA, whereas if it is the sensitive relay #7006, then its resistance is 75 ohms, giving a current of 80 mA. These values are all given on page 8 of the second URL of your first post.

Regards,

Sarah.

[vk6zgo]

The coil resistance of a relay is simply that--- resistance!
If you measured the thing with the ohms range of your DMM, you would have known it a month ago!
( It seems you already have the relay, because you talk about testing it with the "diode test" function of your DMM).